Notifications

Clear all

Need help maximising COP of 3.5kW Valiant Aerotherm heat pump

DavidB · 2026-01-31T08:25:35Z

Last September we installed a 3.5kW Valiant Aerotherm heat pump and the associated app. Over the winter I have been getting to know the system and how it operates under different conditions. The app provides a COP figure under its “Energy” tab. The figure is 3.5 for the current week. The system is set up with weather compensation and heat curve to 0.6. The building heat loss at -4C is about 3kW. At an outside temperature of +5C, the Vailant pre sales data suggests a COP of over 4 at the heat curve flow of roughly 35C. The system works well and we are happy with both the heating and hot water supply. Sadly OVO have recently withdrawn the heat pump tariff of 15p per kWhr and reverted to our normal 26p. Our installed Smart Meter does not operate so I am focusing on how to maximise COP. Any ideas or suggestions?

Page 3 / 3 Prev

Air Source Heat Pumps (ASHPs)

Last Post by JamesPa 4 hours ago

30 Posts

5 Users

1 Reactions

312 Views

RSS

DavidB

(@davidb)

Trusted Member Member

Joined: 1 week ago

Posts: 19

Topic starter 05/02/2026 10:35 pm

@adrian thanks for the explanation Adrian. Sounds as if I should experiment with pure weather compensation for a day or 2, keep the stove off and see what happens.

👍

ReplyQuote

JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 4164

05/02/2026 10:57 pm

@davidb Further to my previous post one further comment I would make is that 300l system volume is not consistent with 7 radiators. Unless you have a large buffer tank or volumiser (do you, if so how large) then I would guess a lot of this was used to flush the system

If you provide the data from the app that I mentioned it might clarify matters further.

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.

ReplyQuote

DavidB

(@davidb)

Trusted Member Member

Joined: 1 week ago

Posts: 19

Topic starter 06/02/2026 7:45 pm

Thanks for requesting this info - I hadn’t seen this data before. Live and learn. Not sure if 1000 cycles is good or bad or period of measurement.

ReplyQuote

DavidB

(@davidb)

Trusted Member Member

Joined: 1 week ago

Posts: 19

Topic starter 06/02/2026 7:46 pm

January info

ReplyQuote

DavidB

(@davidb)

Trusted Member Member

Joined: 1 week ago

Posts: 19

Topic starter 06/02/2026 7:48 pm

Yield info for January. I live on a Scottish island.

ReplyQuote

JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 4164

06/02/2026 10:31 pm

OK. What Im seeing looks fairly normal TBH:

1 start per hour is good (1028 on off cycles in 1303 hours); there is no evidence of short cycling

Unfortunately you haven't split out heating and DHW (you really should), which denies us some important information, but an overall COP of 3.6 in January given the ratio of DHW to space heating displayed compares to mine of 3.87 for the two combined, but with a much lower proportion of DHW in my case. I would estimate guess you achieved a COP of perhaps 3.8 for space heating alone, which is pretty reasonable for January, and therefore that you can reasonably expect a space heating SCOP of 4 or more (mine is 4.2). Your heating consumption of 241kWh compares to mine of 907kWh. My house is 7kW at design temperature suggesting yours is actually only about 2kW. This is consistent with 1 start per hour which is definitely OK but not 'top notch' for January,; the heat pump is somewhat oversized but with a 2-3kW loss thats absolutely inevitable and anyway necessary to give you decent DHW reheat time.

Basically I don't think you have any problem and should easily achieve a SCOP of 4 plus for space heating. DHW will always have a lower SCOP because you are heating to a higher temperature, I don't know if you have the opportunity to reduce this but if you do it will help.

I don't think you have anything to worry about but can I suggest you keep monitoring however to monitor space heating COP separately from DHW COP?

This post was modified 4 hours ago 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.

ReplyQuote