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What happens when the outside temperature exceeds the upper WC point?

 
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Air Source Heat Pumps (ASHPs)
Last Post by bontwoody 5 months ago
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 Old_Scientist
(@old_scientist)
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Joined: 1 year ago
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03/04/2025 10:10 pm  

Posted by: @ashp-bobba
↑

@old_scientist 35 DegC outdoor air temperature?

Yes, that's the default value, but can be set between 10C to 35C.

 


Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.


   
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 ASHP-BOBBA
(@ashp-bobba)
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Posts: 230
03/04/2025 10:19 pm  

@old_scientist I see, thats good, so set for a couple Deg above design and you have an over heat stop point. I am sure most manufacturers have something like this somewhere in the vast control settings.


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bontwoody
 bontwoody
(@bontwoody)
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Topic starter 03/04/2025 10:34 pm  

@ashp-bobba @old_scientist 

thanks both. Very useful. 


House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
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Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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 Gary
(@gary)
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04/04/2025 8:25 am  

Mitsubishi Ecodan just runs the same flow temp when it reaches the limit of the set curve. 

I am not aware of any way of telling the heat pump not to run above a certain outside temp.



   
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Mars
 Mars
(@editor)
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04/04/2025 8:36 am  

Mitsubishi Ecodan just runs the same flow temp when it reaches the limit of the set curve.

I am not aware of any way of telling the heat pump not to run above a certain outside temp.

On a podcast a few months ago, one of the panelists mentioned that most heat pumps (and possibly boilers with outdoor sensors) are designed to stop running when the CIBSE outdoor temperature threshold is reached. I don’t remember the exact number offhand, but I think it was a very specific 15.5C.

I haven’t come across specific documentation confirming whether Mitsubishi Ecodan follows this principle, but it might be worth checking the service menu or installation manual to see if there’s a parameter for a high outdoor temperature cut-off.

In our case, I’ve not seen this setting anywhere, but I’ll check again today. That’s the reason we just turn ours off manually to prevent heating if, for example, the temp drops to 14.5C for a period of time.

 


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 RobS
(@robs)
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04/04/2025 8:44 am  

Posted by: @gary
↑

Mitsubishi Ecodan just runs the same flow temp when it reaches the limit of the set curve. 

I am not aware of any way of telling the heat pump not to run above a certain outside temp.

See my post https://renewableheatinghub.co.uk/forums/postid/44973 - it's called summer mode and is in the service menu. 

 



   
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 JamesPa
(@jamespa)
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Joined: 2 years ago
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04/04/2025 8:51 am  

Posted by: @editor
↑

Mitsubishi Ecodan just runs the same flow temp when it reaches the limit of the set curve.

I am not aware of any way of telling the heat pump not to run above a certain outside temp.

On a podcast a few months ago, one of the panelists mentioned that most heat pumps (and possibly boilers with outdoor sensors) are designed to stop running when the CIBSE outdoor temperature threshold is reached. I don’t remember the exact number offhand, but I think it was a very specific 15.5C.

I haven’t come across specific documentation confirming whether Mitsubishi Ecodan follows this principle, but it might be worth checking the service menu or installation manual to see if there’s a parameter for a high outdoor temperature cut-off.

In our case, I’ve not seen this setting anywhere, but I’ll check again today. That’s the reason we just turn ours off manually to prevent heating if, for example, the temp drops to 14.5C for a period of time.

 

My Vaillant definitely has a 'Max outside temp for heating' parameter.

What it doesn't have, unfortunately, is a 'Max solar irradiance for heating' parameter.  For much of this week its been quite chilly outside.  Solar gain has dominated during the day, but then in the evening the house starts cooling.  So really I need to turn off the heating during the daytime, and put it back on evening and night.  I could set up a timed program to do this I suppose!

 


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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 Gary
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04/04/2025 12:54 pm  

@robs What controller do you have I think mine is too old to have that, I don't recall ever seeing summer mode in the service menu.



   
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 Judith
(@judith)
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04/04/2025 2:28 pm  

@jamespa use expanded mode! It’s ideal for that, and I’ve just moved back to it.


2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC


   
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 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 2 years ago
Posts: 2914
04/04/2025 2:36 pm  

@judith Thanks, Ill give it a go.

Given the tight hysteresis do you turn up the target temperature a bit to ensure it switches back on early enough in the evening?


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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 RobS
(@robs)
Estimable Member Member
Joined: 11 months ago
Posts: 55
04/04/2025 9:51 pm  

@gary We've got the FTC7, maybe older controllers didn't have that setting? It's under Operational Settings on the FTC7.



   
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 BruceR
(@brucer)
New Member Member
Joined: 6 months ago
Posts: 2
05/04/2025 12:19 pm  

Vailant arotherm+ has a setting to turn off heating when OT is above the set point. 16°c by default 



   
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