Reeeeaaally slow tripping single pole breaker.

[craff]

Happy Friday,
I have a 120-240V sg phase three wire meter pedestal serving a common area outdoor lighting system in a residential environment. Two single pole hot conductors with one neutral and one ground wire leave the pedestal in the same conduit.
Problem: Our first electrician went out and said it was a extremely slow trip on one single pole 20A breaker. He took an amp reading on the tripped breaker after resetting it and read 10.9A. He waited two hours and it never tripped again.
I returned and read the same load and checked the other circuit, it read 8.7A. I made some repairs to some loose connections in vaults and was able to balance the outbound loads to within .5A measured on the load side of lighting contactor (9.4A and 9.6A). However, the neutral conductor reads 3A. Shouldn't the neutral in the panel read the difference between the two loads?

 

[cadpoint]

If they were there for two hours, I think I'd of have them rip the circuit open.

Meggar.

It seems your time there was not the same basis of the time where things were observed.

Amps add in AC, you went in and balanced after the fact, how did you determine the load on the circuits?

Seems one could only meter the service to see the results...

 

[broadgage]

I would not worry about 3 amps on the neutral, even when this is unexpected from the currents in the hot conductors.
Can be caused by different power factors on the 2 hots.

As regards the breaker tripping, I would suspect an intermitant fault such as a bad ballast or buried cable joint.
With a common outdoor lighting system, dont forget theft of service as a cause ! illegal connection to common parts lighting system, and theft of enough current to trip the breaker.

 

[Sierrasparky]

I woud say megger it, you lhave a nick in the wire and a wet conductor.

 

[Rick Christopherson]

I don't know what part of the country you are in, but it is HOT outside right now. It sounds like this is an outdoor load center. Circuit breakers don't care where the heat comes from, they simply react to it. If your breaker is getting hot from ambient conditions, it will take very little circuit current to reach the trip threshold.

Your description sounds like a trip from ambient heating, not circuit overloading. A simple test for this is to shield the load center from direct sunlight or other heat source.

 

[kwired]

I don't know what part of the country you are in, but it is HOT outside right now. It sounds like this is an outdoor load center. Circuit breakers don't care where the heat comes from, they simply react to it. If your breaker is getting hot from ambient conditions, it will take very little circuit current to reach the trip threshold.

Your description sounds like a trip from ambient heating, not circuit overloading. A simple test for this is to shield the load center from direct sunlight or other heat source.

Don't you think it is usually cooler outside when the lights would normally be running? That is the way it works where I live.

 

[Rick Christopherson]

Don't you think it is usually cooler outside when the lights would normally be running? That is the way it works where I live.

If you have a personal grudge with me, it would be best to keep that discussion in the specific thread, and not confuse this poster with non-applicable banter.

 

[bob]

Rick,
You may have missed a point in the op post. He said "I have a 120-240V sg phase three wire meter pedestal serving a common area outdoor lighting system in a residential environment. Kwired is assuming the load comes on at night. I don't think an grudges was intended.

 

[kwired]

Rick,
You may have missed a point in the op post. He said "I have a 120-240V sg phase three wire meter pedestal serving a common area outdoor lighting system in a residential environment. Kwired is assuming the load comes on at night. I don't think an grudges was intended.

My comment at the end of the post was a little uncalled for and I apologize.

We are having a disagreement in another thread is what that is all about.