MHG Heating LtdUNVENTED WATER HEATERS

INSTALLATION MANUALINCLUDING SOLAR VESSELS

TechniTechniT cal data & installation instructions for MHG direct & indirect unvented water heaters

including solar models.

Your water heater is made from Duplex Stainless Steel, which is one of the toughest and best grades of steel currently available.

Each unit has been individually tested and inspected to industry standard.

Your water heater uses advances in technology and innovative techniques to provide you with a high performance water heater at the best price possible.

The MHG unvented water heater can be fed directly from the mains water supply to provide high pressure hot water capable of meeting the needs of the modern household.

MHG solar cylinders enable the use of alternative energy solutions to be integrated into domestic water heating systems.

Built to the same exacting standards as the rest of our MHG range, they exceed market standards for insulation and build quality.

No other type of water heater can provide all of the benefi ts that can be achieved from unvented units such as the MHG unvented water heater.

All MHG unvented water heaters are covered by a 25 year guarantee (please refer to manual for terms and conditions).

IMPORTANT NOTICE FOR INSTALLATION

READ THESE INSTALLATION AND MAINTENANCE INSTRUCTIONS BEFORE COMMENCING

Unvented cylinders are designed to BS standard and installed to relevant building regulations.

THE RELEVANT REGULATIONS ARE:England & Wales - Building Regulation G3Scotland - Technical Standard P3Northern Ireland - Building Regulations P5

The information contained in these instrcutions referring to connection of solar cylinders details how to connect the MHG solar cylinder to a solar primary circuit. In order to control this primary circuit some other controls may be necessary according to the requirements of each individual system. Please refer to the relevant documentation for your particular system for instructions on how to integrate these controls with the MHG solar cylinder.

On completion of the vessel installation and commissioning, the Benchmark log book, included at the rear of this manual, must be completed in full by the competent installer and left with the household who should countersign to accept completion.

THIS MANUAL IS TO BE LEFT WITH THE USER

CONTENTS

IntroductionMHG Range p3

Specifi ers GuideHG Range p3

Specifi ers GuideHG Range p3

The law and unvented p3The benefi ts of unvented systems p3The benefi ts of MHG unvented water heaters p3MHG solar water heaters p3

Dimensions and performanceMHG Indirect and direct p4MHG solar p5

Installation InstructionsMHG solar p5

Installation InstructionsMHG solar p5

Siting the MHG unit p6Storage & handling p6Check water pressure and fl ow rates p6Connecting the water supply p6Cold water valve & drain tap p6Pipework to taps p6Taps and fi tting p6Expansion vessel & immersion heater (MHG solar) p7Primary & Secondary circulation p8Fitting the thermal cutout & primary connections P8Wiring p9Fitting immersion heaters P9 Tundish p10External expansion vessel p10Scale p10G3 requirement p11Discharge pipework p11Commissioning the MHG unit p12Fault Finding p13Part component references p14Warranty p14

DiagramsWarranty p14

DiagramsWarranty p14

Dimensional data for the MHG range p4Typical installations p7Secondary circulation connection p82 x 2 (S-plan) valve system p92 port valve + 3 port mid position valve (Y plan) p9Immersion heater p9Schematic discharge pipe arrangement p11Internal expansion commissioing diagram p12

2

INTRODUCTION

The MHG unvented water heater is a high quality stainless steel unvented cylinder to provide hot water from a cold mains water supply of between 3 bar and 12 bar. Reduced performance is available at lower pressures although the units are not suitable for pressures lower than 1.5 bar and a fl ow rate of less than 20 litres per minute. The indirect heat exchange surfaces are designed to provide a rapid heat up time. The unit comes complete

with all the necessary safety equipment to comply with legislation governing the installation of such systems.

The MHG solar unvented water heater has been designed for use with all solar panels and ground source heat pump systems requiring a storage and heating vessel please ensure compatibility prior to installation.

SPECIFIERS GUIDE

THE LAW AND UNVENTED THE LAW AND UNVENTED THE LAW AND UNVENTED THE LAW AND UNVENTED

It is legal to fi t an unvented unit into any property, UK water byelaws were amended to allow this change.There is no longer a requirement to have an old-fashioned ‘ Tank in the Roof’ system.

THE BENEFITS OF UNVENTED SYSTEMS THE BENEFITS OF UNVENTED SYSTEMS THE BENEFITS OF UNVENTED SYSTEMS THE BENEFITS OF UNVENTED SYSTEMS

• A real Power Shower without the noisy pump• No tanks in the roof• No ball cocks to jam or leak• All your water, hot and cold, is direct from the mains• Site the MHG unvented water heater wherever convenient• The MHG fi lls your bath in minutes and will run two at the same time (subject to good plumbing and fl ow rates)

• The MHG can work off electricity (Economy 7), alternative energy systems or any oil or gas fi red boiler (not suitable for solid fuel boilers)

THE BENEFITS OF MHG

• Annual inspection as per warranty• Duplex stainless steel• High quality fi nish• Low heat loss for maximum economy• No sacrifi cial anode - low maintenance

MHG SOLAR MHG SOLAR MHG SOLAR MHG SOLAR

The MHG solar range is available in four vessel capacities in both direct electric or indirect models. Each cylinder has been specifi cally designed for use with an alternative energy heating system and includes a large corrugated coil that provides optimum heat transfer from the alternative heat source to the water in the cylinder.

The MHG solar unvented water heater should only be used as part of a solar or ground source heat pump installation and confi gured as shown. Additional safety devices may be required if the cylinder is operated with other heat sources.

STANDARD EQUIPMENT STANDARD EQUIPMENT STANDARD EQUIPMENT STANDARD EQUIPMENT

Before commencing installation check that all the components of your MHG unit are contained in the kit.

• 3kW Incoloy 825 heating element - incorporating thermostat 70 degrees Celsius and re-setable safety cut-out set at 80 degree Celsius

• Cold water control valve comprising line strainer, check valve & appropriate pressure reducing valve

• Pressure relief valve with non-return valve set at 6 bar

• Tundish 15mm x 22mm Female x Female

• Temperature / Pressure relief valve set at 90 degrees Celsius and 7 bar pressure (factory fi tted)

• Motorised valve (indirect units only)

• Cylinder thermostat maximum setting 85 degrees Celsius (factory fi tted to indirect units only)

• Thermal cut-out set to operate at 87 degrees Celsius, +/-3 degrees (indirect units only)

• Expansion vessel, where required, with capacity to suit vessel size

Note: The solar range must always be installed with an expansion vessel.Standard indirect and direct units can accommodate internal expansion and hence

do not require an external expansion vessel. In this instance a 2 bar PRV should be fi tted. Where external expansion is required the PRV should be a3 bar version. Please refer to installation schematics.

3

DIMENSIONS & PERFORMANCE

MHG INDIRECT & DIRECT MHG INDIRECT & DIRECT MHG INDIRECT & DIRECT MHG INDIRECT & DIRECT

MHG - Direct Heat Exterior Reference DimensionsReferenceVolumes

LitresA B C D E

130 957.5 196 182.5 331.5 388150 1085.5 196 182.5 340 438175 1242.5 196 182.5 252 489.5215 1462 196 182.5 368.5 465.5255 1752.5 196 182.5 388 484305 2029 196 182.5 409.5 488.5

MHG - Indirect Heat Exterior Reference DimensionsReferenceVolumes

LitresA B C D E F G

130 957.5 212.5 192.5 331.5 196.5 182.5 339150 1085.5 212.5 192.5 341 196.5 182.5 339175 1242.5 212.5 262.5 352 196.5 182.5 379.5215 1462 212.5 262.5 368.5 196.5 182.5 379.5255 1752.5 212.5 262.5 388 196.5 182.5 379.5305 2029 212.5 262.5 388 196.5 182.5 379.5

MHG - PerformanceNominalCapacity

Litres

Heat upModel IDH

mins

Heat up Model DH

mins

ReheatModel IDH

mins

ReheatModel DH

mins

Heat loss in 24hrskw/hr

80 33 64 23 53 1.12130 28 115 21 90 1.5150 33 138 24 104 1.82175 27 167 24 124 2.10215 35 212 30 153 2.64255 42 263 35 184 2.73305 50 313 42 220 2.88

Slight variations may occur with changes to water mains supply pressure.

Reheat times are those to heat 70% of the cylinder from cold.

Test carried out by the BBA, an independent testing agency.

The heat loss of each MHG unvented unit while maintaining the temperature of the stored water at 65 degrees Celsius is given in the performance table opposite.

4

Indirect HeatDirect Heat

(Fig 1) (Fig 2)

All measurements are in mm.

MHG - SOLAR Direct Heat Exterior Reference DimensionsReferenceVolumes

LitresA B C D E F G H I

130 957.5 300.5 348 225.5 192.5 212.5 182.5 182.5 455150 1085.5 300.5 398 225.5 192.5 212.5 182.5 182.5 513175 1242.5 469 398 225.5 267.5 212.5 182.5 182.5 589215 1462 590 398 225.5 267.5 212.5 182.5 182.5 589255 1752.5 469 398 225.5 267.5 212.5 182.5 182.5 589305 2029 5590 398 225.5 267.5 212.5 182.5 182.5 589

DIMENSIONS & PERFORMANCE

MHG MHG MHG MHG SOLAR

MHG SOLAR - PerformanceNominalCapacity

Litres

Heat upModel IDH

mins

Heat up Model DH

mins

ReheatModel IDH

mins

ReheatModel DH

mins

Heat loss in 24hrskw/hr

175 18 20 13 14 1.78215 21.5 24 16 17 2.19255 25 28.5 19 20 2.31305 30 34 22 24 2.51

MHG - SOLAR Indirect Heat Exterior Reference DimensionsReferenceVolumes

LitresA B C D E F G H

130 957.5 182.5 212.5 192.5 505 192.5 301 225.5150 1085.5 182.5 212.5 192.5 505 192.5 301 225.5175 1242.5 182.5 212.5 267.5 579.5 262.5 469 225.5215 1462 182.5 212.5 267.5 579.5 262.5 590 225.5255 1752.5 182.5 212.5 267.5 579.5 262.5 590 225.5305 2029 182.5 212.5 267.5 579.5 262.5 590 225.5

5

Slight variations may occur with changes to water mains supply pressure.

MHG solar data is based on a primary fl ow solar data is based on a primary fl ow solartemperature of 60 degrees Celsius and heating water from 15 to 60 degrees Celsius. The immersion of the cylinder or external boiler must be used to raise the temperature to 60 degrees Celsius from the maximum temperature achieved at any time by the solar system.

Reheat times are those to heat 70% of the cylinder from cold.

Test carried out by the BBA, an independent testing agency.

The heat loss of each MHG Unvented unit while maintaining the temperature of the stored water at 65 degrees Celsius is given in the performance table opposite.

(Fig 3) (Fig 4)Solar - Direct Solar - Direct HeatHeat Solar - Indirect Solar - Indirect Heat

All measurements are in mm.

MHG UNVENTED INSTALLATION INSTRUCTIONS

WARNING: Under no circumstances must the factory fi tted temperature pressure relief valve be removed. This will totally invalidate any guarantee or claim. The cold-water inlet valve assembly must be fi tted or the MHG unit will not perform satisfactorily.

DO NOT ATTEMPT TO VENT THE PRIMARY CIRCUIT THROUGH THE MHG UNIT.

All boilers should be installed to manufacturers instructions and the primary circuit through the MHG unit must be pumped.

SITING THE MH SITING THE MH SITING THE MH SITING THE MHG UNIT

The unit can be placed anywhere convenient. Since it is connected directly to the mains water supply it is equally effi cient on any fl oor – ground, fi rst or second. Avoid areas that may be subject to frost. Try to keep pipe runs as short as possible for maximum economy, especially hot water discharge pipes running down from the MHG unit.

The unit can be fi tted into a conventional airing cupboard and does not require any additional insulation.

ALL MHG UNITS MUST BE STORED VERTICALLYFOR INDOOR USE ONLY.

The water supply to the cylinder should be potable water direct from a public mains supply with any water treatment equipment functioning correctly.

CHECK WATER PRESSURE & FLOW RATES RATES RATES RATES

We suggest 1.5 bar pressure & 15 litres / minute fl ow rate to be the minimum requirements for satisfactory operation. Below this the unit will still operate but you will not be able to run two, or more, outlets at the same time. 85% of all UK homes have more than 2 bar pressure.

The mains supply must not exceed 16 bar. If it does a special pressure-reducing valve will be required.

Consideration should be given to the routing of the discharge pipe and the location of the solar panel or alternative energy source.

STORAGE STORAGE STORAGE STORAGE & HANDLING

If the cylinder is not being installed immediately, it should remain in its carton with all pipe end protective caps in place to prevent damage.

CONNECTING THE WATER SUPPLY CONNECTING THE WATER SUPPLY CONNECTING THE WATER SUPPLY CONNECTING THE WATER SUPPLY

• Pipework is not supplied

• All pipework should be installed using good plumbing practice. We recommend 22mm mains cold water supply is used.

• Install a Stop Cock Valve before the cold water inlet assembly on the incoming mains water supply so the unit can be isolated if required.

COLD WATER VALVE COLD WATER VALVE COLD WATER VALVE COLD WATER VALVE

The combined cold water valve (supplied) can be connected anywhere on the cold water mains prior to the unit. It can even be located at a point near to where the mains supply enters the premises if this is more convenient. When installing the cold water valve, ensure that the arrow is pointing in the same direction as the mains water supply fl ow when connecting, see fi g 7 and 8.

The cold water balancing port, on the valve, allows you to connect the cold water mains to the rest of the property thus giving balanced pressure throughout. If this facility is not required leave the cap on.

DRAIN TAP

A drain tap to drain the unit must be fi tted to the cold-water inlet pipe somewhere between the MHG unit and the cold water valve assembly and at as low a level as possible, see fi g. 7 and 8.

PIPEWORK TO TAPS PIPEWORK TO TAPS PIPEWORK TO TAPS

Ideally a 22mm pipe run should supply the outlets throughout the property with short lengths (max 1 metre) runs of 15mm going to baths, showers, and basin taps. Smaller bore pipe can be used to suit taps.

TAPS & FITTINGS TAPS & FITTINGS TAPS & FITTINGS TAPS & FITTINGS

All taps and fi ttings incorporated into the unvented system should have a rated operating pressure of 7 bar or above.

INLET GROUP INLET GROUP INLET GROUP INLET GROUP

The inlet group will vary according to whether the vessel is fi tted as internal or external expansion, see fi g. 7 and 8.

6

RECOMMENDED INSTALLATION SCHEMATICS

7

(Fig 5) EXTERNAL EXPANSION SCHEMATIC

(Fig 6) INTERNAL EXPANSION SCHEMATIC

(Fig 7) INLET GROUP INTERNAL EXPANSIONEXPANSIONEXP

(Fig 8) INLET GROUP EXTERNAL EXPANSIONEXPANSIONEXP

INSTALLATION INSTRUCTIONS

PRIMARY CIRCUIT

The motorised valve supplied and the thermal cut-out (Hi limit stat) must be fi tted to the primary fl ow. Use compression fi ttings only.

Operation of the cut-out and motorised valve

To comply with BBA regulations and to prevent the temperature reaching 100 degrees Celsius the thermal cut-out supplied must be fi tted.

The thermal cut-out is wired in series to the cylinder thermostat. When the thermal cut-out senses an abnormal rise in temperature in the primary fl ow the electrical supply to the motorised valve will be cut, and the valve will be in the closed position thus cutting of the primary water from the boiler to the indirect coil in the cylinder. If this occurs it must be reset manually. If the thermal cut-out operates check the cylinder stat and / or boiler stat.

SECONDARY RETURN SECONDARY RETURN SECONDARY RETURN

Secondary circuit connections MUST be made to the cylinder in accordance with the recommended installation diagram. A drain cock (not supplied) should be fi tted in the cold water inlet to facilitate draining of the cylinder.

This is particularly easy to fi t on the MHG units; and is illustrated in Fig.9 opposite. A swept tee (not supplied) is needed for all indirect models if secondary circulation is required and is fi tted as per the illustration. A non-return valve (not supplied) must also be fi tted to prevent backfl ow. A pump will be required to circulate the hot water (not supplied). The return feed is in 15mm pipe and all work can be done on site.

PRIMARY C PRIMARY C PRIMARY CIRCUIT (MHG SOLAR)

MHG solar cylinders are suitable for connecting to a solar collector system and, where a twin coil is present (INDIRECT) to a gas or oil central heating boiler.to a gas or oil central heating boiler.to a gas or oil central heating boiler

SOLID FUEL OR WOOD BURNING BOILERS AND GRAVITY CIRCULATION SYSTEMS MUST NOT BE USED ON THE PRIMARY CIRCUIT OF AN UNVENTED HOT WATER SYSTEM.

The cylinder should be installed in accordance with the solar installation instructions for connection to the primary fl ow and return.

The MHG solar range must only be connected to solar solar range must only be connected to solar solarinstallations containing a hydraulic station with two non-return valves (one in the fl ow to the collector and one in the return) such as the MHG Solar Eclipse System. This will prevent thermal . This will prevent thermal .siphoning of the heat transfer fl uid when the pump is switched off. Where two non-return valves are not present or hydraulic station is not used in the solar system, a second two-port valve must be installed into the fl ow of the solar coil and wired to the lower two-port valve.

SECONDARY CIRCULATION (MHG SOLAR)

The temperature and pressure relief valve (factory fi tted) should not be removed from the cylinder or tampered with in any way. The valve is pre-calibrated to lift at 7 bar or 90 degrees Celsius and any attempt to adjust it will invalidate the warranty and could affect the safety performance of the unit.

IMPORTANT. If a secondary circulation circuit is installed then a larger expansion vessel may be required to handle the

increase in water volume. Calculate the additional increase in water volume. Calculate the additional water volume and contact our customer services department regarding suitable vessel sizes.

8

The MHG solar is supplied with one two-port motorised valve which should be connected in the fl ow to the auxiliary coil and wired to the upper twin thermostat of the cylinder.

Solar Pump - the lower twin thermostat should be connected in Solar Pump - the lower twin thermostat should be connected in Solarline with the solar pump power supply.

(Fig 9)

Check valve

Secondary (Fig 9) Secondary (Fig 9) Return

Secondary circulation pump

Cold water supply

Swept tee

Cold inlet connection

WARNING: All electrical wiring should be carried out by aby aby competent a competent a electrical contractor and must conform to the latest IEE wiring regulations.

Do not switch the power on until the unit has been fi lled with water and all wiring has been earthed.See Fig 10, 11 and 12.

IMMERSION HEATER (MHG SOLAR) IMMERSION HEATER (MHG SOLAR) IMMERSION HEATER (MHG SOLAR) IMMERSION HEATER (MHG SOLAR)

For direct solar (single coil) cylinders, the immersion heater should be connected and suitably controlled to bring the water temperature to 60 degrees Celsius following heating by the alternative energy source.

FITTING IMMERSION HEATERS FITTING IMMERSION HEATERS FITTING IMMERSION HEATERS FITTING IMMERSION HEATERS

These are supplied as standard. An O ring is supplied as the seal and must be fi tted against the fl ange of the element. Take care not to cross thread and DO NOT use any other type of seal.

As our heating element is Incoloy 825 and is fi tted with a cut-out and thermostat for safety, a non-standard 13/4” boss ” boss ”is fi tted to the unit. Replacement elements can be obtained through your authorised service agent.

IMPORTANT: ensure that the immersion heater thermostat is set to 60 degrees Celsius.

9

WIRING INSTRUCTIONS

(Fig 10) 2 PORT (Fig 11) 3 PORT

L N EL N E

Mains isolatersupply 240V.50HZ

Fuse 5 AMP

Roo

m t

herm

osta

tR

oom

the

rmos

tat

Prog

ram

mer

Prog

ram

mer

Boile

rBo

iler

Pum

pPu

mp

(2-Port (DH

W)

Thernostat

Cut out

3-Port mid postn

Roo

m t

herm

osta

tPr

ogra

mm

erBo

iler

Pum

p

(2-Port (DH

W)

Thernostat

Cut out

2-Port (HG

T)

L N E

Mains isolatersupply 240V.50HZ

Fuse 5 AMP

(Fig 12)

WIRING INSTRUCTIONS

TWO PORT VALVE

The two port valve should be wired to the thermostat as per Fig 10 or 11 depending on required confi guration. Connect the live supply to the thermal cut-out and connect the brown wire of the two port valve to terminal 2 on the thermostat. Earth and Neutral supplies can be connected directly to the valve. The orange wire of the two port valve should be connected to the central heating boiler and the cylinder thermostat set to 60 degrees Celsius. The power supply to the pump station should be connected via the lower valve.

TUNDISH, EXTERNAL EXPANSION & SCALE

FITTING THE THERMAL CUT-OUT & FITTING THE THERMAL CUT-OUT & FITTING THE THERMAL CUT-OUT & FITTING THE THERMAL CUT-OUT & PRIMARY CONNECTIONS PRIMARY CONNECTIONS PRIMARY CONNECTIONS PRIMARY CONNECTIONS

The motorised valve supplied and the thermal cut-out (Hi limit stat) must be fi tted to the primary fl ow. Use compression fi ttings only.

Operation of the cut-out and motorised valve; to comply with BBA regulations and to prevent the temperature reaching 100 degrees Celsius the thermal cut-out supplied must be fi tted.

The thermal cut-out is wired in series to the cylinder thermostat. When the thermal cut-out senses an abnormal rise in temperature in the primary fl ow the electrical supply to the motorised valve will be cut, and the valve will be in the closed position thus cutting of the primary water from the boiler to the indirect coil in the cylinder. If this occurs it must be reset manually. If the thermal cut-out operates check the cylinder stat and or boiler stat.

TUNDISH TUNDISH TUNDISH TUNDISH

The tundish supplied must be fi tted so it is visible to the occupier. The discharge pipe must be 22mm copper pipe. Regulations do not permit more than 3 x 90-degree bends between the MHG unit and the outfl ow. Between the temperature & pressure relief valve and the fi rst 90-degree bend there must be a fall of at least 300mm. The fall of the pipework must be continuous and the pipe should terminate in the gully or be bent backwards onto an outside wall, in a place where discharge cannot be injurious to persons.

If you need to site the MHG unit in the middle of the house your discharge pipe to the tundish can be as far away as 9m, which in most cases is enough to run the fi nal discharge point. After 9m, increase the pipe size to a greater diameter than 22mm and accordingly for subsequent 9m lengths, see table 1 on page 12.

EXTERNAL EXPANSION VESSEL EXTERNAL EXPANSION VESSEL

This smaller tank is connected to the cold-water inlet side of the vessel. Mount the tank according to separate manufacturers instructions provided with the External Expansion vessel. See fi g 8 page 7.

A suitable expansion vessel with a pre-charge pressure of 3 bar is supplied with the MHG solar. The expansion vessel should be Tee’d off between the pressure relief valve and the cylinder (see installation diagram) and should always be positioned with the entry point at the bottom. Installation should always be by means of a standard T connector ensuring no other valve is between this and the cylinder. Adjust the pressure to 3.5 bar.

SCALE

In hard water areas lower water temperatures can result in less scale being deposited.

If a water softener is used it should be capable of fl ows of approximately. 50 lt/min, this will maintain maximum performance of the MHG unit.

If no descaler or softener is used then the heating element(s) will need descaling periodically for maximum effi ciency.

10

(Fig 13)

28mm

Tundish

22mm

22mm

Pressure Pressure relief valve

15mmT & P Valve

IMPORTANT: regular checks should be carried out to ensure that the expansion vessel is correctly pressurised to 3.5 bar at all times.

DISCHARGE PIPEWORK

11

G3 REQUIREMENT

‘...there shall be precautions...to ensure that the hot water discharged from safety devices is safely conveyed to where it is visible but will not cause danger to persons in or about the building.’

G3 GUIDANCE SECTION 3.9

The discharge pipe (D1) from the vessel up to and including tundish is generally supplied by the manufacturer of the hot water storage system. Where otherwise the installation should include the discharge pipe(s) (D1) from the safety device(s). In either case the tundish should be vertical located in the same space as the unvented hot water storage system and be fi tted as close as possible and within 500mm of the safety device e.g the temperature relief valve.The discharge pipe (D2) from the tundish should terminate in a safe place where there is no risk to persons in the vicinity of the discharge, preferably be of metal and:a. be at least one pipe size larger than the nominal outlet size

of the safety device unless it’s total equivalent hydraulic resistance exceeds that of a straight pipe 9m long ie. discharge pipes between 9m and 18m equivalent resistance length should be at least two sizes larger, than the nominal outlet size of the safety device between 18 and 27m, at least 3 sizes larger and so on. Bends must be taken into account in calculating fl ow resistance. Refer to Table 1 overleaf and fi g. 6.

An alternative approach to sizing discharge pipes would be to follow BS 6700:1987 specifi cation for design installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages, Appendix E, section E2 and table 21.b. have a vertical section of pipe at least 300mm long, below the

tundish before any elbow or bends in the pipework.c. be installed with a continuous fall. d. have discharges visible at both the tundish and the fi nal point

of discharge but where this is not possible or is practically diffi cult there should be clear visibility at one or other of these locations.

Examples of acceptable discharge arrangements are:i) ideally below a fi xed grating and above the water seal in a

trapped gully.ii) downward discharges at low level; i.e. up to 100mm above the

external surfaces such as car parks, hard standings, grassed areas etc. are acceptable providing that where children may play or otherwise come into contact with discharges a wire cage or similar guard is positioned to prevent contact, whilst maintaining visibility.

iii) discharges at high level; e.g into a metal hopper and metal down pipe with the end of the discharge pipe clearly visible (tundish visible or not) or onto a roof capable of withstanding high temperature discharges of water and 3m from any plastics guttering system that would collect such discharges (tundish visible.)

iv) where a single pipe serves a number of discharges, such as in blocks of fl ats, the number served should be limited to not more than 6 systems so that any installation discharging can be traced reasonably easily. The single common discharge pipe should be at least one pipe size larger than the largest individual discharge pipe (D2) to be connected. If unvented

hot water storage systems are installed where discharges from safety devices may not be apparent i.e. in dwellings occupied by blind, infi rm or disabled people, consideration should be given to the installation of an electronically operated device to warn when discharge takes place.

Note: The discharge will consist ofscalding water and steam. Asphalt, roofi ng felt and non-metallic rainwater goods may be damaged by such discharges.

WORKED EXAMPLE OF DISCHARGE PIPE SIZING

The example below is for a G1/2 temperature relief valve with a discharge pipe (D2) having 4 No elbows and length of 7m from the tundish to the point of discharge.From table 1: (overleaf)Maximum resistance allowed for a straight length of 22mm copper discharge pipe (D2) from G1/2 temperature relief valve is 9.0mSubtract the resistance for 4 No 22mm elbows at 0.8m each = 3.2mTherefore the permitted length equates to 5.8m, 5.8m is less than the actual length of 7m therefore calculate the next largest size.Maximum resistance allowed for a straight length of 28mm pipe (D2) from a G1/2 temperature relief valve equates to 18mSubtract the resistance of 4 No 28mm elbows at 1.0m each = 4.0mTherefore the maximum permitted length equates to 14mAs the actual length is 7m a 28mm (D2) copper pipe will be satisfactory.

(Fig 14)

Table 1 – Sizing of copper discharge pipe (D2) for common T&P relief valve sizes

Valve outlet Size Minimum size of discharge pipe D1

Minimum size of discharge pipe D2

Maximum resistance allowed, expressed as a length of straight pipe (i.e: no elbows or bends)

Resistance created by each elbow or bend

G1/2 15mm 22mm up to 9m 0.8m28mm up to 18m 1.0m35mm up to 27m 1.4m

G3/4 22mm 28mm up to 9m 1.0m35mm up to 18m 1.4m42mm up to 27m 1.7m

G1 28mm 35mm up to 9m 1.4m42mm up to 18mm 1.7m54mm up to 27m 2.3m

COMMISSIONING

12

COMMISSIONING A NEWLY INSTALLED COMMISSIONING A NEWLY INSTALLED COMMISSIONING A NEWLY INSTALLED COMMISSIONING A NEWLY INSTALLED UNVENTED CYLINDER WITH AN UNVENTED CYLINDER WITH AN UNVENTED CYLINDER WITH AN UNVENTED CYLINDER WITH AN INTERNAL AIR GAP INTERNAL AIR GAP INTERNAL AIR GAP INTERNAL AIR GAP

1. Before turning on the mains supply to the cylinder a hot water tap should be opened, preferable on the same fl oor or the fl oor below where the cylinder is located.

2. Turn on the supply to the cylinder and fi ll until water runs from the open hot water tap.

3. Turn off the supply to the cylinder and wait for the water to stop running from the open hot water tap.

4. Operate the temperature and pressure relief valve until water stops fl owing.

5. Close the hot water tap and temperature and pressure relief valve.

6. Connect an air pump to the Schrader valve, located on the pressure reducing water inlet valve.

7. Open the shut-off valve8. Pump air into the Schrader valve until a pressure of .7 bar is

reached.9. Remove the pump and close the shut-off valve.10. Turn the mains supply back on and bring the cylinder up to

working pressure.

REPLACING AIR SPACE IF LOST DURING SERVICE

1. Turn off the mains supply to the unvented hot water cylinder2. Open a hot water tap, preferable on the same fl oor or the

fl oor below where the cylinder is located.3. Operate the temperature and pressure relief valve until

water stops fl owing.4. Close the hot water tap and temperature and pressure relief

valve.5. Connect an air pump to the Schrader valve, located on the

pressure reducing water inlet valve.6. Open the shut-off valve7. Pump air into the Schrader valve until a pressure of 1.2 bar is

reached.8. Remove the pump and close the shut-off valve.9. Turn the mains supply back on and bring the cylinder up to

working pressure.

DRAINING DRAINING DRAINING DRAINING

Switch off electrical power to the immersion heaters and/or shut down the boiler. Close the stopcock valve to isolate the MHG unit.

Attach hosepipe to the drain cock having suffi cient length to Attach hosepipe to the drain cock having suffi cient length to take water to a suitable discharge point.take water to a suitable discharge point.

Open drain cock.Open hot water tap nearest MHG unit.Open hot water tap nearest MHG unit.If water fails to drain from the MHG unit, vent the system by If water fails to drain from the MHG unit, vent the system by opening the temperature and pressure relief valve.opening the temperature and pressure relief valve.

(Fig 15) INTERNAL EXPANSIONCOMMISSIONICOMMISSIONING DIAGRAMNG DIAGRAM

FAULT FINDING

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USERS INSTRUCTIONS USERS INSTRUCTIONS USERS INSTRUCTIONS USERS INSTRUCTIONS

Your MHG unvented hot water duplex stainless cylinder has been designed to give many years of trouble free service and is made from hygienic high grade steel. It includes a 3kW electric immersion heater which heats the water to 60°C once pre-heating of the solar system is completed (MHG solar only).

The fl ow temperature of the hot water can be set to your requirements on the immersion heater ideally 60°C. Higher temperatures can cause tripping of the high limit thermostat and introduces more energy loss from the cylinder.

When a hot tap is turned on there may be a short surge of water, this is quite normal with unvented systems and does not mean there is a fault.

When you fi rst fi ll a basin the water may sometimes appear milky. This is due to very tiny air bubbles in the water which will clear very quickly.

WARNING: If cold/warm water exits from the temperature and pressure relief valve

(TPV) or from the pressure relief valve (PRV) call your installer or the MHG customer service centre. If very hot water exits from either valve switch off the heat source immediately and isolate the electricity supply to the cylinder and separate heat source.

The solar system is confi gured to heat the water to its maximum economic temperature which may vary with outside temperature and weather conditions. The immersion may be programmed to operate during fi xed periods of the day or night.

If the hot water runs cool it may be necessary to manually switch on the immersion to heat the water – please see the relevant instructions for your alternative energy device.

Fault Fault Possible cause Remedy

No hot water No hot water 1. Mains supply off 1. Open stopcock

2. Strainer blocked 2. Strainer blocked 2. Turn water supply off, remove strainer and clean. (see 10.6) strainer and clean. (see 10.6)

3. Pressure reducing valve 3. Pressure reducing valve 3. Re-fi t with arrow pointing in (PRV) fi tted the wrong way direction of fl ow

Water from hot taps is cold Water from hot taps is cold 1. Programmer set to heating 1. Set programmer to call only or not switched on for hot water only or not switched on for hot water

2. Central heating boiler malfunction 2. Central heating boiler malfunction 2. Check boiler operation if faulty consult your boiler manufacturers instructions boiler manufacturers instructions

3. High limit thermostat has tripped 3. High limit thermostat has tripped 3. Check and re-set

4. Pump malfunction 4. Pump malfunction 4. Check wiring and/or plumbing connections to pump connections to pump

Intermittent water discharge Intermittent water discharge 1. Expansion vessel has lost its 1. Turn off stopcock open a hot through tundish on warm-up charge pressure water tap check vessel charge pressure and recharge to 3 bar pressure and recharge to 3 bar

Continuous water discharge Continuous water discharge 1. Pressure reducing valve (PRV) 1. Check pressure from PRV if not working greater than 3.5 bar replace cartridge 2. Expansion relief valve not seating correctly 2. Expansion relief valve not seating correctly 2. Manually lift the valve once or twice to clear any debris from the twice to clear any debris from the seat otherwise replace valve seat otherwise replace valve

3. Temperature and pressure relief 3. Temperature and pressure relief 3. Manually lift the valve once or valve not seating correctly twice to clear any debris from the seat otherwise replace valve seat otherwise replace valve.

1. Mains supply off

2. Strainer blocked strainer and clean. (see 10.6)

3. Pressure reducing valve

1. Programmer set to heating only or not switched on for hot water

2. Central heating boiler malfunction boiler manufacturers instructions

3. High limit thermostat has tripped

4. Pump malfunction connections to pump

charge pressure pressure and recharge to 3 bar

2. Expansion relief valve not seating correctly twice to clear any debris from the seat otherwise replace valve

3. Temperature and pressure relief seat otherwise replace valve

strainer and clean. (see 10.6)

boiler manufacturers instructions

connections to pump

water tap check vessel charge pressure and recharge to 3 bar

greater than 3.5 bar replace

twice to clear any debris from the seat otherwise replace valve

twice to clear any debris from the seat otherwise replace valve

WARNING: disconnect electrical supply before removing any electrical equipment cover.

WARRANTY

CONTACTS

SERVICING & MAINTENANCE

MHG Heating Ltd guarantee all electrical and mechanical controls supplied with the cylinder excluding the immersion for a period of 5 years from the date of purchase provide that they have been installed for their intended use by a competent person and have not been modifi ed in any way. The immersion(s) are guaranteed for a period of 2 years, excluding any failure caused by lime-scale.

In addition MHG Heating Ltd guarantees the stainless still inner hot water cylinder for a period of 25 years from the date of purchase against faulty material or manufacture provided that:

(a) The vessel has been installed by a competent person in accordance with this installation manual and all current regulations and codes of practice in place at the time of installation.

(b) It has been used solely for the purpose of heating potable water that complies with current (at the time of installation)EU standards and is not fed with water from a private source.

(c) It had not been modifi ed in any way.(d) It has not been subjected to excessive pressure or electrolytic action from dissimilar materials, or attack from any salt deposits.(e) It has been installed indoors in a frost-free environment.(f) The cylinder is connected to a public water supply maintained by a local water authority.(g) The warranty card is completed and returned to MHG Heating Ltd within 90 days of installation.

This warranty is not transferable. This warranty does not include claims due to frost or lime scale damage. Proof of purchase will be required against any claim. This guarantee does not affect your statutory rights.

MHG Heating LtdUnit 4, Epsom Downs Metro CentreWaterfi eldTadworthSurreyKT20 5LRTel: 0845 6448802Fax: 0845 6448803Email: info@mhgheating.co.ukWebsite: www.mhgheating.co.uk

Servicing and maintenance should only be carried out by a competent unvented hot water installer or MHG authorised personnel.

Before any work whatsoever is carried out on the installation, it must be isolated from the electricity supply.

Both the primary and secondary systems will contain very hot water that will scald, therefore care should be taken when opening any joints, seals or valves.

Only use spare parts authorised by MHG.The use of other parts will invalidate the warranty.

MHG operating using internal expansion will require period checking and recommissioning of the internal air gap - please see commission procedure for details.

Spare part numbers:

Expansion Vessel 24 litre SC07011 19 litre SC07002Expansion Vessel Bracket 24 litre SC07002 19 litre T&P valve 7bar 90°C SC0700415 - 22mm straight tundish SC060043Kw Immersion heater SC070011/1222mm pressure reducing valve kit SC0701522mm 2-port motorised valve SC06005Twin thermostat SC06006

For further assistance please contact the MHG Heating Ltd Customer Services Department.

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