For some background im changing over from one generator to a new generator at work. I have a panel by the old one that feeds the emergency lights and I have a panel by the new one that will feed the emergency lights from now on. I turned the breaker off on the old generator but left the neutral and hot terminated in the panel. I turned on the breaker in the new panel hooked up normal to test it and the breaker instantly tripped. The panels are both on different seperatly derived systems but the neutral on both ends were still hook up so they were tied together. I unwired the terminations in the old panel turned the breaker on again and everything works. Is that neutral why my breaker was tripping? Thats what I was thinking please let me know what your thoughts are!
Neutrals tied togther from two different systems. Will breaker trip?
- Thread starter kjroller
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
All separate SDS neutrals are connected together so I'm not sure if that was your issue.
For the new generator the system is seperatly derived but for that i had to switch the neutrals im under the impression that if you neutral is shared and the bonded at 2 sperate ends you must switch the neutral other wise it is not seperatly derived? But these two systems both had a MBJ at each panel and were tied together if that explains it any better
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Is there a step down transformer involved? 480 to 120/208?
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
That may have been the problem, the transformer was not bonded, and there was a fault to ground, but because it wasn’t bonded, it didn’t trip the ocp. The new system was bonded, so the fault had shown up.