UNIDO/SIRIM STANDARD

UNIDO/SIRIM

STANDARD

UNIDO/SIRIM XX:2021

ICS: 27.160

Solar water heating system - Design

specification

© Copyright 2021 UNIDO and SIRIM Berhad

UNIDO/SIRIM XX:2021

2 © UNIDO and SIRIM Berhad 2021 - All rights reserved

UNITED NATION INDUSTRIAL DEVELOPMENT ORGANIZATION (UNIDO) UNIDO is the specialized agency of the United Nations that promotes industrial development for poverty reduction, inclusive globalization and environmental sustainability. The mission of UNIDO, as described in the Lima Declaration adopted at the fifteenth session of the UNIDO General Conference in 2013, is to promote and accelerate inclusive and sustainable industrial development (ISID) in Member States. The relevance of ISID as an integrated approach to all three pillars of sustainable development is recognized by the 2030 Agenda for Sustainable Development and the related Sustainable Development Goals (SDGs), which will frame United Nations and country efforts towards sustainable development in the next fifteen years. UNIDO’s mandate is fully recognized in SDG-9, which calls to “Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation”.

SIRIM SIRIM Berhad is a premier total solutions provider in quality and technology innovations that helps industries and businesses to compete better through every step of the business value chain. SIRIM Berhad is the centre of excellence in standardisation, facilitating industries and businesses in enhancing their production and competitiveness, protecting consumers’ health and safety, and giving them the choice for quality products and services.

UNIDO/SIRIM STANDARD UNIDO/SIRIM Standard is developed according to SIRIM standardisation procedures, which are in line with international practices that ensure appropriate notification of work programmes and participation of interested parties. As a standards development organisation, SIRIM Berhad has extensive expertise in standards research and consultancy which helps industries and businesses meet local and international requirements and practices. UNIDO/SIRIM Standard is developed by UNIDO through collaboration with SIRIM which provides requirements, specifications, guidelines or characteristics that can be used to ensure that materials, products, processes and services are fit for their purpose. UNIDO/SIRIM Standard is developed through consensus by established committee, which consists of experts in the subject matter. The use of this standard is voluntary, and it is open for adoption by regulators, government agencies, associations, industries, professional bodies, etc. © Copyright 2021 For further info or enquiries, please contact: Training, Standards and Consultancy Department SIRIM STS Sdn Bhd 1, Persiaran Dato’ Menteri Section 2, P.O. Box 7035 40700 Shah Alam Selangor Darul Ehsan Tel: 60 3 5544 6314/6909 Fax: 60 3 5510 8830 Email: [email protected] http://www.sirimsts.my

UNIDO/SIRIM XX:2021

© UNIDO and SIRIM Berhad 2021 - All rights reserved i

Contents

Page Foreword ............................................................................................................................... ii 0 Introduction ............................................................................................................. 1 1 Scope ...................................................................................................................... 2 2 Normative references .............................................................................................. 2 3 Terms and definitions .............................................................................................. 4 4 Systems classification ............................................................................................. 5 5 General recommendations ...................................................................................... 5 6 Requirements .......................................................................................................... 6 7 Simulation ............................................................................................................... 7 Annex A Factory-made solar heating systems ................................................................ 17 Annex B Bacterial growth and safety in solar water heating (SWH) systems ................... 18 Bibliography ........................................................................................................................ 24

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ii © UNIDO and SIRIM Berhad 2021 - All rights reserved

Foreword This SIRIM Standard was developed by the Project Committee on Solar Water Heating System established by SIRIM Berhad. This standard was developed with the following objectives: a) to provide comprehensive document in accordance with the current technical requirements

for solar water heating system; b) to educate and create awareness among the stakeholders on solar water heating system

best practices; and

c) to provide guide on design specification best practices of solar thermal. There are other standards related to solar water heating system as listed below: UNIDO/SIRIM XX:2021, Solar water heating system - Installation guidance UNIDO/SIRIM XX:2021, Solar water heating system - Testing and commissioning UNIDO/SIRIM XX:2021, Solar water heating system – Operation and maintenance This standard will be subjected to review to reflect current needs and conditions. Users and other interested parties may submit comments on the contents of this standard for consideration into future versions. Compliance with this standard does not by itself grant immunity from legal obligations

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© UNIDO and SIRIM Berhad 2021 - All rights reserved 1

Solar water heating system - Design specification

0. Introduction

Solar water heating system is suitable for various applications such as domestic hot water heating, space heating, swimming pool heating, and commercial and industrial process heat purposes. For commercial and industrial process heat purposes, some of the usages include hospitals, hotels, guest houses, laundries, apartments, office buildings, dairy farms, commercial premises such as office buildings, indoor swimming pools and the food manufacturing industry. Solar water heating systems commonly available in the market are factory-made or custom-built systems. Factory-made systems are batch products with one trade name, sold as complete and ready to install kits with fixed configurations. Systems of this category are considered as a single product and assessed as a whole. In comparison, custom-built solar heating systems are either uniquely built or assembled by choosing from various components. Systems of this category are regarded as a set of components. The components are separately tested, and test results are integrated into an assessment of the whole system. The series of UNIDO/SIRIM Standard for solar water heating systems is applicable for the following. a) Small custom-built systems: All components and possible system configurations are

specified in the assortment file. Each possible combination of a system configuration with components from the assortment is considered one custom-built system.

b) Large custom-built systems: Uniquely designed by engineers, manufacturers or other experts for a specific situation.

Apart from the above, other systems are not described in the standards and may be available in different publications, such as MS 1367, which provides the specification for domestic solar water heaters. These UNIDO/SIRIM Standards on solar water heating systems were developed to provide standardised information on the requirements, specifications, or guidelines used by system designers, installers, and building owners when dealing with custom-built solar water heating systems.

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The scopes covered by the standards are as detailed in Figure 1.

Figure 1. Scopes of the solar water heating system standard

UNIDO/SIRIM Standards are developed by UNIDO through collaboration with SIRIM, which provides requirements, specifications, guidelines or characteristics that can be used to ensure that materials, products, processes and services are fit for their purpose. By having these standards, the relevant stakeholders will have a standardised document that provides the relevant industry's best practices for implementation. UNIDO/SIRIM Standards are developed through consensus by an established committee consisting of experts in the subject matter. The use of this standard is voluntary, and it is open for adoption by individuals, regulators, government agencies, associations, industries and professional bodies.

1. Scope This standard specifies system design for small and large custom-built solar heating systems for commercial and industry including residential buildings with a capacity of more than 700 L. This may include but not limited to drying (water-based), space heating and cooling, swimming pool heating or for large buildings such as multiple dwelling buildings.

2. Normative references The following normative references are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the normative reference (including any amendments) applies. MS 1597-2-21, Household and similar electrical appliances - Safety - Part 2-21: Particular requirements for storage water heaters

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MS IEC 60335-1, Household and similar electrical appliances - Safety - Part 1: General requirements ISO 9459-1:1993, Solar heating - Domestic water heating systems - Part 1: Performance rating procedure using indoor test methods ISO 9806, Solar energy - Solar thermal collectors - Test methods ISO/TR 10217, Solar energy - Water heating systems - Guide to material selection with regard to internal corrosion BS 5918:2015, Solar heating systems for domestic hot water - Code of practice for design and Installation EN 806-1, Specifications for installations inside buildings conveying water for human consumption - Part 1: General EN 806-2, Specifications for installations inside buildings conveying water for human consumption - Part 2: Design EN 809, Pumps and pump units for liquids - Common safety requirements EN 1993‑1‑1, Eurocode 3: Design of steel structures - Part 1-1: General rules and rules for buildings EN 1999‑1‑1, Eurocode 9: Design of aluminium structures - Part 1-1: General structural rules EN 12977‑1, Thermal solar systems and components - Custom-built systems - Part 1: General requirements for solar water heaters and combisystems EN 12977‑2, Thermal solar systems and components - Custom-built systems - Part 2: Test methods for solar water heaters and combisystems EN 12977‑3, Thermal solar systems and components - Custom-built systems - Part 3: Performance test methods for solar water heater stores EN 12977‑4, Thermal solar systems and components - Custom-built systems - Part 4: Performance test methods for solar combistores EN 12977‑5, Thermal solar systems and components - Custom-built systems - Part 5: Performance test methods for control equipment EN 16297‑1, Pumps - Rotodynamic pumps - Glandless circulators - General requirements and procedures for testing and calculation of energy efficiency index (EEI) Factories and Machinery Act 1967 (Act 139) JKR Standard Specification for Structural Steelwork IEA SHC Task 49, Technical Report A.1.2, Overheating prevention and stagnation handling in solar process heat applications

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3. Terms and definitions For the purposes of this standard, the following terms and definitions apply. 3.1 assortment

Complete list of components (collectors, stores, controllers, pumps, etc.), which a company offers for its solar water heating systems. NOTE: The “company” can be the manufacturer of all or of parts of the components in the assortment; this company can also be only a consulting engineer who just produces the technical documentation and purchases the components from suppliers.

3.2 assortment file

Technical documentation file for small custom-built systems of a company, which includes:- the complete assortment for small custom-built systems;- the complete description of all system configurations;- the complete description of all marketed combinations of system configurations and components including the component dimensions and number of units;- further technical information. 3.3 large custom-built system Solar heating system for hot water preparation and/or space heating/cooling, which is designed for a specific situation by combining various components to a unique system.

NOTE. In general, the collector area is greater than 30 m2 and the storage volume is greater than 3 m3.

3.4 small custom-built system Modular solar heating system of the remote storage type for hot water preparation and/or space heating and/or cooling.

NOTES: 1. The system has a well-identified configuration (see 3.5). It is assembled from components chosen from the market and described in an assortment file prepared by a company.

3.5 space heating Delivery of useful heat from a heat source into a surrounding or adjacent living space. 3.6 system configuration Characteristics of a solar heating system including its hydraulic scheme (hydraulic connections between the collector array, the storage(s) and other components) and its control concept. NOTE. Systems differing by any other parameter, by the type or dimensions of the used components or the controller settings are considered to have the same configuration.

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4. Systems classification 4.1 Small custom-built systems

Small custom-built systems are classified as described in ISO 9459-1:1993, Clause 5. According to the purpose of these systems, the additional classification in Table 1 applies.

Table 1. Classes of small custom-built systems according to their purpose

Class Purpose

A domestic hot water preparation only

B space heating only

C domestic hot water preparation and space heating

D others (e.g. including cooling, swimming pool heating)

4.2 Large custom-built systems Large custom-built systems are classified in accordance with Table 2.

Table 2. Classification of large systems

Class Purpose

A A system in which the storage(s) and the collector array(s) are located in one building for which the heating or cooling is provided. No storage and no thermal energy distribution network outside the building are included.

B A system which consists of a central heating or cooling plant and one or more collector array(s). The thermal energy is transported via a distribution network to the plant and/or to other buildings. No storage is included.

C A large custom-built system which mainly consists of one or more large collector array(s) and in which the thermal energy is transferred to a storage or directly into a distribution network.

D Others

NOTE. Descriptions of factory-made solar heating systems are described in Annex A.

5. General recommendations 5.1 General layout of main components The selection of storage vessels should be based on their intended location in a facility, with consideration to reduce pipe lengths to the collectors and the need of a backup heat source for the SWH system, as well as proximity to the draw-off locations. A decision on the location of the main components should be made to achieve the best overall performance of the entire system.

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Note. The combination of pressures and volumes intended for a system will determine whether the requirements of Factories and Machinery Act 1967 (Act 139) apply, which might require further tests of the design by a third party.

5.2 General considerations for layout of solar collectors A solar collector should be located where it is least shaded, tilted up from horizontal and facing towards south, and at the shortest practicable distance from the heat storage. Collectors may be located in or on a variety of building components, such as roofs and ground. Access for inspection or maintenance should be provided without detrimentally affecting the building’s appearance or aesthetics. Locations near to trees should be avoided where possible, as these are likely to cause significant overshading, with the potential for leaves and tree sap to build up on the collector glazing. Consideration should be given to future tree growth. Locations near to high-rise buildings should be carefully assessed for shading potential. NOTE. Large reflective landscape features, such as glazed facades or water features, located in front of inclined collectors can improve annual performance.

5.3 Mitigation of bacterial growth The potential for accumulation and growth of microorganisms, such as Legionella, should be determined by a risk assessment and appropriate mechanisms for microbial control should be identified, e.g. periodic heating of storage vessels, pipes to disinfection temperatures or/and continuously to the cold feed source such as by ultraviolet (UV) disinfection or other treatment, in accordance with Annex B.

5.4 Layout of storage vessels The design should take into account the strong effect of solar storage on the performance of the whole solar heating system, principally the size of solar storage and stratification effect.

6. Requirements 6.1 General

6.1.1 Suitability for drinking water All materials coming into contact with water intended for human consumption shall present no risk to health at temperature up to the maximum working temperature. They shall not cause any change of the drinking water in terms of quality, appearance, smell or taste. The product which is in permanent or in temporary contact with water intended for the conveyance of water for human consumption shall comply with MS 1583 series for non-metallic products and AS/NZS 4020 for metallic products, whichever applicable.

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6.1.2 Water contamination The system shall be designed to avoid any cases of water contamination. 6.1.3 High-temperature protection 6.1.3.1 Scald protection System which the temperature of the hot water delivered to the user can exceed 60 °C, shall be fitted with an automatic cold-water mixing device, or any other device to limit the temperature to a maximum of 60 °C. 6.1.3.2 High-temperature protection for materials The design of the system shall ensure that the system does not exceed the highest permissible temperatures to which the system components may be exposed, taking into account pressure conditions, if relevant. According to the EN ISO 9806:2017 test report, maximum temperature in the collector is the collector stagnation temperature. In cases under stagnation conditions, where steam or hot water can enter the collector pipes, pipework, distribution network or heat exchanger(s), measures/care should be taken according to IEA SHC Task 49, Technical Report A.1.2, Overheating prevention and stagnation handling in solar process heat applications. NOTE. Maximum temperature in the rest of the collector loop depends on safety valve pressure setting and the actual fluid.

Guidelines for the determination of the highest temperature, depending on safety valve and fluid, should be provided. 6.1.3.3 Overheating prevention Method of pre-cooling shall be used to prevent overheating at solar loop. Below are the methods: a) Drain-back system Drain the entire system at a pre-defined temperature below the manifold of the collector field to avoid overheating of the heat transfer medium and steam formation. b) Heat dissipator

i) Active cooling For certain system designs, active re-cooling devices should be used to avoid stagnation of the system or overheating system components up to their maximum temperature resistance (e.g., insulation, valves, pumps, and membrane of expansion tank).

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ii) Passive cooling For certain system designs, finned-tube heat exchangers should be used to significantly reduce the steam range and hence the steam volume (see Figure 2).

Figure 2. Possible placement of dissipators like air coolers in the solar primary loop

NOTE. For more detailed explanation on pre-cooling method, refer to IEA SHC Task 49, Technical Report A.1.2, Overheating prevention and stagnation handling in solar process heat applications. 6.1.4 Reverse circulation prevention The installation of the system as described in the hydraulic scheme shall ensure that no unintentional reverse flow occurs in any hydraulic loop of the system. 6.1.5 Pressure resistance The storage tank and heat exchangers shall withstand at least 1.5 times the manufacturer's stated maximum individual working pressures. The system shall be designed so that the maximum allowable pressure of any component (material) in the system is not exceeded, taking into account temperature conditions, if relevant. Every closed circuit in the system shall contain a safety valve. This safety valve shall withstand the highest temperature that can be reached at its location. It shall conform to EN 1489. If thermostatic valves are used, these shall conform to EN 1490. In addition, collector arrays of large custom-built systems should be designed in a way so that they can also withstand high-pressure peaks of short duration, e.g. arising from sudden evaporation of liquid within the collectors at the beginning of stagnation. NOTE. If, due to stagnation, considerable heat transfer medium quantities in the collector array evaporate, pressure peaks may occur due to high flow velocities of steam or liquid. These pressure peaks may significantly exceed the release pressure of the safety valve.

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6.1.6 Electrical safety See MS IEC 60335-1 and MS 1597-2-21. There shall be means to interrupt the power supply to the pump(s) manually. 6.2 Materials It shall be stated in the documentation for the installers that materials exposed to weathering shall be resistant to rodents, birds, UV radiation, thermal shocks and other weather conditions over a prescribed lifetime. All materials used in the collector loop should comply with ISO/TR 10217 in order to avoid any internal corrosion. 6.3 Components and pipework 6.3.1 Collector and collector array

The collector shall meet the requirements given in EN 12975-1.

For parts and joints of the collector array, see 6.3.8.

Care should be taken in order to ensure long-term durability and tightness of the collector joints.

If the collector array includes several parallel connected rows of collectors, the maximum divergent of the mass flow rate per unit collector area of each row should not exceed 20 % of the nominal flow rate per unit collector area of the whole array, unless explicitly stated by the manufacturer.

NOTE. In general, balanced flow can be reached by means of hydraulic adjustment of collectors and tubes. If this is not possible, the flow can be controlled by suitable fittings.

6.3.2 Supporting frame The manufacturer shall state the maximum possible loads for their metallic supporting frame in accordance with JKR Standard Specification for Structural Steelwork, EN 1993‑1‑1 and EN 1999‑1‑1. For non-metallic supporting frames, the maximum acceptable load shall be stated. This shall be mentioned in the documents for the installer. Installation of the system is dependent on national requirements. Guidelines can be found in UNIDO Solar thermal system - Installation guidance. 6.3.3 Collector and other loops Collector and other loops shall be able to withstand expansion/contraction due to thermal mechanical influences (e.g. faulty equipment, stagnation and thermal shock).

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Marking of water flow shall be included to differentiate the piping for supply and return at the primary and secondary loop. Example is as Figure 3 below.

Key Supply

Return

Figure 3. Example of marking of water flow direction

6.3.4 Circulation pumps See EN 809, EN 16297‑1 and EN 12977‑5. 6.3.5 Expansion vessels 6.3.5.1 General Generally, expansion vessels shall be included in the design using pressurised tanks. For certain system designs, e.g. non pressurised storage tank, a separate expansion vessel in the collector loop is not necessary, on condition that the integrated expansion facility is adequately designed to fulfil its task, in terms of volume, temperature and pressure resistance. 6.3.5.2 Small systems

The expansion device of the collector loop shall be dimensioned in such a way that even when solar irradiance is at a maximum after an interruption of the power supply to the circulation pump in the collector loop, operation can be resumed automatically after power is available again and the absorber is refilled with liquid, i.e. vapour has re-condensed.

The expansion vessel shall be able to compensate for the thermal expansion in the whole loop plus the volume of the heat transfer medium in the whole collector array. This includes all connection pipes between the collectors plus 10 % of this volume.

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Alternatively, when the system does not automatically resume operation after stagnation conditions, a warning shall be added to the operating instructions.

The manufacturer's instructions shall be followed.

6.3.5.3 Large systems

There are no requirements for large systems. However, it is recommended that expansion devices for such systems are designed to take into account all potential thermal expansion.

6.3.6 Heat exchangers

See EN 307.

If the system is intended to be used in areas with high water hardness and at temperatures above 60 °C, heat exchangers in contact with drinking water shall be designed so that scaling is prevented or there shall be a means for cleaning.

NOTE. High temperature difference between the metal surface of the heat exchanger and the surrounding drinking water mainly causes scaling. This can be avoided by increasing the heat exchanger area.

Any heat exchanger(s) between the collector loop and the hot water supply system should not reduce the collector efficiency indicated by the manufacturer.

When the solar gain of the collector has reached its highest possible value, the reduction of the collector efficiency induced by the heat exchanger should not exceed 10 % (absolute). A method for calculating this reduction is given in EN 12977-2. If more than one heat exchanger is installed, this value should also not be exceeded by the sum of reductions induced by each one of them. This criterion also applies if a load-side heat exchanger is part of the system.

If only one heat exchanger is used between the collector loop and the storage of a small custom-built system, the heat transfer capacity rate of the heat exchanger per unit collector area should not be less than 40 W/(K x m2) under typical operating conditions.

6.3.7 Water storage(s)

Storage of small custom-built solar heating systems should be tested as described in EN 12977-3. The stand-by heat loss capacity rate, (UA)sb,s,a of storage of small custom-built systems should not exceed the value given by Formula (1):

(UA)sb,s,a

=0.16 √Vn (1)

where (UA) sb,s,a is the stand-by heat loss capacity rate of the storage, in Watts per Kelvin; and Vn is the nominal volume of the store, in litres.

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There is no requirement on the heat loss rate of storage of large custom-built systems. However, it is recommended that Formula (1) be applied to such systems as well. 6.3.7.1 Nominal storage volume The nominal storage volume (Vn) is measured as follows:

a) The mass of empty water heater is to be measured; the mass of taps on inlet and/or outlet pipes shall be considered.

b) Then the storage is filled with cold water in accordance with the manufacturer’s

instruction at cold water pressure. The water supply is then cut off.

c) The mass of filled water heater is to be measured.

d) The difference of the two mass (mact) is to be converted into the volume in litres by using the Formula (2).

Vn= mact

0.9997 (2)

where mact is the mass in kg.

This volume is to be reported in litres to the nearest one-tenth litres.

Alternatively, the nominal storage volume can be determined in accordance with EN 12897. 6.3.8 Pipework The pipe length of the system shall be as short as possible. The pipes and fittings shall be selected from materials that are compatible with the components included in each loop, according to the fluid of the loop as specified in ISO/TR 10217. The design of the system and the used materials shall be such that there is no possibility of clogging and lime deposit in its circuits which would significantly deteriorate the system's performance during its lifetime. The pipework for drinking water shall comply with the requirements specified in EN 806-1 and EN 806-2. The materials for pipes and fittings shall be able to withstand the maximum operating temperature (stagnation conditions) and pressure. The pipework shall withstand thermal expansion without any damage or detrimental deformation. Venting of the system (removal of unwanted gasses) shall be possible. No automatic vents shall be placed in parts of the collector loop where vapour can occur (e.g. the top of the collector array), except:

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a) where a manual valve is placed between the pipe and the automatic vent, this valve

being closed during normal operation of the system; or

b) where a warning is added to the operating instructions indicating that the system does not automatically resume operation after stagnation conditions.

6.3.9 Thermal insulation The thermal insulation of all connecting pipes and other components of the system shall comply with the requirements given in EN 12828. The collector loop shall be insulated without any gaps between the components. For example, where thermal bridges are concerned, incorrectly installed mounting clamps should be avoided. In particular, the thermal insulation of the pipework shall be from materials which are resistant to the maximum temperature of the circuit and resistant to deformation and remain functioning. If the insulation is installed outdoors, it shall be protected against (or resistant to) solar radiation, environmental conditions, ozone and any mechanical impact or deformation. Insulated pipes for underground installation shall comply with EN 253. 6.3.10 Control equipment See EN 12977-5. 6.3.11 Monitoring On-site monitoring system shall be installed for performance monitoring and to detect any abnormalities or possible faults in the system. It is recommended to log sufficient data for related parameters such as temperature and flow rate to measure the performance. Data required for system performance monitoring are as follows: a) Primary loop

i) Thermal energy ii) Flow rate iii) Pressure iv) Supply and return temperature

b) Storage

i) Temperature ii) Pressure

c) Secondary loop

i) Supply and return temperature

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d) Weather station

i) Irradiance ii) Wind direction iii) Wind speed iv) Ambient temperature

6.4 Safety equipment and indicators 6.4.1 Safety valves Each section of the collector array that can be shut off and every closed circuit in the system shall be fitted with at least one safety valve of suitable dimension. The safety valve shall be resistant to the temperature conditions which it is exposed to, especially the highest temperature that can occur and shall resist the heat transfer fluid. The safety valve shall be dimensioned so that it can release the highest flow of hot water or steam that can occur. The dimension of the safety valve(s) shall be confirmed by any suitable means. 6.4.2 Safety lines and expansion lines The safety line shall not be capable of being shut off or deformed in such a way that would reduce its discharge capacity below that necessary to maintain the system pressures to be below the stated maximum for hot water or steam escaping from the safety lines. The safety line and expansion line shall be dimensioned so that for the highest flow rate of hot water or steam that can occur, the maximum allowed pressure is not exceeded at any place in the collector loop, also taking into consideration the pressure drop in these lines. The dimensions of the safety line and expansion line shall be confirmed by calculation or experimental means. The junction of the expansion line and the safety line shall be set out in such a way that any accumulations of dirt, scale or similar impurities are avoided. 6.4.3 Blow-off lines The blow-off lines shall be laid in such a way that they cannot freeze up and that no water can accumulate within these lines. The orifices of the blow-off lines shall be arranged in such a way that any steam or heat transfer medium issuing from the safety valves does not cause any risk for life, materials or environment. 6.4.4 Storage isolation valve Storages of large custom-built systems with a volume of more than 20 m3 shall be fitted with isolation valves or other suitable devices to stop unintentional outflow of the storage contents in cases of system failure. 6.4.5 Indicators and sensors 6.4.5.1 Indicators for collector loop flow The system shall be fitted with indicators to confirm the collector loop circulation. This could be a flow rate indicator, two thermometers which indicate the actual flow and return temperatures of the collector loop or other appropriate method.

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6.4.5.2 Pressure gauge For the indication of the system pressure in case of filled systems, collector loops shall be fitted with a pressure gauge at a visible spot of the installed system. Pressure gauges shall show the permissible operating range of overpressure in the system or at least the filling pressure of the system. 6.4.5.3 Heat meter There are no requirements for small custom-built systems. For large custom-built systems, at least the collector loop shall be equipped with a heat meter. 6.4.5.4 Weather station The following devices shall be included in the design of solar water heating system.

a) Pyranometer - Irradiance b) Anemometer - Wind speed c) Wind vane - Wind direction d) Ambient temperature sensor

7. Simulation The performance of the system can be predicted by means of a validated simulation programme. The system parameters shall be taken from the design requirements. Simulation programme may be in simulation software, excel spreadsheets and other means.

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Annex A (informative)

Factory-made solar heating systems A.1 EN 12976‑1 and EN 12976‑2 describe factory-made solar heating systems. A.2 Factory-made solar heating systems are batch products with one trade name, sold as complete and ready to install kits, with fixed configurations. Systems of this category are considered as a single product and assessed as a whole. If a factory-made solar heating system is modified by changing its configuration or by changing one or more of its components, the modified system is considered as a new system. Requirements and test methods for factory-made solar heating systems are given in EN 12976‑1 and EN 12976‑2.

Table A.1 shows the division for different system types.

Table A.1. Division for factory-made and custom-built solar heating systems

Factory-made solar heating systems (EN 12976‑1 and EN 12976‑2)

Custom-built solar heating systems (EN 12977‑1, EN 12977‑2, EN 12977‑3, EN

12977‑4 and EN 12977‑5)

Integral collector-storage systems for domestic hot water preparation

Forced circulation systems for hot water preparation and/or space heating/cooling, assembled using components and configurations described in a documentation file (mostly small systems)

Thermosiphon systems for domestic hot water preparation

Forced circulation systems as batch product with fixed configuration for domestic hot water preparation

Uniquely designed and assembled systems for hot water preparation and/or space heating/cooling (mostly large systems)

NOTES: 1. Forced circulation systems can be classified either as factory-made or as custom-built, depending on the market approach chosen by the final supplier. 2. The performance for both factory-made and custom-built systems for domestic hot water preparation are tested under the same set of basic reference conditions as specified in EN 12976‑2:2017, Annex B and in EN

12977‑2:2018, Annex A, respectively. In practice, the installation conditions may differ from these reference conditions. 3. Solar heating systems for both heating and cooling can so far not be performance tested; if the cooling option is not considered, then the solar heating system can be performance tested as a space heating system.

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Annex B (normative)

Bacterial growth and safety in solar water heating (SWH) systems

NOTE. The subject of Legionella is covered extensively in BS 8580, but this does not specifically cover preheating of the cold feed water or the addition of heat from solar primary circuits. The risk reduction measures indicated in this Annex are intended to clarify to the assessment of volumes of dedicated solar storage.

B.1 General Irrespective of the source of heat for providing hot water, cold feed water should typically start at below 45 °C to reach the intended target of hot water draw-off temperature, typically 45 °C to 60 °C.

The vessel that contains dedicated solar storage of water may be considered as preheating the cold feed water before passing the water to receive additional heat from a backup heat source, which completes the heat treatment before distribution as hot water. NOTE. Throughput and residence times are similar to a non-solar system, but if water is kept still for several days without draw-off at temperatures between 20 °C and 46 °C and where a biofilm is present on the walls containing the water, bacteria such as Legionella can start to colonise on the biofilm. These bacteria are already present intermittently in the cold feed in low concentrations and normally pass through cold and hot water supplies with little effect.

During typical occupancy, the volume of water dedicated for solar storage should pass through the backup heating in less than one day. Non-operational or plant shutdown periods will exceed this and should be considered in the risk assessment. NOTE. For these reasons, cold feed and preheated water is not suitable for distribution until its temperature has been raised to a sufficient level and for sufficient time as to minimise or sterilise bacterial growth. In buildings with appliances that produce an atomised spray that is likely to be inhaled from hot water terminals, e.g. mixer showers, there is a higher risk of inhalation of bacteria such as Legionella if that water has not been fully treated. The highest risk of infection is to people who are immune suppressed, such as those in hospitals. In buildings where there are long runs of hot water pipes (dead legs) or unused T-junctions (dead-ends), there is a much higher risk of bacterial growth irrespective of the heating sources.

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B.2 Risk assessment B.2.1 General A risk assessment should be carried out for every installation of SWH system. Where any part of the system already exists, an on-site inspection should be carried out by a competent, experienced person(s). Where the building or SWH system has yet to be built, the person doing the inspection should be skilled enough to understand drawings of the proposed system. A minimum of the following components should be assessed: a) location and size of the cold feed; b) location, size and quality of any existing cold-water storage (CWS) cisterns, including

examination of silt build-up; c) daily, weekly and annual regime of hot water use; d) risk of immunosuppressed persons using mixer showers or spray mixer taps supplied by

the storage; e) type, thermostatic response and power output of any backup hot water heating; f) length, diameter and insulation of hot water pipework; g) length of time for furthest hot water outlet to reach at least 50 °C; and h) presence of any secondary return pumped circulation systems. The risk assessment should provide a basis for quantifying and recording the bacterial risk. The scoring method should be the responsibility of the person completing the risk assessment and an example is given in Figure B.1. System design should have no greater risk of bacterial growth reaching atomised hot water terminals than would otherwise occur without solar heating. An overall positive score should be sought, and Table B.1 should be adapted for each application. NOTES: 1. Some measures can cause extra use of electricity or backup hot water heating to the extent that the energy benefit of the SWH system becomes nullified. 2. Storage de-stratification rarely succeeds as sufficient heat does not reach the bottom of storage vessel, i.e. where sediment biofilm exists. Where storage vessels are to be sterilised, see Table B.1.

UNIDO/SIRIM XX:2021


Table B.1 Specimen bacterial risk assessment overview such as for Legionella

Features of hot water system Typical score if item present

Example dwelling with twin-coil tank and automatic boiler

Absence of atomisation of hot water (e.g. showers, spray taps or

spray bidets)

+++ 0

Solar preheating in series with backup heater prior to hot water distribution (for example, solar

store or combination boiler)

+ +

Solar preheating in parallel with backup heater direct to hot water

distribution (for example, combination boiler with bypass

valve)

− − − 0

Diverter valve in parallel with backup heater

− − 0

Downstream disinfection of hot water on a periodic basis

See Table B.2 +++

Upstream disinfection of store on a periodic basis

See Table B.2 0

Dead legs − 0

Dead ends − − − 0

Thermostatic mixing valve (TMV) set permanently to less than 43 °C

at shower or spray tap

− 0

Central TMVs with less than 55 °C distribution

− 0

Greater than 55 °C hot water distribution

++ ++

CWS and/or part of cold feed not meeting regulations

− 0

Peak hot water draw-off exceeding re-heat of backup heat source

− 0

Dedicated solar storage more than daily hot water use

− − 0

Secondary pumped return at > 55 °C to include shower and

spray taps

++ 0

Heat exchanger hot water content less than 15 L

+ 0

Chlorine permanently added on site to cold feed

+++ 0

Non-operational or shutdown exceeding four days

− − − −

Inspection hatch and cleaning regime for all storage vessels

++ 0

Total N/A +++

UNIDO/SIRIM XX:2021


Table B.2 Specimen bacterial risk assessment for disinfection temperatures and times

Temperature (°C) Residence time (min)

Above 55 °C >3 h +++

Above 55 °C >2 h ++

None of above and high flush-rate +

None of above and typical flush-rate Neutral = 0

None of above and low flush-rate − − −

B.2.2 Disinfection of dedicated solar storage The surfaces of the dedicated solar storage container should be disinfected periodically where the need for this is identified by a risk assessment. It occurs more regularly with higher performance collectors. The frequency and timing of disinfection should be chosen in accordance with the hot water usage patterns, peak draw-off time and the relative power of the backup hot water heater. NOTES: 1. Where a backup heat source is chosen for disinfection, it implies that the volume is no longer dedicated to only the storage of solar energy, which can result in loss of solar performance and increased storage losses. 2. In some cases, it is almost impossible to disinfect the base of a container where a draw-off is maintained due to the continual influx of the cold feed. A weekly disinfection regime might be sufficient in many instances. Many solar controllers provide a thermostatic and timer relay facility (a Legionella switch) to maintain a regular disinfection with least reduction of solar contribution. 3. For combined tanks heated to 60 °C daily and with the backup heated volume exceeding the design daily hot water load, solar preheated water is likely to occupy the backup zone for sufficient time to achieve thermal inactivation of the bacteria such as Legionella.

Where the base of the combined tank is to be disinfected, it should be attempted during periods of low draw-off rate as indicated in 4.14.2 of BS 5918:2015. Where the SWH system has a secondary circulation system, a motorised valve connecting the hot water return pipe to the cold feed may be used. NOTE. The motorised valve can be controlled separately from the circulator (e.g. a time switch, enabled for several hours once per week). Systems without return circulation can use a shunt pump between hot outlet and the cold inlet controlled in similar manner.

Separate preheated storage prior to storage calorifiers provide superior residence time and temperature bacterial control as compared to instantaneous heaters, so store disinfection requirements similar to combined tanks may be used. NOTE. Non-storage calorifiers and instantaneous appliances might require higher temperatures and/or more frequent disinfection. Water disinfection for showers is particularly important because of its aerosol effect. The use of flow limiters to maintain a target temperature might be required, particularly for instantaneous appliances, e.g. combi-boilers, single point electric heaters.

There is higher bacterial risk with large dedicated solar storage and intermittent draw-off patterns. A cleaning hatch to facilitate routine inspection and cleaning may be specified.

UNIDO/SIRIM XX:2021


NOTES: 1. Insulation to the base of storage vessels can maintain higher temperatures. 2. The use of low power or low temperature backup heat sources, such as solid fuel stoves or heat pumps, might require an additional electric immersion heater to ensure disinfection under peak draw-off rates.

B.2.3 Bypass of backup heating Automatic or manual diverter valves are sometimes used with a separate preheated cylinder (referred to as “sun-to-tap” systems) that acts to bypass preheated water past the backup heater. This arrangement should be avoided, taking into account the following: a) the disinfecting SWH storage or other heat source is bypassed; b) the motorised valve or thermostat might fail with the valve in the open position; c) (motorised) valve materials can be incompatible with secondary water; and d) the SWH cylinder can continue to heat to 60 °C, irrespective of solar storage with resultant

loss of heat. The valve should limit the inlet temperature to any instantaneous appliance in accordance with 4.6c) of BS 5918:2015. B.3 Scalding and safety issues NOTE. The temperatures used to treat preheated secondary water can present a scalding risk. High hot water temperatures can also encourage limescale formation (see B.4) and accelerated metallic corrosion with some water types. The risks of bacteria control and protection against scalding are closely related. Some measures intended to minimise scalding increase bacterial risks.

Storage vessels over 25 L capacity should be prevented from exceeding 100 °C in accordance with BS 8580 for vented and BS EN 12897 for unvented cylinders. Unvented cylinders should be kept < 75 °C to prevent nuisance cut-outs from safety thermostats. A thermostatic mixing valve (TMV) in accordance with BS EN 15092 may be fitted to reduce scalding risks. This should be installed within 450 mm of the point of use of the hot water to reduce the hot water outlet temperatures. Where used in central locations, any TMV should be adjusted to allow mixed water temperature outlets to achieve a temperature of between 55 °C and 60 °C. The hot water draw-off rate should not be unduly affected and any safety vents should not be obstructed. NOTES: 1. Instead of using a centrally-mounted TMV, a system can be specified to be “hydraulically secure”, i.e. that the primary input of solar heat can be thermostatically controlled without requiring user intervention or release of transfer fluids. 2. Keeping components in contact with secondary water below 60 °C can reduce scalding issues although this might conflict with bacterial protection.

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B.4 Limescale Limescale deposition on heat exchange surfaces decreases system performance over time unless control measures are in place. In high-risk areas, the temperature of the stored water should be controlled to lower limits as the rate of deposition rapidly increases with temperature. Higher temperatures of storage allow more solar energy to be stored per litre, but can also increase the scalding risk, interfere with DHW terminal devices and reduce the life of components. Solar primary systems should allow accurate adjustment of maximum storage temperatures through the use of an electronic thermostatic control. A means of physically removing limescale deposition may be provided as part of a normal service, e.g. cleaning hatches located near the heat exchanger or using demountable plate exchangers. NOTE. Keeping components in contact with secondary water below 60 °C can reduce limescale deposition, although this might conflict with bacterial protection.

UNIDO/SIRIM XX:2021


Bibliography [1] EN 12976‑1:2017, Thermal solar systems and components - Factory made systems -

Part 1: General requirements [2] EN 12976‑2:2017, Thermal solar systems and components - Factory made systems -

Part 2: Test methods

© UNIDO and SIRIM Berhad 2021 - All rights reserved

Acknowledgements SIRIM Berhad would like to thank the members of the Project Committee on Solar Water Heating System who have contributed their ideas, time and expertise in the development of this standard. Prof. Dato’ Dr. Kamaruzzaman Sopian (Chairman)

Universiti Kebangsaan Manalysia (Solar Energy Research Institute (SERI))

Prof Dr Sohif Mat (Deputy Chair) Independent expert

Ts Dr Amir Abdul Razak (Project Leader)

Universiti Malaysia Pahang (Faculty of Mechanical and Automotive Engineering Technology)

Ts Norfaizah Nasir (Technical Secretary)/ Ms Zulaikah Zulkifely (Technical Secretary)/ Ms Nor Azwamiza Abu Samah (Technical Secretary)

SIRIM STS Sdn Bhd

Ir Dr Abdul Muhaimin Mahmud/ Mr Mohd Quyyum Ab Rahman

Jabatan Kerja Raya Malaysia (Cawangan Kejuruteraan Elektrikal)

Ir Ahmad Ridzauddin Ibrahim/ Ir Ts Faiz Fadzil

Jabatan Kerja Raya Malaysia (Cawangan Kejuruteraan Mekanikal)

Ir. Dr. Khairul Azmy Kamaluddin/ Ir. Noor Muhammad Abd. Rahman/ Ms W Fatin Zuharah W Musthapa

Kementerian Kesihatan Malaysia

Dr Rohaya Md Zin/ Mr Mohd Faisal Zulkapli

SIRIM Berhad

Ms Salwa Denan SIRIM STS Sdn Bhd

Mr Kong Kam Onn (Edison)/ Mr Mohammad Kamil bin Abdullah

Solar District Cooling Sdn. Bhd.

Mr Zulkiflee Umar/ Mr Mohamed Nadhir Zainal Abidin

Suruhanjaya Tenaga

Mr Ishamuddin Mazlan

Sustainable Energy Development Authority Malaysia (SEDA Malaysia)

Prof. Madya Dr. Nofri Yenita Dahlan Universiti Teknologi MARA (Faculty of Electrical Engineering)

Ir. Ts. Dr. Baljit Singh a/l Bhathal Singh

Universiti Teknologi MARA (Faculty of Mechanical Engineering)

© JKR Malaysia and SIRIM Berhad 2020 - All rights reserved

Dr Azmi Idris/ Ms Hashimah Hasan/ Mr Ahmad Zafuan Mohamed Kassim

United Nations Industrial Development Organization (UNIDO)

Ir. Dr. Saiful Hasmady bin Abu Hassan Universiti Tenaga Nasional (Dept of Mechanical Engineering)

Prof. Ir. Dr. Haslenda Hashim

Universiti Teknologi Malaysia (School of Chemical & Energy Engineering)

Assoc Prof Ts.Dr. Haslinda Binti Mohamed Kamar/Dr Aminuddin Saat

Universiti Teknologi Malaysia (School of Mechanical Engineering)

Mr Azhar Md Isnin Zamatel Sdn Bhd

© UNIDO and SIRIM Berhad 2021 - All rights reserved

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