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Replacing my 18 month old Hitachi Yutaki ASHP

 
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Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 45 minutes ago
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 JamesPa
(@jamespa)
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Joined: 3 years ago
Posts: 3590
30/11/2025 11:12 am  

Posted by: @trebor12345
↑

@jamespa Can I check something that I done some weeks ago.

My underfloor manifold is set via the 12 flow gauges to a total of 20 l/m.  In the UI of the indoor unit I have reduced the primary pump from 28.5 l/m to 24.3 l/m.

Why did I do this.  I was seeing a lot of mixing in the buffer tank.  Reducing the primary pump flow rate to 24.3 l/m reduced the amount of mixing.  Therefore the return temperature to the heat exchanger is reduced slightly (approx 0.5C). Hope this makes sence.

Yes this makes sense.  Ideally you match flow either side of the buffer, at which point it is pointless (but that is anyway the case).  Since a perfect match isn't possible its better to have slightly more flow in the primary than in the secondary.  This should force the cold water to the bottom of the tank thus (hopefully) reducing the flow temperature loss across the buffer to near zero.

Posted by: @trebor12345
↑

Nothing really new, except that these Thermo Off periods are way tooooo long at 1hr 20 mins and 2hrs 20 mins. 

Way too long based on what criterion.  From what I recall from your earlier post the house wouldn't cool much in this time.  So why does it matter?

 


This post was modified 42 minutes 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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