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Grant Aerona3 - Home Assistant control via Modbus

 
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Air Source Heat Pumps (ASHPs)
Last Post by Johnmo 3 hours ago
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 Uk_pete_2000
(@uk_pete_2000)
Estimable Member Member
Joined: 6 months ago
Posts: 78
13/05/2025 10:17 pm  

Posted by: @johnmo
↑

WC just changes the flow temperature in line with the energy likely to be lost on lower temps outside.

 

Hate to burst people bubbles, but WC will never match the house heat loss. The only way to do that is by using the internal house temp and adding / removing heating as required and inorder to do that you have to either understand your own house or automate it by controlling the flow temp.

Even a well setup WC will add more or less heat, rather than the correct amount and keeps needing changes to work. When people say they are using "setback" overnight the system is either turned off or the WC never got to the correct temp anyway. Only a few HP actual turn down the WC to match the setback.

As for costing, we use 1300kwh over 150 days. The house covers over 500m2

 

 

 


   
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 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 2 years ago
Posts: 2429
13/05/2025 10:21 pm  

Posted by: @uk_pete_2000
↑

Hate to burst people bubbles, but WC will never match the house heat l

On what do you base that assertion please?

There are plenty of people on this forum running on pure wc achieving comfortable and stable house temperatures.  Properly adjusted it works remarkably well in many, possibly most cases (maybe with a temperature limiter set a couple of degrees above target to deal with solar gain). This is not surprising because it follows the science.

 

This post was modified 4 hours ago 2 times 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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 Uk_pete_2000
(@uk_pete_2000)
Estimable Member Member
Joined: 6 months ago
Posts: 78
13/05/2025 10:48 pm  

@jamespa 

Yes there are a lot of people running WC  and there are a lot of people who make changes to those WC curves during the winter as the house gets too hot or cold.

WC has its place and its good in the back ground, but it should not be seen as the only reliable way of running a HP.

How many times did you adjust your WC curve ?

WC does not take  into account the number of people in the house, which equipment is turned on. Nor does it take account of wind or rain or snow. It depends on where the temp sensor is place, which direction it is facing. Solar gain.

By running on internal temp, once you reach the correct temp you take down the flow temp, say 3°. Once internal temp goes down increase 2°. After a few small changes the flow temp will match the heat required. Then as house gains / loses heat flow temp is adjusted.

This post was modified 3 hours ago by Uk_pete_2000

   
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 Johnmo
(@johnmo)
Noble Member Member
Joined: 2 years ago
Posts: 496
13/05/2025 11:19 pm  

Posted by: @uk_pete_2000
↑

By running on internal temp, once you reach the correct temp you take down the flow temp, say 3°. Once internal temp goes down increase 2°. After a few small changes the flow temp will match the heat required. Then as house gains / loses heat flow temp is adjusted

My boiler had that control, unfortunately with thick screed UFH, the boiler spent the whole time completely out of sink with the house needs. Was pretty rubbish.

But you can do that with a simple low hysterisis thermostat connected to your second set point connection. Your only issue is the whole inertia of the floor. Basically have a low and high WC curve. When you hit target temp you go on low curve and below target high curve. Running UFH floor will buffer heat quite easily for a higher than idea flow temperature. 

But why bother with the complexity a simple 0.1 hysterisis thermostat works way better. Just set flow temp to suit coldest day.

Where do you live - are you getting a big swing in outside temperature?

 

Maxa i32V5 6kW ASHP (heat and cooling)
6.5kW PV
13.5kW GivEnergy AIO Battery.


   
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