Chromagen Midea 170L Heat Pump Hot Water System - Modbus Integration Success

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Finally managed to get my Chromagen HWS properly into HA - I’d previously tried a simple Shelly on/off switch but had some issues with not being able to monitor temperature while it was off.

This is only possible due to the integration work by BrittonA on github here

I didn’t want to use that module style though and thought I’d try the cheapest seemingly suitable module from Aliexpress, found here. I chose the one with ethernet adapter cable and bracket, although didn’t endup using the bracket.

You generally want to follow the steps on Github, but for steps 1-3 do this instead:

  1. hook the EW-11 up to power (5-36V). Connect to its hotspot. you then have two options, i’d try 2a first then 2b if no luck:
    2a. Visit 10.10.100.254 using a browser. You should see a fairly nice web interface:
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2b Or use the clunky OEM software “IOTService” to configure. It can be downloaded from an OEM FTP server here, but it was very slow when I grabbed it

3 Now you will want to configure your wifi credentials. Modify mode to ‘STA’ and enter your SSID and password. Reboot the stick and check your router to make sure it has connected - now is a good time to give it a static IP address using your router controls. Don’t proceed until you have a stable wifi connection - you will be able to visit the EW-11 config page by entering the new static IP address in your browser.

NOTE: the reset button on the web portal doesn’t reboot the device, it resets the settings. Go to ‘Others’ to reset the hardware.

4 Configure the Modbus/RS485 connection using the following settings, found on the ‘Serial port settings’ page:

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Also configure the TCP server settings:
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5 connect the EW-11 to the HWS - use the github instructions: “The cables are Yellow = GND, Gray = B, Black = A.”

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6 You will need to provide power to the EW-11. I can’t give you specific advice here as I am not an electrician, but something like a 5v power adapter wired into 240v would do the job, but of course don’t do this if you are not an electrician. There are open L/N/E spade terminals inside the HWS control box.

7 mount the EW-11 somewhere to give the antenna plenty of clearance, and button the unit back up

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8 continue on with the HA configuration as per Github - you will need to enter the correct TCP Server IP and port details in your Modbus.yaml. You will know it is working correctly if the web portal Status page reports sent/received frames.

9 all done. your HWS is now controllable by HA, with all relevant temps reporting as sensors.

Extra info:
Seems like quite a handy little device - there are options for MQTT and other broadcasting modes in the server settings tab.

EW-11 User Manual
EW-11 application guide

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I have the same unit, but in 300L. Your instructions were great, thank you.

I bought the same Elfin-EW11 RS485 transceiver, and used this sealed 220v > 12V power transformer: https://www.aliexpress.com/item/1005005937263063.html

It is probably overkill using a 12W adapter, but that means its lightly-loaded and being sealed means living inside the housing at the back of my house it’s probably going to be safe as houses.

It’s been raining all day, so I haven’t had a chance to wire it up yet. I will this weekend and post the results.

Great write-up, thank you.

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No worries, glad it helped. Hadn’t seen those converter modules before, they look handy.

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Hi,

Your DIY is very good and very detailed. I have a question. Is it possible to modify some parameters of this water heater through Modbus? For example, change the temperature, change the time, change the timer switch, change mode, etc.? If you can answer, it will be very grateful.

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Yep you can change mode, on/off, thermostat temp etc

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Thanks ! That’s perfect ! Is there any more detailed installation photo that you can share? Thank you ! I am planning to integrate the same :blush:

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Sorry just the ones in the first post. Good luck!

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Hey thanks for sharing your project. I have followed your instructions and successfuly set up my EW11 and added it to my HA. I’m having trouble with getting any communication between my heat pump and the EW11. The web portal is not showing any sent/recieved frames and the comms light is not flashing at all. Did you experience any issues here? I’ve set up the EW11 the same way as you have shown.

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I did experience issues, but it was configuration related, and the resolution was setting it up with the settings in the screenshot - do you have the same model heat pump? it possibly will have a different MODBUS configuration and you might just need to trial and error it.

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Thanks for the response!
I do have the same heat pump. It’s about 3 years old now, so perhaps there are some differences between versions. When you say configuration, is that specifically the serial port settings? I have very limited experience with modbus so I’m generally in uncharted territory! What configuration settings did you change to get it working correctly?

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mine is a bit older than that so possibly the same model.

the settings I’m talking about are in the ‘Serial Port Settings’ screenshot above. If you have them configured the same way already, I would investigate the wiring and make sure you’ve got it hooked up right.

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Thanks.

I tried again over the weekend without much luck. The actual comms light on the EW11 never flashes at all so there is either an issue with the EW11 or the heat pump.
I’m going to try a direct usb to RS485 connection next and will let you know if I have any luck!