Code W 1994

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The Chartered Institution of Building Services Engineers

Delta House, 222 Balham High Road, London SW12 9BS

First published 1989

Revised edition

Registered charity number 2781 04

ISBN 0900953675

Typeset by CIBSE Technical Deparlment

Foreword

The effective operation of any water system is highly dependent on satisfactory circuitbalancing and co/hermmissioning. It is important, therefore, to have a design objective thatensures commissioning requirements are taken fully into account at the conceptual stage.

Designers should ensure that these requirements are reflected in an unequivocal speci-fication so that satisfactory commissioning can be assured. Discussions at an early stagewith an approved and accredited commissioning specialist will assist the designer to thisend.

Procedures for the balancing and commissioning of water systems have evolved over thelast two decades and are now acknowledged as being an essential factor in the completion ofa design through to the final handover stage.

The CIBSE Commissioning Code W represents standards of good practice which arepresented in the form of recommendations and guidance generally accepted within thebuilding services industry.

The 1989 edition has been completely reviewed and updated adding more technicalinformation and advice that not only sets out to create a superior Code for water regulationbut also points out those extremely imponant areas where design and installationtechniques are vital in aiding commissioning.

The latest technological improvements to components have been considered, together withthe most up-to-date methods employed by commissioning specialists. Where appropriatethese have been included in this revised Code.

The tolerance statements in previous Codes have tended to be somewhat exacting, requiringtoo much time and effort to be expended in working to close tolerances, with very litdeapparent environmental benefit. A completely new section has widened the tolerancerequirements appropriate to differing performance effects and the particular temperature ofthe medium.

R M Bishop (Chairman)

Task Group

RM Bishop (Chairman)I G AllanA BlackJ F CoppinR ClarkRJ Oughton

Publications Secretary

K J Butcher

Editor

R Yarham

Note from the publisherThis publication is primarily intended to provide guidance to those responsible for the.design, installation, commissioning, operation and maintenance of building services. It isnot intended to be exhaustive or definitive and it will be necessary for users of the guidancegiven to exercise their own professional judgement when deciding whether to abide by ordepart from it.

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Contents

1

1

2

3

3

3

3Wl

3

3

3

3

4

5

6

6

7

Precommissioning checksWI.I Objective

WI.2 State of the system

WI.3 Checks before filling

Wl.4 System flushing and cleaning

WI.S System filling and venting

WI.6 Mechanical checks

WI.7 Electrical checks

Wl.8 Static completion records

W2 Setting to work

W2.1 Checks before pump start

W2.2 Initial run

W2.3 Further venting

W2.4 Completion certification

7

7

7

8

8

8

8

8

8

10

10

10

12

14

15

15

Balancing water flow ratesW3.1 Objective

W3.2 Flow rate measurement tolerances

W3.3 Basis ofbalancing

W3.4 Pump shut-off head test

W3.5 Preliminary flow rate check

W3.6 Constant-volume systems

W3.7 Variable-volume systems

W3.8 Balancing by compensated method

W3.9 Regulation by temperature balance

W3.10 Commissioning certification

Evaluation and witnessing of commissioned systems

W4.1 Objective

W4.2 Witnessing arrangements

W4.3 Duties of witnessing agent

W 4.4 Commissioning documentation

1515

15

16

16

IntroductionWO.l Scope

WO.2 Definitions

WO.3 Specification

WO.4 Inspection

WO.5 Commissioning records

WO.6 Responsibilitv

Appendices

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17

17

17

18

19

19

19

19

WAl Design

W AI.I Design requirement

W AI.2 Design considerations

W AI.3 Provisions for measuring pressure and determining flow rate

WAI.4 Easeofaccess

W AI.S Flushing and cleaning

W AI.6 Chemical cleaning

W AI.7 Design information required

2020

20

2020

WA2 Installation

W A2.1 Installation requirement

W A2.2 Installation cleanliness

W A2.3 Installation inspection

W A2.4 Pressure testing

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202021

222222

23

23

WA3 Flow measurement and regulation

W A3.1 Flow measurement devices

W A3.2 Factors affecting measurement accuracy

W A3.3 Double-regulating valve

W A3.4 Access to flow measurement and regulating devices

W A3.5 Constant flow regulator (CPR)

W A3.6 Instrumentation

W A3. 7 Flow coefficients

References 24

Bibliography 24

Index 26

t

wo Introduction Accuracy -flow measuring device

The variation in indicated volume flow rate from the truevalue due to manufacturing tolerances in the flow measur-ing device.

WO.l Scope

This Code deals with the work involved in balancing waterflow rates in water distribution systems. All allied mechan-ical and electrical services and devices must be thoroughlychecked and proved to enable this to be carried out. Thiswhole procedure is known as commissioning. This Coderepresents standards of good practice which are presentedin the form of recommendations and guidance generallyaccepted within the building engineering services industry.

.')vNote: a manufacturer's stated accuracy is the probableaccuracy that can be achieved and should be stated as apercentage of the designed signal flow coefficient (kys) ofthe device.

Accuracy -instrument

The variation in reading from the true value due tomanufacturing tolerances in the instrument.Unless adequate provision has been made by both the

designer and the installer of a water distribution system, itmay not be possible to balance and commission the systemin accordance with this Code. Appendix sections W Al andW A2 therefore draw the systeQl designer's and installer'sattention to the requirements which will ensure that a watersystem can be balanced and commissioned.

Note: a manufacturer's stated accuracy is the probableaccuracy that can be achieved and be should stated as apercentage of the full scale deflection.

Balancing

The Code sets out to inform on the requirements foraccurately balancing and commissioning water systems. Amanual published by the Building Services Research and

A\ Information AssociationCI) describes the practical aspects in'" a step by step format.

The process of adjusting the flow rates of a fluid in adistribution system to achieve the design flow rates withinthe specified tolerances.

Capacity testing

WO.2 Definitions Demonstrating the capacity of an installation or com-ponent to achieve and maintain the performance criteriarequired by the specification.

For the purpose of this Code the following definitionsapply.

Chemical cleaning

Accuracy The internal treatment of a pipework installation accordingto a formal procedure with chemical fluids.

The overall accuracy is a compounding of the followingfactors: instrument accuracy; flow measuring device accu-racy; measurement accuracy. Refer to the BSRIA Appli-cation Guide 2/89 The commissioning of water systems inbuildings (section A6) for further information(lJ.

Commission able systems

Systems designed, installed and prepared to specified re-quirements in such a manner as to enable commissioning tobe carried out.

Accuracy -error measurement

CommissioningAny error in instrument reading due to inaccuracy ofoperator observation such as errors of parallax or the in-strument reading being subject to pulsations.

The advancement of an installation from the stage of staticcompletion to full working order to specified requirements.

WATER DISTRIBUTION SYSTEMS

Commissioning management Precomm;ss;on;ng

The planning, organisation, co-ordination and control ofcommissioning activities.

Specified systematic checking of a completed installation toconfinn its suitability for commissioning.

Note: precommissioning is a post-installation completionactivity.Commissioning manager

!he firm (or person) appointed to manage the commission-mg process.

Pressure and leakage testing

The measurement and recording of a specified pressureretention or loss within a system or system component.

Commissioning specialist

Setting to workThe firm (or person) appointed to carry out specified dutiesin connection with commissioning engineering services.

The process of setting a static system into operation

Commissioning specification Static completion

The document which prescribes the requirements withwhich the various commissioning services have to comply.

'1The state of a system when it is installed in accordance withthe specification, i.e. clean and ready for setting to work. Inthe case of water systems this includes flushing, cleaning,pressure testing, filling and venting.Note: the specification must refer to drawings, schedules

and relevant parts of the Code, manuals, guides and otherstandards.

System

A set of connected components for heating, cooling, ventil-ation or air conditioning consisting of plant, distributionducting, piping and terminal units and arrangements tocontrol their operation. -

Design criteria

The specified numerical quantity together with allowabletolerances.

System provingDiversity

Measuring, recording, evaluating and reporting on theseasonal performance of the system against design criteria.The ratio between the design maximum system load and

the summation of all terminal loads.

TestingFine tuning

The measurement of the performance characteristics of aninstallation or parts of an installation.Local adjustment to the system where usage and system

proving have shown such a need. This may also include there-assessment of control set points and values to achieveoptimum performance.

Note: this includes off-site testing.

Tolerance (for balancing procedures)

Flow rate -measured The permissible range of variation which is acceptable fromthe design value of a measurable characteristic. For fluidflow rates this is usually expressed as a percentage of thedesign value.

The flow rate derived from an instrument connected to apipeline device having a known characteristic. .

Note: designers should specify tolerances in their designcriteria.Flushing

The washing out of an installation with water to a formalprocedure to remove detritus. WO.3 Specification

This Code assumes that the system is complete and properlyconstructed to an agreed specification. This specificationmust state the tolerances within which the installationshould operate, and to which the system should be bal-anced.

Installation

.A system placed in position as required by the design orspecification.

PRECOMMISSIONING CHECKS

.

WO.4 Inspection

wo.s

WlPrecommissioningchecks

Wl.l Obiective~~

WO.6 Responsibility

Wl.2 State of the system

f WO.7 Practical considerations of flowrate balancing

The measurement, regulation and balancing of flow rates ina water distribution system as applied in commissioningprocedures is a means to an end. The prime objective is toensure that the heating or cooling output of a commis-sioned installation can maintain the space environmentalconditions specified by the designer with optimum systemefficiency.

Wl.3

The degree of accuracy in flow rate balancing required tomeet this objective will depend on a number of factors.These include the assumptions made by the designer inarriving at the specified heating or cooling loads for theconditioned space and the performance characteristics ofthe heat exchangers or terminal units serving the con-ditioned space. The difference between the temperature ofthe circulated fluid and the space temperature influencesthese performance characteristics. Consideration shouldalso be given to UK climatic conditions which fluctuatemore rapidly than those for large continental land masses,hence placing greater demands on system performance.

Particular checks should include, but not be limited to,

ensuring that the following have been fulfilled.

(a) All equipment and components have been installedin accordance with the manufacturers' instructionsfor the medium used (e.g. chilled, low-, medium- orhigh-temperature hot water).

(b) Pump and valve gland packing and special valvelubricants are compatible with any chemical to beused in the cleaning, flushing and corrosion in-hibition of the system.

(c) Permanent water connections have been made.

(d) Flow measurement devices have been installed inaccordance with manufacturers' instructions andsection W A3 of this Code.


(e)

f;(f)

Wl.4.2 Flushing procedure(g)

(h)

(i)Systems should be cleaned and flushed in accordance withan agreed and approved method plan. Throughout thecleaning and flushing process, the carrying out of pro-cedures in accordance with the method plan should beverified by the installing contractor and inspected by therelcvant witnessing authority.

(j)

(k) Satisfactory compliance may be ensured by certification.Additionally, the commissioning specialist should be satis-fied that the system has been adequately cleaned, by refer-ence to the certification, by assurance from the witnessingauthority or by witnessing aspects of the work him/herself.

.(1)

The following procedures are recommended.

(a) Flushing should be supervised only by qualifiedstaff.

(m) (b)

(n)

(c)

(0)

(P)(d)

A flushing schedule should be provided by the in-stallation contractor and approved by the designerbefore the physical process commences.

The schedule should be based on schematic draw-ings with all sub-circuits, branches and terminalsuniquely identified. All valves, coils, tubes andother equipment liable to choking should be clearlyidentified.

Flushing should be carried out methodically fromthe top to the bottom of the system. .

(e)

(q)

(r)

(s)

(t)

Probe pockets, pressure gauges, siphons and testpoints have been installed.

Manual air vents and automatic air vents, wherespecified, have been fitted at high points includingcontinuous venting at low-velocity sections.

Drain valves and overflows of the Correct size havebeen fitted. (See section WI.4.)

Connections to heater and cooler batteries andother heat exchangers have been made correctly inrelation to the design air and water flow directions.

Control, double-regulating and non-return valvesare installed in accordance with the flow directionarrows or other indications marked on the devices.

Relief valves have been installed to operate withoutrestriction and in accordance with the manufac-turers' instructions. The outlets are piped away tosuitable drain points.

Expansion devices are aligned and free from ob-struction and installed to manufacturers' instruc-tions including anchor points and guides.

Strainers with the specified mesh have beeninstalled in an isolatable section (see section WI.4).Changeover devices for duplex strainers are fitted.(Drain-down cocks are recommended for largerstrainers.) Access and lifting facilities have beenadequately provided for.

All washers, cisterns, tanks, nozzles and fittingshave been inspected for cleanliness.

All valves and cocks have been set in the opera-tional position as given in the valve schedule (e.g.open or closed).

The cold feed or mains connection has been locatedcorrectly.

All pipework and fittings have been adequatelysupported, and, where provided, spring supportscorrectly adjusted to fully support the weight 'of thepipework, components and water content in ac-cordance with the specification.

All test points are accessible to probes.

All pipework has been correctly identified andmarked.

Adequate access is maintained to all manual valvehandwheels and to actuators on automatically con-trolled valves.

The system is safe to fill and that personnel are keptclear of areas which might be hazardous due to un-foreseen failure during filling.

(f)

Equipment liable to choking should be bypassed,isolated or completely removed and replaced by aspool piece to ensure system flow continuity. Theuse of flexible connections on terminal units mayprovide an easy means of bypassing the terminal. Itmay, however, be economic to install permanentbypasses.

Note: in the unlikely event of sensitive equipmentnot being works pressure tested, the equipmentshould be pressure tested with clean water on anindividual basis on-site before connecting to thesystem. See section W A2.4.

Every effort should be made for the flushing watervelocity to be generated externally and not by use ofthe system pumps. It is recommended that systempumps be bypassed, isolated or removed and thecircuit completed. To ensure effective flushing,velocities should be in accordance with BSRIAApplication Guide 8/91 Pre-commission cleaning ofwater systems(3), as highlighted in Part C: System dy-namic flushing.

Wl.4 System flushing and cleaning

Wl.4.1 General

uCare must be taken during construction to keep the internalsurfaces of pipework systems as clean as possible. Seriousblockages in equipment will prove damaging and expensive

4

PRECOMMISSIONING CHECKS

(g)

(k)

(i)

with details of jointing and gland materials used in pumps,valves, lubrication materials of cocks and similar material.

(a) Chemical cleaning should be preceded by flushingand carried out in a similar manner to that des-cribed in section Wl.4.2, but with frequent sampletesting as necessary by specialist chemical cleaningpractitioners.

(b) The system must be completely flushed and pas-sivated immediately after chemical cleaning toinhibit metal surface corrosion.

Systems should not be left empty. Frost protectionsystems must be active after chemical cleaning toavoid system drainage and the loss of chemicalsduring cold periods.

Where the whole system is not being chemicallycleaned at the same time it is recommended that theisolating valves be locked in order to avoid pollu-tion from untreated sections.

(J)

(c)

(k)

(d)

(1)

Reference 5 recommends that water introduced into abuilding water system for commissioning purposes shouldbe completely drained away unless the system is to be putinto service immediately. It should be noted that for closedwater systems, at low risk of disseminating Legionnaires'disease, this practice would be both costly and unnecessary.See also References 6 and 7.

(m) Wl.4.4 Water treatment

Dosing pots and other water treatment apparatus must befilled and set up in accordance with specialist instructionsby the installing engineer.

Wl.5(n) System filling and venting

Fill the system with water (treated, where specified) inaccordance with an agreed method statement, prepared bythe installing contractor. To ensure effective venting fillslowly from the bottom upwards, thus forcing the air tohigh points for venting to atmosphere. Careful consider-ation should be given to the setting of valves and air ventsbefore and during filling to avoid airlocks and excessivespillage, particularly where the fill is treated. Take care notto exceed the working pressure of the system when fillingfrom a high-pressure source. When the whole system isfilled, disconnect the filling source, open the permanentsupply connections and adjust the feed tank water levels.

(0)

(P)

The pipework distribution system should beseparated into isolated sections of high to lowpoints.

Each section should incorporate a drain valve at itslowest point. The full bore valve should be of linesize and at least 50 mm on larger diameters allhaving access to drainage.

Each section should incorporate a suitable quick-fill point.

Each section should be flushed in tUrn, startingwith the highest point. The section valves shouldbe open, including bypass and drain valves; com-mence flushing downwards.

Each section should be isolated in tUrn until testsamples do not contain significant signs of detritUs.Strainers should be inspected at regular intervalsduring this process.

After the final high-velocity flush, the systemshould be filled with clean water together withsuitable cleaning additives. Circulation through thesystem to be cleaned should be in accordance withthe recommendations made by the specialist sup~plier and the cleaning and flushing method plan.This procedure should assist in removing thesludge, which adheres to the pipe wall, and keep itin suspension for draining.

Once the system is clean it should be drained andfllled immediately from the bottom up. Fillingshould be slow, taking care to remove air fromextremities and high points. The system shouldthen be dosed to prevent further corrosion and leftcirculating. Dosing and venting should be monitor-ed frequently in the early stages of system.

On no account should any part of the system bedrained and left empty and wet for longer than 24hours after cleaning, as this will promote rapidcorrosion and possibly necessitate are-clean.

Where chemical cleaning is not specified, the drainvalves and the water inlet 'should be closed. Allitems which have been removed or isolated shouldbe replaced or reinstated.

This work should be carried out before the commis-sioning specialist balances the system. Evidenceshould be produced to show that flushing andcleaning have been done effectively, since systemcleanliness has a marked bearing on balancing andsystem performance.

On complex systems consider the use of proprietary airseparators. Consideration should also be given to thevariQus techniques available to limit air and other ventingproblems.

Wl.4.3 Chemical cleaning

This is a specialised operation and should only be carriedout by a competent operator using established methods asdefined by the Health and Safety Executive. Refer to theCIBSE Guide(4) Section B7 Corrosion protection and watertreatment.

Mter static filling and venting the pumps should beoperated for a period of about one hour and the ventingrepeated. Complete system venting may take up to a week tocomplete.

Before chemical cleaning is commenced a complete list ofmaterials must be provided by the designer and installer.This should include all metals used in the system together

Safety warning: do not attempt to fill the system via apressurisation set. A pressurisation set should only be usedfor final system top-up.

5


Wl.5.1 Frost precautions (b)

(c)

(d)

(e)

Where the work described in sections, Wl.4, Wl.5, Wl.6and W A2.4 is being carried out in cold weather it isessential that any equipment susceptible to frost damage beprotected, by heating the system water, by local space heat-ing, or by draining down during prolonged non-workingperiods. Draining down should be avoided as damp inter-nal surfaces can be a primary cause of corrosioD:.

(f)

(g)

(h)

(i)Mechanical checksW1.6

that the valve spindles are free to move

the bearing lubrication

the rigidity of the mountings

the valve stroke, mechanical couplings and linkagesfor correct geometry

for freedom from excessive play in the linkage

the fit of pins

the tightness of locking devices

that actuators have been fitted to manufacturers'recommendations with access to electrical connec-tions.PumpsWl.6.1

W1.6.3 General system check

Check every moving piece of equipment visually for free-dom of movement.

I)

Electrical checksW1.7

Before the first operation of any electrical component orappliance the following procedure should be adopted. Allrequirements of the Electricity at Work Regulations 1989(8),the Health and Safety at Work etc. Acr<9) regarding the safetyof the specialist and other personnel must be strictly ob-served.

The lEE Regulations for electrical installations(lO) require a'permit to work' procedure for some operations. Ensurethat all earth bonding has been tested and complied with inaccordance with the lEE Regulations.

Checks with all electrical suppliesisolated

Wl.7.1

.

The following checks should be made with the system fullof water. Check that:

(a) external parts of the pump are clean

(b) flow direction is correct

(c) all components, bolts, fIXings and fittings are secureand that no distortion has taken place on the base intightening

(d) the impeller is free to rotate

(e) the level and plumb of pump and motor shaft andslide rails are correct; direct-driven pumps requireparticular attention in this respect, widl referenceto manufacturers' recommendations

(f) the anti-vibration mountings have correct de-flection

(g) the correct drive has been fitted

(h) the pipework imposes no strain at the pump con-nections

(i) pulleys and couplings are secure and their align-ment is correct

(j) the belts are tensioned and matched

(k) the bearings are clean

(1) the lubricant is of the correct grade and is fresh

(m) the coolant is available at the bearing or seal

(n) the glands, where fitted, have been correctly packedand the gland nuts are not more than finger tight,pending adjustment to correct drip rate after start-

up(0) .drive guards have been securely fitted with proper

access for tachometer readings and belt changes

(P) pressure test points have been fitted at both thesuction and discharge points of the pump to facili-tate head tests to confirm inferred pump perform-ance.

Automatic control valvesW1.6.2

Check to ensure that:

(a) appliance and control circuits are locally isolated

(b) there arc no uDshrouded live components withinthe panels

(c) panels and switchgear are clean

(d) appliances and surrounding areas are clean and dry

(e) transit packing has been removed from contactorsand other equipment

(f) there is no mechanical damage to switchgear

(g) all connections on busbars and wiring are tight

(h) all power and control wiring has been completed indetail in accordance with the circuit diagram,paying special attention to circuits for star-delta-connected and specially wound motors

(i) all fuse ratings are correct(,) all mechanical checks on the pump, motor and

automatic valves are complete (see section Wl.6)

(k) on-site insulation tests on the motor have been

performed satisfactorily

Check:

(a) that the valve ports are correcdy orientated withrespect to water flow

6

SETTING TO WORK

internal links on the starter are correctW2

(m) starter overloads are set to the motor full loadcurrent (FLC)

(n) dashpots (where used) are charged with the correctfluid and the time adjustment levels are identical

(0) the adjustable thermal cut-outs are set correctly(check manufacturers' test certificates)

Note: where a secondary system is included, this should beisolated in its entirety throughout the following checks onthe primary system, i.e. sections W2.1 to W2.2.4.(P) all electrical water heating appliances are free from

damage and all associated thermostatic controlshave a suitable temperature range (see sectionW2.1) W2.1 C'--ecks before pump start

(q) all the cover plates are replaced. With the system filled check that:

(a) all 'normally open' valves are fully open

(b) all bypass and 'normally closed' valves are fullyclosed

all thermostatically controlled valves are fully openand will not be affected either by ambient air orwater temperature during balancing procedures

., a method of operating automatic control valves isavailable and that these are motored to normal

operating mode

I the pump suction and return valves are fully openon the selected pump

the delivery valve is closed on any standby pumpunless non-return valves are fitted; the suctionvalve should be left open (it is not good practice toleave any vessel full of water and completely iso-lated, as a temperature rise could cause an excessivebuild-up ofpressure)the pump casing is vented of air

the selected pump discharge or flow valve is partial-ly closed to limit the initial start current.

W1.7.2 Checks with electrical supplyavailable

~ (c)(a) Check that correct provision has been made forlocal isolation of plant for both electrical andmechanical safety.

(d)(b) Check that the declared voltage is available on ail

supply phases.

(c) (e)Where motor power ratings are substantial, re-duced voltage starting is used, or complex inter-locks are involved, the control circuit logic andstatter operation should be tested before the motoris rotated. The supply should first be isolated bywithdrawing two power fuses not associated withthe control circuit, or by disconnecting cables. Thecontrol circuit fuse must be checked to ensure thatit is rated to give the correct discriminatory pro-tection to the control circuit cables.

(f)

(g)

(h)The control circuit should be actuated and thestarter operation observed, adjusting the timerswhere necessary. Check for positive operation of allcontactors, relays and interlocks.l", W2.2 Initial runWhen these checks have been made, open isolators,reinstate power fuses and close isolators. W2.2.1 Checks on activating the motor

starter(d) Where small motors have direct on-line starting

and simple control circuits, the starter operationetc. should be checked when first starting themotor.

(e: Electrical valve actuators should never be energiseduntil mechanical checks under section Wl.6.2 havebeen completed.

W1.8 Static completion records

Great importance is attached to the provision of staticcompletion records to ensure that all defects have beenrectified before setting to work and balancing. It is recom-mended that the results of all checks and any requiredremedial works be documented fully. (See sections W2.4and W4.4.)

Where appropriate check that:

(a) the direction and speed of rotation of the motorshaft are correct

(b) the motor, pump and drive are free from vibrationand undue noise

(c) for star-delta starters the starter sequence timinghas been adjusted as necessary in the light of motorstarting current

(d) the motor running current is balanced betweenphases and does not exceed the motor nameplatestated rating

(e) there is no sparking at the commutator or slip ringswhere titted

(f) there is no overheating of the motor


W2.4(g)

(h)

Completion cer1ification

On the satisfactory compliance with the provisions ofsections WI and W2 a cenificate should be completed bythe installation contractor to that effect. The cenificateshould be countersigned by the designer or his rep-resentative. Cenification should include the documentsappenaining to chemical cleaning and flushing. Copies ofthese certificates should be passed to the commissioningspecialist before the system is balanced. (See section W4.4.)

(J)

u)

(k)

there is no seepage of lubricant from the housing

there is no overheating of the bearings

the water flow to water-cooled bearings is sufficient

on multi-speed motors, motor running currents arecorrect

the ventilation systems of air-cooled motors areoperating correctly.

W3 Balancing water flowrates

W3.1 Obiective

The aim of balancing is to apply a disciplined procedure ofadjustment to water flow rates throughout a system to meetthe particular requirements of the design. The balancing ofwater flow rates should be carried out to specified toler-ances (which may vary for different sections of the samesystem). A typical schematic circuit is illustrated in Figure1.W2.2.3 Running-in period

The pumps must be 'run in' in accordance with the manu-facturer's instructions. Do not either leave pumps un-attended or allow them to run outside working hours. W3.2 Flow rate measurement

tolerances

It is the responsibility of the system designer to stateacceptable tolerances for the balancing of flow rates forvarious sections of a particular system. In deciding on theappropriate tolerances to set, the designer should bear inmind that the cost of regulation can increase significantlywhere close tolerances are specified. Tolerances are dis-cussed in detail in section W AI.2.2.

Check that:

(a) all bearing and motor temperatures remain withinmanufacturers' specifications

(b) pump gland nuts are adjusted to give correct driprates (this does not apply to mechanical seals)

(c) after four hours running all strainers are inspectedand cleaned. If they are excessively dirty then con-tinue frequent inspection and cleaning. Where the commissioning specialist considers that the

tolerance levels required by the system designer are im-practical (e.g. due to inadequate provisions in the systemdesign) he/she should formally advise the designer of this,clearly stating and explaining his/her reasons.

W2.2.4 Standby pump(s)

The standby pump should be commissioned as detailed insections W2.1 and W2.2.

Where flow rate tolerances are not stated in the designparameters, the commissioning specialist should obtain theformal agreement of the system designer on the tolerancerequirements before commencing regulation.

W2.2.5 Secondary pump(s}

After checking the primary strainers, isolate the primarysystem. The secondary system valves can be opened and thesecondary pumps started. Initial running should be inaccordance with section W2. Re-open the primary circuitvalves.

W3.3 Basis of balancing

Prior to balancing the flow rates in a system the com-missioning specialist should produce a written methodstatement which provides details of the intended balancingprocedures. This method statement should be formallyagreed with the principal contractor and system designerand form part of the overall commissioning plan.

Further ventingW2.3

After initial running of the pumps (primary/secondary asapplicable) the pumps should be stopped and the system re-vented. It may be necessary to repeat this a number oftimes. After applying heat to a heating system, furtherventing may also be required.

Proportional balancing ~s used for constant-volume sys-tems and maximum flow for variable-volume systems.However, heat balance methods are sometimes necessary in

. 8

BALANCING WATER FLOW RATES

I Evaporator I ff i

Secondary Secondary SecondaryVODR valve pump mixing valve

I ::) T"@' I ~

Fixedbypass ...

Variable~' bypass

Low lossheader...

j ~ ~ 'I }ol' , @ T

Primary PrimaryVODR valve pump

(Branch A using commissioning sets)~-~ -~"! tI

8 '1 ).11I

~ ~ 1Key

Pressure/temperatu retapping

-1-

~ Strainer

I

(Branch Busing VODR valve)I ?" "V' -I p::,; ~ :

~ Commissioning set

,'; t I -+:f-128

Variable orifice doubleregulating (VODR) valve

Flaw measuring orifice closecoupled to an isolating valve

-:t.T+?" ~

2C -H- Double regulating valve (DRY)

Air/water heat exchanger

8(Branch C using fixed orifice close coupledto an isolating valve plus a DRY)

I ~~ -I ~~ t--1-

,~T~ '1).1' I

I~~

t'- (3-way valve mixing)

(3-way valve diverting)

!

~T~ I-

(Wild cooling coil)---I

--~-1-I 1i)IT+.

Figure 1 Typical schematic circuit

Q


terminal and the most remote terminal are equalwithin the specified tolerance. Record the in-

, strument readings, DFR and valve settings for bothterminals and lock the valves.

(e) Continue by adjusting the balancing valve for thenext terminal towards the pump until the DFR forthis terminal is equal, within the specified toler-ance, to that for either of the two terminals bal-anced in stage (d). This value will probably havealtered from that recorded at stage (d) so it is essen-tial to re-measure the flow for every comparison ofDFR values. Record instrument readings, DFR valuesand valve settings for both terminals and lock thevalve.

(g)

(h)

(i)

(f) Continue balancing the upstream terminals to-wards the pump as in stage (e) using the samereference terminal for comparison of the DFR valuesuntil all terminals on the branch are balanced.(j)

Make certain that the primary flow measuringstation at the pump is indicating in excess of theDFR. This ensures that there is enough flow tobalance the system to the designer's requirementwithin the specified tolerance. See section W AI.2.2.

Starting from the pump, identify the mains, head-ers, risers, branches and terminals in the systemwhich are receiving the highest flow rate in terms ofDFR. This will be the most favoured circuit.

List the branches in descending order of DFR. Thelowest DFR is the least favoured (index) circuit.

Balancing consists of the progressive closure ofregulating valves starting with the most favouredbranch in the most favoured circuit. This reducesthe excess flow rate in those areas to increase theflow rate in areas with underflow.

On review of the initial readings against designvalues, the commissioning specialist should iden-tify:(i) whether any of the initial readings indicate

that excessive pressure loss is being causedin the circuit by any measuring/regulatingdevice

(ii) whether excessive throttling will be re-quired to a large proportion of the circuitregulating devices in order to achieve aproportional balance.

(g)

(h)

If results indicate that either a regulating valve or measur-ing station has been undersized, or that some other systemfactor is preventing correct flow, then consideration needsto be given to removing the device and installing one whichwill have less of an effect on the overall circuit.

(i)

(j)

If it is found that the balancing valve for the indexterminal has to be adjusted to achieve balance, thisindicates that the balancing valve on the mostremote terminal was closed too far at stage (c). Inthis case open the balancing valve for the leastfavoured or index terminal, return to stage (c) andfollow the procedure again.

Proceed to the next most favoured branch on theriser and carry out terminal balancing as in stages(a) to (g).

For the complete riser, each branch terminal is nowin balance with the other terminals on the samebranch. Branches now have to be balanced.

The procedure for balancing branches on a riser isidentical to that for balancing terminals on abranch. Stages (a) to (h) should therefore be follow-ed after any branch valves closed at stage (a) havebeen re-opened.

If a system is over-regulated this can lead to pump, motorand/or impeller changes being required. See section W3.6.2paragraph (b).

(k) When several risers are fed from a common headerthe same procedure should be used to balance therisers.

W3.6.2 Balancing terminals, branches,risers and headers by proportionalflow

If the DFR for a branch is above l500J0, reduce thebranch flow rate to give DFR = 110%.

Balancing or double-regulating valves should notbe set less than 25% open (75% closed) or asrecommended by the valve manufacturer. Thisminimises the risk of noise, cavitation, erosion andthe collection of solids between the seat and disc ofthe valve. See section W A3.3.

Identify the least favoured terminal, which is theone with the lowest DFR. This is defined as thebranch index terminal. In a typical distributionsystem this will be the furthest measuring point onthe branch. If it is not, reduce the flow to the mostremote terminal until the DFR is equal to that of theindex...terminal within the specified tolerance, i.e.the furthest terminal has now been made the index.

Adjust the balancing valve for the next terminalnearer the pump so that the DFR values for this

(1)(a)

(b)

(m)

(c)

At this stage each branch, riser, and header areproportionally balanced within the specified toler-ances. Flow rates throughout the whole system willnow retain the same proportional relationship forany setting of the main regulating valve.

Adjust either the main regulating valve or thepump speed to bring the total flow to the designflow within the specified tolerance. Lock the valve,record the instrument readings, the flow rate andthe main balancing valve or pump speed setting.

On completion of (m), all terminal and branchvolumes should be recorded as final readings fordocumentation purposes.

(n)

Report to the design engineer any balancing valvesthat are more than 75% closed (see section W4.4.1).

(0)

Lock all balancing valves in their regulated pos-ition.

(P)(d)

11


final branch or terminal distribution. This involves tem-perature measurements.

The reason for the low flow rate condition should beinvestigated and, where possible, corrective measures im-pfemented prior to balancing the system.

Safety warning: balancing a system requires the couplingof manometer probes into pressure test points. In a chargedsystem, the water temperature must be below 55°C whenthis is done. Under no circumstances must an MTHW orHTHW system be commissioned at operating temperature asserious injury may result.

W3.6 Constant-volume systems

The system is balanced on the basis of the ratio of actualflow rate to design flow rate. In anyone branch the thermalemitter units are regulated to the same proportion as theleast favoured (index) in that branch. This is also the casewith each branch on one riser and each riser on one header.This is achieved by measuring the pressure differentialacross flow measuring devices and regulating the flow todesign flow requirements by regulating valves.

In MTHW and HTHW systems self-sealing pressure ortemperature measuring points on valves or orifices must bepreceded by a manually operated" isolating device (see BS7350<11)).

W3.4 Pump shut-off head te~;tW3.6.1 Identification of least favoured

(index) and most favoured circuitsTo verify the operational performance of a pump it isnecessary to check the measured performance against testdata provided by the manufacturer. Figure 2 illustrates the positions of the least favoured

(index) and most favoured circuits.

(a) Open all line circuit valves and close all bypassvalves.

(b)

The performance test should be carried out as follows.

(a) Connect a suitable differential pressure gaugeacross the suction and discharge pressure testpoints of the pump.

(b) With the pump running, slowly close the dischargevalve. Do not run in this condition for longer than15 min or the pump will overheat.

(c) Determine the 'shut-off' pressure differential,check against the manufacturer's data for zero flowthen slowly re-open the discharge valve.

(d) Where the test result coincides with the manu-facturer's test data proceed to paragraph (e). Wherethis is not the case, draw a curve parallel to thatshown on the published data, starting at the shut-off head pressure.

(e) Record the total pressure with the differentialpressure gauge at full flow rate and read the actualflow from the manufacturer's data, or from thecorrected graph curve as appropriate.

(f) If performance is inadequate refer to the instal-lation contractor and design engineer.

(c)

(d)

(e)

Set automatic control valves manually to full circuitflow.

Start pump(s).

Using a schematic drawing for reference purposes,measure the pressure differential at each measuringstation with a manometer to determine the flow rateand record results. In some instances it may benecessary to arbitrarily throttle the most favouredbranches to near design values where the measure-ment signals in least favoured branches are too lowfor accurate results to be taken. Check againstdesign values.

For each measuring station evaluate the design flowrate as a percentage

DFR(%) = lOOfa/fd

where fa is the actual flow rate and f d the designflow rate.

Preliminary flow rate Ch4~ckW3.5

With all valves fully open, measure and record the totalactual flow rate and compare this with the total systemdesign flow rate. Where necessary, close the main regula-ting valve to provide a flow of approximately 110% designflow rate. See also section W2.2.2 paragraph (c).

Where the initial measured flow rate is less than 100% ofthe design flow rate with the systeD).ofully open, then a valueof less than 100% will result at the conclusion of balancing .

Regulation of a system at less than 100% of design flow rateshould not be attempted without formally advising theinstalling contractor and system designer. Figure 2 'Circuit identification


W3.6.3 Secondary regulation of bypasscircuits

recirculation, measure the injection rate from the t'primary circuit and calculate its DFR. Then regulatethe primary injection regulating valve to bring theDFR within the specified tolerance for the secondarycircuit.

Figure 3 illustrates the regulation cfbypass circuits.

In constant-volume circuits which incorporate three-portcontrol valves, the bypass regulating valve should beadjusted to give the same pressure differential across theflow measuring station when the three-port valve is set tobypass as measured with the three-port valve on full flow tothe system or the flow rate specified on the systemschematic. Some systems have a fixed bypass and variablebypass both of which need to be regulated. See Figure 4.

Note: while most injection circuits incorporateautomatic three-port mixing control valves thisneed not always be the case and some applicationsmay utilise two-port motorised valves to performthis function. Some injection circuits may requiresecurity of shut-off and may, for example, use anautomatic three-port control valve and two motor-ised two-port isolating valves. Proper analysis ofeach system is required to ensure that the system isin the desired mode of operation for each phase ofbalancing.

(c) Close the secondary circuit automatic controlvalve(s) fully to primary circuit injection and openfully to secondary circuit recirculation. Regulatethe recirculation regulating valve to provide thesame DFR as obtained in paragraph (b) above. )

It should be noted that in some injection circuits the flowrate controlled by the automatic control valves may besmaller than the total flow required from the secondarycircuit pumps. In such cases, a bypass circuit will parallelthe recirculation control circuit and this bypass circuitmust be regulated to provide a flow equal to the differencebetween the required circulation rate and the maximumrequired injection rate.

W3.7 Variable-volume systems

Fundamental to all variable-volume systems is the applic-ation of two-port control valves. These two-port valveseither modulate or open and close in accordance withthermal demands thus varying the flow rates through theterminal units served within the overall pipework system.

Figure 3 Regulating bypass circuits

3

~

93 5

I9I

3

I

In order to ensure system stability, variable-volume systemsare usually dynamically controlled to ensure that the sys-

't Key2 8 6I I I f 1 Primary pipewark

2 Secandarypipework

3 Isolation valve

4 Commissioning set

5 Three-port mixing valve

6 Flow temperature detector

7 Thermometer

8 Pump set

9 Unions on screwed valve sets

10 Minimum straight length= 10 diometers

11 Minimum straight length= 5 diameters

I

t~--{~J~.r::AJ

4

I

~

I !~~~-@_.!1_-Q -I 9T .Llj~~t_k__~J::

! I. 11 .14 10:-[

~10

Figure 4 Injection circuil

12

-M..rf'f;T"


tern pressures and/or flow rates are stable under the varyingdemands of the system.

(a) Do not attempt to balance this type of networkupstream of the DPR or FCR with conventional regu-lating valves as they will merely undermine controlauthority of the DPR or FCR.This dynamic control is achieved by devices installed with-

in the pipework system and can take many forms depend-ing on the system complexity. Devices such as differentialpressure regulators, flow control regulators, excess pressurerelief valves, multiple- or variable-speed controls for pumpsmay be applied for this purpose.

(b) The DPR must be set at the design pressure dif-ferential across the branch it serves.

(c) The FCR must be set at the maximum allowabledesign flow rate value for the branch it serves.

Small systems, typically, have thermostatic radiator valvesand excess pressure relief valves. Large systems have zonedifferential pressure regulators (DPRs) and/or maximumflow control regulators (FCRs) combined with variable-speed pumping.

(d) Using tappings installed on each side of the devicesprovided:

(i) check the operation of each DPR to ensure itcontrols the differential pressure within itscontrol limits under varying load condi-tions and document the resultsVariable-volume system design frequently incorporates a

diversity factor. This means that at no one time will themaximum flow rate be available simultaneously at allpoints in the system. Refer to section WO.2.

(ii) check the operation of each FCR to ensure itlimits the flow rate to the maximum setvalue under varying load conditions anddocument the results.Because of the variation in design of variable-volume sys-

tems it is important that there is an agreed commissioningprocedure, documented before commissioning starts. Thismust be approved by the system design engineer.

W3.7.2. Sub-systems downstream of differentialpressure regulators and flow control

regulatorsW3.7.1 Balancing variable-volume systems

The techniques required to balance variable-volume sys-tems differ from constant-volume systems in that pressuredifferentials and flow rates in main branches are usuallyautomatically controlled to meet the varying demands ofthe system. The main commissioning procedure is, there-fore, not one of water balancing but of setting up and prov-ing that the pressure differential differences and maximumflow rates in the branches are controlled under varyingconditions.

Each sub-system controlled by a DPR or FCR requires thefollowing commissioning procedure.

(a) The operation of two-pon control valves must betested and recorded.

(b) Under normal operation, with all terminal two-portvalves fully open, and using the pre-fitted pressuretappings installed olJ each side of the devicesprovided:

(i) check and record the differential pressureacross each sub-system DPR fitted

(ii) check and record the flow rate across eachsub-system FCR fitted.

Automatic regulation of the circulating pump drive may beprovided to match the aggregate flow rate in the system asrequired by the branches and terminal units. This may bearranged by sensing pressure variations at a representativepoint in the system and modulating the pump speed tomaintain a nominally constant pressure. This control loopwill require setting up and balancing in parallel with theproving of the automatic pressure and flow control devices.

Note: if the values of either the pressure or flow arebelow design value due to system diversity, tem-porarily valve off other sub-systems as necessaryrecording the actions taken.

Proportional balancing of all sub-circuits will generally stillbe required downstream of all automatic pressure or flowcontrol regulators and should follow the appropriate proce-dures as detailed under section W3.6 above.

(c) With the sub-circuit DPR or FCR operating at itsdesign value, proportionally balance all branchesand terminals downstream of the DPR or FCR start-ing from the most remote branch or terminal andfollowing the procedure shown under section W3.6above.Note: suitable pressure tappings should be provided at the

measuring positions on differential pressure or flow controlregulators to monitor the controlled set point. Cd) Re-check the DPR and FCR operation after the down-

stream proportional balance and record pressuresand flow rates.

W3.7.2 Large single-building systemsAfter setting up all differential pressure or maxi-mum flow control regulated sub-circuits, ensurethat any that were temporarily valved off to com-pensate for diversity, as listed on the record ofactions taken, are re-opened. See note above inparagraph (b).

(e)These are generally fitted with automatic differential pressureregulators (DPRS) or automatic flow control regulators (FCRS) on

~ sub-systems serving groups of terminals. The DPR or FCRautomatically balances the main branch distribution up-stream of its location.

3


W3.7.2.2 Main pump flow branch valve (external to all terminal circuits) which isknown as the 'partner valve'.

When the reference valve is a variable-orifice double-regulating "Valve this should be pre-set, by calculation, togive a minimum pressure drop of 3 kPa at design flow rateand then locked in that position. Variable-orifice double-regulating valves are described in section W A3.1.4.

When the reference valve is a fIXed-orifice double-regulat-ing valve (commissioning set) it should be locked in thefully open position.

The main pump flow and operating pressure should bemeasured, recorded and plotted on the pump curve at aminimum of four operating points:

(a) with all two-port automatic valves fully open atdesign diversity flow

(b) with all two-port automatic valves closed at no flow(closed head pump test)

(c) at two intermediate points, with sufficient two-portvalves closed, to give approximately 30% and 60% ofdesign maximum flow.

W3.8.1 Balancing a branchW3.7.3 District heating and cooling systems

A manometer is connected to the reference valve. Thedesign flow in the reference valve is regulated by thepartner valve. A second manometer should be used to setand adjust the terminal balaI!cing valves starting with theterminal next to the reference terminal and proceedingupstream.

These consist of large circulating mains serving a numberof buildings.

The installation within each building generally takes theform described in section W3. 7.2 and similar balancingprocedures to those listed in section W3. 7.2 should beadopted.

Adjust each terminal commissioning valve to give thedesign flow in that terminal but maintain observation of thereference valve manometer. If this changes more than 10%during the balancing process then bring the pressuredifferential back to the original by operating the partnervalve only.

Continue with all other commissioning valves in thebranch, working upstream; observing the reference pres-sure drop and adjusting it with the partner valve. In thisway all terminals on that branch will be in balance at designflow.

Additional pump controls are frequently fitted to thesystem to ensure minimum differential pressure is alwaysavailable at the index building and these should be bal-anced and checked as part of the regulation process usingthe following procedure.

(a) Establish the design pressure setting required forthe sensing device.

(b) Where the unit is not factory pre-set, adjust to therequired pressure using the manufacturer's instruc-tions.

(c) Using portable test instruments to check the actualsystem pressure at the sensor, close off downstreamvalves until actuation of pumped flow rates occur.

(d) Check and record system pressure at actuation.

If, when adjusting a terminal valve, the design flow cannotbe obtained with its balancing valve fully open, thisterminal is termed the 'index unit'. In this case, measure theactual maximum flow obtained in this terminal anddetermine the DFR as a percentage (see section W3.6.1paragraph (e)). Re-adjust the referencc valve to give thesame DFR, then lock in position.W3.8 Balancing by compensated

methodThe design flow in the reference valve is obtained by re-opening the partner valve and the balancing procedurerepeated using the new setting on the reference valve.

The compensated methodCl2) of balancing is an extension ofthe proportional method described above and allows forbalancing on constant-volume and pre-balanced variable-volume systems before they are completed.

Provided that the pump circuit is operational, branches canbe balanced individually, as they are completed, thus savingcommissioning time and delay with balancing taking placeas the system is being installed.

With pump connected, via a header and riser to a completedbranch and with all other riser valves closed, the completedbranch can be balanced.

The compensated method (see Figure 5) relies on thebalancing valve in the furthest terminal (not necessarily theindex) which is known as the 'reference valve' and the Figure 5 Balancing by compensated method

14

EVALUATION AND WITNESSING OF COMMISSIONED SYSTEMS

W4Balancing remainder of systemd W3.8.2

By using the same methodology as in section W3.8.1, eachbranch, riser and header can be balanced as the systemconstruction progresses.

Evaluation andwitnessing ofcommissioned systems

W4.1 ObiectiveW3.9 Regulation by temperature

balance The objective is to witness formally, on behalf of the clientor his/her representative, the degree to which the commis-sioning requirements of the specification have been met.

Where either a complete system or part of a system consistsof relatively small terminal units, e.g. radiators and con-vectors, it will often not be economic to install a flowmeasuring device at every terminal unit. The technique ofproportional balancing given in sections W3.6 and W3.7must therefore be adapted to the particular system.

W4.2 Witnessing arrangements

W4.2.1 Witnessing period

A specific period of time for client witnessing should beindicated in the initial project programme, with a writtencontingency allowance.

The temperature balance method should be confined tolow-temperature hot water heating systems, where the sametemperature difference is required through each terminalunit.

W4.2.2 Witnessing requirementsW3.9.1

All requirements for witnessing should be expressed in anagreed written format, copies of which are made available tothe commissioning specialist. This format must containfull details of the tolerances applicable to all parameters.Similarly, consideration should be given to permissibletolerances on repeatability of measurement readings.

Ca,

(b:In deciding the detailed requirements for witnessing com-missioning, the interaction of various aspects of an in-stallation in determining its overall performance must beborne in mind. The commissioning of a water distributionsystem might be witnessed against the requirements of thisCode and the project specification. However, witnessing theperformance of heat exchangers connected to water di-stribution systems, for example, would interact with thecommissioning of air distribution and automatic controlsystems as well as of boiler and refrigeration plant. Witness-ing is thus an all-embracing and interactive task and thismust be reflected in the agreed written format.

Procedure

Operate the system at a moderate flow temperature.This will be governed to some extent by the am-bient temperature but a minimum of 60°C issuggested.

If the system is controlled by an outdoor com-pensator this should be adjusted to ensure that aconstant flow temperature is maintained during thebalancing.

Throttle each terminal unit regulating valve untilall returns register an equal temperature measuredby a contact thermometer consistently applied.

W3.9.2 General

« When using the heat balance method a procedure similar tothat recommended for balancing terminals fitted with flowmeasuring devices should be adopted, that is, regulate fromthe index back towards the pump. Particular arrangements for

witnessingW4.2.3

The heat balance and regulation on the terminals on anybranch should be completed before the final regulation andflow measurement on that branch.

An essential aspect of the agreed arrangements for wit-nessing is the provision of definitive statements of the siteattendance availability of the witnessing agent, the stand-ards required, the extent of witnessing which will be per-formed and added requirements in the event of defaults(e.g. the number of additional items which must be wit-nessed for every one which fails to comply).

Commissioning certificationW3.10

When the procedures of section W3 have been satisfactorilycompleted the commissioning specialist should certify thatthe system has been commissioned in accordance with thisCode and the project specification. The certificate should becountersigned by the accepting authority who may be thecontractor, design engineer or client or some otherwitnessing authority.

Witnessing liaisonW4.2.4

The witnessing agent should liaise in detail with theinstaller and the commissioning specialist, as necessary,with regard to:(a) the means to be used to demonstrate that mass or

volume flow rates are within the specified toler-ances

The certificate should be accompanied by the documentslisted in sections WAI.7 and W4.4 together with copies ofthe static completion certificates.

1~


~b:

co-ordination requirements where the performanceaspects to be witnessed interact with other systemsor equipment.

Actual pressure drop (kPa or mm H2O:

Actual flow (Vs)

DFRW4.3 Duties of witnessing agentRegulating DRY number

DRV setting position (should be fully open)

Note: the formal recording of data in the intermediatestages of balancing is also recommended.

Final scan

Final pressure drop (kPa or mm H2O)

Final flow rate (I/s)

Final DFR thIl'-Final setting position of DR V (not more than 75% closed)

Bypasses (generally set on final run only:

Valve number

Setting position for final DFR

CommentsW4.4 Commissioning

documentation W4.4.3 Pump details

The design of standard proforma for the various require-ments for commissioning records and certification isoutside the scope of this Code, and is a matter for agreementbetween parties. However, as a minimum, the followingbasic information should be detailed. The units andmanner of presentation are typical conventions used inpractice.

Serial numberae!

Drive type

W4.4.1 Impeller diameterFlow measurement, double-regulating and automatic controldevices Pump speed (rev/s)

Measuring device position number Motor speed (rev/s)

Type of measuring device Motor full-load current (A)

Size (mm) Motor power (kW)

Design flow rate (l/s or kg/g) Belt

Design pressure drop (kPa or mm H2O)Pulleys

Manufacturers' performance data for measuring devicesused Manufacturers' performance data/charts

.t 1..

VI'System dataW4.4.4Flow rate balancing dataW4.4.2

A table in the form of Table 1 should be completed,First scan

DESIGN

Table 1 System data

Parameter values

Design Actual % design

Flow rate (I/s)

Pump head (kPa or mm H2O)

W4.4.5 Method used to determine flow rate

There should be a complete record of all instrumentationused in commissioning including manufacturers' serialnumbers and, where appropriate, calibration dates.

W4.4.6 Conclusion

These documents should be signed, dated and witnessed, asa true certification of the full working order of the watersystem.

Figure Al Flow rate versus thermal OUtpU1

Table Al Flow rate deviation, performance effect and typical installation

applicationsWA1 Performance effect Typical installation

applicationFlow rate deviation

LowLargeWA 1.1 Design requirementMedium MediumEffective operation of any system will depend on satis-

factory commissioning.

An important design objective is to ensure that balancingrequirements are considered fully at the conceptUal stage.To facilitate this, design engineers are recommended toensure that these requirements are taken into account andan unequivocal specification is provided so that satisfactorybalancing and commissioning are assured. Early discus-sions with the commissioning specialist will assist thedesign engineer.

Small High

LTHWheating <11°C~tMTHW, HTHW

LTHW heating> 11 °C ~tChilled water, comfort airconditioning

Heat reclaim

Latent cooling with relative

humidity

Chilled water servingcomputer or processinstallations

evaluate the effect of deviations from specified flow rates.(See Figure AI.)Design considerationsWA1.2An indication of the influence of deviation of volume flowrates on performance effect and suggested relationshipswith typical applications are given in Table AI.

Perlormance effectsWA1.2.1

Heat transfer performance of heat emitters and other heatexchangers is influenced by water flow rate in a non-linearmanner. TolerancesWA1.2.2

Suggested ranges of practical tolerances related to systemperformance effects are given in Tables A2 and A3. Systemsregulated to the appropriate tolerance band should be cap-able of meeting the design intent in operational use.

In some applications, large variations in flow rate have onlya small influence on heat exchange performance. For con-venience, this is referred to as 'low performance effect'.Conversely the outpu~ of 'high performance effect' heatexchangers will be affected by only a small deviation in flowrate. The nominal tolerances apply to repeatable readings prod-

uced by the measuring device with associated instrumen-tation and do not account for any inaccuracies within these

components.The design engineer should consider particular relation-ships between thermal output and fluid flow rate and


Where flow rates to terminals are very low and likely togenerate pressure differentials of less than 1.0 kPa, then thescope for accurate and repeatable measurement of flow willbe severely limited. Measurements will be affected byinstrumentation accuracy and low velocity and it may benecessary to make arbitrary tolerance allowances in excessof the ranges shown above.

.

Table A2 Tolerances for flow rate balancing in heatingsystems (%)

Where proportional balance tolerances are based on designflow rates it should be noted that any subsequent increasein total flow rate could lead to some aspects of the balanceexceeding the stated upper tolerance limit. (e.g. a terminalactually balanced to a 15% limit could exceed this figurewhere the total flow rate is increased at the end of theregulating procedure). The design engineer must clarify inadvance where this possibility is considered to be un-desirable.

Mains -0

+10-0

+10-0

+10

t Note: for a proponional balance to be achieved, theupper and lower tolerance limits should not be exceeded.The lower value, i.e. the negative value, is the minimumvalue the least favoured or index unit should achieve.Wherever possible the remainder of the proponionalbalance should be achieved within the overall toleranceand should aggregate to a Ininimum 1000/0.

Where proponional balancing is carried out to the extremevalues of the upper and lower limits of the tolerance bands,it should be noted that the cumulative effect of successivetolerances (i.e. terminal, sub-branch, branch and total)may, in some circumstances, lead to some aspects of the bal-ance being marginally outside the stated tolerance limits.Such an occurrence, therefore, need not infer that theregulation procedure has not been followed correctly.

Table A3 Tolerance for flow rate balancing in chilledwater systems (%)

Perfonnance effect

Low Medium High

Component

-7.5+15

:-0+10

-0

+10

-0

+10

:!:sTerminal units whereflow rate <O.ll/s t

AHU coils whereflow rate is >O.ll/st

Branches t

Tables A2 and A3 are based on the accuracy offlXed orificedevices and venturi. When using a variable-orifice regulat-ing valve the pressure differential reading is usually takenacross the seat of the valve; hence the accuracy of themeasurement is affected by the position of the regulatingdisc in relation to the seat. With a correctly sized valve thenormal regulating position should be between fully open to50% closed. If the disc is in relatively close proximity to theseat (less than 25% open) additional turbulence can occurwhich, in turn, may affect the differential reading. For thisreason, the allowable tolerances shown in the tables aboveare only applicable to the measurement across the seat ofthe valve when the valve is no more than 50% closed.

-0

+10

-0

+10

-0

+10

Mains

t See note under Table A2

WA 1.3 Provisions for measuringpressure and determining flowrate

BS 7350<11) and/or the valve manufactUrer should be con-sulted if the valve is closed further than this.

WA 1.2.3 Flow velo,city Pressure tappings should be included as follows:

(a) either within two pipe diameters up and down-stream of the pump flange faces (i.e. between thepump and isolating valves) or installed in purpose-made pump flange drillings

(b) flow and return connections at all major heatexchangers

(c) flow and return connections at all terminal units-(such as secondary cooling coils in fan coil units)

where multiple identical units are connected to self-balancing pipework

(d) upstream and downstream of main strainers to de-tect an increase of pressure differential indicating aclogged screen

(e) orifice devices, variable-orifice valves, venturi dif-ferential pressure regulators and control valves orother measuring devices.

The limiting minimum water velocities given in BSRIAApplication Guide 8/91 (3), section Bl.13, should be adoptedto minimise static air pockets in horizontal pipes at lowvelocity or noise and cavitation at high velocity.

Pump flow rate marginWA1.2.4

The pump should be sized to provide a flow rate in accord-ance with the mains requirement shown in Tables A2 andA3 against the calculated pressure drop of the index circuit.

Valve sizingWA 1.2.5

8Double-regulating valves should be sized to provide therequired flow regulation with the final setting not less than25% open. (See section W A3.3.)

DESIGN

(1

WA1.4 Ease of access Note: where equipment selection is made by the installerand this differs from the design engineer's specification, theinstaller should amend, or add to, the document accord-ingly. The design engineer should be advised of all suchvariations from the specification.

The design engineer must provide access to all pressure testpoints, flow measuring devices, double-regulating valvesand concealed items of equipment requiring adjustmentduring commissioning and maintenance.

WA1.7.1 Schematic drawings

WA1.S Flushing and cleaning

The pipework system design should incorporate, wherepracticable, line-size drain points at the base of each isolat-able circuit section. These drain points should be adjacentto suitable drainage gullies. Further guidance is given inBSRIA Application Guide 8/91(3). If discharge is belowdrainage levels additional temporary pumping arrange-ments need to be considered. (See section W1.4.)

Complete schematics of all systems should be preparedusing standard graphic symbolsBS 1192(15). The schematicdrawings should be included on the drawing or accompany-ing tabular matter. These should include, where possible:

(a) pipe sizes

(b) pump flow rates and pressures

(c) the positions of all flow measuring devices and thenecessary straight pipe runs upstream and down-stream of these devices (see section W A3)

(d) the locations and sizes of all double-regulatingvalves

(e) the system flow coefficients kvs should be notedagainst each flow measurement and regulatingdevice (see section W A3.6)

(f) the flow rate and estimated system pressure loss foreach flow measuring device (see section W A3.1.6)

(g) the flow rate and an estimation of the pressure droprequired across each double-regulating valve tocompensate for circuit imbalance

(h) flow rates and either estimated or manufacturers'quoted pressure drops across heat emitters, heatexchangers and other items of plant

(i) flow rates in all branches of heat exchange stationsand primary/secondary circuit interconnections

()) flow rates and either estimated or manufacturers'quoted pressure drops at automatic control valves

(k) measuring station, double-regulating valve andautomatic valve numbers from specification sched-ules with predicted settings of the valve indicatedwhere appropriate

(1) anticipated design pressure drops throughout thedistribution system covering, as a minimum, thewhole of the index circuit, risers and main branches

(m) the differential temperature used in the design cal-culations

Provision should also be made for:

C ) (a) suitable flushing connections including temporary

high-velocity flushing points.

(b) adequate water supply; portable tankers with back-wash filters and pumps may sometimes be neces-sary

(c)

(d)

(e)

(f)

connections for bypassing plant components andother equipment during flushing

water treatment and sampling as appropriate

air separation and venting at low-velocity points inthe system; the system should be designed for con-tinuous venting with adequately sized fIll points atlow level (see section WI.S)

flushing, cleaning and venting should be completedbefore commissioning begins.

WA 1.6 Chemical cleaning

The design engineer should decide whether chemicalcleaning of the distribution system is needed and ensurethat the appropriate requirements are specified clearly,either in terms of performance or in more detail. The speci-fication should state that chemical cleaning be carried outbefore the start of commissioning. (See section WAl.7.2,paragraph (k).)

Safety note: attention is drawn to the Health and Safety atWork etc. Act<9), the Environmental Protection ACt<13, 14) and

other legislation that may apply, on the storage and disposalof all chemicals and associated treated water.

(n)

(0)

Design information requiredWA1.7(P)

To ensure that flow rate measurement and regulation canbe carried out correctly, the following information shouldbe properly documented by the design engineer in aninstallation and commissioning brief for transmission tothe services installer and commissioning specialist togetherwith a full description of the intended operation of thesystem explaining the control sequence and logic.

(q)

(r)

on composite designs, draw-off rates for cold waterand domestic hot water systems

regulating devices approved by the local water com-pany to control cold water and domestic hot watersystemscold feed, pressurisation unit, feed and expansiontank points of connection

control valve port identification to show correctflow direction

provision for system flushing and bypass connect-ions to main plant, together with a typical terminaldetail of the bypass


(s) for variable flow systems, the system diversity. WA2.2 Installation cleanliness

WA1.7.2 Documentation Pipes should be supplied fitted with end caps. They must bestored in suitable pipe racks so that, when installed, theyare in a clean condition. Site building materials such assand, cement etc. must be kept clear. Contaminated pipesshould be cleaned internally by using a 'pull through'before fitting. Ends of cut and screwed pipe must be pro-tected from damage and ingress of dirt by temporary endcaps. During installation equal care should be taken toensure that all components are kept clean. (See sectionWI.4.)

Schedules of all items of plant with technical data as fol-lows:

(a)

(b)

(c)

WA2.3Cd) Installation inspection

Inspections are required throughout the installation period(see section WI.2). Much time is spent at the commission-ing stage in rectifying problems, principally as a result ofdirt and foreign matter within the pipes, which should nothave occurred.

(e)

(f)

'1

WA2.4 Pressure testing(g)

Hydraulic pressure testing of the system should be carriedout in accordance with an HVCA Guide to good practice(16).As work proceeds each section should be tested in turn atthe specified pressure and duration.

(h)

(i) Pipework pressure testing is not normally regarded as acommissioning operation; it is carried out during in-stallation. However, the operation should be properlydocumented and included with other commissioning in-formation.

(j)

(k) Pressure testing entails filling the system with water anddraining it afterwards. The procedure may be an importantconsideration when determining causes of corrosion inpipework. Avoid leaving pipework empty for long periodsand consider using a corrosion inhibitor in the water (see'section WI.4).(1)

pumps: duty, impeller size, speed and characteristiccurves

boilers: duty, operating temperatures and pressure

calorifiers: flow rate and pressure drop, primaryand secondary flow and return temperatures, shelland coil pressures

refrigeration condensers: flow rates and pressuredrops, flow and return temperatures

refrigeration evaporators: flow rates and pressuredrops, flow and return temperatures

flow measuring devices: identification number,size, flow rate, pressure drop and signal k (seeWA3.7) in the form of a schedule with m~ufac-turers' graphical data

double-regulating valves: identification number,size, flow rate,Pressure dropand System k or kv vmaxschedule with manufacturers' graphical data

terminal units: identification number, flow ratewith the tolerances and pressure drops

control valves: identification number, flow rate andpressure drop and ky

heat exchangers: identification number, flow rateand pressure drop, primary and secondary flow andreturn temperatures as installed

highlighting of all glands and other componentsused in the system made from materials likely to beaffected by chemical cleaning (see sections WI.4and W Al.6)

for differential pressure control regulators, themaximum and minimum differential pressures foreach valve, the design maximum flow rate andky.

WA3 Flow measurement andregulation

WA 1.7.3 Other information

(a) Associated diagrams for electrical and pneumaticequipment used with the water distribution system.

(b) Manufacturers' setting to work, operating andmaintenance instructions for equipment.

All flow measuring and regulating devices should conformtoBS 7350<11).

WA3.1 Flow measurement devices

WA2 Installation Manufacturers of flow measurement devices should pro-vide data describing the characteristics of the measuringdevice either in a graphical or a tabular form suitable for useby the commissioning specialist. The published datashould be produced from component type test readings andquote the accuracy tolerance of the device.

WA2.1 Installation requirement

The objective is to interpret the design requirementscorrectly and so bring the system to static completion.Installation includes all cleaning and soundness testingbefore commissioning in accordance with the specification.

.The manufacturers' quality control procedures should besuch that the quoted accuracy can be traceable to standards.

FLOW MEASUREMENT AND REGULATION

) WA3. 1. 1 Orifice plate WA3.1.6 Selection and installation of flowmeasurement devices

This is a plate, within a carrier, having a circular opening ofa diameter less than the internal bore of the pipe, which isinserted into the pipeline and positioned concentrically inaccordance with the manufacturers' instructions. Eachplate has a kvs coefficient.

Devices should be selected so that the pressure differentialsignal is suitable for the measuring instruments to be usedand appropriate to providing reproducible readings (seesection W A3.6). As a general rule the signal measuredshould be betWeen 1 kPa and 10 kPa. A measured pressuredrop of less than 1 kPa indicates that the water flow couldbecome critical and laminar, thus undermining the per-formance of the measuring device.

Three types of orifice plates are available:

(a) small sizes cast in one piece having male and femalethreaded ends A confused flow through a measuring device directly affects

the pressure differential across it. This in tUrn will lead to afalse flow rate inference. To minimise the tUrbulencethrough the measuring device, current practice is to have astraight pipe length equivalent to a minimum of 10 diamet-ers upstream and up to 5 diameters downstream clear of anydistUrbing influences such as bends, tees, valves andvessels, unless otherwise stated by the manufactUrer.

one-piece flanged carrier ring with integral orifice(b)

wafer plate fitted into a carrier ring.(c)

Pressure tappings are fitted upstream and downstream ofthe orifice in accordance with BS 7350<11) and are used tomeasure the pressure differential signal across the orificeplate. In forms (a) and (b) above, the pressure tappings arecorner tappings drilled integrally through the carrier ring.

Where a flow measuring device of less than line size has tobe used to generate a pressure differential signal suitable forthe relevant instrumentation, lengths of pipe of the devicediameter equivalent to at least 10 diameters upstream andup to 5 diameters downstream should be used, unless other-wise stated by the manufacturer.

WA3.1.2 Venturi meter

This is a carefully profiled wasp-waisted tube which isinserted into the pipe in accordance with the manu-facturer's instructions. Its function is to accelerate and thendecelerate the fluid velocity with minimum pressure loss.Pressure tappings at the throat (maximum velocity) and atthe maximum diameter (minimum velocity), in accordancewith BS 1042(17), enable the pressure differential signal tobe recorded for conversion to a flow rate using the flowcoefficient kvs factor for the device provided by the manu-facturer.

WA3.2 Factors affecting measurement

accuracy

Orifice valveWA3.1.3

This is a threaded or flanged pressure-tapped 'Y'-patternglobe valve used with the disc in the fully open position.The seat of the valve acts as a measuring orifice.

WA3.2.1 Incorrect pipe jointing

(a) Screwed threads: cut and threaded pipes must bedeburred or reamed carefully where a threadedmeasuring device is to be screwed onto the pipe,otherwise the flow or pressure drop characteristicsof the device may be affected.

(b) Jointing material: hemp and jointing compound orpolytetrafluorethane (PTFE tape) on pipc cn& multlnot protrude into the pipe bore.

(c) Flanged joints: joint rings used with flanged orificeplates must not protrude into the orifice chamber.Full-face rings of the correct size should be used sothat the inside diameter of the ring is greater thanthe inside diameter of the orifice plate chamber. Aflanged orifice plate should be centralised accurate-ly to ensure that its axis is concentric with that ofthe pipe.

Variable-orifice double-regulatingvalve

WA3.1.4

This is a threaded or flanged pressure-tapped 'Y'-patternglobe valve provided with a calibrated disc to vary the areaof seat available for fluid flow and titted with pressuretappings either side of the seat. Use of pipe other than 8S J 387<18)

medium gradeWA3.2.2

Variations to standard methods ofme~surement

WA3.1.5 Manufacturers' performance charts are generally based onmedium-grade steel pipe(18) unless otherwise stated. Thisgives a known inside diameter (within specified tolerances),from which the beta ratio of the orifice device is deter-

mined.

Commissioning set: an orifice plate or device fittedto the upstream inlet of a double-regulating valve.(a)

J (b) Isolating orifice: an orifice plate or device fitted tothe upstream inlet of a gate or other full flow isolat-

ingvalve.

The inside diameters of BS 1387 heavy grade pipe, copperand plastic pipes, differ sufficiendy to alter the beta ratio


enough to require different flow rate data. The manu-facturer should be consulted for either an amended perfor-mance graph or a suitable conversion factor.

WA3.3.1 Correct sizing and positioning ofdouble-regulating valves

Double-regulating valves are used in system balancing toimpose additional resistance in local sections of a system soas to meet the design performance requirement for thewhole system. To do this effectively a regulating valveshould have an appropriate valve characteristic and, moreimportantly, should be chosen to give authority appropriateto each particular application. Double-regulating valvesshould be selected so that this authority operates between100% and 25% of maximum disc lift with ball and butterflyvalves between 30% and 70% of opening.

WA3.2.3 Use of anti-freeze mix

The presence of anti-freeze in water changes its specificgravity, viscosity and surface tension. The performance ofthe volume flow rate measuring device will vary accordingto the proportion of anti-freeze used. The device manu-facturer should be consulted for a corrected performancegraph or conversion factor appropriate to the anti-freezemix.

To minimise the risk of noise, cavitation, disc erosion bydissolved air and the build-up of solids between the discand the seat, these valves should not be used with the discless than 25% open. Valves of other than line size should beconsidered for use where it is necessary to obtain theauthority required commensurate with the pressure dropacross the device. Double-regulating valves which are notused in association with flow measuring devices may beintroduced anywhere in the system and can be used withreducers immediately connected to them.

WA3.2.4 Venting of air

Aerated water has modified fluid flow characteristics andthe presence of air will severely affect reproduciblemeasurements. Complete and thorough venting of thesystem is of considerable importance.

WA3.2.5 Direction of flow

WA3.4 Access to flow measurementand regulating devices

All flow measuring devices should be identified and instal-led correctly with respect to the flow direction.

WA3.4.1 Pressure test point accessWA3.2.6 Oscillating manometer reading

Pressure test points on flow measuring devices require aminimum clearance of 100 mm from objects within thepath of the axis of the pressure test point. This enables thecommissioning engineer to insert and withdraw mano-meter probes without kinking the tube. Where adjacentpipework is lagged sufficient space must be left for commis-sioning probes.

Care should be taken when reading a water manometergauge with an oscillating manometric fluid meniscus as anaverage reading will have to be taken.

WA3.2.7 Low-volume flow rates

WA3.4.2 Scale settingsAt very low flow rates the measuring of a pressure dif-ferential signal can be affected by air bubbles or detrituscollecting across the measuring orifice. This problem willmanifest itself more when using regulating valves of theglobe valve type which are closed down more than 75%.(See section W A3.3.1.)

The scale settings on all types of double-regulating valvesshould be visible and accessible in all instances.

WA3.5 Constant flow regulator (CFR)

Double-regulating valve These devices reduce the need for proportional waterbalancing on terminal units, thus shortening the commis-sioning time. They are analogous to constant-volume de-vices in air systems. CFRs maintain a constant flow withindefined limits (usually :t5%) provided that the differentialpressure across the CPR is within the manufacturers' re-commendations for consistent and stable performance.

WA3.3

A double-regulating valve is a threaded or flanged 'Y'-pattern globe valve with a seat reduced in diameter fromthat of the mating pipe bore. The valve has a disc-to-seatopening scale device to indicate the number of turns open,or the percentage open, relative to the closed position. Thevalve lift can be set and locked at the regulated position byan external mechanical device so that the valve will closeand re-open to the preset position.

The principle of a system with all terminal flows controlledby these devices is that of automatic flow balancing. In-correct balance could only occur if the pressure differenceacross any device is outside the rated range or if solids

.~.~,suspended In the system water cause blockage or sticking of ,,~the regulating mechanism. These devices cannot provideflow measurement readings. Where flow rates are reQuired

Note: other types, such as needle, ball or butterfly valves,may be used providing the valve authority is sufficient forthe circuit and that pre-setting devices are available.

FLOW MEASUREMENT AND REGULATION

.for documentation and other purposes additional flowmeasurement devices must be included.

WA3.6 Instrumentation

All instruments must be regularly cleaned and serviced inaccordance with manufacturers' instructions and, whereappropriate, instruments should be calibrated at periodicintervals by a recognised testing laboratory to traceablestandards.

Commissioning procedureWA3.5.1

The following instruments and accessories are necessary tocarry out the commissioning procedures prescribed in thisCode.

WA3.6.1 Manometers

The choice of manometer listed in Table A4 will depend onthe flow measurement device selected.

Table A4 Manometer types and attribute

1.88

13.6

There is limited experience in commissioning HVAC sys-tems with constant flow devices. The following procedureis suggested.

(a) Normal pump and system pre-checks.

(b) Cleanliness of the system is of paramount im-portance if the CFR units are to function correctly.All cleaning and flushing of the system should becarried out with the CFR units removed or bypassed.When the system has been thoroughly flushed andis known to be clean, the CFR units should be re-fitted. When re-installing the CFR units, care mustbe taken to ensure that no PTFE or jointing com-pound is allowed to contaminate the system or itscomponents.

(c) The pump flow rate should show no more than 5%margin over the sum of the CFR flow rates. Thepump pressure should include a small margin forunpredictable system changes plus an allowance of1.5 times the minimum pressure differential of theCFR in order to ensure that all CFRs operate withintheir pressure band.

(d) The pump flow rate and pressure, which should bemeasured and recorded, should be within :t5% ofthe sum of the CFR units where measuring stationshave been included as part of the system design.Verification of the system terminal flow ratesshould be carried out and recorded

Fluorocarbon

Mercury

Digital electronict

Analogue diaphragmt

t Should be calibrated regularly and a calibration cenificate issued.

WA3.6.2 Thermometers

Sling psychrometer (wet and dry bulb thermometer).

Contact and immersion electronic thermometer.

WA3.6.3 Other instruments

WA3.5.2 Further CFR commissioning

guidanceMulti-purpose electronic meter for measuring current.

Tachometer (revolution counter or stroboscope).Where there is a discrepancy in the pump flow and/or signs

1) of lack of terminal thermal performance, a scan of pressure," differentials across the CFRs and terminal flow rates is

necessary. Record all measurements and annotate thosewhich lie outside the specified tolerances.

WA3.7 Flow coefficients

Flow coefficient ky is defined as the flow rate in cubicmetres per hour (m3/h) at a pressure drop of one kilogramforce per square centimetre (kgf/cm2). 1 kgf/cm2 is approxi-matelyequal to 1 bar.

Where the flow is lower than the design flow rate, with thepressure differential within the rated band, clean the cart-ridge or other internal components of the CPR.

The signal flow coefficient kyS' a constant for a given device,is proportional to the flow rate divided by the square root ofthe pressure drop which occurs across the measuring deviceat the pressure tappings. This will be given by the manu-facturers.

Where the pressure differentials are too high, de-rate thepump by speed change, where possible, or by throttling orchanging the impeller.

Where pressure differentials across all CFRs on a particularcircuit are too high, throttle the affected circuit until alldifferentials are within the rated band.

The system flow coefficient kv' a constant for a given device,measured 3 diameters upstream and 10 diameters down-stream, is proportional to the flow rate divided by thesquare root of the pressure drop imposed on the system dueto the device. The system flow coefficient is normallyhigher (lower loss) than the signal flow coefficient due tostatic pressure regain, except where items are close-coupledand the system flow coefficient therefore could be apprec-iably less (higher loss). This should also be stated by themanufacturer.

Where flow and pressure differentials are both low, increasethe pump duty. Throttling other circuits will not neces-sarily correct this fault.

.Further remedial action is generally only necessary if thesystem is dirty or there have been serious design or instal-lation errors.


WA3.7.1 Useful formulae 7

These symbols are used in ~e following formulae:

-Q is the flow rate (Vs)-~

is the pressure dtop (kPa)

-kvs is the signal flow coefficient.

8

9

10

11(a)

12

For use by the design engineer:

To select a device within an allowable ~ band:

kvs = 36Q/(~Y/2

Select the device with the next lower rated kvs.

To find the signal ~!with a knownkvs:

~ = (36Q/kvsl I

13

14

IS

To find the flow velocity (v) from a known flow rateand the nominal pipe bore (bn):

v = 1152.7Q1bn216

17

18

The control of Legionellosis, including Legionnaires' disease t

Guidance Note HS(G)70 (London: Health and Safety

Executive/HMSO) (1993)

Electricity at Work Regulations 1989 (London: HMSO) (1989)

Health and Safety at Work etc. Act 1974 (London: HMSO) (1974)

Regulations for the electrical installations 16th edn (London:Institution ofE1ectrica1 Engineers) (1991)

BS 7350: 1990 Specification for double regulating globe valves and

flow measurement devices for heating and chilled water systems(London: British Standards Institution) (1990)

Petitjean R Total hydronic balancing (Ljung, Sweden: Tour andAndersson AB) (1994)

Environmental Protection Act 1990 (London: HMSO) (1990)

Waste management -The duty of care, a code of practice (London:

HMSO) (1991)

BS 1192: Pan 3: 1987 Recommendations for symbols and other

graphic conventions (London: British Standards Institution)(1987)

Guide to good practice for site pressure testing of pipework (London: 'Jt

Heating and Ventilating Contractors' Association) (1980)

BS 1042: Measurement of fluid flow in clased conduits (London:

British Standards Institution) (1989)

BS 1387: 1985 Specification for screwed and socketed steel tubes andtubulars and for plain end steel tubes suitable for welding or for

screwing to BS 21 pipe threads (London: British Standards

Institution)(1985)

To find the nominal pipe bore from a known flowrate and velocity:

bn = (1152.7Q!v)1/2

(b) For use by the commi$sioning engineer:

To find the actual fl~w rate from a known signalflow coefficient:

Q = kvs(~)1/2/t36

To find signal flow cqefficient from a known flowrate and pressure dropt

kvs = 36Q/(~r/2

J'

References ..., I.

1 Parsloe C J The commissioning of water systems in buildings

Application Guide 2/89 (~racknell: Building Services Researchand Information Association) (1989)

2 Wild L J Commissioning HVAC systems -Division of

responsibilities Technical Memorandum 1/88 (Bracknell:Building Services Research alnd Information Association) (1988)

Parsloe C J Pre-commission cleaning of water systems ApplicationGuide 8/91 (Bracknell: $uilding Services Research andInformation Association) (1991)

CIBSE Guide Section B7: Corrosion protection and watertreatment (London: Charte~d Institution of Building ServicesEngineers) (1986)

Badenoch J Second Repon of the Committee of Inquiry into theOutbreak of Legionnaires' Disease in Stafford in April 1985(London: HMSO) (1986)

) The prevention or control of Legionellosis (including Legionnaires'disease) Approved Code of Practice L8 (London: Health andSafety Executive/HMSO) (1991)

3

4

~

,~jl,V

BibliographyBS 2871: Part 1: Specification for copper and copper alloys. Tubes (London:


BS 3528: Specification for convection Iype space heaters operating with steam orhot water (London: British Standards Institution) (1977)

BS 4856 Methods for testing and rating fan coil units, unit heaters and unitcoolers (London: British Standards Institution) (1983)

BS 4857 Methods for testing and rating terminal reheat units for air distribution

systems (London: British Standards Institution) (1983)

BS 4941: Specification for moror starters for voltages up to and including 1000 VAC and 1200 V DC (London: British Standards Institution) (1977/9)

BS 5000: Part 10: 1978 (1984) General pu!:t'ose induction motors (London:


BS 5000: Part 11: 1973 (1984) Small-power electric motors and generators

(London: British Standards Institution) (1984)

BS 5316: Specification for acceptance tests for centrijitgai, mixed flow and axial

pumps (London: British Standards Institution) (1977)

BS 5643: 1984 Glossary of refrigeration, heating, ventilating and air-

conditioning terms (London: British Standards InstitUtion) (1984)

BS 5750: Quality systems (London: British Standards Institution) (1987)

BS 5875: 1980 Glossary of terms and symbols for measurement offluidflow inclosed conduits (London: British Standards Institution) (1980)

BS 6683: 1985 Guide to installotion and use of valves (London: BritishStandards Institution) (1985)

BS 6860: Code of practice for low temperature hot water heating systems output

greater than 45 kW(London: British Standards Institution) (1988)

Automatic controls Applications Manual AMI (London: CharteredInstitution of Building Services Engineers) (1985)

24

BIBLIOGRAPHY

.Guide to practice in corrosion control II (London: Department ofIndustry/HMSO) (1982)

Scheme for approving commissioning specialists in HV AC (London: PropenyServices Agency/HMSO) (1986)

Stondard specification (mechanical and electrical) No.3 (London: PropenyServices Agency/HMSO) (1986)

Procedural standards for testing, adjusting and balancing of environmentalsystems (Vienna, VA: National Environmental Balancing Bureau) (1992)

Hydronic systems: Analysis and evaluations (Atlanta, GA: American Societyof Heating, Refrigerating and Air-conditioning Engineers) (1968)

Commissioning Engineers Compendium (Cambridge: CommissioningSpecialists Association) (1991)

Proc. Con! TESCOM '77 (London: Chartered Institution of BuildingServices Engineers) (1977)

Proc. Con! Commissioning by design (London: Chartered Institution ofBuilding Services Engineers) (1986)

Proc. Con! Quality assurance in building services (Bracknell: BuildingServices Research and Information Association) (1986)

Quality management systems Applications Manual AM9 (London:Chartered Institution of Building Services Engineers)

0

iJ

't


IndexSectionWO.2WO.2WO.SWI.IWAI.7WO.2WO.2WI.7W2.2W2.4WA3.SWI.7WI.3WAI.7WI.7WI.7WI.3

Page223319

management, definitionmanager, definitionrecordsspecialist

SectionWA3.4

Page22

Access to equipment

Accuracydefinition

Accurate measurementfactors affecting

Adequate accessAerated waterAir

WO.2 1

WA3.2WI.3WA3.2

214

222778226419764

free ventilation ofseparationventing

Anti-freezemixture

Authorityof valve

Automaticair Ventscontrol valves

W2.2WAI.5WAI.5

81919

definitionspecification, definition

Complex interlocksCommutatorCompletion certificationConstant flow regulators (CPR)ContactorsControl valves

WA3.2 21

WA3.3 22

WI.3WI.6W3.6W3.7WAI.7

46101319

WA3.2WA3.3

2122

Control circuit fuseControl wiringCooler batteriesCorrect sizing

orifice

double-regulating valve

WI.?WI.?WO.2WAI

77117

WAI.S 19

W3.3W3.6W3.8W3.6W3.6W3.9W3.7W3

81114111015138

24201165712161919

WAI.2WO.2WI.2W3.6WAI.7WAI.7WAl.IW3.7WAI.7WA3.2WI.7

1723101919171319227

DashpotsDeclared voltageDefinitionsDesignDesign

considerationscriteria, definitiondrawingsflow rate (DFR)information requiredpressuresrequirement

Differential pressure regulators (DPR)Differential temperatureDirection offlowDireCt on-line starters

Diversitydefinition

Documentation

WAI.7W3.6WI.7WI.4W2.1W3.6W4.4WAI.7WAI.S

Backwash filtersBalancing

basis ofbranchesby compensated methodby% proportion

constant-volume systemstemperature methodvariable-volume Systemswater flow rates

BibliographyBoilersBranch index terminalBusbarsBypass

WO.2W4.4WAl.7WAl.7Wl.4Wl.3WAl.7WAl.7WA3.3WAl.7Wl.3Wl.3

2162019541920221944

Bypassing the plantDomestic hot water systemsDosingpotsDouble-regulating valves

CalorifiersCapacity testing

definitionCavitation

WAl.7 20

WO.2W3.6WAI.2WA3.3

1111822

Drawings and schedulesDrain valvesDuplex strainers

Ease of accessElectrical actuatorsElectrical checksElectrically controlled valvesEvaluation and witnessingExpansion devices

Checksbefore fillingprior to pump starr

Chemical cleaning

Wl.3W2.1

WAI.4WI.?WI.?W2.IW4WI.3

37

1976715

WI.4WAI.6WAI.7WO.2WI.3WO.2WA3.7WAI.7WI.3

5192014123194

W4.4 16

WO.2 2

W2.2W4.4

816

definitionCisternsCoefficients

flowCold waterCold feedCommissionable system

definition

Commissioningcertificationcontractdefinition

WO.2 1WAl.5WA3.2

1921W3.IO

WI.lWO.2

1531.

Final runFine tUning

definitionFirst

checkscan

Fill pointswater

Flanged jointsFlow

coefficient (k..) WO.2WA3.7

123

INDEX"SectionWA3.1WA3.1W4.4W3.7WAI.7WI.3WAI.7WA3.1WAI.7WA3.1W3.7W3.6W4.4W4.2WO.2WAI.3W3.2WAI.2WA3.1WAI.2WA3.6WI.4WAI.7WO.2WI.4WAI.5Wl.4Wl.4WAI.5WA3.6WA3.7WA3.7WA3.7

Page2121171419320201921131016152188172118234192419441923242424

confusedcritical and laminarinstrumentsmeasurement

SectionW3.?WI.4WI.?

Page1357

Isolated pressure tappingsIsolated sectionsIsolation of plant

measurement device Jointing materialWA3.2 21

ky flow coefficientkvs signal coefficientky system coefficient

Live componentsLocal isolationLubricant seepage

WA3.7WA3.7WA3.7

232323

WI.?WI.?W2.2

668

Mains feedManometers

analoguedigitalfluorocarbonmercury

Manual air ventsMechanical checksMinimum clearanceMost favoured circuit

Wl.3 4

WA3.6WA3.6WA3.6WA3.6WI3WI.6WA3.4W3.6W3.6W3.6WI.?W2.2W2.2WI.?W2.2W2.2W2.2W2.2W2.2

positioningselection

Flow control regulators (FCR)Flow rate

datamassmeasured, definitionmethods used to detenninetolerance

charts10 up and 5 down rule

velocityFluorocarbon manometerFlushing

23

2323234622101111

f)definitionprocedure

schedulewater velocity

7777777

branchMotors

direction of rotation

overheatingpowerrunning currentspeed of rotationstarterstarting currentvibration

Formulaefor designersfor commissioning engineers

Frostprotectionprecautions

Fuse rating

WI.4WI.5WI.7

566 Noise

W2.2W3.6WAI.2WA3.3WI.3WI.3

71118224

Wl.3WA3.1

320

Gland packingGraphsGuide to good practice (HVCA)

pressure testing Non-return valvesNozzlesWA2.4 20

HeatfJ' emitters, exchangers WAl.7

WA3.1WA3.1W3.9Wl.3W2.2W2.2

WAl.7Wl.3WAl.7WAl.7Wl.3Wl.4

20212l15487

19419204

5

Operating and maintenance manualsOrifice plate or deviceOrifice valveOutdoor compensatorOverflows

Overheating bearingsOverheating motor

Heater batteries

High-velocitypumping

Index circuitW3.6WAI.7W3.6

101910

WI.7W3.8WAI.2WI.3WAI.7

6

1417419

W2.2W3.6W3.6WO.4

711123 WA3.2 21

WA3.2WO.7

213

WA2.2WO.2WA2.3WI.2WA2.IWI.2WI.7WA3.6WI.7WI.7

20220320362367

Wl.3WO.2W3.5

3210

identification ofInitial

runscan

Injection circuitsInspectionInstallation

cleanlinessdefinitioninspectionproceduresrequirementstandards of

1/,'\ ' lEE Regulations for electrical installations

Vi InstrumentationInsulationInterlocks

Panels and switchgearPartner valvePerformance effectPipeworkPipe sizesPipe jointing

incorrectPipe

other typesPractical considerations of flow rate balancing

Precommissioningchecksdefinition

Preliminary flow rate checkPressure

differentialdrop

WA3.1WAI.7WA3.1WI.3

2119214gauges

WATER DISTRIBUTION SYStEMS

SectionW2.1W3.7WA2.4

Page71320

Section Page

WO.2WI.8WAI.7WI.7WI.3WI.3WI.7

27197446

WO.2W3.6W3.6WI.3W3.6W3.6WAI.3

212114111118 WI.4

WAI.7WO.2WO.2WAI.7WAI.7WI.5WI.4WI.6WAI.7WO.2WI.3

42012191954619

W2.2WAI.7WAI.2WAI.7W2.2W3.4W3.6W2.2W2.IW2.IWI.6WI.7WAI.7

8

1918198101187766

19

Static completiondeflDitionrecords

Straight pipe nInStarters, direct on-lineStrainersSupportsSwitchgearSystem

cleanlinesscoefficient, kvcommissioning, definitiondefinitiondescriptiondiversityfilling and ventingflushing and cleaninggeneralpressure lossproving, definition

Siphons

isolation

tappingstesting

Pressure and leakage testingdefinition

Primary circuitPrimary regulating valvesProbe pocketsProportional relationshipProportional balanceProvisions for measuring flowPump

excessive pressureflow rate

marginspressurerunning-in periodshut-offhead testspeed adjustmentstandbystartsuction

Pumps4 ,.JWI.3

WA3.1W3.6WAI.7

4211120

TanksTen up and five down ruleTerminal units

Testingdefinition

Testpoints

Wo.SW3.6WI.7W3.8WAI.7

3

1171420

RecordsRecord of instrument readingsReduced voltage startingReference valveRefrigerationRegulation

WO.2 2

WI.3W3.4WA3.4WA3.6WI.7W2.1W3.7WI.7WI.7

4102223771376

W3.2W3.6WAI.7W3.6WAI.7WI.7WI.3WO.6W3.6

81219101974310

Regulating valve

WOo2WAlo2

217

pressureThermometersThermal cut-outs

Thermos1:a-tieally eenttolled valvesThermostatic radiator valvesTimersTransit packingTolerance

definitionperformance effect

RelaysReliefvalvesResponsibilityRiserRunning-in period

pumps Valvesauthoritydouble-regulating

W2.2 8 Wl.6WA3.3WI.3WAI.7WAI.7WA3.3WI.7WI.3WAI.7W3.5W3.5WAI.2W2.1W3.6W3.7W3.7W3.7WA3.I

622419202273191010187121213

1321

Scale settingsSchematic drawingsScrewed threads

Secondarypumppump systemsregulation of bypassthree-port control valve

Setting to workdefinition

WA3.4WAl.7WA3.2

221921

J:

W2.2W3.6W3.6W3.6

8121212

WO.2WAI.7WA3.6WI.3WI.2W2.2WO.3WO.2W3.2W3.6W1.2W2.IW2.2WI.7WI.7W1.2

2202343721811378773

Signal flow coefficient, kvsSiphonsSite cleanlinessSlip ringsSpecificationSpecified tolerance

electrically controlledlubricantport identificationprimary regulatingregulatingsizingthermostat -controlledthree-port control

Variable-volume systemsdesignregulating

Variable-orifice double-regulating valvesVenting

continuousVenturi meter

WAl.5WA3.1

1921

Standards ofinstallationStandby pumps Washers

Watercompanycooled bearingsheating appliancessampling

WI.3 4

Starteroverload

State of the system

WAI.7W2.2WI.7WAI.5

198719

INDEX

SectionWI.4WAI.5WI.7WAI.7

Page519619

treatment

Wiringdiagrams

Witnessingarrangementsrequirementsduties

W4.2W4.2W4.3

ISIS16

,

Documents

Code W 1994