joeccv avatar image
joeccv asked

AC circuit protection In vs Out while using Powerassist with Multiplus 3kVA

I am planning out my first ground up installation with a Multiplus 3kVA in a cargo trailer buildout. I'm trying to figure out how to plan circuit breakers and panel layout for using both AC out 1&2.

Inverter input will draw from either a 30 amp shore inlet or a 3.5kW generator with 30 amp 120v output. On AC out 1 I will have one main and two branch GFCI circuits. On AC out 2 will be an air conditioner.

In theory, the powerassist will only come on to supply the inverter AC out 1 with power when necessary, such as when the AC unit is drawing a large load on the generator.

My question is, when 30 amp shore/gen power is present and the Multiplus offers power assist, is it possible for AC out 1 to output more than 30 amps of power? And in this case do I need to put a 50 amp main circuit breaker on the inverter AC out 1?

Ideally, I'd like to use a Progressive Dynamics PD5500 panel with two 30 amp main circuits to house both AC out 1 and AC out 2, but this is not possible if one of them needs to be fused at 50 amps.

Thanks for you input!

MultiPlus Quattro Inverter ChargerSolar Panelpowerassist
2 |3000

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1 Answer
Kevin Windrem avatar image
Kevin Windrem answered ·

Choice of main breaker size and cable from the Multi depends on your anticipated loads.

With power assist, you can essentially add shore power to the Multi's inverter output, so roughly 60 amps for the Multi 3000 with 30 amp shore power. But you don't need to use it all. Also output 2 would be limited to the internal 50 amp relay used to shed that load when AC input is lost.

Keep in mind the PD panels you reference are designed for split-phase power sources which puts the legs 180 degrees of phase. Each hot bus would be capable of handling the specified current (30 or 50 amps depending on model). However the neutral bus might not be able to handle the current of both legs in phase. Plus AC outputs 1 and 2 should not be connected to the same neutral bus. It's probably against code to tie neutrals together down-stream of the source.

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