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Grant R290 DHW Cycle Interuption

 
Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 3 weeks ago
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 Steam Powered
(@steam-powered)
Active Member Member
Joined: 2 years ago
Posts: 15
Topic starter 19/09/2026 10:43 am   [#3168]

I have just had a Grant R290 9Kw HP installed to replace my Grant R32 15kW unit which was way oversized against my 7.2kW heating requirement. After two winters of short cycling, high power consumption and a lot of frustration enough was enough!

Having tested it as best I can in mild weather it looks very promising. I have one bug which I will discuss with the installer but would also like to share here to see if anyone else has experienced it. I have DHW programmed twice per day, 04:00 & 14:00. Over sixteen days of operation three of the am DHW cycles have been interupted for a few minutes and then resumed. The attached trace shows one of these. They were at 04:04, 04:07 and 04:09 and each for around three minutes.

Clearly not a huge issue, but something I would like to resolve if possible. Does anyone have any experience of the same or suggestions please?

DHW cycle short drop out 19.09.26.pdf

 

 



   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 4 years ago
Posts: 5520
19/09/2026 2:22 pm  

It looks like some sort of short pre-run.  The question is, do other grant owners see the same? 

 

Is there any kind of 'live' display, possibly in the installer menu, telling you what the heat pump is currently doing?


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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