Stacking lugs at a ground bar

[sticko]

A contractor has stacked three ILSCO 2 hole lugs, one on top of each other to a ground bar. I have always assumed that the lugs are to make contact to the ground bar on one side as they are torqued. Is there a NEC or standard that backs this type of installation?

 

[infinity]

So you're saying that only one lug is actually in contact with the ground bar and the other two are stacked on top of the first?

Similar to this on the enclosure:

 

[sticko]

Pretty much. Two lugs are back to back and installed vertically, the third is stacked horizontal. The two that are back to back are in full contact with the ground bar but the third one on top is only making contact with the lug and not the ground bar.

Actually they installed a total of five lugs. Two sets are stacked back to back and mounted parallel to each other. The fifth lug is mounted perpendicular and each of the two holes in the lug is shared with the vertical lugs. They are in a "H" form, if that helps. The top lug only makes contact at the bolts holding all of the lugs to the bar, but only the vertical lugs are in full contact.

Is this a violation to NEC or any standards?

 

[petersonra]

as long as it is a good connection I don't have an issue with it. stacking of lugs is a common practice.

 

[mivey]

Stacking is not such a good idea if the load has not been considered. With loaded lugs it would be akin to wire-nutting several wires together to a single wire and taking the single wire to the bus. The bus contact of the final lug can only handle so much and in fact is probably not rated to carry additional piggy-back loads.

With heavy loading I would be concerned because each connection has some slop and hot spots. Not so sure burying these hot spots is a great design.

 

[kwired]

Doesn't it really come down to whether or not there is enough surface contact between separate components to transfer any intended current without overheating? So this would make a lug with its smallest rated conductor possibly acceptable but maybe with the largest rated conductor not so much acceptable in some cases.

Might want to look into white page requirements for listing of these devices, there may be something relevant there.

 

[petersonra]

Stacking is not such a good idea if the load has not been considered. With loaded lugs it would be akin to wire-nutting several wires together to a single wire and taking the single wire to the bus. The bus contact of the final lug can only handle so much and in fact is probably not rated to carry additional piggy-back loads.

With heavy loading I would be concerned because each connection has some slop and hot spots. Not so sure burying these hot spots is a great design.

what hot spots? these are being used as ground lugs.

 

[mivey]

Doesn't it really come down to whether or not there is enough surface contact between separate components to transfer any intended current without overheating? So this would make a lug with its smallest rated conductor possibly acceptable but maybe with the largest rated conductor not so much acceptable in some cases.

I would buy that.

 

[mivey]

what hot spots? these are being used as ground lugs.

Oh sure, get all snooty just because you paid attention and I didn't.