3 years ago i rewired my barn for 240/120 service with a new box and new wires. i used the existing wires that run from the breaker box at the pole overhead to the barn they are 4 gauge wire.everything was fine then all of a sudden one night while i was working late i saw sparks come from the outside of the building and then the some of the light bulbs blew, replace bulbs and they act like they are at half power. upon inspection the main wires coming into the building was the shorting culprit. there was not a weather head the wires just ran through the metal wall and you could see where it was shorting out. put in a weather head and ran conduit. now that everything is hooked back up the lights still act like they are at half power.

 

Have you checked the voltage level at your box?

 

Sounds like an open neutral somewhere.

 

here is the weird thing , i measured the voltage coming in at 120v . if i have the upstairs breaker and the down stairs breaker on the upstairs lights quit and the downstairs lights go real bright. if i shut the downstairs breaker off the upstairs lights work perfect. i measured these 2 breakers and they test at 240v . these are 2 separate circuits that do not join any where. the rest of my breakers are dead no voltage at them at all .

 

You need to check for 240 volts across the subpanel's main breaker. It sound like a dead leg more then a open neutral.

 

When you unhooked the feed wires going directly through the barn wall and connected them to the weatherhead, you might have reconnected the wires in the wrong order causing 240 volts to be put across one side of the barn subpanel.

 

i never disconnected it outside i unhooked at box pulled it out and fed it through the conduit. i rechecked the main wire is at 120. possible my box shorted out some how?

 

To properly determine what's going on you need to do what Ray suggested earlier:That said, if you found 120V from each leg to neutral and the neutral is bonded in the subpanel, you may have an open neutral and be reading 120V hot-to-ground.

Let us know what you find with this test.

 

Considering the hack job you had, you should follow ray's advice first and then go back over every connection in the service and check to be sure they are all tight. Check voltages at every termnination as you go. Then, replace the service entrance wiring that was shorting to the metal barn siding. Just putting those existing wires in conduit does not fix that problem.

 

ok i replaced wiring coming in and measured the voltage at all connections on the way down to the breaker box at 120 v. my box doesn't have a main breaker. i measured the legs at 240v on the left side and 120v on the right side. i even went to the pole and checked the breaker voltage there and it was at 120 each side of the breaker.(it is a 50 amp double pole breaker)

 

That doesn't make sense. Sounds like you have the neutral connected to the wrong place. What voltage do you get when you measure across the main lugs of the panel? As previously written that is not what you need to check. You need to check between the two terminals of the breaker.



If it has room for more then six circuits it should have a disconnect of some kind even if it is forty years old but we can discuss fixing that later.

 

Across the main lugs 240v . I rechecked the wires and they are hooked up right. Their is a place for a main breaker but i didn't put one in since it is on a 50 amp at pole.

 

Then what did you mean when you wrote:

 

If you have spaces for more then six circuits then you must have a disconnect. The subpanel main breaker is used strictly as a disconnect. You could also use a freestanding disconnect but using a main breaker equal to or greater than the BC breaker is usually simplest. Is this then a main lug and main breaker panel? If not how are the feed wires connected?

 

It has 12 circuits. Since there is a main box over at the pole i don't have a main in the box at the barn.the wires are connected using lugs like the picture you used as an example minus the main breaker

 

That isn't code compliant. You must have a disconnect at the barn since you have more then six circuits. A main breaker in the subpanel is one way to provide a disconnect. The breaker at the main panel isn't a substitute. The disconnect must be at the barn.

So are you having the same problems with the electric at the barn? If so have you measured the voltage at the lights?

 

I better get a main then i guess. I measured at the. Wire coming off the breaker and it was 240v i know ot should be 120v. I measure at the lights to see and keep you posted.

 

Across the 2 poles of the breaker should be 240 volts. Either single pole to ground or to neutral should be 120 volts. If you have something different, you are close to the problem. Can you provide some pictures of the service and breaker disconnect.

 

I went back down and measured at the light 120v ... as soon as i turn the upstairs on it jumps to 240v. I even swapped the breakers to the other leg and got same results. I try to get pictures as soon as i can.

 

• Is the voltage between the upstairs neutral to ground ~0 volts?
• Is the upstairs voltage ~120 volts neutral to hot?
• Is the upstairs voltage black to ground 120 volts?

.

Will await pictures.

No, 240 is correct.

 

At the pole the breaker looks just like that. If i hold probes on screws i get 120v. If i go to the barn and measure at the lugs the main wires go into 240v . If i measure the single pole breaker my lights are on i get 240v if the upstairs light switch is on, shut it off and i get 120v at that single pole breaker.

 

First of all , If he has a 2 pole 50 amp Circuit Breaker " at the pole " feeding the barn , NEC does not require a main in the barn loadcenter . Local codes may or may not .

There is an upstairs and a downstairs , in the barn ?

Please send a photo of your barn loadcenter .

When you turn on thing / lite on and it changes the voltage of something else , it REALLY sounds like you lost your neutral & are running off of the earth ground .

Either the ground rod , metal building steel , cold water ground , etc. . Reguardless , it is not safe ! :-(

Just a thought , measure between the incoming neutral and earth ground . This is not conclusive , if the neutral is bonded to earth ground . But try it , with various lites and / or other loads turned on .

I repeat , it sounds like a bad neutral . Could be at the " pole " which is feeding the barn or at the loadcenter that has the 2 P 50 amp CB ?

God bless
Wyr

 

But a disconnect is required if more the six throws and he has 12. He could use a 60 amp pull out disconnect but main breaker is usually simpler.

 

Are you using a digital meter? If so have you replaced the batteries? There is no way a 2-pole breaker could read 120 and no way I can figure you could get 240 at the barn unless the 240 at the barn is coming from one side of that breaker and a second unrelated breaker.

 

Sorry i mistyped across the 50 amp at the pole each side os 120v across both is 240v

 

Then that's as it should be. Now, how are you planning to install the required disconnect for the panel?

 

We are still missing the solution to his original problem: