parallel MC

[drbond24]

I know it isn't a good idea when running parallel cables to put all the conductors of one phase in the same conduit. Does the same principle apply with MC cable? I have three runs of 350/3 MC cable. Can I make each separate run one phase instead of one conductor from each run? My assumption is that it is a no-no for the same reasons as with conduit, but this is the first time it has come up for me so I thought I'd ask anyway.

Also, is this an NEC violation or just poor design? I can't find a code reference forbidding it, but I'm not the best at surfing the code either.

Thanks for your help.

 

[charlie b]

I think it would violate 300.3(B)(1). All conductors of the same circuit must be in the same cable, and this rule applies separately to each cable in a paralleled set.

Also, I think that paralleling MC cable will probably create a violation of 250.122(F). The EGC in any one of the MC cables will not be large enough to serve, by itself, as the required minimum size EGC for the circuit as a whole.

 

[drbond24]

Aha! More proof that I can't find diddly squat in the NEC. I read all around that article, but never actually found it. I'm spoiled from previously having the CD-ROM with the excellent search funtion.

Thanks!

 

[ed downey]

Charlie,

Actually I have paralleled many MC cables over the years and they do make them available with the grounding conductor sized for the overcurrent device. You do need to make sure you order it that way though.
-Ed

 

[infinity]

I think it would violate 300.3(B)(1). All conductors of the same circuit must be in the same cable, and this rule applies separately to each cable in a paralleled set.

If the EGC was the proper size how would this be a violation? 300.3(B)(1) sends you to 310.4 which allows paralleling of cables as well as conduits.

 

[iwire]

IMO the only road block here is 250.122(F) and it sounds like with enough lead time that can be overcome as well. :smile:

 

[coulter]

Or you can buy MC-HL. The sheath counts as part of the grounding conductor and gets you up to the 3-750 range. I have had to ask okonite send the data sheet with the CU equivalent sheath area; it was not readily available on their web site. 250.118.10 (2005)

carl

 

[RUWired]

The OP was asking if he can make each mc cable an isolated phase conductor.The only exception was in nonmetallic raceways run underground.

 

[iwire]

The OP was asking if he can make each mc cable an isolated phase conductor.The only exception was in nonmetallic raceways run underground.

Well that certainly changes things, then yes I agree with you and Charlie.