Using conduit as EGC

[hhsting]

Please see attached sketch. I have 480/277V three phase coming into switchboard with 4 service disconnects. One of the service disco feeds trough thru FDR #1. Trough their is a tap one feeder FDR #2 goes to tenant 1 meter by utility and another feeder FDR #3 goes to tenant 2 meter by utility. From meter FDR#4 and FDR#5 go to each respective tenants.

Conduits are used as equipment grounding conductor (EGC). FDR #1 utilize two locknuts one inside other outside SWBD and wire trough. FDR #2 ,#3 utilize two locknuts one inside and one outside wire trough and Meter. FDR #4,#5 utilize 2 locknuts on meter side and Grounding bushing on tenant disconnect side.

Question this is not line side of service disconnect but it’s load side and utility meters are load side. In such situation would above mention method of using metal conduit as EGC bonding be per code? If not then what should it be?

 

[Joe Villani]

Please take a look at 250.97

More than likely there are some eccentric of concentric knockouts on the equipment. If that is the case...

You might need additional bonding on the raceways depending on the manufacturers literature.

 

[hhsting]

Please take a look at 250.97

More than likely there are some eccentric of concentric knockouts on the equipment. If that is the case...

You might need additional bonding on the raceways depending on the manufacturers literature.

Ok thank you for your input. I think their is exception for eccentric or concentric knockouts NEC 2014 Section 250.97.

My question is also with FDR 4,5 conduit between POCO meter and tenant disconnect which says ground bushing are being used. I was wonder this is not service conductor only has POCO meters so where would ground bushing come from?

 

[augie47]

as pointed out, likely due to eccentric or concentric knockouts..
you will only know from a ton of research or from the field.
(2) 1" bond bushings shouldn't make or break the job. Not really worth the worry. Specs or prints call for it, do it !
There is no way to answer your specific question without a forensic analysis of each portion of the system. As pointed out in Post #2, comply 250.92 for your particular situation

 

[hhsting]

augie47 my buddy thanks for your input always appreciated. Ok but if they are listed reliable bonding connection then their is an exception see attached. I understand field experience but it is little hard to enforce to have someone do it if NEC 2014 has this exception

 

[electrofelon]

augie47 my buddy thanks for your input always appreciated. Ok but if they are listed reliable bonding connection then their is an exception see attached. I understand field experience but it is little hard to enforce to have someone do it if NEC 2014 has this exception

I guess there will be some different philosophies on this, but I tend to think the plans should mention intent to you the exception. IF not, I would red pen it as a violation. Alternatively, could you just ask the person who submitted the plans if intend to use the exception and show appropriate documentation?

 

[hhsting]

I guess there will be some different philosophies on this, but I tend to think the plans should mention intent to you the exception. IF not, I would red pen it as a violation. Alternatively, could you just ask the person who submitted the plans if intend to use the exception and show appropriate documentation?

Yea I can do that. 250.97 deals with raceways and cables what about enclosures such as tenant disconnect? They need to be bonded to EGC no?

 

[electrofelon]

Yea I can do that. 250.97 deals with raceways and cables what about enclosures such as tenant disconnect? They need to be bonded to EGC no?

Do you really think leaving a metal enclosure floating and not connected to the EGC would be acceptable?

 

[hhsting]

Do you really think leaving a metal enclosure floating and not connected to the EGC would be acceptable?

No I think not but would locknuts, washers, ground bushing that are being used would bond the enclosure thru metallic conduit used as EGC as well or is their another code section for it to additional have bonding jumper to enclosure?

 

[hhsting]

No I think not but would locknuts, washers, ground bushing that are being used would bond the enclosure thru metallic conduit used as EGC as well or is their another code section for it to additional have bonding jumper to enclosure?

I guess their is not one? ??


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[electrofelon]

No I think not but would locknuts, washers, ground bushing that are being used would bond the enclosure thru metallic conduit used as EGC as well or is their another code section for it to additional have bonding jumper to enclosure?

I am going to say that is actually a fair question. Say I have a feeder in EMT serving a panelboard. Lets say we are using the conduit as the EGC. Lets also say the fitting joining the EMT to the panelboard cabinet is a standard EMT set screw connector and the voltage is less than 250 to ground. Getting kinda nitpicky here, but I dont think you will find anything that SPECIFICALLY states that the EMT box connector to cabinet connection is acceptable without additional bonding. Its all sort of indirect. Sure 250.118 says the EMT itself is an acceptable EGC, and I guess it is reasonable to assume that all listed fittings associated with that EMT are themselves acceptable EGC's as well as their transition to other "stuff" but again it is not explicitly stated. 250.96(A) doesnt specifically state it but has wording that paint and enamel be removed or use of fittings that cut thru it. We can also deduce that the box connector to cabinet is acceptable by looking at 250.92(B) and 250.97, in other words they amend the "normal" situation which must be acceptable.