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Help me keep the faith with my air source heat pump installation

AdamK · 2025-03-29T13:05:20Z

i knew when setting out on this road it would be a challenge i just didnt know how much of one it would be. after having many quotes some i couldnt fathom why they were so high i thought id sorted an installer. problem is they are 72miles away so first issue was doing a remote heat loss which has been back and forth several times to get it more or less correct, but still have one room thats 2m2 smaller than what i measured. anyway the next issue was getting the 28mm primaries in before the new kitchen ceiling goes in. they sent a plumber that proceeded to bugger the job up as the wall sleeve kit hadnt been supplied to him. so sent him on his way. was promised the sleeve kit the next day and i said my plumber could fit it to save them sending an engineer. next day no kit. add to this all the mods im having to do to pipe work to maximise efficiency and im seeing why the take up is tiny in the UK. im not naming the company as they are a recommended one and have apparently done good work else where but maybe thats in there local area. i know living in Boston creates its own issues being miles from any proper trades so if someone asked me would i recommend getting a heat pump in my area id have to say no. theres just not enough skilled trades where i live.

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Air Source Heat Pumps (ASHPs)

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JamesPa

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19/10/2025 6:25 pm

Posted by: @toodles

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@jamespa Don’t the ‘Decorator’s Caps’ just shut the valve completely when they are fitted? Toodles.

If you screw them right down yes, but not if you don't. The ones that came with my TRV4s actually have moulded arrows on them labelled ,+/-

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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AdamK

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Topic starter 20/10/2025 2:12 am

@jamespa tonight I’ve set the senso to 21 (it’s set to active), upped the curve from 0.4 to 0.5, and opened all the trvs. What I’ve noticed is after several hours the house seems stuck at 20.6c. It’s as if increasing the ft via the wc curve has had no effect.

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JamesPa

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20/10/2025 7:34 am

Posted by: @adamk

↑

@jamespa tonight I’ve set the senso to 21 (it’s set to active), upped the curve from 0.4 to 0.5, and opened all the trvs. What I’ve noticed is after several hours the house seems stuck at 20.6c. It’s as if increasing the ft via the wc curve has had no effect.

If its set to active then the HP will adapt the WC curve (to an undisclosed extent and with an undisclosed timescale) to achieve the set temperature, so I wouldn't necessarily expect a small change in the WC slope to have much effect because its going to be opposed by the 'active' function.

The difference between 0.4 and 0.5 when its 12C outside is only about a degree anyway. This will anyway take some time to have an effect. Opening all the TRVs is a good, increases available system volume; getting the remaining rad in (I think you said you had one or more rad still to fit) also good. Do you happen to know your system volume, installer should have calculated it but it may not be in the documentation. Mine is about 200l; Im guessing yours may be a fair bit less.

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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AgentGeorge

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20/10/2025 7:56 am

Posted by: @adamk

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@jamespa

Here is the same day from my HP, I have temp set at 20 at all times, im getting a COP in mud 4s this month.

The 1pm spike is the hot water boost, I found HP used less energy during day when it’s warmer than at 7am or 10pm

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AgentGeorge

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20/10/2025 8:08 am

@toodles only if you screw them down tight

just dropping them on and half a turn is enough to keep the valve clear of debris and rad hot

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Toodles

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20/10/2025 9:34 am

@agentgeorge Ah! Thanks very much - one lives and learns.😉 Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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AgentGeorge

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20/10/2025 10:25 am

@toodles i learnt by not screwing down enough, assuming water now cut off and undoing the radiator, to then get spurted with water; not most fun you can have with DIY plumbing

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Toodles

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20/10/2025 10:39 am

@agentgeorge 😳 Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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AdamK

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Topic starter 20/10/2025 5:01 pm

@jamespa ive found out today the Thermix plinth heaters have an adjustable flow temp all the way down to 25c, which is adjustable via the wireless stat which controls both plinth heaters.

will have a fiddle when i get in.

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AdamK

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Topic starter 20/10/2025 11:12 pm

@jamespa ok got home and I can indeed set the flow temp yay. So at moment I’ve set it to 27c which has lengthened the cycle time for the fans from secs to minutes. I think this might be better for stretching the compressor cycling as it’s shedding more heat into the kitchen. The house today has reached 21c but I’m not sure how much of that is the heat pump catching up finally or solar gain.

on the down side checking the flow rate it looks like I might have lost 150l/h so might have an issue with debris being eroded off by the flow rate.

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Grantmethestrength

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21/10/2025 7:13 am

@adamk have you checked your filters? It is a fairly easy thing to do once you know how.

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AdamK

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Topic starter 21/10/2025 9:46 am

@grantmethestrength yes took the main magnetic strainer one out last week and cleaned it, the flow jumped from 725l/h to 1100l/h. its now at about 985l/h. trouble is with the pump being on auto im not sure if that might be because at that moment it was modulating, though i did go into the test menu and have the pump setting on 100% before moving onto the flow rate reading.

This post was modified 4 months ago by AdamK

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