Midea ASHP – how to set weather compensation

Curlykatie · 2023-01-20T17:15:11Z

After lots of help from @derek-m around balancing the system I am now looking for some advice on how best to set weather compensation. We have moved into a 4 bed new build with a Midea ASHP and underfloor heating throughout and individual thermostats in each room. I have looked at the manual and on YouTube but still rather confused as to the best way to set weather compensation. On the main panel I have found the option to select the weather compensation curves- when I click through it says ‘zone 1 high temp mode’ and ‘zone 2 low temp mode’- I have found the high and low temp curves in the manual but unsure which I should be selecting? I also came across a video on YouTube about setting for weather compensation within the serviceman settings? Thank for everyone’s kind help, Katie

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Air Source Heat Pumps (ASHPs)

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Tasos

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03/09/2025 5:13 pm

Posted by: @cathoderay

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Posted by: @tasos

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The Midea pump is controlled by its wired controller, which houses the weather compensation curve (which is straight line, but ignore this) and its internal thermostat. These two should be operated in unison. The weather curve should tell the pump the outlet water temperature corresponding to a set of outside air temperatures. So at below zero outside temperatures, I should indicate maximum power (i.e. 60-65 C in your case). The internal thermostat should be at the required room temperature in the "coldest" room, say 21 C. This implies that you should position the wired controller in the "coldest" room.

This simply isn't true. Midea heat pumps of the type we are talking about are controlled in one of two ways:

(a) using weather compensation (WC): the flow (leaving water) temp is set from the outside air temp (sensor is in the outside heat pump) using the WC curve (which I agree is a straight line, curve being used here as a generic term for a line on a graph). The internal (to the wired controller) thermostat is not used, nor any external room temp thermostats (beyond setting them high eg 30 degrees, ie always on and always calling for heat). The only exceptions are 'set-backs' and 'set-forwards' which we are not talking about here, and crude on/off switching ie turning the heat pump off for the summer by setting an external room stat low eg 10 degrees. In normal day to day running, all the control comes from the WC curve, which only uses the outside air temp.

(b) using a fixed flow temp ie there is no weather compensation, in which case some sort of indoor thermostat is used, be it the one in the wired controller if it is in a sensible place (not always the case) or an external one. This mode of running is the same mode as normally used with fossil fuel boilers in the UK, and while it can be done, it is not the best way to run a heat pump.

I think we are talking about the same type of Midea heat pumps. I attach the operation manual of mine, which in Section 10.2.5, p. 59, states what I am saying. Unless I understand wrongly.

Midea MHCV10WD2N7 R290, 4.8kW peak energy community solar power.

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