A/C Neutral and Ground issue

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allankay
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My RE system: VFX2812

A/C Neutral and Ground issue

Post by allankay » Sat Aug 08, 2020 2:37 pm

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?

raysun
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Re: A/C Neutral and Ground issue

Post by raysun » Sat Aug 08, 2020 3:10 pm

Aloha!

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.

Mike Curran
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My RE system: Outback - Garage roof:
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- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
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All self-designed and self-installed
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Re: A/C Neutral and Ground issue

Post by Mike Curran » Sat Aug 08, 2020 4:32 pm

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.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

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