Heat pumps. Some observations and opinions…

There has been endless coverage in the press about heat pumps and while most people grasp the concept of extracting heat energy from the outside air and raising the temperature of it to heat your house, very little of the press coverage delves into the details that lots of people want to know about, including me! So although I’m no expert on heat pumps, here are some things not often pointed out in newspaper articles or sales brochures.

Most heat pumps are “air source”. This means they collect energy from the outside air, and they do this by blowing the air in your garden through an outside collector unit containing a big fan. A really BIG fan. So big that this outside box (with fan) will need two strong people to carry it into position. Paradoxically the bigger the fan, the more quietly the outside unit will run. The outside garden heat collector will be roughly the size of a washing machine and makes a quiet humming noise all the time it is running, which is most of the time. Some people find this annoying. Most don’t. 

Alternatively you can have a “ground source” heat pump which has vast lengths of pipework buried in the ground to collect energy directly from Mother Earth. Much more expensive but almost totally silent, and no large ugly boxes in your garden.

Once you have sorted out in your mind the types of outside heat collector available, then you can go on to consider which type of heat delivery you want to have inside the house. There are two types, each with a major advantage and a major disadvantage. Air or water. The air type have huge boxes fixed to the walls high up in each room. These when connected to outside air collectors are known as “air to air” heat pumps and blow out warm air into the room. The smallest will have only one warm air delivery unit, fitted in one room. Larger systems can have warm air delivery units in multiple rooms. Their major advantage is they can also supply cooled air in hot weather! Yay! The other type delivers hot water into the house which connects to conventional radiators and work in a similar way to a gas boiler. Except they will have a far lower output so consequently need to run all (or a high proportion of) the time in cold weather. Also, if you feel a bit chilly on a cool summer’s evening, you can’t just boost them to get a slug of extra heat like you can with a gas boiler, the ‘weather compensation’ control system will prevent you (I think). Or maybe someone reading this can say otherwise. PM me! This system will, if using an air collector be called an “air to water” system, or if using a ground source collector it will be a “ground to water” system. The major advantage of an air to water or ground to water heat pump is it will heat up your hot water tank too. With an internal warm air delivery system, they cannot heat your hot water.

Another difference between an “Air to Air” heat pump and an “Air to Water” is the two parts of the air to air (inside and outside units) are connected with a pair of pipes containing refrigerant, while most air to water heat pumps have “monoblock” external units which simply deliver hot water for radiators as their output. Now working with refrigerant is a different trade from plumbing and heating with different qualifications so you’ll need a refrigeration or air conditioning installer to fit an air to air heat pump, while an air to water heat pump can be fitted by a regular domestic heating engineer.

Next, I’ll add some photos and images to this page…

Mike

12/3/23.