gfi breaker issue

[Tim Leach]

Looking for some input. I have a customer who has old bx wiring(2 wire) that feeds the countertop of the kitchen. There is no gfi protection and with that I was hoping to install gfi breakers instead of individual gfi's. The customer has special wall plates that can't be replaced to fit if we do individual gfi's. The issue is that when the neutral is connected to the breaker and the factory neutral is connected to the neutral/grnd bar it automatically trips when power is restored. Is this because the bx is bonded to the cabinet and because the bonding screw is installed through the ground bar to the cabinet, its tripping because the shared connection between ground and neutral?

[Marc]

No, it shouldn't.  Maybe the GFCI breaker is simply doing it's job.  Maybe there is leakage.  Takes only about 5/1000 of an amp to trip it.

Pull out the 1st receptacle in the string.  Leave it connected but, at that point, disconnect the rest of the string then try again.  See if it trips.

If you're removing power from the bus, reset the GFCI breaker after the bus is live.

Edited February 6, 2020 by Marc

[mtwitty]

Tim, that circuit is most likely sharing a neutral with another circuit.....very common in older wiring installations. The imbalance of neutral current in the two circuits will cause the GFCI to trip, or as Marc said, there could actually be a ground fault on the circuit. If it is sharing a neutral with another circuit, your customer may just have to lose their affection for the old plates. Then you can use GFCI receptacles for the countertop receptacles, as long as you don't use the load terminals for other downstream outlets/receptacles.

Edited February 7, 2020 by mtwitty

[Jim Katen]

16 hours ago, mtwitty said:

If it is sharing a neutral with another circuit, your customer may just have to lose their affection for the old plates.

I see a 3-d printer in their future . . . 

[Tim Leach]

On 2/7/2020 at 9:02 AM, mtwitty said:

Tim, that circuit is most likely sharing a neutral with another circuit.....very common in older wiring installations. The imbalance of neutral current in the two circuits will cause the GFCI to trip, or as Marc said, there could actually be a ground fault on the circuit. If it is sharing a neutral with another circuit, your customer may just have to lose their affection for the old plates. Then you can use GFCI receptacles for the countertop receptacles, as long as you don't use the load terminals for other downstream outlets/receptacles.

Thank you.