Inverter Bonding Neutral to Ground

[brulaz]

Here's a picture of how a Kisae 2000W inverter's GFCI outlet is wired.

The neutral side is not bonded to socket ground other than through a capacitor, as is the hot side. I guess the caps have something to do with the GFCI? Otherwise there's nothing connected to Grd on the socket internally.

However the neutral is connected to the case ground via a green wire with a big black blob in it. Any ideas what that would be?

And case ground will go to the chassis, so this socket's AC Neutral will go to chassis via the blob.

But over at the trailer's AC distribution centre, AC Grd goes to chassis. AC neutral is not bonded to AC Grd over there.

So it seems AC neutral will be bonded to AC ground via the chassis when this inverter is connected? (Initially will just run an extension cord from the inverter to the trailer's 120V input)

[brulaz]

Tried the Kisae by plugging in the trailer's 120VAC input cord.

This would create a neutral to ground bond via the Kisae's neutral-to-case, case-to-chassis and then the trailer's chassis-to-120VAC_Grd connections.

And sure enough, my Prog. Dyn. EMS accepted it. This EMS requires a bonded input.

On the other hand, if I don't use the trailer's 120VAC system with it's ground-to-chassis, and plug some appliance directly into the Kisae. It will NOT be bonded. :R

[brulaz]

RCMAN46 wrote:
The two blue things that you thought are capacitors are most likely Metal Oxide Varistors that provide transient protection . If you look on the side we can not see there should be a device ID number.

Turns out they're glued to the socket with no identifying marks visible. I see something similar on the DC inputs as well.

[brulaz]

SCVJeff wrote:

road-runner wrote:
A lot of 2-wire output inverters and generators have one of their conductors bonded to ground. While not all do it, it's a standard thing and I see no issue with it. The black blob could possibly be a ferrite bead to suppress electrical noise transmission between the chassis ground and inverter, but with no visibility under the shrink tubing it's only a guess.

Thats sure what it looks like with the shape and the ground wire appearing to loop

Got a closer look. It's a metal cylinder with the green wire going through it, looping back and going through it again. Then the whole thing covered in black shrink wrap.

[road-runner]

DrewE wrote:

I am having a difficult time understanding your logic here.

There is good logic in letting the inverter or generator's output float. Unfortunately, there's also good logic to bond it to ground. If there's no failure in the electrical system, either way is perfectly and equally safe. When there's a failure, one method or the other will give an advantage in either protecting against shock or making the failure known. For example, when unbonded, if the metal case of an appliance became connected to either of the power conductors, there would be no significant shock potential if a person were to touch the appliance and RV chassis at the same time. In the bonded situation, there would be full shock potential. On the flip side, in a bonded situation if the ungrounded (i.e hot) conductor shorts to ground, a breaker will be thrown, while the same situation unbonded will give no indication that a failure has occurred. IMO there's no clear best solution, which is why the debate hasn't ended and may never end.

[DrewE]

MrWizard wrote:
Do NOT BOND THE NEUTRAL to ground on the inverter
There is no earth ground safety when off grid on inverter power
Bonding the inverter neutral would make the RV frame part of the electrical circuit for the inverter
It would be the neutral, this is not safe
Do Not Bond neutral to ground

I am having a difficult time understanding your logic here. Certainly the inverter (or anything else in the RV) should not bond ground and neutral when operating on external shore power; but when running disconnected, I don't see any potential problem. That does presuppose a proper transfer switching arrangement, either a transfer switch or a plug and socket setup or dedicated inverter only circuits, but that's rather essential anyway so the inverter output and shore power can not fight each other.

Standard practice for built-in RV generators is to bond neutral and chassis ground when operating off of generator power. I know for a fact my Onan is wired that way; the neutral and ground outputs are connected to the same metal bit attached to the chassis. Why should an inverter be different?

(Bonding and grounding are, of course, quite separate safety measures, and serve different purposes. Grounding is used to tie the overall potential of the electrical system to something reasonably close to earth potential, so it doesn't float to a dangerous level. That's far more important in large area distributed electrical systems than in local, self-contained ones. Bonding is done to provide a low-impedance fault current return should there be a short circuit to equipment chassis or whatever, which hopefully trips the breaker or blows the fuse, rather than having the chassis be energized and some unfortunate person form the current return path.)

[brulaz]

road-runner wrote:
From the picture it sure looks like it was already bonded at the factory.

120VAC Neutral is not bonded to the 120VAC socket's Ground screw, but to what look's like the case ground.
EDIT: That's definitely the case ground.

And the case ground is wired to the frame/chassis ground, which is wired to the 120VAC Ground back at the 120VAC distribution centre, which ends up back at the inverter.

So yes, ultimately, when running the inverter, it looks like 120VAC neutral and ground are bonded.

[Bill_Satellite]

The Kisae and Heart inverters that I have looked at automatically bond neutral and ground when in inverter mode (no shore/generator power). This is not optional. It is the only way the inverter functions.
The inverter DOES NOT bond neutral/ground when connected to an external 120V source and is acting in pass-through mode.

[road-runner]

From the picture it sure looks like it was already bonded at the factory.

[MrWizard]

Do NOT BOND THE NEUTRAL to ground on the inverter
There is no earth ground safety when off grid on inverter power
Bonding the inverter neutral would make the RV frame part of the electrical circuit for the inverter
It would be the neutral, this is not safe
Do Not Bond neutral to ground

[BFL13]

brulaz wrote:

road-runner wrote:
I didn't see where the OP stated whether his inverter was with or without built-in transfer switch. If it's without, the GFCI outlet is the only AC output and it has a hardwired bonded conductor.
...

............ I purchased this Kisae on sale at the Buffalo NY WestMarine for US$343 and wasn't really sure about it's reputation.

These local guys sell them and I know they are very fussy about what they sell, since it comes back to them if it is no good, so they have to be careful.

http://www.wegosolar.com/categories.php?category=Off-Grid-Inverters/KISAE

[brulaz]

road-runner wrote:
I didn't see where the OP stated whether his inverter was with or without built-in transfer switch. If it's without, the GFCI outlet is the only AC output and it has a hardwired bonded conductor.
...

This one is without a transfer switch. Model SW2420

"Hardwired bonded conductor" ?? With*in* the GFCI socket ??

You can see from the picture that the 120VAC Grd connection on the socket is only connected to the two varisters (or ?).

By the way, I am pleased see several Kisae users out there. Apparently without major complaints, hopefully? I purchased this Kisae on sale at the Buffalo NY WestMarine for US$343 and wasn't really sure about it's reputation.

[BFL13]

I had one of those CanTire PSW 1000w inverters that was wired internally like that. I also had a battery disconnect switch on the neg side.

With that switch open and no shore power cable plugged into the inverter, I had no 12v in the rig. BUT as soon as I plugged the shore power cable into the inverter the 12v things (lights etc) worked!

I decided it must be the way the inverter is on the battery for input, and that the rig's 120v and 12v share the frame as a ground and somehow the way the inverter chassis ground went to the frame plus the weird way the inverter's receptacles were wired up for GFCI and its chassis, Not quite sure how it all connected but it did.

Nothing bad happened, but it did negate my neg side disconnect switch between battery and frame. "They" do warn you about neg side disconnects, where the pos side is left live and "anything" can make a neg path you were not expecting.

[brulaz]

MEXICOWANDERER wrote:
What sayeth the manufacturer?

The manual? Is pathetic compared to others like Samlex. But they do insist upon grounding the case with a min 8 awg for RV apps.

By the way, this is the Kisae SW2420, 2000W, 120VAC from 24VDC.

[brulaz]

time2roll wrote:
I don't think there is any pass-through with this inverter so it can be bonded all the time.
What is the issue?

Exactly. This a simple inverter only.
No transfer switch, no pass-thru.

The simplest scenarios is that when using the inverter I just plug the trailer's 120VAC input cord into it via an adapter. And When plugged into shore power I obviously unplug the input cord from the inverter and plug it into shore power. I don't see any problem when plugged into shore power.

It's the bonding between Neutral and Ground via the chassis when using the Inverter that I was wondering about.

My current 1000W inverter is not bonded and works fine.

From what RoyB and others are saying bonding is not a problem (and maybe it's a feature?).

(In reality I do use a transfer switch.)