BS/EN 12977-1-2018 pdf download.Thermal solar systems and components- Custom built systems Part 1: General requirements for solar water heaters and combisystems.
6.2.4.2 High-temperature protection for materials
The design of the system shall ensure that the highest permissible temperatures to which the system components may be exposed are not exceeded, also taking into account pressure conditions if relevant.
Maximum temperature in the collector is the collector stagnation temperature according to the EN ISO 9806:20 17 test report.
Care should be taken in cases where under stagnation conditions steam or hot water can enter the collector pipes, pipework, distribution network or heat exchanger(s) (see [4J).
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.
6.2.5 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.
6.2.6 Pressure resistance
The storage tank and heat exchangers shall withstand at least 1,5 times the manufacturer’s stated maximum individual working pressures.
The drinking water circuit shall withstand the maximum pressure required by national/European drinking water regulations for open-vented or closed drinking water installations.
The system shall have been designed in such a way that the maximum allowed pressure of any component (material) in the system is never exceeded, taking into account temperature conditions if relevani
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.
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.
6.4.2 Supporting frame
The manufacturer shall state the maximum possible loads for their metallic supporting frame in accordance with EN 1993-1-1 and EN 1999-1-i.
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 EN 1991-1-3 and EN 1991-1-4.
6.4.3 Collector and other loops
Collector and other loops shall be able to withstand expansion/contraction due to thermal mechanical influences.
6.4.4 Circulation pumps
See EN 809. EN 16297-1 and EN 12977-5:2018.
6.4.5 Expansion vessels
6.4.5.1 General
For certain system designs, e.g. drain-back systems, 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.
6.4.5.2 Open-vented expansion vessels
Each open system shall be provided with an expansion vessel or similar means, the volume of which shall be dimensioned so that It is capable of absorbing at least the entire expansion of the heat transfer medium between the lowest and the highest possible operating temperature. BS/EN 12977-1-2018 pdf download.