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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cathodeRay

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23/09/2025 8:10 am

Posted by: @benson

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Regarding the warm end of the WC curve, are there any particular parameters that people would recommend?

The real answer is trial and error, because there are a lot of variables, and no two houses will be exactly the same. A good starting point for an average property with radiators might be 30 @ 15 for the right hand warmer OAT end of the curve, and then the design parameters at the left hand cooler OAT end of the curve, eg 45 @ -2, but this will vary eg given the space constraints I have radiators that are on the small side, and so I need a higher LWT at the lower end of the curve, currently 52 @ -2, which is down a bit from the design parameters of 55 @ -2. The right hand end of my curve is currently 31 @ 15. It is also worth bearing in mind that outside the OAT endpoints, the 'curve' flat lines, ie 31 @ 15 is really 31 @ 12 and above degrees, and 52 @ -2 is really 52 @ -2 and below degrees.

Posted by: @benson

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Furthermore I guess this is the time of year when the heating might just need to be turned on and off when a bit cold as it isn't quite 'full' heating season yet...

Mostly for historical reasons, ie habit, I try to have one day, preferably in October, when the heating goes on and stays on. But with a heat pump, there really is nothing to stop you putting it on a bit earlier if it is nippy and turning it off again if things warm up. My kitchen room temp this morning when I got up was 15 degrees, if it gets much lower I shall say weather be damned, and the heating will go on!

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

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