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Midea Monobloc 10kW ASHP - serious issues

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(@heacol)
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@mmiuse The Midia unit is a very simple basic unit, but it can perform reasonably well if installed and set up correctly, however it is what it is. If you have a buffer tank or system separation, that is probably your problem with heating, but there is something blocking the water flow to cause the low flow errors, more than likely the Honeywell type (brass tube with a silver box on top) valves.

I can probably help, PM me and we can discuss it.

Professional heat pump installer: Technical Director Ultimate Renewables Director at Heacol Ltd


   
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(@derek-m)
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Posted by: @mmiuse

@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.

Are you operating the system in weather compensation mode, and if so, what are the settings?

The heat pump will heat the water to the temperature required by the setting, for hot water production the setting can be much higher than that required for central heating. If the heat pump is instructed to only heat the central heating water to 31C, then that is what it will produce. This may not be warm enough to heat your home to the required indoor temperature.

I would suggest that you check if your heat pump is operating in WC mode, and if the settings are correct.

 

This post was modified 1 year ago by Derek M

   
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(@mmiuse)
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Weather comp was on (set by installer, but I turned it off to see if it would make any difference (it did not). 

 

Here are the weather comp settings:

 

image

Here is a bunch of other info from the dashboard (note the Tado temp is irrelevant, I use heatmiser Neo stats and they are currently set to 22, the flow temp changed to 255 after turning weather comp off, but target flow is set to 42 on controller and shows as that everywhere else):

image

 

image
image
image

As you can see, the pattern is rhythmic through the night bouncing up to a max of 33. I think the higher flow temps during the day are most likely heating the water. I should add that I have used the immersion heater a lot in the last few days, which will affect the graph, because I didn't want any energy to be spent on water as the house is well below temp so wanted all energy to go into heating at night.

This post was modified 1 year ago by mmiuse

   
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cathodeRay
(@cathoderay)
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@mmiuse - I'm interested to know what those images come from, they are not from the standard Midea wired controller, yet the data could only come from the wired controller, suggesting you have something connected to and recording data from the Midea controller. Elsewhere I have a thread on trying to do this with Home Assistant and a module (written in python) called midea_ac_lan, with only very limited success. The last image shows historical data, it looks like you have both real time and historical data available, exactly the goal I am after, hence asking how you have managed to do it!

I'm not sure what to make of your last image. Ignoring Comp Dis Temp (don't know what it is, something to do with the compressor?), what I see is the LWT/RWT fluctuating between around 30 degrees and 55 to almost 60 degrees. The difference between the two at any one point in time is mostly about where it should be, 5 degrees, and for much of the time the LWT is between 35 and 40 degrees, ie a bit below your weather curve set LWT values. But those big spikes up to almost 60 degrees? If they are the heat pump heating the DHW, that is an awful lot of DHW to be heating! Do you use that much? If not, then something is wrong with those charts.

  

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


   
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(@derek-m)
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Posted by: @mmiuse

Weather comp was on (set by installer, but I turned it off to see if it would make any difference (it did not). 

 

Here are the weather comp settings:

 

image

Here is a bunch of other info from the dashboard (note the Tado temp is irrelevant, I use heatmiser Neo stats and they are currently set to 22, the flow temp changed to 255 after turning weather comp off, but target flow is set to 42 on controller and shows as that everywhere else):

image

 

image
image
image

As you can see, the pattern is rhythmic through the night bouncing up to a max of 33. I think the higher flow temps during the day are most likely heating the water. I should add that I have used the immersion heater a lot in the last few days, which will affect the graph, because I didn't want any energy to be spent on water as the house is well below temp so wanted all energy to go into heating at night.

I suggest that we test your system in a logical and systematic manner to try to locate the root cause of your problem and hopefully arrive at a solution.

My first question would be what is the size and type of your home?

Do you have a buffer tank or low loss header installed?

Is your system zoned in any way?

 

This post was modified 1 year ago by Derek M

   
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(@derek-m)
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Posted by: @mmiuse

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. 

To answer question 1.

The amount of heat energy transferred from your heat pump into your home is dependent upon two main factors, the water temperatures (LWT and RWT) and the water flow rate.

The temperature difference (DeltaT) between LWT and RWT is often controlled at 5C, so the factor which determines the quantity of heat energy is the water flow rate. If the flow rate is increased from 10 litres per minute to 20 litres per minute, then the quantity of heat energy produced by the heat pump will be doubled.

The amount of heat energy absorbed by your home is again dependent upon the DeltaT, but this time between LWT and the actual indoor temperature, so the higher the LWT, the more heat energy will be transferred into your home.

In weather compensation (WC) mode, the heat pump controller varies the LWT dependent upon changes in the outside air temperature, which in turn will vary the amount of heat energy absorbed by your home, to balance the heat loss. If more heat energy is transferred from the water into your home, the DeltaT between LWT and RWT will increase, and the heat pump controller will speed up the water pump to increase the flow rate, and thereby reduce the DeltaT to the specified 5C.

If your heat pump is operated with a fixed LWT, the water flow rate will only vary slightly, and the indoor temperature will vary with outside temperature variation.

Operating your system with a fixed water pump speed may reduce its ability to regulate the amount of heat energy produced by the heat pump.

The fact that your system was tripping out on low water flow rate, could indicate that the setting of the water flow switch was too high, or that there was some restriction to the flow of water around your system. A further possibility could be if the LWT is too high, which would cause the controller to reduce the water pump speed to achieve the required DeltaT of 5C.

 


   
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(@mmiuse)
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@cathoderay Freedom installed it (well sent it to me to install, it is a small box with what looks like an arduino or pi inside that wires in to the controller and then you can log in to an online dashboard to view data). They sent it as their engineers couldn't find out what was wrong after several visits, I think it is  a new bit of monitoring kit they have only recently had available. It is good (but I suspect they normally charge extra for it - they didn't charge me, obviously!).

This post was modified 1 year ago by mmiuse

   
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(@mmiuse)
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@derek-m I have a bungalow. 4 bed. around 100m2. fully refurbed in 2020/2021 with UFH throughout, each room is a separate zone. yes there is a low loss header.


   
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(@mmiuse)
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@derek-m Interesting. Thanks. Surely this is something Freedom, if not the installer, would pick up? they have had engineers here literally for entire days at a time.


   
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(@mmiuse)
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The COP seems low to me at 1.84 over the last 30 days. My original quote/estimate was 4. My MSC certificate says 3.37. But the monitor says 1.84 🙁 at that rate, a gas boiler would be cheaper 🙁

image

   
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cathodeRay
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Posted by: @mmiuse

@cathoderay Freedom installed it (well sent it to me to install, it is a small box with what looks like an arduino or pi inside that wires in to the controller and then you can log in to an online dashboard to view data). They sent it as their engineers couldn't find out what was wrong after several visits, I think it is  a new bit of monitoring kit they have only recently had available. It is good (but I suspect they normally charge extra for it - they didn't charge me, obviously!).

Thanks, that's very interesting, it sound's like Headroom Heat Pumps' (as they are known in this parish) 'incredibly simple to install piece of hardware' that taps into the H1/H2 terminals in the wired controller and supplies the data over modbus/RS-485 and then wifi. Don't worry about the jargon if you don't know what it means, it is just about how the widget is likely to work. The data then gets sent to the cloud or I think rather more specifically HHP's servers where they harvest all your personal heating data for free, and give you online access to the data as a reward. My Beginner's guide to heat pump monitoring thread is all about my attempts to achieve the same thing locally, ie without letting Headroom get inside my head, or rather my airing cupboard. 

As all the data is coming from the Midea controller, it is still subject to all the black box concerns about how Midea source slice and dice the data before making it available. I don't think we have any idea, for example, how it measures flow rate, or determines energy in and out (and so COP). What I do know is that the Midea app (which uses exactly the same data) appears to over-estimate energy used, based on comparing its numbers to those given by an independent external energy meter that only measures energy used by the heat pump. Odd that, because it could mean their estimate of COP is poorer than it would otherwise be. Or maybe they also bump up the energy produced? Who knows?

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


   
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cathodeRay
(@cathoderay)
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Posted by: @mmiuse

The COP seems low to me at 1.84 over the last 30 days. My original quote/estimate was 4. My MSC certificate says 3.37. But the monitor says 1.84

At 1.84, either something is seriously wrong, if the number is right, or the number is wrong. The black box problem I referred to earlier...

Here's my heating and DHW daily COP from the end of November to date, based on manual transcription of the data from the Midea Mdim Life app, so basically data coming from the same source, but from my heat pump:

Midea App Readings

The heating COP is sort of credible, at least it goes up and down as you might expect eg the December and recent cold snap drops in COP are clearly visible. The DHW COP is all over the place, very likely because of rounding absurdities. There are also days when it managed to produce energy out with no energy in, which is truly an achievement beyond all recognition, but in a speadsheet it produces a divide by zero error, so I have just floored those values to zero.

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


   
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