Since many enjoyed the puzzle Henry posted the other day I thought I would add one that had me stumped.
A few years ago (NEC 1999) a contractor called me to check out a problem with a new inground swimming pool.
The problem was that the GFI receptacle kept tripping.
He then went to the sub panel and showed me that the breaker for the receptacle was in the OFF position. We then reset the receptacle and it tripped, with the breaker off.
What do you think was causing it ?
Since it was in the 'off' positon and not the 'tripped' position, I'd say the breaker was defective
Where was the sub-panel located, inside or out?
My 2 cents on this puzzle.
If the breaker was OFF and the GFI receptacle had power but tripped the test/trip buttons on the receptacle, then the breaker must be defective.
If the breaker was OFF and you couldn't rest the test/trip buttons on the GFI receptacle, maybe you needed power in order to reset the buttons on the receptacle.
It must be interesting or it wouldn't be posted here. I'll guess hot and neutral reversed.
My guess is that the load side of the GFI receptacle is being backfed from another circuit.
It was tripping from current through the neutral and a neutral-ground fault.
Breaker was in a sub panel located indoors near the pool.
The breaker was in the OFF position, not tripped.
When the reset was pushed ON the receptacle it would quickly trip.
The receptacle was on a dedicated circuit, no shared neutral.
Additional Information.
Thinking that the breaker was defective the black wire to the breaker was disconnected.
The GFI receptacle was reset*, and then tripped !
*Older GFIs could be reset with the power OFF.
Alan Nadon
Panel connections wrong/bad? Rod
Breaker was in a sub panel located indoors near the pool.
Neutral connection between the main panel and the sub panel was open?
Did the GFCI stop its peculiar behavior when the main breaker feeding the sub panel was opened?
Larry C
Neutral and ground tied together by mistake at the load at the pool? Coupled with a weak neutral connection at the meter or such place going to the POCO, (or bad neutral in the sub-panel, and another circuit in the subpanel is drawing current) and some neutral current wanting to get back to the POCO's transformer's neutral finds a path thru the GFCI's neutral, to get to that ground by mistake? MIght not need a bad neutral, Just some normal neutral current being diverted to the mistaken ground connection (more than 7 or so ma of several amps would do it).
This had everyone stumped for two days. POCO was called to check the house. Everything was fine. They also checked the neighbors house and found an open neutral.
The neighbors house, 200 feet away, was sending enough voltage through the earth to the new inground pool, with rebar and steel mesh in the apron, to be picked up by the GFI receptacle.
The older GFIs would trip on an imbalance between the black and white as well as anything on the ground.
It was the only time I ever saw a GFI trip when it had no power going to it.
Open neutral... I'm having a hard time envisioning an open neutral that would cause ground current. Unless you mean that the poco's neutral line to the house was broken, and all the neutral current was flowing through the neighbor's ground rod to the ground rod by the pole? Well, not counting the current flowing through your pool ground
Nice puzzle!
Neutral was open at the weatherhead on the house.
Ground rod and water bond as well as the earth to the swimming pool were the only return pathes. They worked well enough that the house wasn't experiencing an unbalance between the phases.