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#49810 - 03/17/05 07:48 PM GFCI wiring predicament
Rich Thomas Offline
Member
Registered: 03/09/05
Posts: 48
Loc: Seattle, Washington, USA
Last weekend I decided to add GFCI protection to a couple of bathrooms. The house is 1976 vintage so many current NEC rules are not followed, such as to provide separate circuits for outlets in each bathroom. In this house, the outlet in two baths are on the same branch circuit, and unfortunately, so are many other outlets.

My intended approach was to use one GFCI receptacle wired at the first outlet of the branch circuit to protect all other outlets down stream. I found the first outlet for the two baths in the bedroom next to the first bath.

After carefully making sure all power was off at the outlet and studying the wiring to make sure to make the correct connections I proceded to complete the installation. When I was sure everything was correct, I closed the circuit breaker and returned to the GFCI to run the test. The GFCI would not reset to normal. I'd push the RESET and it would immediately trip, acting as though a ground fault existed.

My first thought was a mistake with my wiring. This may be a typical reaction for an engineer I checked the wiring and everything looked OK. So, it was time for some deeper trouble shooting.

I soon found that the neutral on the load side of the GFCI wiring was grounded. Knowing that the neutral should not be grounded except in the sevice entrance panelboard, I knew what the problem was. I spent several hours trying to located where the neutral was being grounded and never found it.

To achieve the needed ground fault protection, separate GFCI receptacles were installed in each outlet needing the protection. This approach works fine.

I've been trying to figure how the neutral down stream of the first outlet is grounded. There are many possibilities. The most likely one I think is that the neutral wires from two different branch circuits are incorrectly connected together in an outlet box (one I did not open most likely.) When these two neutrals are connected, even though one of the neutrals is disconnected in the first outlet, the neutral returns to the neutral bus in the panelboard through the connection with the other circuit's neutral.

This situation is probably not serious, do you think?
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#49811 - 03/17/05 09:08 PM Re: GFCI wiring predicament
nesparky Offline
Member
Registered: 06/21/01
Posts: 642
Loc: omaha,ne
Have seen a lot of wiring mistakes and other causes be the reason a GFCI will trip and not reset. With older houses the cause can be almost any of the numerous errors including but not limited to a neutral to ground connection in or out side of a box.
Sometimes a portion of the neutral will have been damaged so some one decides the ground willwork s the neutral rather than cutting into a wall to replace the wiring.
Have had cheapy light fixtures be the short between the neutral and ground. Another hard to find is a staple driven a bit to hard cutting a bit into the sheath of romex and causing a neutral to ground intermintent or a low to high resistive connection.
Finding this cause can consume a lot of hours and be fustrating. be patient and keep looking The cause could be not dangerous but in one case I found a neutral wire arcing in an attic that had paper used for insulation. The paper was chared when I found it after 2 days looking for this same type of problem. Somebody's big foot had stepped on it despite running boards. Fortunatly the HO wanted it fixed and did not put a time or cost limit on me.
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#49812 - 03/18/05 07:45 AM Re: GFCI wiring predicament
mustangelectric Offline
Member
Registered: 02/08/04
Posts: 494
Loc: Bentonville, AR
Hi,
Rich- You said: "to provide separate circuits for outlets in each bathroom"

The nec only requires that a bathroom outlet be on a 20A breaker..AND/OR that it MAY supplly no other outlet except another recept in another bath.

I can use ONE 20A circuit to provide that outlet in more than ONE bathroom.

myself i usually will only go for two baths and not ALL!

As far as the gfi tripping..first turn off the MAIN..

then just take those gfi outlets and replace them with a gfi breaker...way better than a gfi outlet and all you have to do is swap the breaker..just make sure the neutral from the load side goes to the breaker and not the ground or neut bus..take the pig tail from the breaker and land that on the neut/gnd bus..

turn the power back on and locate each outlet that the circuit feeds..then turn the power off again..

tear it all apart and make sure that you have the correct wiring.

once you do that if you still cant find the problem abandon that circuit and install a new one between the two places where you cant get it to clear.

my guess is that somewhere in the system the neutral is making contact with something that is grounded..could be a metal box, yolk, or just plian miswired.

I hope you find it!

good luck

-regards

greg




[This message has been edited by mustangelectric (edited 03-18-2005).]
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