@schnetf — here are some photos from my 'How to' thread showing a bit more detail:

Thank you for clarifying @mosibi @cathoderay @majordennisbloodnok

I got confused because the svenar product images show cables connected to H1 and H2 (modbus) and I don't have those on my terminal. But as I understand now, outdoor unit communicates to the wall unit via the 5 cables. And then modbus picks up the data on H1 and H2. So the svenar image shows the terminal after adding the necessary modbus cables not before *facepalm*

So if the modbus is not required for comms of outdoor and wall unit, why is it there? What's the incentive for manufacturers to put it on the board? Only a fraction of private consumers will bother with such a connection (I guess). Is this for industry applications?

Sorry for a naive and off-topic question, I am just trying to understand what modbus is typically used for.

It's not a naive question at all, @schnetf, especially since there are plenty of manufacturers who do not do so.

I don't know the Midea system well enough, but if I had to guess I'd probably say it's likely the wall box is already using Modbus as the method of communicating with the heat pump and so adding another couple of terminals to allow an extension to the modbus chain is of little consequence to the manufacturer. I could, however, easily be wide of the mark.

Posted by: @majordennisbloodnok

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I don't know the Midea system well enough, but if I had to guess I'd probably say it's likely the wall box is already using Modbus as the method of communicating with the heat pump and so adding another couple of terminals to allow an extension to the modbus chain is of little consequence to the manufacturer. I could, however, easily be wide of the mark.

Like you, I don't know, but my guess is you are right. Midea use modbus to communicate between the outdoor heat pump and the wired controller. There is some evidence for this. The wired controller has A and B terminals, and these are the modbus terminal letter, but without the + and - signs (left image). Something very similar appears on the outdoor unit main PCB, where the connection to the wired controller terminates (right image):

This doesn't prove it uses modbus, but it is suggestive. I suspect the H1 and H2 terminals (which are just the Midea names for the modbus B- and A+ terminals) are there to provide a way for Midea engineers to connect to and communicate with the system — as it turns out, a very useful piece of foresight for us Midea owners. Midea do mention a USB connection in one of their brochures: 'USB Function: Realize setting transmission between wired controllers / Realize program upgrade with one key and save the time of on-site installation' but i have never seen a USB port (or header that I recognise) anywhere and my installer 'realize' anything with a USB stick during my unit's installation. But again it does suggest 'connectivity' is part of Midea's way of thinking.    

@schnetf i also do not know why the modbus terminals are there, I can think of a few purposes like factory testing and for engineers to debug issues, but that’s speculation instead of knowing 🙂

@cathoderay the USB port is on the mainboard of the internal/indoor unit I you have a split.

Posted by: @mosibi

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the USB port is on the mainboard of the internal/indoor unit 

Ah, got it, thanks. I have a mono rather than a split, but it looks like I have the same PCB with a USB port in the same place.

Hi! 

i am new to the forum. I am an installer in Greece. I do own an older R32 midea heat pump with the same controller as you guys have and it works wonders the last 4-5 years with the smart home app. 

however lately I installed 2 new heat pumps on 2 different homes (different WiFi) and both customers call me back to let me know that the WiFi has disconnected from the app. I tried to stop band steering changed AP, forced 2,4ghz channel and many more. It seems that they both have an android smart phone. I do have an iPhone maybe smart home app has problems on android? I don’t know. Power cycling the heat pump does the job for 10 days. The 2 heat pumps we have the problem have the same controller but they are the newer compact (c2) type. I’m thinking of trying the home assistant integration but it seems like an extra cost for my customers and to be honest they just want to turn their heat pumps on and off via the app. Midea support has been nothing but helpful with this matter. 

I tried searching about manual updating the controller and I couldn’t find anything. It seems like this heat pump is very popular on the market but you cannot find anything if a problem occurs.

Update: 

On the other side I’m thinking of buying a raspberry pi to run HA and a USB to RA485 adapter hoping I can set this all. But I think pi zero 2w is not that powerful so I propably need at least pi4 or 5 for graphs etc to work. Plus I was thinking of adding this inside the heat pump and maybe get voltage from the usb port there??? Propably not going to work. But any thoughts? 

Welcome to the forum. We have a number of Midea owners here as you will have seen.

Posted by: @xristostsilis

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I do have an iPhone maybe smart home app has problems on android? I don’t know. Power cycling the heat pump does the job for 10 days. The 2 heat pumps we have the problem have the same controller but they are the newer compact (c2) type.

I think the general consensus is that the Midea smart home app is flaky, and even when it does work, the controls and data it provides are limited, but if all your customers want to do is turn their heat pumps on and off then maybe it is sufficient (when it works). I for one have given up on the app, as have others. For those who want more data and control there are various options, but they do all require time and money (a lot of the former, less of the latter). I Use a wired modbus connection to the wired controller with python scripts to collect the data, other have made extensive and successful use of Home Assistant.

There are various manuals available online, including in various places here on this forum, sometimes they are helpful, sometimes less so. But I don't think I've ever seen anything in them about how to fix poor wifi connections. 

I do wonder however why your customers want to turn the heat pump on and off. Normally this is a very rare event, most of the time the heat pump should be running low and steady on weather compensation. If it is only a rare event, it can be dome manually via the wired controller.  

Posted by: @xristostsilis

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Update: 

On the other side I’m thinking of buying a raspberry pi to run HA and a USB to RA485 adapter hoping I can set this all. But I think pi zero 2w is not that powerful so I propably need at least pi4 or 5 for graphs etc to work. Plus I was thinking of adding this inside the heat pump and maybe get voltage from the usb port there??? Propably not going to work. But any thoughts? 

We cross-posted! I use a mini PC, but from what I've seen out of the corner of my eye your proposal or something very similar should work. The HA website may (or rather should) have enough information to get you started. 

Posted by: @cathoderay

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Welcome to the forum. We have a number of Midea owners here as you will have seen.

Posted by: @xristostsilis

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I do have an iPhone maybe smart home app has problems on android? I don’t know. Power cycling the heat pump does the job for 10 days. The 2 heat pumps we have the problem have the same controller but they are the newer compact (c2) type.

I think the general consensus is that the Midea smart home app is flaky, and even when it does work, the controls and data it provides are limited, but if all your customers want to do is turn their heat pumps on and off then maybe it is sufficient (when it works). I for one have given up on the app, as have others. For those who want more data and control there are various options, but they do all require time and money (a lot of the former, less of the latter). I Use a wired modbus connection to the wired controller with python scripts to collect the data, other have made extensive and successful use of Home Assistant.

There are various manuals available online, including in various places here on this forum, sometimes they are helpful, sometimes less so. But I don't think I've ever seen anything in them about how to fix poor wifi connections. 

I do wonder however why your customers want to turn the heat pump on and off. Normally this is a very rare event, most of the time the heat pump should be running low and steady on weather compensation. If it is only a rare event, it can be dome manually via the wired controller.  

 

thanks for the fast response.

So here in Greece due to some days having great weather many people choose to turn heat pump off and let clean air through the house. I mean today we had 18-19 degrees outside 

Posted by: @xristostsilis

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So here in Greece due to some days having great weather many people choose to turn heat pump off and let clean air through the house. I mean today we had 18-19 degrees outside 

Fair enough. Here in the UK we can only dream about great weather most of the time. Here it is another grey soggy nine degrees outside today. 

Edit: I should have said central southern UK, maybe elsewhere it is warm and sunny!