Faulty gfci

[Jackca]

I have bathroom gfci circuit with two gfci in series, the down stream tripped wouldn't reset. Found line potential on both the neutral and hot wire. Further investigation found the up stream unit failed. Has anyone else ever seen this problem. Also the upstream gfci wasn't tripping.

 

[Lucien Nunes]

It sounds like the upstream GFCI might have been open-circuit in the neutral pole or lost its neutral connection from the panel. That could cause the neutral on the output side to appear hot, a condition which might prevent the downstream unit being reset, as some designs test for the correct relationship between hot, neutral and ground and trip if abnormal.