Residual Current Protections/GFCIs crane transmission rails that are live and exposed.

[Zeno Black]

I am looking for what the NEC defines as necessary for the Residual Current Protections for crane transmission rails from the manufacturer called Vahle, similar to what is there on an overhead crane, but in this case, the rails are mounted at floor level. This crane traverses on a rail at floor level, and the transmission busbar rails are also at floor level.

We have been trying to find what UL508A requires for residual current protections for personnel protection, but there is not much on this standard that speaks about what is necessary in terms of what UL classification of GFCI protections are available or needed for 480VAC.

We have omitted the residual current protections in the past for previous installations to be UL508A compliant since we have not been able to find UL compliant GFCIs for 480VAC three-phase in the market, but we are now worried that we might not have been code compliant at the installation level since we only focussed on having the control panels UL508A approved. Our client uses such panels for distributing power to these cranes, and they have not required us to use differential protections; we are very concerned for personnel safety.

 

[petersonra]

UL508a has a special set of requirements for crane control panels to be found in sections 68-72. I see nothing there that mentions any special GF protection requirements.

NEC article 610 covers cranes. I don't recall any special requirements for GF protection there but you might want to carefully read that article.

What the NEC or UL508a requires does not get you off the hook from OSHA though as far as providing a safe work environment for employees. If there is some definable hazard, you have to protect employees from that hazard.

 

[Zeno Black]

UL508a has a special set of requirements for crane control panels to be found in sections 68-72. I see nothing there that mentions any special GF protection requirements.

NEC article 610 covers cranes. I don't recall any special requirements for GF protection there but you might want to carefully read that article.

What the NEC or UL508a requires does not get you off the hook from OSHA though as far as providing a safe work environment for employees. If there is some definable hazard, you have to protect employees from that hazard.

Hello Petrsonra, I agree, the challenge is to find GF protections that are UL labeled for 480VAC three phase. We have not been able to find these type of protections for the use of them in the feeder circuit. Also, I am not sure how the SCCR is determined for GF equipment that uses current transformers/toroids since those are never connected directly to the Feeder but monitor the current passively. That is the real challenge, how to label the control panel under UL508A if that standard does not consider GF equipment for the feeder circuits. Any ideas where to start?

 

[Krusscher]

Obviously its best to eliminate the hazard but is there a practical way to put safety gates with switches to open a contactor that feeds this crane if anyone enters and write up a procedure for lock out tag out for entering that area?

 

[don_resqcapt19]

Hello Petrsonra, I agree, the challenge is to find GF protections that are UL labeled for 480VAC three phase. We have not been able to find these type of protections for the use of them in the feeder circuit. Also, I am not sure how the SCCR is determined for GF equipment that uses current transformers/toroids since those are never connected directly to the Feeder but monitor the current passively. That is the real challenge, how to label the control panel under UL508A if that standard does not consider GF equipment for the feeder circuits. Any ideas where to start?

Have you looked at Special Purpose GFCIs? They are also known as Class C, D and E GFCIs. The work on your voltage system with a 20 mA trip, meeting the same time to trip requirements of the standard Class A GFCI. Not sure what the maximum current is for the Special Purpose GFCIs. The are listed to UL 943C.

The 2023 code added them in Article 680 for pool equipment that operates from a voltage system that operates above 150 volts to ground.
There are additional installation requirements such as a "ground check" conductor in addition to the equipment grounding conductor.

The 20 mA trip is based on preventing ventricular fibrillation, the same idea used in the European RCDs.

 

[jim dungar]

Have you looked at Special Purpose GFCIs? They are also known as Class C, D and E GFCIs. The work on your voltage system with a 20 mA trip, meeting the same time to trip requirements of the standard Class A GFCI. Not sure what the maximum current is for the Special Purpose GFCIs. The are listed to UL 943C.

The 2023 code added them in Article 680 for pool equipment that operates from a voltage system that operates above 150 volts to ground.
There are additional installation requirements such as a "ground check" conductor in addition to the equipment grounding conductor.

The 20 mA trip is based on preventing ventricular fibrillation, the same idea used in the European RCDs.

But are they available for 480V like the OP?

 

[don_resqcapt19]

But are they available for 480V like the OP?

Yes, they are, some versions are for up to 600 volts. Here is the decision matrix from UL 943C.