250.122 (F) Conductors in Parallel.

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tgroce

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Statement: This has been revised from the 2005 code.

From the Code: Where conductors are run in parallel in mutiple raceways or cables as permitted in 310.4, the equipment grounding conductors, where used, shall be run in parallel in each raceway or cable.

Example: I have a 800 amp feeder. Using 3-3C/350MCM w/gnd, XHHW-2 Rounted in tray with 3-3" conduits on each end to drop into the switchgear and into a
mcc. Aprox 3' lenghts of conduit on each end.

Per code the equipment grounding conductor for an 800 amp protective device is an 1/0 copper. The standard equipment conductor within a 3/c350mcm w/gnd is a #3 awg. This is therfore not adequate.

Are the following valid options?
1. Order special cable with correct size EGC. (yes)
2. use 3-3c350mcm w/no ground and pull a seperate (1)- 1/0 EGC in cable tray from point A to point B in a seperate conduit???
3. Pull (3) - 1/0 EGC in cable tray from point A to point B and route in the 3conduits with the phase conductors even though they are only short conduit drops. Since the code says in each raceway

Also, since the code say IN cable is a seperate external ECG cable acceptable or does it have to be part of the multi-conductor cable?
 
tgroce said:
This has been revised from the 2005 code.
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Not in essence, or at least not to the point where it changes your question. The revision from 2005 to 2008 eliminated one way of picking a size for the parallel EGCs.
tgroce said:
Are the following valid options?
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Option 1 is the only one of the three options that works. 300.3(B) requires all circuit conductors, including the EGC, to be in the same cable (if you are using multi-conductor cables), or within the same raceway (if you are using single conductors). That is why I prefer to use single conductors, rather than multi-conductor cables, when I am paralleling conductors. Single conductors, by the way, would be Option 4.
tgroce said:
Also, since the code say IN cable is a separate external ECG cable acceptable or does it have to be part of the multi-conductor cable?
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It has to be in the cable. There are two cases in which an EGC is allowed to be outside the cable, and your example is not among them.

Welcome to the forum.
 
tgroce said:
. . . does it have to be part of the multi-conductor cable?
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"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.

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."

You are correct, a 1/0 grounding conductor must be in each cable. You may also use a metallic conduit system and allow the conduit to be the grounding conductor instead of pulling one into the conduit. However, if you do decide to pull a grounding conductor in conduit, the grounding conductor in each raceway shall be sized to the overcurrent device (1/0 in this case)

Note that my answer is based on the 2008 NEC. Welcome to the forum. :smile:
 
You could avoid the use of a special cable by using a 4 conductor 350kcmil cable and use the 4th 350 as the EGC.
 
wasasparky said:
Don't use one. have the conduit/tray be your ground.
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That is another available option, unless, of course, the local rules do not allow it. I have heard of some jurisdictions that require the EGCs to be separate wires, even if the NEC allows the conduit type to be used as an EGC.
 
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