Best method of operating Air Source Heat Pump

Old 04-24-19, 12:16 PM
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Question Best method of operating Air Source Heat Pump

I am considering installing an air source heat pump to replace my ageing and inefficient oil boiler. The two on my short list currently are Global Energy Systems, and Grant, installed by Next Generation Renewable Energy. Some of the suppliers and an existing user are telling me that it is "inefficient" or otherwise ineffective to switch the heat pump system on and off, like one would with a normal boiler, but that it should be left on all the time, meaning all night, all day, and even when one goes away for a few days. They say that it takes a long time (and by implication a lot of electricity) to restart after stopping. This is highly counter-intuitive for me. I have always thought that heating any room or any part of the house to a higher temperature than one needs at the time, or heating it when it is unoccupied, is wasting energy, i.e. is increasing the heat loss from the house, which energy then has to be replaced at unnecessary cost to me. By instinct therefore I would install a temperature sensor in every room, and have a separate time zone for every room (or group of rooms with the same use) so that I could set the appropriate temperature (including "off") for each period of hours through the day. I might also install an occupancy sensor in each room, so that the heating could be turned off when no-one was using the room. According to the above people, this is not a good idea with an ASHP, and will make the system less effective. One of the reasons why I find this argument difficult to accept is that in fact these people ARE turning the heat pump on and off all the time, by their thermostat, just not with a time clock. The ASHP surely cannot tell whether it is being turned off by a time clock or by the thermostat, so it it is inefficient to turn it off via time clock, then it is also inefficient to turn it off via thermostat.

What are your views? Who is right? Is it in fact ineffective to turn the ASHP on and off on a time clock? If so, please explain WHY. Or would I save energy by having time zones as I described, with the possible disadvantage that the system would have to be switched on a long time before heat was required (because it takes a long time to warm up), thus reducing any possible energy savings?

Thanks - Rowan

Last edited by rowan.bradley; 04-24-19 at 12:17 PM. Reason: Change notification option
Old 04-24-19, 02:40 PM
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Welcome to the forums from abroad.

An air source heat pump is a basic heat pump. We can't help you much on choice of units or installer as this is a predominately a North American based site.

The problem with heat pumps is that they heat slow and steady. Based on the outside temperature it could take an hour to increase one degree. If you're in a cold zone your system will have back up electric coils for heating. What happens is when the inside temperature is three or more degrees below the setpoint.... the electric heat is turned on to help the system recover faster. The electric heat coils are much more expensive to run then the heat pump itself.
Old 04-25-19, 06:02 AM
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A boiler should not be cut on and off all the time as well

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