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Preparing for 2nd winter in new build house.

 
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Air Source Heat Pumps (ASHPs)
Last Post by Transparent 7 months ago
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 sbm74
(@sbm74)
Active Member Member
Joined: 7 months ago
Posts: 9
Topic starter 19/09/2025 12:34 pm  

The setting is on the room stats. That room has 2 loops. The ASHP is using weather compensation so the OAT would have to be around -15° before it got to 60°.  According to the heat loss calcs the maximum flow temp should be 50°.



   
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Carpenterstation
 Carpenterstation
(@carpenterstation)
Trusted Member Contributor
Joined: 1 year ago
Posts: 46
19/09/2025 12:56 pm  

Welcome to the forum. I am commenting as there are similarities with our property. Relatively “new” build and 450m2 and 250m2 ground floor is all UFH.

 

Our install was not great (temps far too hot, excessive cycling, heat literally thrown away by a diverter when circulating temp was too high).  We fixed by setting all in room thermostats to 20 degrees all the time acting as limiters, set the upstairs to 18deg, reduced flow temp to 32degees and switched on weather compensation. After a few weeks of tweaking w/c, system settled down - and the house is now permanently warm enough.

efficiency isn’t everything. You need to be careful that you aren’t  just efficiently producing too much heat. 

 

 



   
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 sbm74
(@sbm74)
Active Member Member
Joined: 7 months ago
Posts: 9
Topic starter 19/09/2025 1:46 pm  

@carpenterstation Good to know. Looks like that's the way forward.



   
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Transparent
 Transparent
(@transparent)
Famed Member Moderator
Joined: 4 years ago
Posts: 3134
19/09/2025 2:43 pm  

Posted by: @sbm74
↑

The setting is on the room stats.

Yuch!

So that's basically just an on/off control.

It either lets water flow through a loop at anything up to 60°C, or it doesn't.

 

The thermal lag for UFH within screed will be at least an hour.
My kitchen/diner area (9m x 4m) has a lag of around 4hrs with <40°C flow.

Measuring the air temperature in the room is next to useless.

The 'correct' approach is to remove the thermostatically-operated valve on the manifold.
Fit a manual valve, and adjust it to maintain a steady flow.

IOW you're using it like a lock-shield valve on radiators, to balance the flow throughout all UFH loops.

The longer the loop, the more open the manual valve will need to be.


Save energy... recycle electrons!


   
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