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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ASHP-BOBBA

(@ashp-bobba)

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24/09/2025 10:09 pm

@adamk Is your vibration the one with the base thats slightly unlevelled and large glass doors reverberating? forgive me if I confused you with another

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AdamK

(@adamk)

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Topic starter 24/09/2025 10:55 pm

@ashp-bobba sounds like me yep.

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JamesPa

(@jamespa)

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24/09/2025 11:14 pm

Posted by: @adamk

↑

@drei I’ve not been able to find a local installer let alone someone who can pop round to have a look. I think I might be the only Vaillant 7kw in a 20 mile radius. My issue, after they finally sort the breakers out in October (only 3 months of chasing), will be hopefully only be the humming noise which whilst drives me nuts I would think is fixable even if I have to get the primaries run around the outside of the house and abandon the ones in the ceiling.

By way of encouragement I think you are right about the hum, its fixable.

Regarding the breakers I really wouldn't fret about these.

Best practice is a Type B RCD (which protects people against electrocution in the event of several types of fault) + an MCB. However the IET regulations, which are definitive, don't require an RCD for fixed external plant. This is left to the discretion/judgement of the sparks, who is free to do a risk assessment and conclude that an MCB alone (which protects the cable from fire, and thus the building ditto, but doesn't really protect people at all) is required.

Now if you read very carefully the Vaillant instructions they say 'if the installation requires it then a type B RCD must be used'. The key here is the wording ''if the installation requires it', ie Vaillant are not saying it does, they too are leaving this to the sparks judgement and local regulations. They are only saying that if the sparks determines that an RCD is required then it must be type B.

Thus a MCB only is consistent, at least in my reading, with both the IET regs and the Vaillant rubric. Since a Type A RCD (the default) offers more protection that an MCB alone, it follows that this is no less safe than something that is perfectly acceptable. As the RCD cant damage the heat pump, it is no worse than just having an MCB, which is legit.

I'm not saying that you shouldn't insist on the swap out, merely that I wouldn't stress about it in the mean time. There are, after all, plenty of houses where all the internal circuits are protected only by MCBs or even fuses. The protected circuits will include the ring main, into which you plug a variety of devices on flexible leads, and which are much more likely to develop a potentially dangerous fault than a fixed ASHP (like, for example, a steam iron)

When this issue first came up in another thread, I searched for any case of a person being killed or injured by an aircon unit, of which there must be millions in the UK, many protected only by MCBs. I found one case of an engineer who was killed due to faulty wiring whilst he was servicing an aircon unit, but the wiring in question had nothing to do with the unit. Of course I cant guarantee that my search was comprehensive, as I have access only to the same information as you, but its clearly an event which is highly unlikely to occur

FWIW my ASHP is on a MCB only, because this is what would fit in the existing CU and my electrician, who I have known for 12 years, have interrogated on many occasions and thoroughly trust, assessed that his was sufficient. I'm guessing yours did the same. In my case this will likely change when the CU gets replaced, which will likely occur when I decide to add an EV charger and an induction hob. Until then it can live on the MCB alone!

I reiterate that I'm not saying that you shouldn't insist on the swap out, merely that I wouldn't stress about it in the mean time.

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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