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I installed a dedicated 20amp circuit home run to support a single duplex outlet in a bathroom. The GFCI breaker is wired correctly. However, When I plug in a load such as a light a the breaker trips. Could there be an underlying problem with existing circuits in the home which could be causing this issue such as a neutral and a ground touching each other somewhere on an existing circuit or circuits throughout the house? The panel is a G E T M 2020C and the breaker I installed is a THQL 1120 GFP. I believe that the issue is being caused by some sort of feedback through the neutral bar causing a ground fault condition when a load is plugged into the new outlet. I would appreciate any feedback.

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marked as duplicate by BMitch Sep 8 at 12:32

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Have you used a circuit tester to verify wiring of the outlet? It sounds like you may have used an existing circuit/outlet and put it on its own breaker: how was it wired before and what exactly did you change (eg, how did you split it from the previous circuit)? There's not really enough info to go on here so far, but it sounds like either you have a faulty breaker or something is miswired. –  gregmac Jun 18 '13 at 15:55
This is a dedicated home run supported by a GFCI circuit breaker. There is power to the outlet when it is energized. however, when you plug in a device such as a lamp the GFCI trips. The wiring is ok, the outlet is ok the breaker is new and compatable with the panel. Could there be an underlying groung fault feeding back to the panel from another circuit somewher in the home. –  Joe Cario Jun 18 '13 at 17:37
Is it possible for a neutral and ground from another device supported by another circuit to feedback through the nuetral bar causing the GFCI breaker to trip when a load is placed on it. The GFCI breaker is installed as per the spec. Pig tail to neutral bar. black to the GFCI load terminal and white to the GFCI neutral terminal on the breaker. –  Joe Cario Jun 18 '13 at 22:36
Question revision Is it possible for the dedicated 20 amp home run supported by a GFCI breaker trip under load. If there was a neutral and a groung touching each other from a device such as an outlet or switch from another circuit in the home somewhere and feeding back to the main panels neutral bar? –  Joe Cario Jun 19 '13 at 12:13
@JoeCario No. There is a fault somewhere on this circuit (most likely neutral to ground), which is causing the breaker to trip. Try replacing the GFCI breaker (they do go bad from time to time), checking the receptacle wiring to make sure everything is wired properly, and checking continuity between and along the conductors. Have you tried plugging in a different electrical device, or are you always using the same (possibly defective) device? –  Tester101 Jun 19 '13 at 13:55

1 Answer 1

A GFCI breaker only detects ground-faults on the circuit it's protecting. It measures the current flowing on the ungrounded (hot) conductor and the grounded (neutral) conductor, and opens the circuit if there is a large enough difference between the two. A ground fault on another circuit would not trip the breaker, unless it was adding or removing current from the circuit (i.e. it was at fault with this circuit).

If this is a dedicated home run circuit with only a duplex receptacle, there are only 4 places a fault could be occurring.

  1. The breaker.
  2. The wire.
  3. The receptacle.
  4. The device plugged into the receptacle.

The Breaker

Make sure the breaker is connected properly, and that it is properly seated in the panel. The white grounded (neutral) conductor from the circuit, should be connected to the terminal labeled "LOAD NEUTRAL". The black ungrounded (hot) conductor, should be connected to the terminal labeled "LOAD POWER". The white grounded (neutral) pigtail, should be connected to the grounded (neutral) bus bar in the panel.

It might also be worth replacing the breaker, as they can fail or be defective.

The Wire

If there is a fault anywhere along the length of the wire, this could cause the breaker to trip. You'll want to test the continuity between the circuit conductors, but you'll first have to isolate them.

  1. Disconnect all circuit wires from the service panel.
  2. Using a multimeter set to measure resistance, or in continuity mode, test the continuity between each combination of wires.

There should be infinite resistance between all conductors. If not, you have a fault.

If you can manage it, inspect the entire length of the cable for damage. Make sure a staple or nail hasn't accidentally punctured the cable.

The Receptacle

It might be worth it to replace the receptacle, just to rule out the possibility of a defective device. You'll also want to inspect the wiring, to insure it's wired properly. The black ungrounded (hot) conductor, should be connected to the brass colored screw terminal. The white grounded (neutral) conductor, should be connected to the silver colored screw terminal. The green or bare equipment grounding conductor, should be connected to the green grounding screw terminal.

Also make sure that when the device is mounted in the box, none of the conductors are coming into contact with each other. This is especially true with the bare equipment grounding conductor, as it's easy to create a fault with the bare wire in a cramped box.

The Device

Try to plug in a few different devices, and possibly check the devices themselves for ground-faults.

I can't think of any situations where a ground-fault on a circuit, would cause the breaker to trip on a different circuit. Unless the two circuits are at fault with each other, of course.

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