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My Grant R290 9kW Heat Pump Installation

 
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Air Source Heat Pumps (ASHPs)
Last Post by GrahamF 12 hours ago
14 Posts
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 petch
(@petch)
Active Member Member
Joined: 3 months ago
Posts: 14
Topic starter 22/04/2026 11:44 pm  

Posted by: @batpred
↑

Posted by: @petch
↑

On the bright side, I've got a COP of 6 so far 

that’s pretty impressive. I cannot remember many pumps beating that..

 

Again, really don't know how accurate this is! 

image

 



   
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GrahamF
 GrahamF
(@grahamf)
Estimable Member Member
Joined: 1 year ago
Posts: 124
14/05/2026 12:02 pm  

@petch I'm very sorry that I have not picked up your post before.  I hope this feedback is still helpful.

Leaving pump blockade off enables the heat pump to know the temperature of the water in the system, so it can decide to turn on the compressor again.  Your system seemed happy to run continuously overnight.  During the day when the outside temperature got to 10C it turned off a few times.  This is probably because it can't reduce the flow temperature any lower than about 27C.

According to the Smart Controller Installer and Operating Instructions table in Section 7.14.1

''DECREASING FIXED WATER TEMPERATURE' applies only to non-weather compensated circuits.  Therefore it does not apply to us.

Section 7.14.2 for Weather Compensated Circuits is confusing.  I think it is meant to apply a setback to the flow temperature during Night Mode.

It says:

During a scheduled night/unoccupied time period, the water flow temperature will be reduced by the configured value 
‘DECREASE WATER TEMPERATURE’ set during system setup or in the circuit settings.

However, confusingly then it goes on to say something that seems to contradict Room Temperature Correction below.

...With a Thermostat...

If ‘THERMOSTATIC PUMP BLOCKADE’ is not enabled, once the target air temperature is achieved the smart controller will use decrease the flow temperature target by the ‘DECREASE WATER TEMPERATURE’ value, which is set correctly will maintain the target air temperature. Refer to 7.3.1.3 for recommended setback values based on heat emitters for the circuit.

Room Temperature Correction

Target temperature with correction = Target air temperature of the thermostat assigned to the circuit minus Current temperature of the thermostat assigned to the circuit x Room temperature correction.

By default, the Room temperature correction value is 4.0, and the value range is 0 - 10.

It is necessary to find appropriate value of the Room temperature correction. The higher the coefficient, the greater the correction of target circuit temperature. If the setting is “0”, the target circuit temperature is not corrected. Note: setting a value of the room temperature coefficient too high may cause cyclical fluctuations of the room temperature.

Bottom line, I think you should use Decrease Water Temperature for Night Time set back and Room Temperature Correction to add some room influence to the flow temperature.  But I could be wrong!

Graham


This post was modified 12 hours ago by GrahamF

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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