Advice on internal circulation pump noise

Air Source Heat Pumps (ASHPs)

Last Post by jtg 11 hours ago

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jtg

(@jtg)

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Joined: 11 hours ago

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Topic starter 16/12/2025 1:40 pm

Hi all - I wanted to share my recent experience of a domestic heat pump install in the hope of finding a way past a current issue that I'm close to reaching an impasse with the installer over.

First up the good news - having spent a few years watching the market (and more time than I would care to admit reading around and learning what I can about the process and technicalities of good heat pump implementations) I finally took the leap and went with one of the more prominent national installers (I'll avoiding naming for now as I don't think that's too relevant.) Having had all the design work/heat loss calculations etc carried out the install was booked in promptly and completed over 4 days. The installers were professional and courteous. Since commissioning the install has been more than capable of keeping the house to design temp (20 degrees) and produces more than enough hot water. There have been a couple of things, post install, that the installer has been very happy to come back and tweak/correct, and everyone I've spoken to - from onsite engineers, to design/office staff - has absolutely been engaged and willing to help address any issues as they've arisen.

The not so good news - while I was well aware of the potential for some noise related to the external unit, and was more than accepting of that, what I was unprepared for was the noise caused by the internal circulation pump in the loft. The constant whine/drone of the pump through the pipework during the day is a little distracting but [mostly] tolerable, but at night with no other background noise it becomes very noticeable and quite disrupting to sleep. I had resorted to dropping the flow speed on the pump manually overnight to reduce the noise to sleep through. The installer has visited a couple of times to look at options, and so far has installed some additional insulation to try to deaden the noise, and have also installed a bigger pump - 6m head increased to 8m - (which has actually made the issue worse, and even on the lowest setting is now worse than the original 6m pump.)

It's a 4x bed (2 storey) detached late 1960s house, 8kW external unit, 40L buffer tank in loft, hydraulic control and divertor valves in loft, additional circulation pump in loft, 300L cylinder, it's plumbed into 5x existing 1st floor radiators, 5x existing ground floor radiators and an existing wet underfloor heating system in a downstairs extension (4x loops totalling around 190m of microbore 10mm piping off a single manifold via a 4x way reducing push fit adaptor) - existing radiators were already oversized high output K3 and K2 rads that more than met the heat loss for each room at delta T50. Existing heating circuit is a mix of 22mm copper feeding to 15mm copper per radiator. The internal circulation pump in the loft is floating on the pipework.

The engineer has been very diplomatic when questioned about the noise, and has explored several things within his immediate control to try to address the issue, but has said he is running out of things to try.

I have tried to explore options with him about relocating the pump elsewhere in the circuit, perhaps downstairs away from bedrooms, and mounting the pump on anti-vibration dampers, but have not got any further than the suggestion that that's too big a re-working of the system that would need to go back up the chain for any sort of approval. I am currently awaiting a call back regarding a supervisor visit to look at further options.

I've also since mapped out some of the internal pipework in the house and identified a couple of points where I think return flow is converging from multiple directions and could feasibly be causing a degree of turbulent/constricted flow. I don't think this is the sole cause of the issue, but wonder if it might be in part contributing.

For those that have read this far and not switched off - thank you - I wonder if anyone has any thoughts or observations that might help find a way forward? Happy to share further photos/diagrams if anyone's in any way interested 🙂

Yours optimistically!

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