Conservation of fuel and power: Approved Document L, Volume 2 — Buildings other than dwellings

L1(b), L2 O N L I N E V E R S I O N Controls for combustion-heated domestic hot water systems 6.26 Domestic hot water systems should have both of the following. a. Time control which is independent of space heating circuits. b. Electronic temperature control. 6.27 Primary hot water circuits for domestic hot water or heating should have fully pumped circulation where this is compatible with the heat generator. 6.28 Direct-fired circulator systems, direct-fired storage systems and indirect-fired circulator systems should have automatic thermostatic control to do both of the following. a. Shut off the burner/primary heat supply when the desired water temperature is reached. b. Shut off primary flow if the system temperature is too high. 6.29 Direct-fired continuous flow systems should include both of the following. a. A flow sensor to control the rate of flow through the heat exchanger. This should both: i. control outlet temperatures ii. if the sensor detects insufficient flow, shut off the burner/heat input. b. A high limit thermostat to shut off the primary flow if the system temperature is too high. Controls for electrically heated domestic hot water systems 6.30 Point-of-use, local and centralised electrically heated domestic hot water systems should have automatic thermostatic control to interrupt the electrical supply when either of the following occurs. a. The setpoint storage temperature is reached. b. The system temperature gets too high. Manual reset should be possible if there is an over-temperature trip. 6.31 Local and centralised electrically heated domestic hot water systems should have both of the following. a. Seven-day time control. b. The facility to boost the temperature by using an immersion heater in the cylinder. 6.32 Water heaters in instantaneous electrically heated domestic hot water systems should include both of the following. a. A flow sensor to control the rate of flow through the heat exchanger. If the sensor detects insufficient flow, it should shut off the electrical input. b. A high limit thermostat to shut off the primary flow if the system temperature is too high. 46 Approved Document L Volume 2, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N