Trouble shooting 208v

[b0b01]

I got a call from a friend that I maybe looking at and I have no idea what to look for. I have 5 light 208v light poles my friend gets 120v line to ground on both lines but only 4v line to line. I asked if both lines are on the same phase, he said no. what would cause this. thanks

 

[charlie b]

He said no, but perhaps he is wrong. Do the lights work?

Welcome to the forum.

 

[Jljohnson]

A 208 volt circuit could give you those readings if one leg of the circuit was dead and the other is feeding throgh the ballasts for the fixtures, thus giving a 120 v-n reading on the dead leg.

 

[b0b01]

hi guys. the lights do not work and i thought he might be wrong but maybe not.
Jim I dont know why i didnt think of that thanks i will ask him to check it out.

 

[Electric-Light]

hi guys. the lights do not work and i thought he might be wrong but maybe not.
Jim I dont know why i didnt think of that thanks i will ask him to check it out.

If V L1 to L2 = 5v, I bet

V L1 to N and V L2 to N are about 5v apart.

In other words, they're probably on the same phase, but different breakers.

 

[kwired]

You likely have a dead line as mentioned. Disconnect the load and check voltage to ground again (with a low impedance meter) and you will have 120 on the good line and nothing on the other if this is the problem.

 

[Electric-Light]

You likely have a dead line as mentioned. Disconnect the load and check voltage to ground again (with a low impedance meter) and you will have 120 on the good line and nothing on the other if this is the problem.

5v difference seems odd though. That is almost like two legs of 120v on same side, but different voltage because of different loading on each leg.

Yeah, 60W light bulb from N to L, N to L2 sounds like a good idea. If that works, but there isn't ~208v, you're on same phase....

Or avoid all this complication and just use two of the channels on an oscilloscope and see the phases.

 

[hurk27]

this is a good example of applying #(5) from the OP from this thread:General Troubleshooting Advice

You must assume it worked before, and if it did 208 volt lights would not be on the same leg in the panel, so I vote for a lost leg and back feeding through the load. check the voltage at the breaker and to the last point it leaves the building, then at the first point it reaches the first load, if still there then it is after this point, if not its lost before this point.

 

[kwired]

5v difference seems odd though. That is almost like two legs of 120v on same side, but different voltage because of different loading on each leg.

Yeah, 60W light bulb from N to L, N to L2 sounds like a good idea. If that works, but there isn't ~208v, you're on same phase....

Or avoid all this complication and just use two of the channels on an oscilloscope and see the phases.

If conductor was lost underground that is not that odd. If you have a clean cut or break then maybe it is.