We have been installing air to air heat pumps in quite a few locations to see how effective they are as alternatives to simple electrical heating. In essence they are air conditioning units but set to warm and there is a danger they can be used for the cooling purpose. Which sort of defeats the purpose which is to save energy.
There are an awful lot on the market. We have been trailing 10 at Powis Castle and Erddig. They are replacing either night storage heaters or convector heaters in tea rooms, shops and offices. They take hours to fit and except for the heat exchanger unit outside ( which needs careful positioning) they are easy retrofits. Getting the sizing right is important to make sure you get max efficiency. COPs of 5 + are claimed but these but are meaningless unless your using when the ambient air temperature is 16c or so. We have been using them with low ish (18c) temp set in the tea room and because they are linked to fan convectors the feeling of warm air moving seems to lull you into feeling warmer.
How do you freeze a castle? Well first thing you do is to place the heat exchanger unit in a turret which has a few arrow slits for the air to move in and out. You then make sure you don’t train the staff how to manage the new system and then they set the system max…thereby ensuring a plenty full supply of very cold air to the turret which guarantees some frost to form. Answer – hand over the system better to staff, set the temp and timer up better and then hide the controller!