ART. 250-122(F)-1...

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LEADFOOT2

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Referring to ART. 250-122(F)-1 ..has it been added to code book some years back, or has it been there for a few decades & i always missed it. I've always seen over the years on drawings, typically that parallel runs of 500-MCM cu. , connected to a 1,200A or 1,600A breaker always had a #3 equipment bonding conductor. Inspector recently brought it to my attention about the ART. 250-122(FA)-1...and the bonding conductor should be larger..!?!?

Thanks..!! :?: :?
 
I looked at the oldest codebook that I have which is the 1987 NEC and it says:

250-95 Size of Equipment Grounding Conductors.
Each parallel equipment grounding conductor shall be sized on the basis of the ampere rating of the overcurrent device protecting the circuit conductors in the raceway...
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Here is the 2005 NEC:


250.122(F) Conductors in Parallel. Where conductors are run in parallel in multiple raceways or cables as permitted in 310.4, the equipment grounding conductors, where used, shall be run in parallel in each raceway or cable. One of the methods in 250.122(F)(1) or (F)(2) shall be used to ensure the equipment grounding conductors are protected.
(1) Based on Rating of Overcurrent Protective Device. Each parallel equipment grounding conductor shall be sized on the basis of the ampere rating of the overcurrent device protecting the circuit conductors in the raceway or cable in accordance with Table 250.122.
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LEADFOOT2
I'm not sure how long the requirement has been in the code but It has been a requirement for a while. If 250.122.F1 applys then the EGC is determined by table 250.122. If you have a 1200 amps breaker with 3 parallel runs then the EGC is 3/0 in each conduit. I do not see how the #3 was determined the be the correct size.
I hope you don't see too many 1200 amp breakers with 3 runs of 500 kcm copper. That would only have a capacity of 1140 amps.
 
Appreciate the replies....

Working in Viriginia, seen a lot of drawings since the early 80's using 500-mcm cu. or 750-mcm al. for 400A feeders & parralleled for higher amperage. Can't explain it..

Haven't worked on a commercial job since mid 90's. Been doing some specilized work since then.

Thanks.. [/code][/quote]
 
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