A/C Neutral and Ground issue

Discussion about OutBack Inverters in Marine Applications

Moderators: OutBack, OutBack Moderator Team

Post Reply
Forum Member
Posts: 8
Joined: Tue Jun 16, 2020 7:29 am
My RE system: VFX2812

A/C Neutral and Ground issue

Post by allankay »

This boat has certain areas with outlets labeled INV 110 and these work off the Outback VFX2812M inverter. Unfortunately, we want power in the master stateroom so need to bring the outlets there into the inverter circuit. Stateroom outlets only work when the generator is on or shore power is connected.

All circuits work fine and the outlet tester gives correct lights for both A/C and inverter outlets.

I went to the wiring board and disconnected the connection marked Master Stateroom (disconnected the incoming hot A/C wire) and then brought a wire to it from the inverter circuit hot A/C.

When powered the master stateroom outlets now indicate a Ground Hot A/C Reversal. The inverter outlets indicate correct wiring. Tried the outlets with a small fan and it will not run in the master stateroom.

Now, wired as described, both of the circuits have the same hot A/C connection but obviously the inverter uses a different ground or neutral. I conclude the inverter outlets have wiring going back to the inverter and not to my wiring panel. Trying to trace wires back through a large boat is nearly impossible.

I did not test the outlets with the generator running to see if A/C is passed through to the outlets and indicate correct wiring.

This is making my head hurt. Can someone please tell me why this happens when using the inverter A/C power on an existing correct circuit?
Forum Emperor
Posts: 5615
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
Honda EU7000is gas fuel generator

Re: A/C Neutral and Ground issue

Post by raysun »


Your description brought back every moment I spent in barges, bilges, and hulls of all manner with an electrical problem. Heartfelt good luck to you.

An obvious first spot to look is where neutral and ground are bonded. There should be only one. For "shore power" the bond is at the service panel of the shore power feed. For Inverter power (disconnected from shore), the Inverter provides the bond. When the Inverter is bypassed with AC IN, its transfer switching opens the inverter's neutral to ground bond so the AC IN source (generator or shore power) is to provide the bond.
User avatar
Mike Curran
Forum Emperor
Posts: 2477
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied VFXR3524A-01's series stacked, replaced GVFX's (2020)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS. Tigo ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input from 14 Talesun 275W, Enphase M215 microinverters

Battery systems operate in grid-tied, battery backup mode
All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: A/C Neutral and Ground issue

Post by Mike Curran »

I think the solution is to do the same thing with the neutral supply to the bedroom as you did with the hot supply - find the existing bedroom neutral connection at your service panel, disconnect it from there and reconnect it to your inverter neutral.

Easier said than done, I know
Trying to trace wires back through a large boat is nearly impossible.
But if you're lucky and the neutral was run in parallel with the hot wire (like Romex) it may not be as big a challenge as you expect. Good luck.
Post Reply