250.102(C) Or 250.122 Help !

[ERIK@DDE]

Making the mistake of not fully understanding this section of the NEC, i completed the wire install of an ATS. With startup coming soon, i ask our city inspector to review my bonding of the underground raceways coming up into an open enclosure, consisting of pvc with rigid nipple's thru the pad.

He failed my install stating that the bond bushings had too small of a ground wire running thru them, based on section 250.122

Here's the details, this is a 3000 amp ATS with 3000 amp OCPD's wired with, all phases, neutral and ground are 700 KCM AL. wire, paralelled 8 sets.

I believe that i satisfied the requirements of section 250.122 with the 700 KCM grounding conductor (which is over sized 100KCM), in each conduit.

This my understanding of the requirements for bonding the raceways per section 250.102(c) and 250.66 using a conductor no less than 12 1/2 percent of of the area of the largest phase conductor...

700,000 x .125 = 87,500 cir. mils , rounding up to 105,600 cir. mils @ 1/0 AWG
size CU. bonding conductor at each conduit.

I have a considerable amount of rework as it is correcting this mistake, adding a 400 KCM to 16 underground 4" conduits bond bushings, per the inspectors interpetation of applying section, 250.122 and not 250.102(c).

Any advice and or ammunition would be greatly appreciated, Erik

 

[infinity]

I have a considerable amount of rework as it is correcting this mistake, adding a 400 KCM to 16 underground 4" conduits bond bushings, per the inspectors interpretation of applying section, 250.122 and not 250.102(c).

I agree with the inspector. You need to use Table 250.122 in the 3000 amp column. Why did you think 250.102(C) would apply?

 

[ERIK@DDE]

Well based on some of the other threads ive read on the subject of bond wire sizing, lead me to 250.102(c), and my thinking that i am not using the raceway for a EGC, there is one in each pipe.

Basicly if i didnt have an open bottom ATS enclosure and terminated the conduits to a sheet metal with two lock rings, that would have effectivly bonded the race ways to the enclosure, correct?

 

[ERIK@DDE]

Here are two examples of what i was looking at:

http://forums.mikeholt.com/showthread.php?t=121115

http://forums.mikeholt.com/showthread.php?t=78448

 

[RUWired]

Erik you are close as far as the article goes but 250.102(D) applies to feeders on the load side of the service disconnect. 250.102(C) works with conductors on the line side of the service disconnect. 250,102(D) allows a single conductor sized per T250.122 to tie all your feeder conduits together.

Rick

 

[augie47]

Your basic guide should be "is there an overcurrent device ahead of this wire?". If so, 250.102(D) (250.122) is your route, if not, 250.102(C) (250.66) is your route.

 

[cpal]

I' m confused is this run upstream or down from ocp?

 

[ERIK@DDE]

Downstream.

And i'll consider this my learning experience for applying the correct grounding methods, from the expanded information from ya'll and chatting a lil more with the inspector this morning.

Thank's, Erik

 

[dana1028]

I agree with the inspector. You need to use Table 250.122 in the 3000 amp column. Why did you think 250.102(C) would apply?

Rob - what am I missing?

This is on the load side of the service; he used full sized EGC's in each raceway. Why would he have to bond each raceway to the enclosure? No mention was made about voltages.

The reason I ask: you answered his question before his post #3 - which then let us know his raceway was not connected to the equipment.

IF his conduits had been connected to the equipment [my assumption before post #3], why would he have had to bond each raceway?

 

[augie47]

he advised it was a PVC system with rigid nipples.....so the isolated rigid nipple at the pad would need to be bonded.

 

[dana1028]

he advised it was a PVC system with rigid nipples.....so the isolated rigid nipple at the pad would need to be bonded.

Darn!! I read that post twice and still missed that.