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What happens during the transition from winter to summer with your heat pump?

 
Air Source Heat Pumps (ASHPs)
Last Post by JohnR 2 years ago
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 AdamK
(@adamk)
Reputable Member Member
Joined: 2 years ago
Posts: 226
Topic starter 02/03/2025 10:55 pm   [#2161]

just curious as obviously if i go down the route of weather comp open loop system setup, which most seem to say is the most efficient, what happens as the weather warms to the point where the house needs less and less heat to maintain 20c say? surely you get to a point where the HP starts cycling as it can no longer modulate down any further, and conversely as autumn approaches when it starts to need more heat.

as ive watched lots of HG and QA vids but most talk about the other end where its maybe -3 and getting to the limit of the HP maybe.



   
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 Gary
(@gary)
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Joined: 4 years ago
Posts: 350
03/03/2025 7:55 am  

You are correct the heat pump will cycle on and off at any temperature if it cannot modulate down far enough to maintain the flow temperature.  Open loop gives the system the best chance of delaying that point by having the maximum amount of water engaged and no rads or ufh zones shut off.

This is when a simple on/off thermostat is useful as the house will get to temp and then shut off the heating till the thermostat calls for heat that could be hours later.

Cycling is only bad for the heat pump compressor when you are stopping and starting multiple times an hour, how many is acceptable is debatable but multiple stop/starts are bad.

My system will go down to 25C flow temp but it won't go below 32C flow without cycling 2/3 times an hour so I don't run it lower than that.



   
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 JohnR
(@johnr)
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Joined: 2 years ago
Posts: 106
04/03/2025 1:30 pm  

You should also be able to set an outside air temperature at which the system will turn off.



   
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