Renewable Technologies – Air Source Heat Pumps

What is an air source heat pump (ASHP)?

Simply put, an air source heat pump uses heat energy from the air, and converts it into energy to heat homes. Grant heat pumps are ‘air-to-water’, which means that they extract useful heat from the outside air, and transfer it into ‘wet’ heating systems such as radiators or underfloor heating. 

How does a heat pump operate? 

Heat pumps use the same thermodynamic principles as refrigerators and the most commonly used system is the vapour compression cycle. Outside air is drawn in through the heat pump evaporator coil where the refrigerant is exposed to this air. The liquid refrigerant evaporates to a gas and absorbs the heat energy within this air. The gas is then compressed to increase the heat content before passing through a heat exchanger. Here, the gas condenses back to a liquid, while the heat is transferred to the water of the heating system. 
 

How quiet is an air source heat pump?

It is a common belief that air source heat pumps can be noisy when running. While the fans in a heat pump do make a sound as they rotate, Grant’s air source heat pumps have been specifically designed to be quiet in operation. This ensures there is little noise impact to the household and neighbouring properties. 

The diagram below shows the sound levels of Grant’s Aerona³ heat pumps compared with other common household appliances and noises. An average fridge freezer, which is considered quiet, has a sound level of 40dB or less. Meanwhile, when two people are having a conversation, they create approximately 60dB of noise. The level of sound that Grant heat pumps generate sits in between these two average values. Grant Aerona³ heat pumps are also considerably quieter than the average washing machine (at 65dB), household hoover (at 72.5dB) and lawn mower (at 80dB).

Choosing the right heat emitters

Air source heat pumps must be correctly sized to ensure they can provide the required amount of heat output at the designed conditions, and the same applies to the heat emitters. Heat emitters with larger surface areas are the best partners for an air source heat pump operating at lower temperatures. A larger surface area allows the heat from the system to be evenly transferred into the property’s occupied spaces. Grant’s Uflex underfloor heating ranges and their Afinia aluminium radiators are both ideal heat emitters to install with a heat pump.

Planning permission

The installation of an air source heat pump on domestic premises is considered to be permitted development and should not require any planning permission, providing that all conditions are met. It is recommended to check with your Local Authority Planning Department prior to any work commencing, because in some cases planning permission may be required.

Cylinders

A hot water cylinder is required for all air source heat pump installations. Grant offer a universal range of cylinders which feature large, high recovery coils making them an ideal partner for air source heat pumps. For heating systems where a heat pump is combined with another heat source such as solar thermal, a twin coil cylinder will be required.