New MCS standard clarifies heat pump performance

Published:  20 September, 2011

The new MCS Microgeneration Installation Standard (MIS 3005) has been released, requiring heat pump systems to be at least 100% sized for a property for 99% of the heating season.

It also requires systems to be designed to a target external design temperature of between approximately -1°C and -4°C, depending where the property is located in the UK. This means the heat pump should be able to almost entirely heat the house without electric or other back up, under all but the most extreme conditions

"Many heat pump suppliers quote a Coefficient of Performance (CoP) figure based on an outside temperature of 7°C and a flow temperature of 35°C,’ says Nu-Heat’s product development manager Mark Millett. ‘This temperature range is potentially misleading.

"Nu-Heat quotes outputs of its heat pump range based on -3°C outside air temperature and water delivery temperatures anywhere in the range of 40°C – 60°C, depending on heating system type. The CoP is really only useful when viewed as a seasonal average."

‘With uncertainty about heat pump performance highlighted by last year’s report from the Energy Savings Trust, and DECC’s reticence to include air source heat pumps in the upcoming RHI tariff list, it is imperative that the industry strives to ensure that heat pumps are sized correctly in order to achieve maximum efficiency,’ added Millett.