This figure will be the size of the heat source (kW) required based on your design hot water flow temperature and any design conditions which may have an effect. 

For example:  When using a heat pump take into account the kW output of the heat pump based on a hot water flow temperature of 55°C and an outside design temperature of -2.2°C.

Most heat pumps are designed at an outside design temperature of 7°C and at a flow temperature of 35°C flow. Therefore, based on your design conditions the kW output will be significantly lower than that of the manufacturer’ s data sheet. Please contact your manufacturer for all the most up to date information on the performance of your heat source based on your design conditions.

For any further questions please speak to your Mentor on Freephone 01244 784 260 or email [email protected]