Equipment Ground Conductors

[dasarmin]

When sizing an Equipment Grounding Conductor, is the following true:
Single Conduit fed from I-Line Circuit Breaker 480V 3-Phase, the Ground conductor should be sized based on the I-Line CB rating. For instance, a 600Amp CB would require at minimum a #1 copper ground wire.
If the feed is a parallel run in 2 conduits from a single I-Line CB, the ground conductor is still size base on the CB size not on the ampacity of the conductors. For instance, a 800Amp CB feeds a panel with (2) conduits. Each Ground conductor would a 1/0 or larger copper cable, not sized based on the current carrying conductors.
If there are multiple circuits in a single conduit, 1 Grounding conductor is permitted if it is sized to largest over current protection. For instance, 3 circuits (20A, 40A and 50A) are all in a single conduit, a single ground conductor of #10 or larger is permitted.

 

[Dennis Alwon]

Correct. Each conduit must have an equipment grounding conductor that is large enough to trip the overcurrent protective device. So if a 1/0 is required for a certain size overcurrent protective device then 1/0 is needed in each conduit to insure that the breaker will trip on a ground fault.

 

[electricalist]

Would a grounding bushing with the correct egc size achieve the same goal?

 

[iwire]

Would a grounding bushing with the correct egc size achieve the same goal?

No.

You are free to add one or more bushings but if there are wire EGCs run in parallel sets each EGC must be full size.

 

[dasarmin]

My original comments are based on table 250.122, which I use for sizing grounding conductors from I-Line, QO Panel Boards to equipment panels. If the feed is from a Switchboard that feeds an I-Line that will feed mulitple equipment I still use table 250.122.
When would Table 250.66 be used, it stated Service Entrance, which would not be for systems described above; Switchboard to I-Line, I-Line to Drive Panel, etc.

 

[dasarmin]

What about Table 250.102(C)(1), would this table apply to any of the feeds described above?

I basically deal with in-house industrial wiring, Switchboards to I-Lines or Equipment Panels (Drive, Heat, etc) and I-Line panel boards to Equipment Panels (Drive, Heat, etc). Doing so, I?ve always used Table 250.122.

 

[petersonra]

if it is metal conduit no wire type egc is required at all.

 

[Dennis Alwon]

What about Table 250.102(C)(1), would this table apply to any of the feeds described above?

That table is for the grounded Conductor (neutral) as well as Bonding Jumpers not the equipment grounding conductor. Table 250.122 is for the equipment grounding conductor no matter what the voltage may be. It is based solely on the overcurrent protective device unless you upsize the conductors then you must upsize the equipment grounding conductor proportionately- article 250.122(B)

 

[roger]

When would Table 250.66 be used, it stated Service Entrance, which would not be for systems described above; Switchboard to I-Line, I-Line to Drive Panel, etc.

250.66 is used for the Grounding Electrode Conductor and 250.102(C) is for the Supply Side Bonding Jumper, see the definition in 250.2


Roger

 

[Dennis Alwon]

For those who may not know T. 250.102(C)(1) is new to the 2014 NEC

 

[dasarmin]

Thanks for the comments.
Sounds like we've used the correct table for sizing grounding conducts.
Just FYI, our in-house policy has always been to run grounding conducts in any conduit, minus maybe communication conduits.

 

[Dennis Alwon]

Thanks for the comments.
Sounds like we've used the correct table for sizing grounding conducts.
Just FYI, our in-house policy has always been to run grounding conducts in any conduit, minus maybe communication conduits.

Many people use an equipment grounding conductor in metal raceway. It is a choice one makes but it isn't necessary is all that was being said earlier

 

[electricalist]

if it is metal conduit no wire type egc is required at all.

That is what i was implying. Alot of times with 277/480. From service equipment i see the addad grounding bushing although not required. Imo the pipe is a better egc