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Buffer tank bypass on EDF Ideal heat pump installation

 
Air Source Heat Pumps (ASHPs)
Last Post by Mars 7 months ago
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 KevB
(@kevb)
New Member Member
Joined: 7 months ago
Posts: 4
Topic starter 20/11/2025 9:27 pm   [#2609]

I have an Ideal Logic Air installed through EDF heat pumps. They insisted on having a buffer tank and CH pump. I argued against and we came to a compromise - by installing a bypass on the buffer (on the flow and return sides). The pump does not have a bypass. Does anyone have recommendations on how best to set this up? I could bypass it completely, have the hot water bypass it, have the return bypass it. Also can I keep the pump running or unplug it (easy to do)?

incidentally the efficiency as stated on the control box is awful SCOP 1.7. But it doesn’t seem particularly expensive and the house is warm. When I called Ideal support they told me not to trust it! 


This topic was modified 7 months ago by Mars

   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 5022
21/11/2025 9:45 am  

I would bypass the buffer tank in one of flow or return only, it will then act a bit like a volumiser. 

The problem you have relatively to a tank that was deliberately plumbed as a volumiser will be stratification.  Really you want input and output at different levels so that it gets stirred up.  Normally the recommendation is to put a volumiser in the flow, but with stratification messing it up a bit Im not so sure.  Try and see.  The symptom of stratification will be additional cycling.  Either way its got to be better to leave it in  than to take it out altogether.

As to the pump you really want to bypass it.  I fear that if you turn it off it will impede flow (try it and find out!).  If you leave it on the two pumps may fight each other but probably not.

Maybe someone else has actually tried this experiment and worked out the best way!

To get value out of bypassing the buffer you will need to adjust your WC curve down to compensate for the loss of temperature across the buffer which will no longer be occurring.


This post was modified 7 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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 KevB
(@kevb)
New Member Member
Joined: 7 months ago
Posts: 4
Topic starter 21/11/2025 12:53 pm  

Thanks James.
I know that the 5kW unit has the same circulation pump as the bigger units but its flow is capped to 70% by default but it can up changed in the settings. If I turn the second pump off at least there is some extra capacity that I can use to try to push through the other pump. If it works I could look at removing it later on. I will try and give an update.



   
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Mars
 Mars
(@editor)
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Joined: 5 years ago
Posts: 4710
21/11/2025 3:37 pm  

@kevb, before you re-plumb, I'd speak to EDF as it may invalidate your warranty if something goes wrong.


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 KevB
(@kevb)
New Member Member
Joined: 7 months ago
Posts: 4
Topic starter 21/11/2025 7:50 pm  

Well I can try the valving which can be undone so I don’t see that’s an issue. But yes removing the pump would be different matter.



   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4710
22/11/2025 12:28 am  

@kevb, many of these companies look for the smallest of excuses to not honour warranties.


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