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Should Our Water Circulation Pump Be Configured to Run All The Time?

 
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Air Source Heat Pumps (ASHPs)
Last Post by damonc 4 months ago
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 Grantmethestrength
(@grantmethestrength)
Reputable Member Member
Joined: 1 year ago
Posts: 182
15/10/2025 10:44 pm  

@steelbadger lol it just made the rest of the house hotter!


Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w + 13x 480w Solar Panels
Sigenergy 10kW Inverter
16kW Sigenstor battery


   
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GrahamF
 GrahamF
(@grahamf)
Estimable Member Member
Joined: 11 months ago
Posts: 114
Topic starter 16/10/2025 9:40 am  

@grantmethestrength

Posted by: @grantmethestrength
↑

if it is heating season I get the unit will be working but most of the summer I find it hard to understand why it needs to be pumping. (#Yorkshirenomics!!!)

In winter, one would hope that the heat pump compressor is running continuously, so then the water pump must be running all the time as well.  I have already had one 24 hour period of continuous operation, so I expect that to become more frequent.  Therefore in winter the "problem" does not arise.

In summer, I agree that it is wasteful.  I could turn the space heating off, but I would prefer to have a completely automated system - just set and forget.

In spring and autumn, I would hope that the system could be a bit smarter - e.g. run the pump more slowly or intermittently when the compressor is idle.


Grant Aerona 290 15.5kW, Grant Smart Controller, 2 x 200l cylinders, hot water plate heat exchanger, Single zone open loop system with TRVs for bedrooms & one sunny living room, Weather compensation with set back by room thermostat based load compensation


   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 4476
16/10/2025 10:16 am  

Posted by: @grahamf
↑

In spring and autumn, I would hope that the system could be a bit smarter - e.g. run the pump more slowly or intermittently when the compressor is idle.

Maybe it will happen as a result of a firmware upgrade, if they push them out which they may or may not do/may or may not be able to do. 


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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GrahamF
 GrahamF
(@grahamf)
Estimable Member Member
Joined: 11 months ago
Posts: 114
Topic starter 16/10/2025 10:18 am  

@jamespa unlike some systems, the Grant Aerona does have the ability to install a firmware upgrade.  The Grant support engineer told me that they are planning some improvements in another area.


Grant Aerona 290 15.5kW, Grant Smart Controller, 2 x 200l cylinders, hot water plate heat exchanger, Single zone open loop system with TRVs for bedrooms & one sunny living room, Weather compensation with set back by room thermostat based load compensation


   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 4476
16/10/2025 1:18 pm  

Posted by: @grahamf
↑

@jamespa unlike some systems, the Grant Aerona does have the ability to install a firmware upgrade.  The Grant support engineer told me that they are planning some improvements in another area.

Noted

The Vaillant doesn't either, other than with a board swap.  A bit mad TBH.

 


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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 KenBone
(@kenbone)
Trusted Member Member Professional Installer
Joined: 2 years ago
Posts: 49
16/10/2025 8:49 pm  

My circulation pump cycles, when the compressor is off, heating is still active on the controller (but all is up to temp), its testing the water (literally).

Once the water temps fall below the threshold, it will spin the compressor up again.

Some heat pumps you can change under parameter settings how many minutes this happens. 

 


This post was modified 5 months ago by KenBone

   
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 Grantmethestrength
(@grantmethestrength)
Reputable Member Member
Joined: 1 year ago
Posts: 182
17/10/2025 6:53 am  

I think my strategy will be to leave it always on during heating season and then change it to sniffing cycle for the summer. I am sure it would be constantly pumping throughout heating season if it was on sniffing cycle due to the weather compensation, I might experiment a little.


Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w + 13x 480w Solar Panels
Sigenergy 10kW Inverter
16kW Sigenstor battery


   
ReplyQuote
GrahamF
 GrahamF
(@grahamf)
Estimable Member Member
Joined: 11 months ago
Posts: 114
Topic starter 17/10/2025 7:01 am  

@kenbone thanks for this input.  It sounds like a better approach.  Please could you tell me the model of heat pump you are using and point me to the manual or controller screens which explain this?


Grant Aerona 290 15.5kW, Grant Smart Controller, 2 x 200l cylinders, hot water plate heat exchanger, Single zone open loop system with TRVs for bedrooms & one sunny living room, Weather compensation with set back by room thermostat based load compensation


   
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 KenBone
(@kenbone)
Trusted Member Member Professional Installer
Joined: 2 years ago
Posts: 49
17/10/2025 5:37 pm  

@grahamf happy to help, ive had 4 heat pumps here to test.

Currently im running an old Samsung unit, fully open loop, 1 pump, my own automated weather compensation-room influence controls.

1950s house, no major upgrades.



   
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 AdamK
(@adamk)
Reputable Member Member
Joined: 1 year ago
Posts: 211
17/10/2025 11:40 pm  

ive got a similar issue with my Vaillant. when it was on expanded the room sensor would turn off the heat pump once up to set point. ive since changed it to active as trying to get more than 3.3 cop. now the pump runs constantly using 35-59w. i might switch back to expanded so its not constantly running, unless there is a mode where it can sniff.

re the low cop, this might be due to at least one of the strainers limiting the flow to 725l/h after i cleaned it i got 1100l/h.



   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 4476
18/10/2025 7:22 am  

Posted by: @adamk
↑

ive got a similar issue with my Vaillant. when it was on expanded the room sensor would turn off the heat pump once up to set point. ive since changed it to active as trying to get more than 3.3 cop. now the pump runs constantly using 35-59w. i might switch back to expanded so its not constantly running, unless there is a mode where it can sniff.

I run my Vaillant on either expanded mode (either end of the season when solar gain is a 'problem') or no room influence.  Certainly on 'no room influence' it turns the water pump off when the compressor is off (there is probably an overrun but, as I cant monitor the water pump directly I cant be sure).  I will check what it does in expanded mode over the next days

Different firmware versions?

 


This post was modified 5 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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 RadWhisperer
(@radwhisperer)
Eminent Member Member
Joined: 5 months ago
Posts: 35
21/10/2025 7:37 am  

This is how Daikin run their heat pumps.

Weather Compensation + Thermostatic control = Water pump runs Continuous or OnDemand (default) - configurable while in installer mode

"pure" weather compensation or LWT mode without thermostat = Water pump runs Continuous or Sample (default) - configurable while in installer mode

 

Only problem I had when enabling LWT + Sample was a water rush while sampling so I reduced the sample pump speed to 60%. No issue since. I may switch to Thermostatic control during the warmer months to stop the sample mode as heating will hardly ever be used.


This post was modified 5 months ago by RadWhisperer

   
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