Ghost voltage

[LD_baugh]

We're in the process of removing 600 some 480v metal halide lights in a warehouse. We are replacing them with 277v electronic ballast fluoresent lights. We are not pulling any new wire, we are reidentifying one of the phases to nuetral.

The metal halide lights all are fed from there own 4x4 j-box via an MC whip. We are installing receptacles in the 4x4, and have cord and plug on the fluoresents.

I was stripping one of the feeders and i saw some sparking. put the meter on it and it read 46vac. I got a journeyman, and his meter, same thing. Another journyman, who is running the job said it was probably ghost voltage. He said it was caused by the electronic ballast's. Something about the nuetral will carry an unbalance load. We already have about 130 lights replaced now. and most of the light circuits(about 40 of them) run in the same general area and are pulled through the same j-box's along the way.

Has anyone heard of ghost voltage that high before. Is this something that needs to be addressed more by the journyman running the job.

Thanks,
Luke

 

[roger]

First of all, are any of these circuits on while you are working on these fixtures?

Roger

 

[jeff43222]

I've seen it has high as 117V on a 120V circuit. I posted something about it a couple of months ago. The consensus was that a true voltage could be found only by measuring it with a high-impedance meter, rather than the low-impedance digital ones we are all used to using.

 

[Jljohnson]

We are not pulling any new wire, we are reidentifying one of the phases to nuetral Luke

I agree with the consensus that a typical digital meter will give some strrange readings like the ones you describe. Am I the only one who's gonna point out that re-identifying a phase conductor is a code violation in this situation? Unless, of course, the phase conductors are larger than # 6 AWG.

 

[iwire]

Am I the only one who's gonna point out that re-identifying a phase conductor is a code violation in this situation?

That is a darn good point.

We're in the process of removing 600 some 480v metal halide lights in a warehouse. We are replacing them with 277v electronic ballast fluoresent lights. We are not pulling any new wire, we are reidentifying one of the phases to nuetral.

That is certainly a violation.

 

[LD_baugh]

Violation!!!
I'm just an apprentice on the job, so my word doesn't mean much. We just went over re-identifying in class the other night and the teacher said it was alright. The feeds are #8's and end up at #12's. And the power is off btw.

Reading 200.6(A) this situation sounds like a big no-no. Should I open my mouth and show them this violation, or just do what the boss says.

 

[mdshunk]

There's no such thing as 'ghost voltage'. I call it 'Phantom Voltage' instead. It sounds just a tad spookier.

 

[George Stolz]

The consensus was that a true voltage could be found only by measuring it with a high-impedance meter, rather than the low-impedance digital ones we are all used to using.

I think that's backwards. A wiggy is a low impedance meter, and a digital multimeter is a high impedance meter.

Luke, do yourself a favor and go buy a wiggy.

I carry this model (the Ideal Vol-Con, available at supply houses and Home Depot) on my toolbelt at all times. It's lightweight, rugged, and will not lie about voltage. It is very sensitive about continuity, which can be a hinderance sometimes. But it will not be decieved about voltage.

It could save your life.

 

[George Stolz]

Reading 200.6(A) this situation sounds like a big no-no. Should I open my mouth and show them this violation, or just do what the boss says.

This is what I do: Bring in the codebook, and very respectfully and quietly say, "It looks as though we are not supposed to be re-identifying ungrounded conductors as neutrals, according to code. Do you want us to start pulling in neutrals, or what do you want to do?"

Whatever answer is given, it falls on the license supervising you. It's their job. If it's, "Shut up and get back to work," then do so. You did your part in bringing to light the violation.

I would view this as a minor violation, myself.

If there is a serious violation and the supervisor rejects safety, then you have a troubling decision to make. I hope you never get stuck in that situation.

 

[jeff43222]

The consensus was that a true voltage could be found only by measuring it with a high-impedance meter, rather than the low-impedance digital ones we are all used to using.

I think that's backwards. A wiggy is a low impedance meter, and a digital multimeter is a high impedance meter.

You're right. You want a low-impedance meter to make sure you aren't looking at phantom voltage.

 

[LD_baugh]

Luke, do yourself a favor and go buy a wiggy.

I have that same model vol-con, but i was using my digital meter. I have to say I probably use my vol-con more than any of my meters, but my digital is still kind of new. I thought I might try it out and get it a little dirty. I'll keep that in mind in the future.

As far as the violation goes: I showed the journyman the Book. To keep it short he said "do it." He didn't take offense though. He is just doing what his boss told him to do.

Thanks for your imput,

Luke