Ground-Neutral bond

[Just_There]

Please help me to understand grounding and neutral bonding. This assumes the transfer switch between shore power and generator switches both hot & neutral. This is how I understand it with a big question at the end.

On-board Generator:
Ground, neutral, chassis all bonded together.

Shore power:
Ground wire, neutral bonded & grounded to earth at or upstream of pedestal.

Battery bank:
Negative through shunt, then bonded to chassis.

PV charge controller:
No ground.

Inverter-charger w/ auto transfer switch:
Case bonded to chassis.
¿Neutral & Ground Bonded? Yes/No

[Just_There]

Let me see if this makes sense:
Add a new main panel with 30a breaker feeding (relocated old) 20a Air-Con breaker and 2000W inverter/charger.
Old main panel becomes sub-panel fed from inverter output to old 30a “Main” breaker, leaving all house wiring & breakers in place, with the exception of relocated A/C and abandoned Converter circuits.
Fridge is AC-Propane option, so I think leave that on inverter and manage manually for now. Water heater is propane only (I think)

[DrewE]

If you have an RV fridge or electric water heater, you probably want those also not powered by the inverter.

Yes, as you realized, you do need a subpanel. The AC and DC sides, although mounted on the same outer chassis, are separated electrically and physically so are not really part of the same panel/enclosure. Besides the main breaker issue, you would need to isolate portions of the main bus, which would require unapproved modifications, and have two separate neutral busses. I think it is possible to have two separate sources in the same enclosure per the NEC with certain required labeling, but I'm not positive about that.

It might work out have the new panel be the main panel and the existing panel as the subpanel; if you need fewer breakers for the main, it might mean being able to use a smaller additional panel.

[Just_There]

Let me try to clarify: I have the factory wiring in a box with empty slots. From the Main I want to feed the A/C and the inverter/charger. All other circuits, i.e. GFI outlets, microwave will be powered from the inverter (with built-in auto transfer). I would like to house those breakers with their existing load wiring in the Main box, rather than have a sub-panel.

I realize there are very creative ways to mess up, but I was always told A-C and DC must be in separate panels, yet there they are together..straight from the factory.

*upon further review, this would not be good because the “Main” breaker would not deinergize everything in the panel. I guess I need to find room for a sub-panel.

[DrewE]

Just There wrote:
I Have room in the main panel to configure the external A-C supply and the A-C from the inverter. Is this:
#1 Safe?
#2 Smart?
#3 Legal?
Also, can these supplies share the neutral bus bar?

You need to be clearer on exactly what you mean by "configure."

If you mean connect the output of the inverter to the panel via a breaker added to an empty slot, that is neither safe nor smart nor up to code.

If you mean connecting an inverter/charger's AC power in to the panel, and then connecting circuits to its output (and so using its built-in transfer switch), then that's a reasonable plan and generally how things are done...but of course there are plenty of ways to make mistakes or do things improperly, as with any wiring project.

[Just_There]

I Have room in the main panel to configure the external A-C supply and the A-C from the inverter. Is this:
#1 Safe?
#2 Smart?
#3 Legal?
Also, can these supplies share the neutral bus bar?

[DrewE]

chuckbear wrote:
One question. In installing the AIMS inverter with the built-in bypass, it shows bonding the inverter case to the RV frame. Is this really necessary? Chuck

Yes. As I understand things, it is there mainly to prevent a fault condition causing the full DC current for the inverter from going through the AC power line safety ground, which would be dangerously undersized for that current. Converters likewise must have their cases bonded to the vehicle frame independently of the AC ground for the same basic reason.

[chuckbear]

One question. In installing the AIMS inverter with the built-in bypass, it shows bonding the inverter case to the RV frame. Is this really necessary? Chuck

[2oldman]

wnjj wrote:
The EMS should be between whatever power source that could have trouble and whatever you want to protect. I don’t think a generator or inverter is likely to have issues..

x2

[Bobbo]

My EMS is 12" from the main breaker. No matter where the power is coming from, I am protected.

[time2roll]

I recommend the EMS/SP should be just before the power distribution panel so that all incoming power goes through the EMS/SP.

[wnjj]

Just There wrote:
Thank you! I now see where the Aims 2000 I’m looking at does indeed have a relay to break the bond with external AC. This goes along with what I’ve always heard: only bonded in one place at source of power. Gets kinda confusing with multiple sources. A follow up question, if I may:
Would the proper place for hard wired EMS surge protection be between the inverter and the Genset/shore power transfer switch?

The EMS should be between whatever power source that could have trouble and whatever you want to protect. I don’t think a generator or inverter is likely to have issues so if it were me, I would probably put one between the shore power cord and the transfer switch. That way even your transfer switch itself is protected. It may come down to wiring and mounting convenience.

[Just_There]

Thank you! I now see where the Aims 2000 I’m looking at does indeed have a relay to break the bond with external AC. This goes along with what I’ve always heard: only bonded in one place at source of power. Gets kinda confusing with multiple sources. A follow up question, if I may:
Would the proper place for hard wired EMS surge protection be between the inverter and the Genset/shore power transfer switch?

[KD4UPL]

You've got it right for most all situations I can think of. Your inverter should bond then neutral and ground when inverting and disconnect them when passing thur AC power from another source. Inverters designed for mobile use typicall have this feature. Inverters designed for use in a structure usually don't.

[time2roll]

Inverter will depend on the model. Although I believe most that are made to wire into an RV/marine electric system will bond during inverting function.