Electrical mystery--set out to fix 2 problems but fixed 3

[agesilaus]

First let me explain a Arctic Fox 25Y stupid quirk. They installed two electrical junction boxes outside the unit on the slide side. One standard 4 inch box is in between and above the two wheels. The other is behind the wheels. The first is 12V and powers the overhead light in the slide. The other is 120V and I did not know what it was for. These leak notoriously and last year I took steps to prevent leaks I also went from 15 to 16 inch wheels which put the wheels closer to the first box.

OK when I started out I had these three issues:
1) Outside box above the port side wheel needed to be replaced since I replaced wheels with 16 inch rims
2) I took out the dining table, which we never used and replaced it with a desk and in the process discovered that there is an outlet under the old table. But it was dead. That answered the quastion of why was there a 120V box behind the port wheels.
3) GFI popped at the BR sink, circuit tester indicated a hot ground (three lights)

So I took care of item one by using a smaller box. Item two, when I opened the box I did find a disconnected black wire. The hot ground. Replaced all the connectors with Levr Lock connectors. Thought well this may be whats wrong with item 3.

Checked inside, the circuit tester I had plugged in above the bed, I thought showed two lights now after I started the generator. The outlet under the table/desk is now working with two lights on a different circuit tester. OK fixed all three I thought. On the way out the bedroom tester was back to three lights?! WTH. It was getting dark so I gave it up until today.

Today I rechecked the 120V box behind the wheel and everything was connected correctly. Went inside after cranking up the generator and still had three lights, tried a different Sperry tester--two lights! Tried an old Sperry tester one light bright and one dim? Bad light?

The receptacle tester that shows three lights is the newest and is this model: https://www.amazon.com/Advanced-Kech...s%2C353&sr=8-5 Based on Mike Sokol's recommendation. Plugging a drill motor into a three light receptacle shows that it is working.

Could the problem be with the generator ground? I'm stumped.

[DrewE]

That's not at all unexpected. Ground from a portable generator is not in any particular way related to the hot or the neutral; the generator output is floating. Usually it will end up floating such that ground is somewhere near "halfway between" the hot and neutral, so 61V is very much in the range of what you'd typically see.

Ground and neutral are at the same voltage (or practically the same voltage) in a house because they are bonded together at the main electrical service panel. If they were not bonded together, they'd generally tend to behave in a similar manner (at least much of the time). It would also be contrary to the electric code for a fixed installation, of course.

[KD4UPL]

That means your ground is floating which is common with portable generators. Thus, no tester will give you a proper indication of whether or not the outlet is wired properly.

[agesilaus]

How about 61V from generator outlet hot to ground?

[BFL13]

Reminds me of when I tested the three-light tester against various inverters.

It showed three lights with all my different model MSW inverters. It showed only the middle light (open ground) with a PSW inverter I had.

It does not show proper lights with my inverter gen floating neutral.

Also there is the business of the inverter gen not being the same as some built in gens which act more like they have MSW.

So, it might be that your gen is one of those non-inverter types that would show three lights, same as a MSW inverter?

[agesilaus]

Well that is something I can do, I have a good DMM I'll doi that in the morning

[KD4UPL]

You're way too deep into electrical to not be using a meter. Those 3 light testers are handy for quick checks but will often confuse things as you have discovered. Get a proper volt meter and check for voltage you have: Hot - neutral, hot-ground, neutral-ground.
Did you ever plug in any of these 3 light testers before when running on generator? If not then you don't know if it's any different now or not.

[wa8yxm]

Ok the issue with 3 lights MIGHT be the generator.. here is why

There is an electronic component called a capacitor the symbol is -||- (note the dashes actually connect to the verticals) this is symbolic of the construction. Two metal plates with an insulator between them (Even air)

Well you have hundreds of feet of ROMEX cable and for this purpose that can be drawn as -|||- with the safety ground sandwiched between the hot and neutral

or more precisely -||--||=

Now in a DC system. that don't matter
But in an ac SYSTEM that forms what is called a voltage divider

So with reference to the NEUTRAL the HOT lead is 120VAC-RMS
And the safety ground 60 VAC-RMS

On many generators the Safety ground is NOT bonded.

And there is your 3rd light.

IS this dangerous? NO, not at all

Why the safety ground
House/Shore power IS bonded and in multiple places (The pole. your entrance service box) and heaven forbid you pick up a hand grinder like one I used for a bit professionally with an internal hot to case short .. YOU become a "neutral" path.

But the generator is NOT grounded so that does not happen.

[agesilaus]

What you're observing is not a fault for a portable generator, but rather an intentional design feature, and would not cause the GFCI to trip

I am aware of the issue and even have one of those plugs wired up. My UPS objected to that being used. But this does not explain how everything worked for over a year with no issues and when I checked outlets I got two lights. Or why two receptacle tester show two lights and one shows three lights.

So that theory does not fit the facts at hand.

[DrewE]

If the generator is a portable generator, then the ground is almost certainly not bonded to the neutral at the generator, but floating. A neon test light between hot and a floating wire can light dimly--for that matter, one between hot and your fingers will work fine. The three light outlet testers are usually nothing more than three neon test lights, internally, arranged one between each pair of wires on the outlet.

What you're observing is not a fault for a portable generator, but rather an intentional design feature, and would not cause the GFCI to trip.

Troubleshooting would be simpler if you plugged into normal utility power, where ground is bonded to neutral. A hot to ground short there would generally cause a breaker or GFCI to trip (a GFCI that you're plugged into, not necessarily the one in the trailer if the fault is not downstream of it).

[Fisherman]

What happens when you plug it into your house receptacle? I'm suggesting the generator is not grounded and will cause a fault to show on your tester, not the fault of your wiring.