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When I place GFCI breaker into panel and turn the power on, there is no power that I can measure on the hot leg. I measure it between white wire (neutral) and the hot leg. Yes, the pigtail white wire is connected to neutral. Tried 3 different GFCI, none of them worked. Regular one has power and measures around 130V. Disconnected everything from panel, took all breakers (3) out and just tested old breaker, and they used 2 more that I bought. Same result.

Background: This is a sub-panel by the pool, that is connected to main panel in the garage via 6AWG wires to a double pole 50 amp breaker. Wires are all in conduit, connections glued. About 30 feet is underground. There are 4 wires, green, white, red, black, rated underground. This has worked without any issues for 2 years, no changes, no digging, no drilling nothing. Just one day, double pole breaker outputs no electricity. I tried resetting it several times, and sometimes it stays engaged, sometimes it does not. Testing works, pressing test button reset is (when it initially stays up). Single pole GFCI breaker will not even stay engaged. I measured voltage between hot legs and neutral at the entrance to subpanel, both have power, 130V.

I disconnected green (ground) and white (neutral) and measured resistance and it shows 0 Ohms. Does this mean that there is short between white and green? Is there a way to confirm this?

UPDATE Well, I feel stupid now, and I apologize to all of you who wasted your time trying to help me. So, here is what happened, my daughter tripped the GFCI breaker in the panel manually, she thought it was a light switch. So, after spending some time yesterday disconnecting everything it dawned on me that in my foolishness I never put the breaker all the way down to reset it. Bahhhh, live and learn. Mind you that I built the whole pool, wiring, plumbing, deck .. everything with my own 2 hands, and then I waste 4 hours of my life on something so stupid.

  • This question would probably be clearer with 1) a sketched diagram showing main-panel, sub-panel, wires between panel, where voltages measured, 2) good photo of subpanel showing wiring connected to GFCI. – RedGrittyBrick Jun 7 '16 at 13:48
  • I'll take it today when I get back home. – epitka Jun 7 '16 at 13:53
  • If you measure voltage between the hot bus bar and neutral, what do you get? Are the contacts on the hot bus bar in good shape? Does this panel have a main breaker? – Tester101 Jun 7 '16 at 14:25
  • @Tester101: Sub-panel is new, I can measure voltage on the hot bus bar and neutral at about 130V. Everything is disconnected from the panel, other then 2 hots coming from the main panel, grounding wire from main panel, and neutral from main panel. Once I place breaker in the panel, breaker does not output any power. – epitka Jun 7 '16 at 14:44
  • Is there a main breaker in the panel? When you're measuring voltage on the hot bus bar, are you measuring from where the non working breaker will connect? When you install the breaker, do you flip it to the OFF position, then back ON? – Tester101 Jun 7 '16 at 15:07
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Uh-oh. Your voltage (hot to neutral) should not be 130V anywhere except a few countries where 127V is common.

Start by measuring across the two hot "legs" in your panel. This value should be 220-240V, tending toward the latter, e.g. 238V.

Now measure each leg to neutral, these should be very close to half that, and very close to each other, e.g. 118-120V.

If they are not, but the two values add up to the first number, you have a very dangerous condition called a "lost neutral": the two "hots" are good, so 240V machines are happy. But the "neutral" is floating, and voltage on each leg is going to vary all over the map as the loads change, e.g. 171V and 67V, which will cause your appliances to catch fire. If you have this, shut off the main breaker now and unplug everything 120V or 120/240 until you fix it for good.

In light of your dryer error, a more likely possibility is that you have lost a leg of "hot". In this case, all the 120V circuits on that leg will be out, while the ones on the other leg work fine. 240V-only appliances will not work. 120/240 appliance controls may work, but the heaters won't. This is not an emergency in the same way as a lost neutral.

You may be having this problem with your entire house, it may have only appeared first at the pool. I gather your dryer is not at poolside.

The answer for any kind of "lost" wire is to give the panel a thorough take-apart and inspection. Look for loose screws (prticularly on heavy-wire lugs), corroded or arced contacts on breakers, burnt busbar, etc.

If you have a smart meter, good chance the power company can turn it off remotely using their SCADA system with a phone call.


White to green: In a properly wired house to code, with the main breaker off, resistance between neutral and ground should be as close to zero as your meter can detect. Voltage should be zero obviously. However, if any circuit is on, all bets are off. Voltage may be somewhat more than zero (but not more than 6 volts), which will make it impossible to measure resistance.

  • I haven't read this whole page, but +/- 10% is still within nominal (although, not desirable) voltage specifications. So, you might be getting anywhere from 108v to 132v. What will not change is the hertz. – Mazura Jun 8 '16 at 1:34
  • I've never seen anything that high in the US. Well, I saw it in a factory once due to how they had jumpered their own 480-240/120 transformer... where they had a lot of other electrical problems. Gee. – Harper - Reinstate Monica Jun 8 '16 at 1:46
  • I've seen 128v, but the transformer was basically on the other side of the wall. – Mazura Jun 8 '16 at 6:33
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I disconnected green (ground) and white (neutral) and measured resistance and it shows 0 Ohms. Does this mean that there is short between white and green?

Yes, assuming you measured between the free ends of the wires. But it is normal for ground to be connected to neutral at the main panel.

Note that measuring resistance of any wiring that might potentially be connected (or misconnected by a fault) to 120V or 240V is a dangerous process and should be performed with great care using suitably rated equipment.

Is there a way to confirm this?

You just did. If you don't trust your measuring device you can buy or borrow a different one.

I'd just test that the voltage from green to (say) black is the same as from white to black.

Single pole GFCI breaker will not even stay engaged

Then you have a fault - either in the GFCI or in the wiring downstream of the GFCI. I'd try disconnecting all the outputs of the GFCI and see if it stays engaged then.

  • In the sub panel I disconnected these two and measured resistance, while breaker in the main panel was tripped. Should I also disconnect at the main panel? I the main panel, grounds are separated from neutral. – epitka Jun 7 '16 at 13:40
  • I disconnected everything from the panel, I am just testing on the breaker itself, without anything being connected to it. – epitka Jun 7 '16 at 13:45
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    @epitka. I think you may be chasing a red-herring with the green-white resistance. If the wires leading to your subpanel have the expected voltage present on them when separated from the subpanel, the fault is in or beyond the sub-panel. – RedGrittyBrick Jun 7 '16 at 13:45
  • Hmm, might be true, as my dryer now does not work, it starts but then after few minutes gives me an LB error code nP, which stands for no power to heating element. Hmmmm, seems like problem might be somewhere else. Should I just disconnect all breakers in main panel, and add one by one and see which one causes problem. Is that simplest way? – epitka Jun 7 '16 at 13:49
  • @epitka - The simplest way, after reading all the dialog here and noting the nature of the problems, is to call in a licensed professional electrician. It will also be the safest path over all the trial and error things you have tried already. – Michael Karas Jun 8 '16 at 9:11

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