2 Inverters sharing a 10-3 line?

Russell2020

Hello, I am currently setting up off-grid power for my cabin instead of hooking it up to the grid. I have two 1600-watt inverters that output 120v each. My question is if each of these two inverters can be connected to a respective "hot" and then share the neutral and ground of a 10-3 wire? Once inside the cabin, the two hot wires go to their respective sides of the panel and never touch, only the neutral and grounds are merged. No 240v devices or 240v breakers will ever be installed. 

BB.

Welcome to the forum Russell2020,

Your question is not a simple yes/no type answer. The first question is what is the brand/model/type of AC inverter(s) you are using?

If they are MSW (modified sine/square wave) type--Then no, you cannot/should not share the AC output neutral. At the very least, risk the chance of letting the "magic smoke" of the the inverters (MSW inverter typically do not have and isolation transformer on the AC output--And the AC outputs will do weird stuff if you tried to "share a common neutral" connection).

If they are PSW/TSW (pure/true sine wave) type--These are typically transformer isolated outputs and will usually support a ground bonded neutral (either inside the inverter, or at the main breaker panel).

Because these inverters are not designed to be paralleled--Their AC outputs will not be (on purpose)n 180 degree phased together. What this means is that the common neutral will be carrying the full current from both 1,600 Watt inverters (in a 120/240 VAC split phase power system, the neutral only carries a maximum of 1x the rated current of one circuit. In full 240 VAC power, the neutral carries close to zero current).

As always, refer to the inverter manual about support of ground bonded AC Neutral connection(s). There can be exceptions.

So:

• 1,600 Watt / 120 VAC = 13.3 Amps per circuit
• 2x 13.3 amps (neutral sum of currents) = 26.6 Amps total (2x that for worst case surge current from inverters)

From NEC (simplified chart), 10 AWG is good for 30 amps:

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

It is possible that two AC inverters sharing a common neutral can "harmonize" against each other and do weird things (lights blinking, noisy inverters, etc.)...

I don't thing the common neutral will catch anything on fire/cause damage... But getting a single 2-3 kWatt inverter (if you need those power levels) would probably be less of an "experimental" project.

You get a bit of an issue if you have an alternate power source later (such as a backup genset, wiring of transfer switches, etc.). Non-typical AC wiring can trip folks up down the road.

Usual disclaimer--The above is my quick take/opinion of what you are trying to do. If I am correct or wrong--This is your project and your decisions. Be safe.

-Bill