GFCI nuisance tripping

[zackrogers]

I'm experiencing some nuisance tripping of some GFCI devices on a new conveyor system I'm commissioning, hoping to get some insight. Please let me know if any additional information is needed.

For most of these circuits there's a Hubbell DRUBGFI20BFAC inside the control cabinets, then connected on the load side is one or two Hubbell GFTW15W receptacle.

During the week, nothing trips and everything is great - however upon returning on Monday (after the system sat idle all weekend), about a dozen of the DRUBGFI20BFAC will be tripped despite most (if not all) of the tripped circuits having nothing plugged in. This is across 4 separate cabinets.

I've megged the circuits as well as visually inspected some of the cables for knicks but everything seemed fine. Everything is inside a climate controlled building, no water in the area so it shouldn't be a moisture issue.

I'm pretty stumped at this point, so any thoughts would be great.

 

[LarryFine]

Welcome to the forum.

This sounds like a job for a data recorder.

 

[ptonsparky]

I've had solenoid coils, small motor and contactor coils trip GFCI as they were turned off.

 

[synchro]

For most of these circuits there's a Hubbell DRUBGFI20BFAC inside the control cabinets, then connected on the load side is one or two Hubbell GFTW15W receptacle.

Does this mean that the GFTW15W receptacles are being powered from the load side terminals of the GFCI in the DRUBGFI20BFAC? If so, perhaps before the weekend you could disconnect the GFTW15 receptacles from one or more of the DRUBGFI20BFAC load terminal outputs and then see whether it makes any difference on Monday. Apparently there's not normally a problem, but maybe on the weekend there is a voltage dropout or surge on the line that could be causing the GFTW15 to power down and back up, and resulting in some type of transient interference that trips the upstream GFCI. This is just speculation, but I assume that it should be relatively easy to do the test I mentioned above.

 

[augie47]

You might inquire about any mechanical work that might have been performed. I have had problems with GFCI protection on conveyor systems and traced it back to electric welding being performed on the conveyors.
(Using the conveyor system as the welder negative lead)

 

[mtnelect]

Are they high efficiency or variable speed motors ? They don't do well with GFCI.

 

[Jraef]

I'm curious as to why you have GFCI receptacles connected downstream of a GFCI protector? Makes me wonder if the PC board power supply inside of the downstream GFCI units is leaking a little current, causing the upstream device to trip, or the self-test feature of the downstream GFCIs is causing it? It's kind of pointless to have a GFCI downstream of a GFCI, so I would do as synchro suggested and disconnect them, that might narrow it down a bit, then evaluate why you are doing it this way.

 

[zackrogers]

Welcome to the forum.

This sounds like a job for a data recorder.

Thanks!
Any recs for a decent, affordable data recorder? We're a small company and don't currently have one.

I've had solenoid coils, small motor and contactor coils trip GFCI as they were turned off.

I've been seeing a lot of that in my searches. We do have something similar on one particular receptacle - which I didn't think to include in the original post because I think that's a seperate issue because that circuit doesn't trip over the weekend, go figure.

Does this mean that the GFTW15W receptacles are being powered from the load side terminals of the GFCI in the DRUBGFI20BFAC? If so, perhaps before the weekend you could disconnect the GFTW15 receptacles from one or more of the DRUBGFI20BFAC load terminal outputs and then see whether it makes any difference on Monday. Apparently there's not normally a problem, but maybe on the weekend there is a voltage dropout or surge on the line that could be causing the GFTW15 to power down and back up, and resulting in some type of transient interference that trips the upstream GFCI. This is just speculation, but I assume that it should be relatively easy to do the test I mentioned above.

That's correct. That seems like a solid idea, at least to narrow the issue down if nothing else. I have been wondering if it's somehow being caused by the series connection of two GFCIs.

You might inquire about any mechanical work that might have been performed. I have had problems with GFCI protection on conveyor systems and traced it back to electric welding being performed on the conveyors.
(Using the conveyor system as the welder negative lead)

To my knowledge, there hasn't been any welding done recently, definitely not this past weekend when they still tripped. I'm reading your message as the problems you had were WHILE welding was being performed, is that correct? Or do you mean that there was some welding done and then that damaged the GFCIs?

Are they high efficiency or variable speed motors ? They don't do well with GFCI.

The couple of motors that are connected through GFCIs are small brushless motors and their drive/controller. However, the GFCIs tripping over the weekend have literally nothing connected - they're receptacles for programmers to use during commissioning/troubleshooting, industrial PCs and/or printers that will be installed at a later date, etc.

I'm curious as to why you have GFCI receptacles connected downstream of a GFCI protector? Makes me wonder if the PC board power supply inside of the downstream GFCI units is leaking a little current, causing the upstream device to trip, or the self-test feature of the downstream GFCIs is causing it? It's kind of pointless to have a GFCI downstream of a GFCI, so I would do as synchro suggested and disconnect them, that might narrow it down a bit, then evaluate why you are doing it this way.

That I'm not sure, it was supplied from the machine builder this way. My best guess is they drew up the plan with the option for using either the upstream ones OR downstream, but somewhere along the line they both got put into place for whatever reason.
I'm definitely going to try synchro's suggestion

 

[retirede]

Anyone with a two-way radio patrolling on the weekend?

 

[zackrogers]

Anyone with a two-way radio patrolling on the weekend?

I believe they do have on-site security on the weekends, they're for sure here during the week though so if it's their radios causing it, I'd think that it would trip while I'm here too. Perhaps they're just more talkative on the weekend?