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chapelier avatar image
chapelier asked

Struggling with the final step.

I am setting up a system with a bmwi3 battery , multiplus ii , mppt 250/60 , mppt 150/100 and a rs450/100 . I was supposed to be doing this with my father in law who is an electrician but COVID has put paid to that for the moment. I have everything up and running the way I want it using the ESS assurant but I’m struggling with the final step of connecting it all to the house due to a lack of understanding.

I’m planning on winter months using a 4 hour cheap rate tariff to charge the battery from grid to complement the solar.

I have a et112 that I think ( correct me if I’m wrong ) needs wiring in between the main incoming fuse and my consumer unit. I’m awaiting a smart meter and isolator before attempting that :)


If correct I think I can work that one out o.k. However, I have some confusion over ac out and ac in. . I’ve read somewhere that ac in is bi-directional so am I simply running a cable from ac in to my supply after the Carlo gavazzi ? Or do I run a cable from ac out to there and a power supply in from my consumer unit ?


many help would be appreciated and if I’ve missed out any necessary information please let me know.

Multiplus-IIESSEnergy Meter
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wkirby avatar image
wkirby answered ·

I did not see any mention of what GX device you have? I presume you do have one.

AC-IN is bi-directional one the ESS assistant is running and is controlled by the GX device.I'd position the meter somewhere after the main switch inside the consumer unit (not before it).
The MultiPlus is always wired after the ET112
Where exactly you position the meter after the main switch depends upon which loads you want to be powered by the MultiPlus and ultimately the battery. Loads wired between the main switch and the meter will not be powered by the battery. You might not want immersion heaters or electric showers taking battery power, so wire these before the ET112.
Any loads wired after the ET112 will be powered by battery if it is charged.
All loads wired as above will not be powered in the event of a grid failure.

AC-OUT will continue to supply energy in the event of a grid failure.
These loads would need to supply a separate consumer unit, your electrician should advise you of how to do this correctly.

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chapelier avatar image chapelier commented ·

Thanks for the help. Yes, I’m using a cerbo gx


I’m pretty much clear on the use of the et112 .

I’m probably being dumb and I don’t have an electricians help at the moment but I’m reasonably capable of learning normally.

I want to supply all the loads of the house , I have a 33kwh battery which will last about a day of typical use. My solar (14kw) should provide even on a bad day 10-15kw so in the winter was planning to charge from grid to full every night unless weather is good.

So In my case you are saying run a cable from ac in to after the et112 ? That will then power all my loads and the grid will provide the rest ?

You then say ac out will supply in the event of a grid failure which is also what I want but I don’t get it sorry , do I then just run a cable from ac out also to all my loads ? It seems with what you are saying I need 2 consumer units ?? That doesn’t seem right .

Also if I’m charging at night from grid wouldn’t that mean ac in would have to come before the et112


im pretty confused


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