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ajspicer asked

AC Coupled ESS Multiplus 2 to existing system - Diagram

We have a multiplus 2 48v 3000va and a Pylon Us5000 4.8kwh battery kit with Cerbo GX kit for an ESS to our existing 10 year old system with 2.25kw of solar via a SMA sun boy inverter.

Please can anyone point me in the direction of the simplest ESS setup diagram so that the installation does not effect our UK feed in tariff?

I understand the Multiplus 2 AC in connection is bidirectional so is this the only power connection needed other than the 48v battery connections?

In addition to the above, is there a maximum distance we should be considering for the position of the Pylon battery from the Multiplus? Cables in the kit are 2m.

Many thanks for your help in advance.

Andrew (Bristol)

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2 Answers
sharpener avatar image
sharpener answered ·

From the Multiplus II GX data sheet:


"Grid in-line topology with PV inverter
PV power is directly converted to AC.
The MultiPlus-II will use excess PV power to charge the batteries or to feed power back
into the grid, and will discharge the battery or use power from the grid to supplement
a shortage of PV power. In case of a power outage, the MultiPlus-II will disconnect the
grid and continue to supply the loads."

If you do not disturb the connection from the Sunny Boy to the Total Generation Meter it should not affect your FIT eligibility, just connect this meter to the Multi instead of directly to the grid.

You need to check for compliance with the "1:1 rule" if you want to connect it to the AC-Out, otherwise connect to AC-In. It is all explained in this link that @nickdb sent you the other day

Both ports of the Multi are bidirectional, but it will not work as a UPS unless you connect the loads in question to the AC-Out, because the internal anti-islanding relays will open in a power cut.

You will also need to make a new application to your DNO to install a battery system but you should be OK with such a small PV setup.

For general wiring info search here for "Wiring Unlimited". For a discussion of some related points regarding on how to wire to a UK consumer unit see @Taddy's diagram in this thread

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sharpener avatar image
sharpener answered ·

Also, you will need to connect the Sunny Boy to the Cerbo, see

If your SB is too old for that option to work then you will need an ET112 meter interposed between the Total Generation Meter and the Multi. Otherwise the Cerbo will not know how much power the SB is contributing. It will still work, but the dashboard will not show the loads separately from the PV output, the difference will be displayed as a net figure.

Forgot to say also that you will need a two-pole lockable AC isolator and separate RCD in the feed to the Multi, you can't just hang it off an existing circuit.


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