Xantrex ProWatt SW inverter neutral bonded to ground?

Gerald55 wrote:
Well I guess it depends what you mean by "MUST". My Xantrex is "for marine" per the website and also claims that it "conforms to UL458 with marine supplement", but does not have any selectable N/G bond.

The idea is probably that you hide the inverter behind an ATS, which will take care of the shore power switching and ensure you are bonded correctly in both cases (the ATS must switch both hot & neutral for this to work, ofc).

You've not seen a pair of $60,000 bronze propellers, and two thousand dollars worth of zincs and through hull fittings disappear off a commercial trawler I guess. Inverter ground bonding must be interrupted when plugging a vessel into shore power. Three phase 100-ampere connection can be ugly, if the hull becomes anodic. We took unbelievable pains to isolate all potential leakages into commercial hulls. Try and TOTALLY INSULATE a 120' steel vessel from both 36 and 12 volt positive and negative oriented leakages. A charger plugged into shore power on a steel vessel presents challenges that would drive an RVer fruitcake. 2ma was the DC limit.

With enough shovel work any molehill can become a mountain...

Looks like you're more interested in arguing than taking advice.

Nothing what anybody says here holds as much value as an actual measurement.

Don't expect any more aid from me.

Gerald55 wrote:

Salvo wrote:

What's wrong with connecting a couple of wires to inverter to verify?

Partly because I wanted to figure this out before I wired it up into its final position. Mostly, however, because it wasn't (isn't?) clear to me that simply measuring 0V between neutral and ground is sufficient evidence.

Salvo wrote:

What's wrong with connecting a couple of wires to inverter to verify?

SoundGuy wrote:
Been following this discussion for 3 pages now in case there's something I too can learn but have to admit I must be missing something here - as suggested, why not just power up the inverter and measure it's output to determine it's design? :h

Partly because I wanted to figure this out before I wired it up into its final position. Mostly, however, because it wasn't (isn't?) clear to me that simply measuring 0V between neutral and ground is sufficient evidence. It's certainly a necessary condition, but not a sufficient one? That is, any two unrelated pieces of metal that I poke will generally measure 0V, so does it prove anything? Certainly a non-zero measurement would be strong evidence against bonding, but why is the inverse true?

On the other hand, the ohmmeter measurement seems like positive evidence in favor of bonding.

Salvo wrote:
No, it's not adequate to just use and ohmmeter.

The only way you will know for sure is if you measure voltage. Many inverters have a internal switchable bond. Meaning, when on shore power the inverter bond is open and when using inverter the neutral-to-ground bond is made.

Right - I was aware of that, but that would simply mean that a "non-connection" measurement when off doesn't exclude bonded GN when running. In this case I measured no resistance when off, so it is apparently bonded when off, and there is no pass-through or anything else on this model, so am I wrong in assuming it must be bonded full time?

Been following this discussion for 3 pages now in case there's something I too can learn but have to admit I must be missing something here - as suggested, why not just power up the inverter and measure it's output to determine it's design? :h

No, it's not adequate to just use and ohmmeter.

The only way you will know for sure is if you measure voltage. Many inverters have a internal switchable bond. Meaning, when on shore power the inverter bond is open and when using inverter the neutral-to-ground bond is made.

What's wrong with connecting a couple of wires to inverter to verify?

Gerald55 wrote:
That's only a test I can do when the inverter is installed - does the omhmeter test not also work?

all you have to do is plug in a lamp
turn the inverter on
read the voltage on the socket that is empty
that will tell you how the inverter is wired
there will be NO capacitance tingle leakage false reading on the empty socket
when there is an actual load on the inverter
anything 60watts or more, should be enough load load to give you an accurate reading

heck.. use an electric heater set on low, about 750 watts, if you want
its only going to be for a couple of minutes
this will give you the info and tell you exactly what you got ..how its wired

60-0-60 or 0-0-120

yeah you got to hook it up temporary to make the test
just connect to the battery, put the load on it, and measure it with the meter

MrWizard wrote:
a correctly wired ATS
will ALWAYS switch both the Hot and Neutral conductors of ALL inputs involved
and the N/G bond or no bond has nothing to do with it

I don't think anyone said otherwise? The reference to ATS above was to clarify that perhaps a UL458 inverter could use permanently bonded GN, even in scenarios where shore power is expected, because it must be installed behind an ATS (as opposed to the pass-thru models with switchable GN bond).

IF you want an inverter with a bonded neutral to use with an ATS for whole house RV use
i suggest you BUY one that specifies that is is wired that way
instead of damaging what you have by doing some wiring mod that is NOT supposed to be

I'm not clear on what you mean here. What wiring am I suggesting doing? I'm just trying to find out if the inverter I have already purchased has a GN bond as I would expect it to, and by all reports so far it does.

I'd love to live in a world where every product was completely documented from end-to-end by subject matter experts, but that's just not what you find. If I restricted my purchases to products that were documented like that, I'd have very little to choose from (sometimes nothing to choose from), and pay several times the price.

a correctly wired ATS
will ALWAYS switch both the Hot and Neutral conductors of ALL inputs involved
and the N/G bond or no bond has nothing to do with it

60v between a conductor and ground is safer than 120v between conductor and gound
and the neutral IS a conductor in the circuit

IF you want an inverter with a bonded neutral to use with an ATS for whole house RV use
i suggest you BUY one that specifies that is is wired that way
instead of damaging what you have by doing some wiring mod that is NOT supposed to be

I dug up a copy of UL458 and spent too long looking at it. I didn't find much at all about GN bonding.

I did find this part:

30.1.3.1 The grounding connection and the output neutral of an inverter that is intended to be connected
to the cigarette lighter outlet of a vehicle shall be bonded to the inverter frame or enclosure.

Which seems to require GN bonding, but only for inverters intended to be attached via cigarette lighter (there are a bunch of relaxations earlier in the document for inverters of this type, so this is probably added to claw back some of the safety given up earlier).

Perhaps this document is old, or perhaps I should be looking at the "marine supplement" or maybe I just missed it.

When I power up the inverter I'll check the voltages.

Sorry about the delay, I was climbing a small mountain.

I dont know about the temporary installation comment. I took it to be ul458 is always bonded. I was concerned when I installed mine so I did find in the manual that it's only ul458 which makes sense to me because the plugs are built into it and it's not flow through.

The magnum inverter that I mentioned and others that flow through may have both ratings. It can be used like our prowatt units or if wired to the panel and beyond to a sub panel it will remove the inverter bond and it will then depend on the shore power bond. In fact on his unit he also needed to make a GN bond plug for his generator because the gb relay drops out when it sees power from the main panel whether that power is pedestal or generator it doesn't know.

I checked mine as Salvo mentioned. I have 125 v from hot to neutral and 120 v from hot to ground. I have continuity between neutral and ground.

This document says that ul458 units have internal switching. I wouldn't say ours have switching. I'd say they are constant bond. I cant check mine right now to see if it looses the bond when powered down. No real reason it should.

Xantrex

Bond


I checked a shoemaker modified 410 watt and it's not bonded. No mention of it in the manual. Putting out 105 volts. :)

My Aims 300 w pure is not bonded. I see no mention of it in the manual. I have been meaning to throw it in the lake but it's still new in box.

Both those units read 35 volts neutral to ground. Probably also along the lines of what Salvo explained.