question

colj avatar image
colj asked

ESS Dump to immersion using CCGX Generator Start/Stop relay

ESS: Quattro (& CCGX)+ Batteries + Solar + Cheap overnight charge window.


I already have a system to try to limit the SoC overnight based on the next days PV forecast, however it doesn't always work and I end up feeding some PV back to the grid (which I want to avoid).


I would like to use a CCGX relay and the Generator start/stop control to turn on my electric immersion as a dump if the SoC gets too high during the day but also be able to run the immersion during the overnight charge window.


Appreciate feedback as to whether the following would work please.


I would use the 'normally closed' connectors on the relay such that when the the CCGX thinks the generator is running my relay connection is open.


Settings:

Using Battery SoC as the main switch:

Stop generator when Soc > 95%

Start generator when SoC <95%


I interpret this would mean the CCGX thinks the generator is running whenever the SoC < 95% (and my immersion would be disabled)


If I also set 'Do not run generator while AC1 in use', then the CCGX would disable the generator during the charge window (enabling the immersion)? If this doesn't work then I could define the quiet hours to match my overnight charge window and set conditions so that CCGX disables the generator through the quiet window?


Colin



ESSRelaygenerator auto start
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2 Answers
matt1309 avatar image
matt1309 answered ·

Hi @colj

I cant help much with your proposed solution but I do exactly what you're looking to do but use Node red with a shelly smart switch connected to immersion instead of the generator start/stop.

I find this gives me more control over criteria for turning immersion on/off.

As you say you can use SoC but with node red you can set other parameters. ie check if SoC > 95% and you've got excess solar. (just have to add in some buffers to the criteria to turn off the immersion just in case sun is in and out).

You can also setup multiple loads in addition to the immersion heater. ie immersion isn't using enough so turn on another load.

(I used http node to turn shelly switch on, it's via local network so no cloud connections)

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colj avatar image colj commented ·
Thanks Matt - looks interesting and more flexible than the direct relay. I'm already using node-red to set my overnight SoC etc so easy to extend. I'll investigate further.


Colin

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matt1309 avatar image matt1309 colj commented ·
Hi @colj


It has been great for me. Only thing to watch out for (the mistake i made) is setting the turn off buffer.

ie criteria for turn on isn't the exact same as criteria for turn off.

Say turn on criteria is you're exporting >300w, dont make your criteria to turn off the switch: if you're exporting <300w

Make your off criteria something like drawing 1000w from battery so you've got the buffer of 1300w, otherwise you can end up in loops of immersion turning on and off ie Where you turn on water heater, system immediately stops exporting so heater turns off, and cycle repeats.


I imagine other smart switches work but I know shelly has a local HTTP endpoint API so you dont need their cloud or even an external internet connection, just need cerbo/venus os running on same network as it.

(The shelly switches can also connect to MQTT if you prefer that, i think some of the models even have built in scripting so you could probably get the system to work the other way around ie shelly queries victron and turns on/off based on data, However i imagine it's more useful to have the logic for turn on/off in one central locations/Node red. I've never tried this though, I've got the older more basic switches).


The switches they sell tend to be rated for 13amps so good for most immersion heaters. And have a "auto turn off" timer, which is a nice safety feature if you dont want it on for too long (although most immersion heaters have internal safety shutoffs anyway).

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jameswest avatar image
jameswest answered ·

I don't know how you're getting on with your Shelly relays but Shelly don't recommend running high current loads for long periods as they tend to over heat and shut off. It's the same with the Shelly Plus and Pro series. Speaking to Shelly they recommend using the shelly relay to control and external relay that can take the load.

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