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Balancing a low loss header/buffer tank on a Grant Aerona 2 13kw r32 system

 
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Air Source Heat Pumps (ASHPs)
Last Post by Uk_pete_2000 8 months ago
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 Uk_pete_2000
(@uk_pete_2000)
Estimable Member Member
Joined: 9 months ago
Posts: 83
Topic starter 26/11/2024 12:37 pm  

@jamespa 

We can ignore the house heating load. Yes it's low on the ch side, it only needs 23° - 25° in the ufh to get to 19° in the room.

Grant ashp lowest setting is 23°, so for the time being we can ignore the wc curve and just set it to a temp. In our case we are having to set it to 28° - 30° to get ch side to the correct setting.

We have run through all the settings from setting the grant to its lowest, mid and highest flows and then taking the pumps though the 6/7 settings they have. Allow it to settle and check temp and nothing seems to make any difference.

I am now running the system on grants highest setting and two of the pumps are turned off. HP set tp 30°. This is what we get ORDER ABCD

20241126 113411

   
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 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 2 years ago
Posts: 2660
26/11/2024 1:56 pm  

Not sure exactly what the picture shows as there appear to be 8 readings.  If its the bottom temp readings that are of interest, the they seem to be 29.2, 28.3, 27.5, 19.2 so A-> C now a bit less than 2.  Isn’t this an improvement?  D seems to indicate deltaT across UFH now 8C, which at current OAT seems quite high, so may be a problem when OAT drops but equally might not matter.  However thats perhaps because the flow rate is low as you have only 1 pump running.

TBH I think you have run through all the simple options and Im not sure I can add much more.  I have the impression you understand the principles, so its a bit of a case of play and see what happens, or wait until someone comes along with a magic solution, if indeed there is one without spending any significant money.

This post was modified 8 months ago by Mars

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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 Uk_pete_2000
(@uk_pete_2000)
Estimable Member Member
Joined: 9 months ago
Posts: 83
Topic starter 26/11/2024 2:36 pm  

@jamespa sorry my bad. Yes it's the middle readings that have a temp probe. The are ordered as ABCD

I've just turned on all the pumps and set them to high load and noticed that B went down and D came up. So the CH is taking from the tank. 

Once it stopped changing so much I lowered the speed of the CH pumps to 1 and will check again.

(I'm sure I had the HP set at its highest speed, but I didn't turn off any pumps last time I tried.)

If the above goes back to major differences then I'll just run the one pump tomorrow and if if things settle down. 


   
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