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Volumisers in Heat Pump Systems: Does Placement Matter?

 
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Thermostats, Volumisers, Buffer Tanks, TRVs, Pumps, Piping, Valves, Radiators & Controls
Last Post by davidnolan22 6 hours ago
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 JamesPa
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17/03/2025 6:39 pm  

Posted by: @abernyte
↑

This whole "hot water from the primary is used in the defrost" is confusing me.  Unless it is not general across all makes the Ecodan reverses the flow of hot refrigerant gas to defrost the evaporator after stopping the fan and primary flow pump.

Are you sure.  Where does the defrost energy come from on that case?

Most stop the fan but leave the primary pump going thus extracting the defrost energy from the house.  There are pumps that can start an inline electric heater and I think someone posted about one that has a built in water tank (not sure exactly how it's used).

The energy must come from somewhere.

 

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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Abernyte
 Abernyte
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17/03/2025 6:59 pm  

Well according to Mitsubishi's technician in the video it is the hot refrigerant gas being reversed via a reversing valve and expansion chamber.  No need to steal heat from the primary circuit or any volumiser.  There may well be brands that do but that seems a very low tech solution compared to using the hot refrigerant gas in the system.


   
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 JamesPa
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17/03/2025 7:51 pm  

Posted by: @abernyte
↑

Well according to Mitsubishi's technician in the video it is the hot refrigerant gas being reversed via a reversing valve and expansion chamber.  No need to steal heat from the primary circuit or any volumiser.  There may well be brands that do but that seems a very low tech solution compared to using the hot refrigerant gas in the system.

Sofaik all others do the same, ie they operate the refrigerant circuit in cooling mode to effct defrost.  They thus cool the house and warm the heat exchanger using heat extracted from the house. 

I think it's highly likely mitsubishi don't switch off the water pump because the water is the source of the energy.   

 

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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 davidnolan22
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17/03/2025 8:04 pm  

@jamespa 

My mitshubishi does not turn off any pumps flows continue and takes some heat from the house.  I’m fairly sure this is normal behaviour 


   
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