Midea Heat Pump expensive to run

NedS

https://forums.moneysavingexpert.com/discussion/comment/81865986#Comment_81865986

I assume you mean lowering the flow temperature, not the flow rate?

Your heat pump will have a minimum output. It's normally around 25% of it's full rated output. If the heat loss of your property (at an given outside ambient temperature and set room temperature) is less than this minimum output (i.e, the heat pump is oversized for the property, putting out more heat than required even when running at minimum) then the heat pump will cycle to further reduce it's output.

You can either run the heat pump in WC mode and allow it to cycle as required (not a bad thing as long as the cycling isn't excessive), or you can control it with a room thermostat to call for heat and turn the heat pump off once the room reaches it's desired temperature, and back on again once the temperature has fallen. They effectively achieve the same thing - they turn off the heat pump for a while as running continuously would put out more heat than the property requires.

There will be a minimum flow temperature that your system can run at, which will be dictated by the heat pump's minimum output and the size of your emitters (radiators/UFH). For example, my heat pump has a minimum output of around 4kW in mild conditions. Knowing the size of my radiators, I can calculate that I need a flow temperature of around 32-33C in order for my radiators to output 4kW of heat. If I were to set my flow temperatures any lower, the radiators could not dissipate the 4kW of heat being produced, so the heat pump would either cycle or the flow temps would rise until the point where the heat can be dissipated and equilibrium is reached. If you have the option to run your heat pump in an "always on" mode to prevent cycling, and you set your flow temps low and leave it to run, you will find this equilibrium temperature, or you can calculate it if you know the heat output ratings of your radiators.

So generally you should set your flow temps as low as possible (because it will be more efficient at lower flow temps) to achieve the desired room temperature, but knowing there will be a minimum achievable flow temperature dictated by the size of your emitters (radiators, UFH) and the minimum output of your heat pump.

akwexavante

You say that you are renovating the property and not living at it.

When working at the property are you opening windows, frequently opening, closing doors etc.

Have you taken up floors / flooring such as carpets etc, put holes in the walls for vents etc and left them open?

If you have a lot of heat loss, loss that's greater than the ASHP can generate then the house will be cold and the ASHP will be working hard, failing and costing a fortune to run.

My own experience is that when renovating a home, doors and windows tend to get left open all day, carpets come up, and you have a drafty floor.

If you are taking up floors, i would replace all 15mm pipework for 22mm as you go and insulate well if you're planning on moving into it, if not then perhaps maybe don't!!!!

I've increased my underfloor 15mm pipework to 22mm as i've worked my way around the house and WOW! What a difference it has made to the home.