Testing new controls/monitoring for Midea Clone ASHP

benson · 2025-09-14T21:44:38Z

Hi all, I thought it might be of interest to others if I document a bit about the above, which is mainly the removal of Homely from our system and the installation of something that essentially uses the manufacturers controls via home assistant, particularly as the native control panel for Midea, and their app, are not great. Over this heating season the plan is to compare how we get on both in terms of comfort levels, and costs, so hopefully this will be a good test. Background: Firstly, a bit about the system, which we've had for just over a year. 160sq m house, with very average insulation so we're never going to be running particularly low flow temps. 16 radiators in total, with estimated heat losses just under 8kW and a 12kW Clivet (midea) installed. Overall, we did not have the smoothest of experiences with our installers. There were a lot of issues with general quality of workmanship, being left a cold room or two, and not being able to achieve the reported design max flow temp of 45 at minus 2. At minus 2 generally we'd need outlet temps of around 47/48 to keep our house warm, after a bit of trial and error. The installers recommended homely and we went for this, which works ok but our general feeling was that it left us with too little control and I personally didn't like that end users have to go through the back door to access their installer dashboard. It also exhibited some slightly strange behaviours with overshooting. Here's an example of some of the isssues we had with Homely: You can see in the graph above that Homely set the flow temp at 50/51 when there was no need to do so. Quite mild outside and the heating essentially was off for a few hours. This would happen once or twice a week and just generally didn't seem to quite align with the low and slow principles. New controls: I researched a lot of potential options, and even contacted Clivet themselves who interestingly just recommended getting an on/off thermostat and connecting this to the ASHP. Not being a fan of the above (mainly due to advice on here), I looked at other options. Planet Atmo seemed like a good option for pure weather comp and was compatible with Midea. This would link to the ASHP via the modbus in the same way Homely does, and allowed a lot of controllable parameters and monitoring, via their app. However, they wouldn't supply direct to the public so that ruled them out. I have tried the Midea Smarthome app but it is quite basic, and it just keeps disconnecting with the control panel. I had been able to relink it but now I just can't get it to work at all so I've given up on that. I then came across a Midea ASHP controller called Svenar. I couldn't fully work out what this device offered, truth be told, but it sounded like it might work so at around £65 I thought we'd give it a punt. It connected via modbus and then allowed control/monitoring via home assistant. Home assistant- We in fact already had this. I purchased the HA green a while back and in fairness hadn't really been using it that much, with only one automation set up for a smart plug on our tumble dryer to notify us when it had finished! For those who aren't familiar, the best way to describe it is an open source system/repository that allows connection and integration of a load of smart devices in your home. You can then set up automations so if something happens to one smart device (or entity within that device so for a temp and humidity sensor the particular entity could be selected as the temperature reading) it can then influence another separate device to run a command. The HA green is a straight out of the box solution which was very easy to set up. Svenar- when it arrived, again very simple to set up and this was immediately discoverable in home assistant, which was a good start. What I didn't realise, which was a massive bonus, was just how many parameters of my ASHP I'd be able to see, and control, within home assistant via Svenar. There are around 200 odd, and hopefully this screenshot gives an idea which is a very small snapshot: Now I cannot profess to know what all of these parameters mean, but a bit of googling, and delving into the instruction manual, allowed me to pick off the key ones that I wanted both viewable, and controllable, in a separate dashboard rather than having to trawl through the list of hundreds. Again, for those that don't know much about HA it allows one to create custom dashboards with cards, or buttons that will display certain entities and allow toggling on/off, changing values etc. It's also worth pointing out that HA works really well on a smartphone so the above dashboard I created is very easy to read there. Even the wife commented that it was easy to use and turn on the heating- a decent endorsement indeed... As you can see on the above, I've added the parameters for the WC curve so I can easily tweak this as required once we see how we get on when the weather turns. Putting it to the test: Today as it hap...

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Air Source Heat Pumps (ASHPs)

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cathodeRay

(@cathoderay)

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03/10/2025 8:02 am

Posted by: @benson

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What I didn't quite expect (or understand perhaps) is that the warmer end temp on the weather curve is actually where heating will disable e.g. WCC warm end parameter set at 16 degrees C, and rather than just continuously running at whatever the set LWT is at that point for 16 and above, it will actually just...turn off. Which works rather well as it happens.

Interesting. I have always assumed, partly because the chart of the WCC in the Midea Engineering Data manual suggests it is so, that at OATs above the right hand set point, the LWT is the same as at the set point ie 30 @ 15 degrees actually 30 @ 15 degrees and above. Ditto at the other end, 50 @ -2 actually means 50 @ -2 or less degrees. True turning off at higher OATs happens not because of the WCC, but because the OAT is higher, and the room stat turns the heating off, as happens in summer. But your chart dies suggest the heat pump stopped producing heat at around 1000 on the 29th. Rather curiously, the LWT actually falls below the IAT, I wonder how it does that? The chart would benefit from also showing the OAT (and the Y axis could range from 0 to 60 rather than -60 to 100, to give a better perspective). Charting the set as well as actual LWT might also provide more information.

Her's my chart for the last two days. I think it bears out the above ie at 15 degrees and above OAT, the set and actual (average) LWT is 30, ie the heat pump doesn't turn off. That will only happen if I dial down the room stat, or otherwise fully turn off the heating:

Posted by: @papahuhu

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Wouldn’t interfacing the heat pump with an unapproved control wholly void the warranty?

I agree with @benson - we are using the manufacturer's interface, as documented in the publicly available manuals. The availability of that information is meaningless if we can't make use of it. Or to put it another way, they shouldn't be at all surprised if we use the information if they make it available!

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

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benson

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Topic starter 03/10/2025 9:06 am

@cathoderay that is so odd. I wonder why mine does this. There's no doubt that mine does this as I've been closely watching it as well over the last couple of days as as soon as we are 16 and above, it will stop heating. There are two time periods on my graph where it does this- around 1000 on 27/09. I just hope that it doesn't do it at the cold end of the curve....

As for the LWT actually being cooler than OAT I hadn't noticed this. Going back to my plotly graph it is only by about 2 degrees C lower so assume this must be where the system water isn't benefiting from solar gain that the climate by the pump would have been, on that day?

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cathodeRay

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03/10/2025 9:33 am

Posted by: @benson

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that is so odd. I wonder why mine does this. There's no doubt that mine does this as I've been closely watching it as well over the last couple of days as as soon as we are 16 and above, it will stop heating.

Maybe plot some more variables to see what is really happening. OAT as I said before, and set LWT, plus something that tells you what the heat pump is actually doing, amps in or compressor frequency. To be truly off, both the latter must both be zero.

Posted by: @benson

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I just hope that it doesn't do it at the cold end of the curve....

I don't think it will, that really would not make any sense. Unless our Oriental colleagues want us to live interesting times.

Posted by: @benson

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Going back to my plotly graph it is only by about 2 degrees C lower so assume this must be where the system water isn't benefiting from solar gain that the climate by the pump would have been, on that day?

I agree, it is not a lot, but something is cooling that water!

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

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