Reverse Polarity

[guschash]

I had a simple job of put up a spot light in the back of the horse barn. Two hour job turn into 6 hours later job. When I got hanging spot light on barn , I checked the receptacles in the barn, they all showed reverse polarity on my tester. I took some apart to check wiring and they were wired right, so I went to the garage where barn is fed from to check it. They all showed reversed polarity. Next I removed panel cover to check it , I didn’t find anything wrong there but checking receptacles in with my tester show that they all showed reverse polarity. I’m thinking something wrong on utility pole or at weather head. It was getting late , so I told owner to call utility and have them check pole and weather head. Was there some else that I could of done to find problem?

 

[ptonsparky]

Tester vs Meter?
What tester did you use?

 

[guschash]

Plug in one

 

[jaggedben]

. .. I’m thinking something wrong on utility pole or at weather head....

Nope. That is, assuming that you're using one of those 3 LED plug testers, they just test whether the EGC prong has the same voltage to the hot as the neutral does. So the problem, if it's not in the tester or the user, is in how the neutral is bonded or in the wiring. Or there are multiple problems, which those 3 LED testers can't diagnose.

I did once see a panel where some yahoo had put all the white wires on the breakers and all the black wires on the neutral bar. That's the sort of thing that would do this. But you said you looked in the panel and it looked fine.
So I'm struggling a bit to come up with a sensible explanation for a split phase service. Is the garage panel only 120V? What is upstream of it?

 

[jim dungar]

Plug in one

They are okay at showing things are good. I don't trust them for showing what is bad, that's when you need other meters and techniques.

What were your L-L, L-N, and most important N-G voltages?

 

[ggunn]

In a related story...

A friend of mine bought a small travel trailer that had been wired for AC shore power by the previous owner; it was "designed" to be powered by a suicide cable, i.e., an extension cord with two male ungrounded connectors. When my friend was running CATV wiring to the trailer, he accidentally touched a connector to one of the aluminum window frame, it arced and burned a notch in the frame. When the previous owner had wired the trailer and cable he had gotten hot and neutral reversed and he connected "neutral" to "ground", which was the trailer frame. Luckily, no one was killed.

 

[jaggedben]

Here is one definite possibility: the EGC to the panel is open (or missing), and there is a hot to EGC fault at the panel or downstream. That would put voltage between neutral and ground on the receptacles. Reading on the tester would be the red light and the middle light, which they call hot-neutral swap, but in this case it isn't. Pretty dangerous situation.

 

[hillbilly1]

Nope. That is, assuming that you're using one of those 3 LED plug testers, they just test whether the EGC prong has the same voltage to the hot as the neutral does. So the problem, if it's not in the tester or the user, is in how the neutral is bonded or in the wiring. Or there are multiple problems, which those 3 LED testers can't diagnose.

I did once see a panel where some yahoo had put all the white wires on the breakers and all the black wires on the neutral bar. That's the sort of thing that would do this. But you said you looked in the panel and it looked fine.
So I'm struggling a bit to come up with a sensible explanation for a split phase service. Is the garage panel only 120V? What is upstream of it?

I’ve run across that before, and was told the military uses white as hot, and black as neutral. Don’t know how true it is.

 

[don_resqcapt19]

A lot of plug in testers will show reverse polarity where the EGC is not connected.

 

[jaggedben]

A lot of plug in testers will show reverse polarity where the EGC is not connected.

Really? The ones I've seen are all pretty simple: there's an LED for each combo of wires. So what they call the reverse polarity indication only happens if there's voltage between neutral and ground and not between hot and ground. A mere open ground will not do that. (However it must be added that these simple testers will *never* identify multiple issues at once.)

 

[qcroanoke]

I would get a piece of wire and and give those receptacles a ground from a known good source. If it shows as proper wiring from that some where you have an open ground.

 

[jaggedben]

I would get a piece of wire and and give those receptacles a ground from a known good source. If it shows as proper wiring from that some where you have an open ground.

Larry's trick of running an extension cord from a known good receptacle is a good one. If the garage is not too far from the house.