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Maintaining temperature on windy day

 
Air Source Heat Pumps (ASHPs)
Last Post by cathodeRay 3 months ago
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 Curlykatie
(@curlykatie)
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Joined: 3 years ago
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Topic starter 22/11/2025 10:36 am  

Hi,

We have a Midea ASHP with underfloor heating throughout and thermostats in each room. The heat pump is running in weather compensation and the temp is pretty well maintained until we have a windy day!
We’ve had a cold snap here and the weather compensation worked well, but today is a little warmer but with a cold wind and the room temps throughout have dropped by 2-3 degrees. 
We are in a new build and quite exposed to strong winds. I suspect it’s due to heat loss from poor quality building but I just wondered if there’s any way of factoring the wind in as well as the outside temp?

Thank you

Katie



   
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JamesPa
 JamesPa
(@jamespa)
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22/11/2025 11:32 am  

Not natively to any heat pump or boiler sofaik.

You could try running on WC + temperature sensor (ideally the midea one not third party thermostats, assuming it's sensibly located) and upping the WC a couple of degrees.  This will cost a few percent in efficiency and may make room temps less stable (or may not), but with a new build that should be well well insulated hopefully not too much cost.

Other than that it' some third party or home grown tool that harvests the weather info.  An anemometer which 'massages' the output of the oat sensor would be an option, or something that interfaces to the modbus.  Thats the sort of tinkering that only some people like doing though, and obviously I dont know if you are (or have access to) one of those!  @cathoderay has done some add on control for his midea so will be able to advise

What are 'thermostats in every room' doing. Hopefully nothing!


This post was modified 3 months ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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 benson
(@benson)
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Joined: 2 years ago
Posts: 272
22/11/2025 12:15 pm  

It sounds like you have the 'cold' end of the WCC set up well. What happens if you adjust the 'warm' end so that the temp remains stable on a day like this? Will the IAT massively overshoot when a little warmer but not windy?

We're near the south coast so quite windy as well, and not particularly well insulated. Our midea WCC has been coping ok, with IATs between 20.5 and 22. Just wondering if it a case of accepting some variation but primarily setting up the WCC so that it doesn't drop below min comfort level? The main annoyance I have with the midea is that any adjustment of the WCC settings turn everything off (utilising modbus connection to alter these remotely via home assistant) thus my general approach has been to try and leave it so I don't have to fiddle with it. As alluded to above, Cathoderay seems to have nailed this with their controls set up and that automatic adjustments to the curve in serviceman settings based on IAT under or over shooting, does not do this.



   
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cathodeRay
 cathodeRay
(@cathoderay)
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22/11/2025 2:26 pm  

Posted by: @jamespa
↑

@cathoderay has done some add on control for his midea so will be able to advise

"done some add on control"??? It's a most elegant solution, might I remind you!

Seriously, it is not complicated, and uses the indoor air temperature (IAT) to adjust the weather compensation curve (WCC). It (it is a python script) could easily be adapted to factor in other things like wind speed as long as you have current wind speed data but I am not sure that is necessary, because the IAT is the product of all the factors acting on it. If the IAT drops because of wind chill, all we need to do is have the control set up respond to the drop in IAT, we don't need the wind speed to do that, although it is probably the case that reacting to wind speed might make the response a bit faster than waiting for the IAT to drop.

The prerequisites for making it work are something that can run python connected over modbus to your wired controller. You then just let the python script run all the time in the background. In my case, it checks the actual IAT against the desired IAT once an hour, and if there is a discrepancy, it moves the WCC in opposite direction ie if the IAT is too low, WCC gets moved up, and vice versa.

I can supply more details if anyone wants to put this into practice.       


Midea 14kW (for now...) ASHP heating both building and DHW


   
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JamesPa
 JamesPa
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22/11/2025 7:57 pm  

Posted by: @cathoderay
↑

"done some add on control"??? It's a most elegant solution, might I remind you!

Of that I have no doubt and apologies for any offence!

 


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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cathodeRay
 cathodeRay
(@cathoderay)
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22/11/2025 8:08 pm  

@jamespa — now that you have done some add on apology, honour is restored.


Midea 14kW (for now...) ASHP heating both building and DHW


   
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 RadWhisperer
(@radwhisperer)
Trusted Member Member
Joined: 4 months ago
Posts: 33
23/11/2025 3:28 pm  

Valiant & Daikin have a form of load compensation or room influence which can dynamically adjust the WDC by a few degrees based on what thermostat is reading. Have search for that feature.



   
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 Curlykatie
(@curlykatie)
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Joined: 3 years ago
Posts: 82
Topic starter 23/11/2025 6:04 pm  

@jamespa thanks so much for your reply- unfortunately the Midea temp sensor is located in with the water tank but I’ll have a little play with adjusting the WC!



   
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 Curlykatie
(@curlykatie)
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Posts: 82
Topic starter 23/11/2025 6:05 pm  

@benson than you- I’ve adjusted the WC over the weekend so will see how we go!



   
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 Curlykatie
(@curlykatie)
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Posts: 82
Topic starter 23/11/2025 6:07 pm  

@cathoderay thanks for your reply! That sounds amazing but a bit over my head!! Do you do home visits 😝



   
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 Curlykatie
(@curlykatie)
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Joined: 3 years ago
Posts: 82
Topic starter 23/11/2025 6:08 pm  

@radwhisperer thank you. I’ve just found that but the temp sensor on the controller is located in with the hot water tank, and with thermostats in every room of the house I have no idea!!



   
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cathodeRay
 cathodeRay
(@cathoderay)
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Posts: 2724
23/11/2025 8:29 pm  

Posted by: @curlykatie
↑

Do you do home visits

I used to, but now I am retired. Mostly I miss doing them, but I will never forget a GP trainee in a rough neighbourhood telling me the trainee on a two week placement to 'stick my doctor's bag through the door first, so the rottweiler bit it and not me'! 

The python script approach I use is a bit geeky as @jamespa rightly implied when he done some comments, but the idea can be applied manually. If you know there's a beast from the east on the way, set the WCC two degrees higher (via the FOR SERVICEMAN menu) and then take it down again when the beast has gone through.  


Midea 14kW (for now...) ASHP heating both building and DHW


   
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