using LT on transformer

[teco]

Hi, I've done a search on this but I'm still a little confused. Would like to hear some of your opinions. Do bonding bushings or bonding type locknuts need to be installed on the primary and secondary raceways of a transformer when using LFMC to enter the transformer enclosure. EGC is used in each raceway. All knockouts are punched in the field. Thanks

 

[augie47]

IMHO, there is nothing to be gained by adding a bonding bushing.
You do not have concentric or eccentric knockouts so any bond bushing requirements for that situation is void, it is not a service so that need is void, you have a separate EG conductor and the limitations of 250.118(6) on LFMC are such that it probably is not a valid EGC for many transformer arrangements anyway.
A bond bushing is needed to assure the grounding continuity of the raceway and is not needed here.

 

[teco]

Thanks Augie, I agree with your opinion. I was told we had to use them. The person asking reason is the transformer is a "new service" so the conductors "service conductors". My answer was a transformer is a separately derived system and not a service. They don't agree with me. Also they want the bonding bushings on both ends of the secondary raceway. I may be wrong, but what purpose would doing that serve if there is an egc in the pipe already?

 

[teco]

I should have pointed out that I'm being told the bonding bushings are required to be installed on these raceways by the NEC. Sorry I left that out of my post.

 

[raider1]

Thanks Augie, I agree with your opinion. I was told we had to use them. The person asking reason is the transformer is a "new service" so the conductors "service conductors". My answer was a transformer is a separately derived system and not a service. They don't agree with me. Also they want the bonding bushings on both ends of the secondary raceway. I may be wrong, but what purpose would doing that serve if there is an egc in the pipe already?

You are correct. The conductors are secondary conductors and regulated as such by 240.21(C) and 250.30, they are not service conductors and 250.92 does not apply to a separately derived system.

I should have pointed out that I'm being told the bonding bushings are required to be installed on these raceways by the NEC. Sorry I left that out of my post.

Ask the people telling you that to point out the code section that backs up their position.

Chris