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Midea R32 Monobloc MHC-V12W in 1989 Detached House: Noise from Pipes/Airing Cupboard, DHW Schedule Not Always Heating – Advice Needed?

Painter26 · 2026-02-19T12:26:57Z

Hi all, I've been reading the posts in this forum with great interest for the last few days, especially @pash44pump journey. I've already had some golden nuggets of support from some of you on the MSE forum but was informed of this resource and wanted to share my own experience and ask some questions if I may? House: 1989 detached brick build, 1900 sq ft, 4 bedrooms, 4 reception rooms, 3 bath, (unheated) double garage. No cavity wall insulation that we are aware of. Loft appears well insulated but survey suggested it may not be quite up to current standards. Located in Hampshire, England. System installed October 2024: Midea R32 Monobloc MHC-V12W/D2N8-B Pump located on east side of house, 400mm away from the wall and mounted on rubber feet (albeit 2 of the 6 bolts appear to be missing and are being replaced). Pipework goes up east side of house into attic space, from where it drops down into first floor airing cupboard. Heating is provided by radiators. I believe that the existing gas boiler pipework was used but new radiators were fitted to all rooms apart from the lounge and hallway. I bought the house a couple of months ago but have only just moved in. The previous owner had the system fitted but subsequently needed to sell the house and move up north so I inherited it just past its first birthday. Heating I'm generally happy with the heat levels I get across the house. The upstairs is slightly warmer as one might expect, and as the rear of the house is south facing it benefits from sun a lot of the time. I'm confused about how to balance heating output with the lock shield valves though. Currently all my TRVs are open fully so not sure if I need to do anything further with lockshields. All the radiators seem to heat up to similar levels, although the lounge, which was one of only 2 radiators not replaced, is a bit cooler (probably exacerbated by not currently being able to close the door fully!). I have a weather compensation curve active which seems to do its job (typically 33 flow temp at 8 degrees outside temp and 38 flow temp at 3 degrees outside temp). I've never lived my adult life in a property with a wet central heating system as I've always been in apartments with electric panel heaters, so I'm totally unfamiliar with the noises that one should hear from the heat pump. The outside pump itself makes a low whirring noise when the fan and compressor are active which can occasionally be heard inside through the adjoining wall to where it's mounted outside - but it's never particularly intrusive. However, I do hear noise inside the property which is louder than I was expecting. When the pump and/or compressor are active I hear a 'buzzy' noise through the inlet/outlet pipes in the loft and down into the airing cupboard. Hard to describe but like 'data scrambling' and, perhaps like the noises I remember my old central heating system as a child making. Because the airing cupboard is sandwiched between my bedroom and one of the spare bedrooms I can hear the faint sound of the internal workings and what can only be described as a very very faint rumble like a wheelie bin being wheeled down a path. Very very faint and not audible in the loft pipes but only occasionally in the house itself. I do have exceptionally sensitive hearing so not sure if I'm overthinking what are perfectly normal noises. As I hear it at night and I'm a light sleeper I wondered if it was worth considering setting back the heat overnight for a few hours or whether the re-heat efforts are not worth it. Additionally, sometimes I hear an intermittent drip noise from the kit in the airing cupboard. There's no visible leak (and because I did have a leaking hot water tank replaced under warranty I'm super paranoid at checking every day). It's not audible elsewhere in the house and it's only occasionally from the pipes somewhere around the 2 expansion tanks. I can't work out if it's just condensation in the pipes or natural dripping noises from water going through the system. Only occasionally and I can't pinpoint it to a set time. Domestic Hot Water I was setting the DHW using the timer tab on the controller for e.g. 14:00-15:00 every day to hit 45 degrees, but I was finding it wasn't always heating up at these set times. Even though the 'squiggles' next to the tap symbol would turn on as planned the tank temp wouldn't increase. I've just changed this to use the 'schedule' function instead and seem to be observing a similar pattern, maybe only every other day will the tank actually heat up. I wonder if this is because my 'tank reheat trigger' point hasn't been met yet (i.e. if my target temp is set to 45 on the timer, my reheat threshold is -5 then the timer will only ever kick in if the actual tank temp falls to 40 or below?) So, for example, at a current tank temp of 41 it wouldn't reheat even if the timer was instructing it to hit 45? On the ...

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Air Source Heat Pumps (ASHPs)

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Painter26

(@painter26)

Active Member Member

Joined: 2 months ago

Posts: 22

Topic starter 27/03/2026 11:33 pm

@benson thank you.

My t4autohmax is also set to 17 so once the weather gets towards that consistently I'll decide what to do.

Part of me think it must be beneficial to keep the primary circuit running periodically to maintain it even though the DHW will be coming on daily. But assume this is not really required and it could stay 'off' all summer?

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benson

(@benson)

Reputable Member Member

Joined: 2 years ago

Posts: 300

28/03/2026 1:37 pm

Personally I would turn it off as I wouldn't necessarily see much if any benefit of keeping the circulator pump going during summer months. The only possible advantage I can think of is that it will keep the system water running through the magnetic cleaner perhaps as I think you are alluding to? Probably marginal gains though...

Plus, in summer the OAT is going to drop below 17 at night but you still aren't going to need any heating so you will probably find it will be coming on when you really don't need it.

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JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 4720

28/03/2026 2:53 pm

Posted by: @benson

↑

Personally I would turn it off as I wouldn't necessarily see much if any benefit of keeping the circulator pump going during summer months. The only possible advantage I can think of is that it will keep the system water running through the magnetic cleaner perhaps as I think you are alluding to? Probably marginal gains though...

Plus, in summer the OAT is going to drop below 17 at night but you still aren't going to need any heating so you will probably find it will be coming on when you really don't need it.

I believe some heat pumps have an anti-seize function whereby they start up the circulator pump once a week or thereabouts if there is no call for heating or DHW. Obviously that will only work if you dont cut the power!

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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benson

(@benson)

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Joined: 2 years ago

Posts: 300

28/03/2026 3:17 pm

@jamespa interesting. Did not know that. That said- I meant just turn the space heating off rather than turning it off completely at the isolator switch obviously.

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