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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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Painter26

(@painter26)

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Topic starter 28/04/2026 12:04 pm

@cathoderay up until the last few days the rads have always had a very small detectable bit of residual warmth but as the outside weather is now getting warmer they are mostly cold to touch during the day until such time as the temp drops and the compressor kicks in.

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cathodeRay

(@cathoderay)

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28/04/2026 5:46 pm

Posted by: @painter26

↑

mostly cold to touch

25 degrees does feel cool/cold, remember blood temp is ~37 degrees. I think you may find your compressor is doing very long cycling to keep the output down. Can you read the leaving water temp from the Midea controller, it is on page 4 of the Operational Parameters (not page 3) as TW_O PLATE W-OUTLET TEMP (just to confuse us)? It should average at about 25 degrees. You could also keep and eye on total lifetime kWh use when the DHW is not on, and see if it increases. The compressor data on page 6 may also tell you something.

This is my heat pump on Sunday, before I turned the space heating off on Monday morning (yesterday morning). Note that during the middle of the day, when the OAT was above my right hand weather curve OAT set point of 15°, it is still running, with long cycling. The big spike at 1300 is my DHW heating.

Midea 14kW (for now...) ASHP heating both building and DHW

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benson

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28/04/2026 6:34 pm

Posted by: @painter26

↑

I could keep my settings as they are but even at night I get a lot of residual solar gain as the house is directly south facing so I would not need the space heating to kick in on a cold night

For this reason as said before I would just turn it off.

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Painter26

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Topic starter 28/04/2026 9:02 pm

@cathoderay I turned the room stat down to 12 degrees earlier this evening which, predictably, turned off the space heating.

Here's my controller now (I should correct my previous post with my current WCC parameters which are 45 flow temp at -4 OAT / 25 flow temp at 15 OAT):

This post was modified 6 months ago 2 times by Painter26

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cathodeRay

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29/04/2026 6:38 am

@painter26 — that all makes sense. Space heating (the sun symbol in the middle panel) shows as off, and the leaving and returning water temperatures are the same, and low, at 17°C. Your space heating is off.

Midea 14kW (for now...) ASHP heating both building and DHW

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Painter26

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Topic starter 29/04/2026 10:32 am

@cathoderay great, thank you.

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Painter26

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Topic starter 07/05/2026 2:52 pm

Just bumping this up for @editor .

Are there any engineers local to Fleet in Hampshire who could advise on whether this is likely the expansion vessel that needs checking again after the new DHW tank was installed? I'm struggling to get any response from the original installer and I would like to resolve the trapped air issue and (very gradual) pressure loss.

This post was modified 6 months ago by Mars

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Mars

(@editor)

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07/05/2026 2:57 pm

@painter26 thanks for bumping this up. I'll circulate this to my professional/installer network to see who'd be available to look into this and help.

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Painter26

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Topic starter 07/05/2026 4:10 pm

Thanks @editor

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Wizard

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07/05/2026 6:59 pm

@painter26 i am in Lightwater and midea trained. Sounds like a pretty straightforward issue but need to see for myself before recommending a plan/doing a fix

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Mars

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11/05/2026 1:23 pm

@painter26, Leading Renewable Change have just got in touch and said that if you call them on 01293 851 459, press service and speak with Ella, they can arrange to send out an engineer. I have no idea wha their charge out fee is.

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Painter26

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Topic starter 11/05/2026 1:40 pm

Thank you!

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