Shared/open ground problem

I'd like to start by saying I have no problem hiring a pro if this isn't a DIY fix, but I would like to understand the problem before I do. There is a tl;dr at the bottom if you don't have time to read the whole thing.

I have two circuits with wiring issues and I think the problems are related. Here is what I have discovered so far:

When an outlet tester is used on a receptacle on Circuit #1, both yellow lights come on (correct).

When an outlet tester is used on a receptacle on Circuit #2, both yellow lights come on, and the red one comes on 1/2 way. Google pointed me to a reference describing this situation as "the wiring is FUBAR".

When an outlet tester is used on a different receptacle on #1, all three lights come on (FUBAR). If I plug a UPS into the other outlet on this receptacle, the red light on the tester goes out (correct) and the UPS's "building wiring fault" light comes on. This receptacle has a ground wire joining it to a ground wire from a light on #2.

#2 has no ground to the panel. But, some of it appears to have been upgraded and now has a ground wire. It's unfortunately not possible to run a ground wire to the panel.

#1 and #2 are on different legs and do not have a shared neutral.

tl;dr: Is it a problem to share ground, particularly if the two hots are on different legs?

Thank you in advance to anyone who would care to tell me their opinion.

 

Outlet testers are fallible. They are good for a quick test everything is okay but they are not reliable for determining what is wrong. For that you need a multimeter (preferably analog). A cheap $8-$15 dollar analog meter is what you need. (A cheap digital can give misleading results.)

Using a multimeter set to voltage on the scale neares to 250 volts you need to make these measurements:

• Hot (narrow slot) to neutral (wide slot). Should be ~120 volts.
• Hot to ground (round hole). Should be ~120v.
• Neutral to ground. Should be about ~0v.

 

Thank you very much for replying.

First outlet I mentioned: (Circuit #1)
Hot to Neutral 150V
Hot to Ground 150V
Neutral to Ground 0

Second outlet: (Circuit #2, no ground at panel)
Hot to Neutral 150V
Hot to Ground 225V
Neutral to Ground 50V

Third outlet: (Circuit #1, ground wire connected to circuit #2.)
Hot to Neutral 150V
Hot to Ground 150V
Neutral to Ground - needle moves slightly when I tested just now, was 45V a couple of hours ago.

I suspect the meter is out of calibration and the 150V is actually correct.

 

Those readings don't look correct. If this is digital meter change the battery.

 

Those were taken with an analog meter.

I would be delighted if you could comment on this question: "Is it a problem to share ground between circuits, particularly if the two hots are on different legs?"

I've opened up about 1/2 the receptacles so far and that was the only thing that appeared majorly out of place.

 

Do you mean to share neutrals on two hots that are on different legs ?

It already sounds like you have a open neutral in three wire circuit.

Analog meters don't require user calibration on the VOLT scales.

 

No, I did in fact meant shared ground.

These are two two-wire circuits, each with its own neutral, not a three-wire circuit.

 

Grounds need to be connected together when there are multiple circuits in the same box.

 

Okay, I understand that. And it's not a problem to connect those grounds together, if one of the circuits doesn't have ground going to the panel?

(Beyond the obvious "both circuits should have ground going to the panel".)

 

Consider MWBC or shared neutral --- two different *hot* legs sharing the neutral and grounding conductors.

Those voltage readings sound fishy.
It's almost like you might see with a neutral problem on a MWBC or at the service.

If you are reading 45 volts between the neutral and grounding conductors there might be some neutral-to-ground connections --- possibly at a receptacle(s). Might be leakage current.

There were some misguided people that believe neutal-to-ground connections were ok when connecting grounding receptacles to 2 wire ungrounded circuits.

2 cents worth.

 

Thanks; that makes sense. I will look elsewhere for the source of the problem.

I hope to get time to inspect the remainder of the receptacles later today.

 

The verdict: interrupted ground between two outlets, and severely degraded insulation on wires at a ceiling light. Thanks to everyone who responded!

 

Glad you figured it out, and thanks for letting us know.