Jumper between main lugs in sub panel?

Status
Not open for further replies.
C

CAsparky

Member
Location
San Diego
I am doing a remodel on an old house that has a 30 amp subpanel. Someone put a jumper with lampcord between the two main lugs. Why would they do this?
 
CAsparky said:
I am doing a remodel on an old house that has a 30 amp subpanel. Someone put a jumper with lampcord between the two main lugs. Why would they do this?
Click to expand...
Probably because it was a do it yourself installation. The feed must be 120 volts coming to the panel and they wanted to utilize the other phase for breakers. Of course you will not be able to get 240 volts from it. I am curious if there is a separate ground from the neutral
 
It was fed with 10/3 from a double pole breaker from the meter main. Grounds and neutrals were not seperated. When I took out the jumper I could get 240volts.
 
CAsparky said:
It was fed with 10/3 from a double pole breaker from the meter main. Grounds and neutrals were not seperated. When I took out the jumper I could get 240volts.
Click to expand...
If it were fed with a double pole breaker and you had a jumper between phase A and Phase B it would be a dead short and blow the breaker.
 
Thats what i thought. But it did'nt. With the jumper in it read 120volt. With the jumper out it read 120 volt each phase and 240 volt in between.
 
Are you sure the jumper was not a capcitor , Varistor or something.
I have seen dIY do this before.

Or The original breaker for the FEEDER could have been half tripped?
 
The jumper was just a short piece lampcord. It was a handled breaker. I think like you said it must have been half tripped or a bad breaker. When I got there the general had the power off. I looked in the subpanel and saw the jumper and was like what the hell? I went out to the main and turned on the breaker and no trip. Went to the subpanel to take a reading and got my 120. Went back to the main, turned it off, took out jumper in sub, main back on and then I got my 240 reading. I must of got both phases on this time. So i think the breaker is bad and one phase has trouble engaging. So a diy put in the jumper for his solution. I'll have to double check next week. Sometimes this electrical stuff runs you in circles. Thanks
 
My guess is the jumper was put in to get power to the other phase because the breaker either half tripped (haven't seen that on a standard DP breaker) or the breaker didn't engage that phase. The HO's fix was a jumper. When you removed the jumper and reset the breaker everything was fine. The breaker may not always engage and may be going bad.
 
are you sure it wasnt two single pole breakers with a handle tie
if so its not common trip and one breaker could trip while the other wont
cause it was not overloaded
 
Status
Not open for further replies.
Top