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djmaxi asked

Powering ET112 during Grid Failure

Good day, when using the ET112 as a Grid Meter, the meter is obviously self-powered. However, when there is a grid failure, then the ET112 is not available to provide any data to Cerbo. This is causing a lot of issues with other systems (such as Home Assistant, to run automations and track usage), as these reads the ET112 data from the Cerbo over Modbus and MQTT. Once the grid fails and the meter becomes unavailable, the connected systems is stuck on the last seen reading.

Is there a way to keep the ET112 powered by an alternative power source, so it can report the zero grid properly to the Cerbo and in turn to connected systems? I am hoping that some of the terminals on the front, could be for low power input, to keep meter operational during grid outage (which is a very frequent occurrence in South Africa). I searched all manuals and cannot find any guidance on this, or what the other terminals on ET112 does (besides the RS485 ones)

Below picture shows the stuck readings (777 W) after a grid failure, for however long the outage last - skewing data and history.

et112-grid-failure.png

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7 Answers
Jason - UK avatar image
Jason - UK answered ·

@DJMAXI It looks like it can only be fed from the AC connection.

1700045777341.png


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mjs500 avatar image
mjs500 answered ·

NO as its feed load L1 and Neutral

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matt1309 avatar image
matt1309 answered ·

Hi @DJMAXI

I'm not familiar with homeassistant (openhab is what i'd use more) but is there a way to write a rule that will set grid to 0 in the event data hasnt been received after x time frame.

That will solve your problems and wont need any editing of the energy meter.

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daza avatar image
daza answered ·

@DJMAXI what @Jason - UK and @matt1309 has said is correct you can’t do it as it needs the grid live to power it, but you may be able to do it with a Shelly on the back upside of the install and throw the CT clamp over the ET112 live and then tell home assistant in the event of a grid down read the Shelly and report grid state. I’m not using home assistant think it’s too much work for me to setup and change all my HomeKit stuff but I know it’s very versatile so could be an option?

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daza avatar image
daza answered ·

@DJMAXI or use the Victron CT clamp to measure the grid then it should be a continuous report as the victron multi is keeping it powered this way less wiring and frees the ET112 to be used elsewhere. Hope that helps

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matt1309 avatar image matt1309 commented ·

Scrap my answer i think @Daza has got the best solution here!!

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djmaxi avatar image
djmaxi answered ·

Thank you for all the replies and good suggestions. Still a pity one cannot keep the ET112 powered during grid down, for the reason that Cerbo shows errors during time and any system connected, still shows issues of inaccurate data during time.

I did manage to visually show on the Home Assistant Power Card, that Grid is down, by using the Alarm State from Cerbo. Though the underlying data recorded still freezes where it left off and errors being accumulated in logs, due to ET112 being unavailable while being polled.

I have a Shelly EM on order, to rather use this for stats.

For interest, here is what card looks like now, using Alarm state for grid:

grid-failure.png


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wim-immelman avatar image
wim-immelman answered ·

I have a similar setup, ET112, Home Assistant and Modbus (and South African Loadshedding) and I found best to wrap my grid power modbus sensor in another template sensor, where I'm checking if the entity is available, else reporting a zero. i use the two "energy from grid" and "energy to grid" sensors as is though.

I was also hoping to rather keep the ET112 powered somehow

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