Portable sign tripping building GFCI

[tater1978]

I'm having problems with a custom built portable electronic sign that when on shore power trips the GFCI on the building it is plugged into. When the sign is first plugged into a GFCI it will work but at some point it trips the GFCI and from that point it will keep tripping the GFCI every time it is plugged back in. But then at some point I will be able to plug it back in and it will work for a non-specified amount of time and the GFCI will trip again.

One thing I have tried is unhooking the ground from the shore power connection and the GFCI will not trip.

What should I be checking for? What are some possible problems?

 

[ramsy]

..One thing I have tried is unhooking the ground from the shore power connection and the GFCI will not trip..

1) Certain florescent lights & ballasts trip GFCI's
2) NEC 210.8 never required building lights to be GFCI protected
3) NEC 555 Marinas, Boatyards, only requires GFCI's for outlets & plugs
4) NEC 600 Electric Signs and Outline Lighting, does not specify GFCI protection
5) NEC 647.7(A)(2), where GFCI outlets exist they must be marked:

WARNING — TECHNICAL POWER
Do not connect to lighting equipment.

6) Check de-energized sign wires for continuity to frame - wires may be shorting to frame thru florescent ballasts.
7) If sign is fed by remote GFCI circuit, and can't hard-wire bypass GFCI outlet, may need to retrofit GFCI compatible light source.

 

[GoldDigger]

It sounds like the electronics of the sign and its controller actually sources current to ground under some circumstances. Probably a design or wiring error, but one that may be nearly impossible to troubleshoot.
You might start by measuring current in the EGC at a time when the sign is tripping the GFCI. But you would have to feed it from a non-GFCI source to do that.
Feeding the sign through an isolation transformer could be a workaround if you cannot remove the GFCI.

Sent from my XT1585 using Tapatalk