A pressure relief valve (P) (spring loaded safety valve set to operate at 3 bar) must be fitted to the heating flow pipe as close as possible to the boiler.
An expansion vessel (B) should be fitted to the heating return pipe close to the boiler and pressurised for the system volume according to the instructions supplied with the vessel.
A pressure gauge (G) (3 bar min.) must be fitted to the heating flow pipe.
An automatic vent (N) must be fitted
Plastic pipework
Do not use plastic pipework on sealed systems.
Plastic pipework used for underfloor heating must be correctly controlled with a thermostatic blending valve limiting the temperature of the circuits to approx. 50ºC. The pipework from the boiler to the blending valve must be in copper or steel (protected from corrosion) if used in a sealed primary water system.
Primary system/connections/valves
Do not use galvanised pipes or radiators.
All system connections, taps and mixing valves must be capable of sustaining a pressure up to 3 bar.
Radiator valves should conform to BS 2767:10.
All other valves should conform to BS 1010.
On new installations TRVs must be used on all radiators except the radiator where the room thermostat is sited, this must be fitted with lockshield valves and left open. All boiler replacement installations should have TRV’s fitted to radiators at least within the sleeping accommodation.
An automatic bypass valve must be connected between the heating flow return where TRVs are used on all radiators.
Drain cocks are required at all the lowest points on the system.
Air vents are required at all the high points on the system.
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