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Midea Monobloc 10kW ASHP - serious issues

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(@mmiuse)
Eminent Member Member
68 kWhs
Joined: 1 year ago
Posts: 10
Topic starter  

I'm hoping for some advice. In July 2021 we had a Midea Monobloc 10kw ASHP installed. I don't want to bore you all with the detail of the story, but will summarise. We have had E8 and E0 (flow rate errors) since install. The water pump inside the ASHP was replaced, the flow switch was replaced, the PCB was replaced, the control unit was replaced and in Nov 2022 the whole AHSP was replaced with a new one. since install we have probably had over 40 engineer visits, 1000s of whatsapp and email messages and I am at the point where I am thinking of rejecting the whole unit, claiming a refund and going back to a gas boiler. Here are the issues we are having:

 

  1. Flow rate errors (E8 and E0). The error would occur a few times each week and would require me to turn off at the fuse board to reset before it would work again. This has recently been resolved by changing the water pump from 'variable rate' to 'fixed rate' - I would love to know what the impact of this is, surely it has a variable rate pump for a reason? Alos, if this is causing the issues it would seem to be a manufacturing issue and others would have the same? If anyone could explain that would be great.
  2. The ASHP only seems to be able to get to 57 degrees on the flow temp - so it cannot heat our water tank above 55 degrees. Is this normal? I read in the spec that it can supply 60 degree flow rate even when minus 20 degrees outside. I have been told I just can't set it above 55 degrees as the target.
  3. The heating 'target temp' is 42 degrees, but the flow rate on hating pretty much never gets over 32 degrees. I have turned off the weather comp in case that was the issue, but it hasn't made any difference. This means that the house is actually not reaching its target temp and the heat pump is running 24 hours per day (this is during Jan, so it is cold, but only around -3 to +8 so well within what should be 'easy' for the ASHP). 
  4. The water tank 310L in the loft, is losing around 1.5 degrees per hour when not in use (i.e. at night) - temp outside is around 1 to 8 degrees during this time, but it seems an incredible high rate of heat loss to me?

In early Dec I told the installer that if they didn't have it all fixed and working properly by the end of Jan I would reject the install and claim a refund (which will mean going to court as they won't pay up I don't think) and I will revert to a gas boiler. I had really hoped that they would get it working in that time, but they have not (I can't deny they have tried though).

 

Any thoughts and advice would be gratefully received. 


   
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(@batalto)
Famed Member Member
3655 kWhs
Joined: 3 years ago
Posts: 1091
 

Your filter is blocked - open it up and empty it of crap

16743025026682759993963928254302

If you look at my main post on my install - ASHP in Hampshire. You'll see I had the exact same issue. It's a 2 min fix (if it's a filter issue)

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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(@mmiuse)
Eminent Member Member
68 kWhs
Joined: 1 year ago
Posts: 10
Topic starter  

Thanks, but that's not it. It's been cleaned many times and with the exception of the first time, it has been totally clean every time


   
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(@kev-m)
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5561 kWhs
Joined: 3 years ago
Posts: 1299
 

Hi and welcome.  Sorry to hear of your problems.  I can't help with 1. That is something the installer would have to sort out and sounds like a design/installation issue. 

2. My ASHP only heats to 55 deg; any hotter needs the immersion.  Why do you want HW at 60 deg, which is enough to scald? 55 deg plus is going to be very inefficient (poor COP)

3. If it's really maxing out at 32 deg then that's a problem (but see my comment below).  Is that radiators of ufh?  If radiators I doubt 32 deg would heat many houses. 32 deg is barely warm to the touch. Do you have a thermometer you could measure the flow temp with to check it? 

4. It's possible if it's in a cold loft.  Do you know the specs for heat loss for your cylinder? The specs are normally for a tank at 60 deg with surroundings at 20 deg. 

Do you have a heat loss calculation for your house? A 10kW Midea ASHP probably won't be able to produce 10kW at-3 deg.  310l is a big HW tank and hour ASHP is going to spend a lot of time heating HW to 55 degrees if you're using a lot. It's possible it's not powerful enough, especially during the cold weather when it will be defrosting regularly. Does it reach its target flow when it's warmer outside?  

There are some other folks with Midea ASHPs who may have more specific experience of these issues (I'm looking at you @cathoderay !)      

 


   
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cathodeRay
(@cathoderay)
Famed Member Moderator
6918 kWhs
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Posts: 1391
 

Posted by: @kev-m

I'm looking at you @cathoderay !

I've had my own problems today! The wired controller lost it's mind, and I had to factory reset it. The problem was the LWT (leaving water temp, flow temp) wouldn't get above 30, and the DHW came on when it shouldn't, I have it on a timer, and that only made the heating even more ineffective. On top of all that, it decided to defrost rather more than usual, because it was indeed cold and foggy. A bit like me...

@mmiuse - welcome. As @kev-m suggests, we really need more details before we can make sensible comments/suggestions. Heat loss (your installer should have given you a copy of the calcs), whether UFH or rads, and if the latter, are they correctly sized for your heat pump, is there a plate heat exchange or low loss header between the heat pump and the heating circuit etc. 

What I can generally observe from my own system is that it does better, and is cheaper to run, using weather comp, rather than fixed flow temp.

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


   
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(@mmiuse)
Eminent Member Member
68 kWhs
Joined: 1 year ago
Posts: 10
Topic starter  

Sorry, here is more info:

 

1. The installers have been out over 20 times to look at this issue. Even the wholesaler has sent out 4 different engineers. The entire heat pump has been replaced in an effort to fix this. I have concluded that they don't know what is wrong or how to fix it (it has taken them a year and a half to figure out that the error stops if they change to fixed flow instead of variable.

2. the only reason I had tried to set the hot water to 60 is that the pump is slow to respond when the temperature lowers, so if we have 2 long showers the second person runs out of heat - we are a family of 5 and potentially becoming 6 so we had asked for a 300l tank to ensure we have enough hot water for a few showers in the morning. I have it set to 55, what happens is it gets to 55, but then loses 1.5 degrees an hour. The heat pump is set (apparently) to start heating again when it drops to 50. Often it gets much colder before it starts heating. If person 1 starts showering when water is 50, by the time they finish it is low 40s, it seems to take up to 10 minutes for the heat pump to start heating water after temp is dropping, so if a second person gets in the shower after the first, they probably have 3 or 4 minutes before the shower is 40 degrees or lower. Similarly when we fill the bath, by the time one bath is full, the tank is not hot any more. I thouoght that setting to 60 would make the pump kick in sooner and stop the water getting to 40 or lower.

3. we have wet underfloor heating throughout the house as our only heating source. Ideally the heating temp would be 37. We have the flow rate set to 42. During the day it seems to get up to 35, sometimes 37. During the night, say from 2100 to 1000 it pretty much sticks at 31 (sometimes 30 and sometimes 32). The house thermostats are permenantly set to 22 degrees (we would probably have it set at 20 or 21 if the system worked properly, but at night some of the bedrooms drop to 18, so by having it set to 22 we hope that the house is generally warmer and therefore not likely to drop as far at night (we have 3 young children, so want warm rooms at night as they don't keep their covers on!).

4. It is a World Heat 300L Cylinder

 

 

This post was modified 1 year ago by mmiuse

   
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(@kev-m)
Famed Member Moderator
5561 kWhs
Joined: 3 years ago
Posts: 1299
 

@mmiuse 

thanks for the extra info. It is possible from what you are saying that your ASHP can't cope with your heating/HW requirements in the winter.  Do you have heat loss calculations? 


   
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(@batalto)
Famed Member Member
3655 kWhs
Joined: 3 years ago
Posts: 1091
 

@mmiuse have you checked the filter on the pipe work. It's not in the unit - it'll be somewhere on your pipework

IMG20220203125944~2
IMG20211103220555

This is what can happen which causes an E8/0 issue

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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(@mmiuse)
Eminent Member Member
68 kWhs
Joined: 1 year ago
Posts: 10
Topic starter  

@batalto yes, we have cleaned that several times - the first time it was dirty (Nov 2021), but it has been clean since.

 

is this the heat loss calcs? At the time, we had 5 quotes, all the others were recommending 7 and 8 kw systems, so 10 was the highest of them all.

image
This post was modified 1 year ago 2 times by mmiuse

   
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(@mmiuse)
Eminent Member Member
68 kWhs
Joined: 1 year ago
Posts: 10
Topic starter  

@kev-m see my last comment re heat loss calcs. The odd thing is that it will have a flow temp of 31, but as soon as I switch to hot water mode it gets up to 50 in no time, so it feels like it can easily generate higher temp but almost like the software is limiting it.


   
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(@batalto)
Famed Member Member
3655 kWhs
Joined: 3 years ago
Posts: 1091
 

@mmiuse the tank and the heating are on different circuits. If you can't seem to get any heat into your system you might have an issue around the pump and the house circuits. I had my low loss header removed and this could be issue to explore

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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cathodeRay
(@cathoderay)
Famed Member Moderator
6918 kWhs
Joined: 2 years ago
Posts: 1391
 

Posted by: @mmiuse

is this the heat loss calcs?

Yes (and that looks very like Freedom Heat Pumps's calculator). Now, there are two ways the heat loss gets entered there. One is from external calcs, entered in the blue cell next to Heat loss if known kW, second is pulled in from FHP's heat loss calculator, in the non-editable grey cell next to Heating loss calculator figure. That means the shown loss, 7.4kW came from elsewhere.

7.4kW is quite a low loss, unless the property is small and/or well insulated (my 3 bed but small leaky old cottage has a loss of over 12kW). I'd be inclined to check the loss calculations, though it would appear all your quoting installers came up with smallish heat losses if they all quoted for smallish heat pumps. Top on my list of things to check would be the heat loss calcs, who did them, do they make sense (for the property they apply to), are there any typos etc.

Heat loss calcs may be based on physics, but they are not an exact science. My quoting installers 'calculated' my heat loss to be anything between 9kW (a comedy value) and I think the top one was 14 if not 16kW.          

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


   
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