Ok here's a good one. I have 6 RV pedestals with 12 GFIs. (2 each) All the pedestals are 100 feet from their service disconnect. Three are served by 1 200 amp disconnect, 3 served by another 200 disconnect. All pedestals have seperate neutral and equipment groung. (all wired correctly as a subpanel, neutrals and grounds separated)all have suplimental ground rods connected to the ground bar only. Each pedestal has two 20 amp breakers serving two GFI receptacles (12 total). With no load, nothing plugged in or nothing connected to the load side of the GFIs, they all trip within a few minutes. Yep, all 12 with no load. All 6 problem pedestals are within the same area however, there are other pedestals near by and supplied from the same power co. transformer, wired exactly the same way, and have no issues. Any ideas?
The neutrals are within the same underground conduit as the supply conductors and the equipment groung. Each pedestal does have its own ground rod however disconnecting the ground rod makes no difference. I tried that but the pedestal itself is metal and burried 2 feet in the ground too.
First thought would be incorrect L-N Terminations at the GFCI Receptacle (Line side Grounded Conductor Terminated to the Load Terminal / Load side Grounded Conductor Terminated to the Line Terminal - and/or a similar scenario for the Ungrounded Conductors)
Next would be N-G connection on the Load Side of the Devices; could be from a nick in the Conductor's Insulation - resulting in an N-G "Leak", could be from bare EGC touching the Silver Screws on the Device, Etc...
After that would be Wiring Fault - Open Common Neutral issues, Neutrals of the Two Branch Circuits tied together at some remote location past the GFCI Device, etc... IIRC, the latest and greatest GFCI Devices are supposed to "Crow Bar" (trip and remain non-resettable) if the Load Side has a Wiring issue.
Then there is the possibility of Current flowing via either of the Two Wires of the Branch Circuit - which is causing the Devices' CTs to sense an imbalance...
Last would be defective Devices.
Start with the "Obvious" and easiest, then work your way down the list until you reach "Defective Devices". If you get that far, exchange with a Device which is known to be functioning properly, then energize the Branch Circuit to see if the properly functioning Device will hold or trip.
To verify if Neutrals for the Two Branch Circuits are tied together "Downstream" of the Devices, turn on One Circuit at a time. If no trip occurs, turn on the Second Circuit. Trip will indicate a Load Side Wiring issue.
-- Scott (EE)
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
Thanks guys but keep in mind there is nothing connected to the devices. Nothing pluged in nothing downstream. As in every case the neutrals go to neutral buss which intern is grounded at the disconnect at the service. I have replaced a few devices with new _same result.
If there is no load on the gfi's and they're tripping on their own it's going to be one of three things..
1) Condensation building up within the gfi's themselves.
2) Line voltage disturbance. (What manufacturer made the GFI's? Some GFI's will trip when power is removed or "browned out", so that you must reset them after power has been restored.)
3) You got a run of defective gfi's.
If the gfi's will allow you to reset them and function, even for a few minutes,I don't see it as a line/load mix up. They shouldn't reset at all..
BTW make sure if there are lawn sprinklers in the area that they aren't hitting your pedestals.
P.S. If all else fails, try a different make of GFI, and stay away from any that say "3Grace" or "General Prohtect" anyplace on them. These have false UL labels on them (There's a thread about when I came across these before someplace in the forums) Stick with the known manufacturers (P&S, Bryant, Leviton, Hubbell, etc..)
Speaking of GFI tripping. I just install a lot of Christmas lights and it seems that 2 of my many GFI receptacles trip. OK, now I know that I can replace them. However once I turn on the lights and see these 2 strings aren't working. I go out unplug lights, reset GFI and plug lights back in. They will work all night long. Next night I turn on all outside recpt. and the same 2 strings (which are on different recpt. and different sides of yards.)do not go on. I rest GFI and they work all night long again.
My question, these are "newer" style GFI that have to have power on to rest. I still have the old style where you can reset without power. Could a rush of current when the lights go on be tripping the GFI? I am more curious than anything else.