12-3 cables, do you use these ?

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Stevenfyeager

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United States, Indiana
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electrical contractor
It seems like we've been getting away from using 12-3 for two circuits around here. Probably because as the years go by, more gfci outlets are added in houses, and can't share neutrals. What about in commercial buildings with conduit/MC cable ? I have to run several MC cables in an artist studio building. Would you use 12-3 MC to save on cost ? Most lighting is LED now, any problems with sharing neutrals? Also, for outlets too ? Thank you
 
I dont think it is the GFCI requirements that has lessened the use of 3 cables, but rather the AFCI requirements. One can still use GFCI receps no problem on MWBC's. Two pole GFCI breakers are available but expensive. AFCI two pole breakers are available too, but were not available at first and people shy away from using them due to the potential increase in troubleshooting/nuisance trips).

12-3 MC is annoyingly expensive, a lot more than 1/3 more, so there is minimal material savings. I think most savings would be in the labor. I often use 12/3 for bringing out 2 home runs in light commercial. As a side note if you really want to see some "annoyingly expensive" stuff, price out 12-4 MC :rant:
 
The MWBC isn't being used anymore in residential because of the requirement for AFCIs. There is no reason not to use them in commercial if they can save you some money.

-Hal
 
hbiss said:
The MWBC isn't being used anymore in residential because of the requirement for AFCIs. There is no reason not to use them in commercial if they can save you some money.

-Hal
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Not used very much in commercial anymore either due to the handle tie or 2-pole breaker rule. They don't want to shut a whole area down to work one just part of it.
 
Stevenfyeager said:
What is the two pole breaker rule ? Thank you
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210.4(B). Worst code change of the 21st century. I hate it so much it's one of the few code sections I have memorized. It's not really a 2 pole breaker rule though, it just says you have to be able to simultaneously disconnect all your hots. Handle ties work to meet the requirement.
 
When I do residential wiring, that is DIY so I don't ask questions about it here.

However recently I noticed that Siemens AFCI double pole breakers at the big orange store were only slightly more expensive than a pair of single pole AFCI breakers. I also got a good deal on 12-3 MC, so I expect that I will be using 12-3 for selected circuits.

-Jon
 
winnie said:
When I do residential wiring, that is DIY so I don't ask questions about it here.

However recently I noticed that Siemens AFCI double pole breakers at the big orange store were only slightly more expensive than a pair of single pole AFCI breakers. I also got a good deal on 12-3 MC, so I expect that I will be using 12-3 for selected circuits.

-Jon
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IIRC the homeline 2 pole AFCI's are the same cost as two single poles, but I do not use them due to potential increased trouble shooting hassle and they dont make them in a dual function version
 
Even if avoiding MWBC's, 3 wire cable is still used pretty frequently for three way switching and for load side of switches to two independent loads from the same supply conductor.
 
The handle tie ruled killed probably 90% of what used to be our usual MWBC work.

I'm sure the copper industry liked the change....
 
Cow said:
The handle tie ruled killed probably 90% of what used to be our usual MWBC work.

I'm sure the copper industry liked the change....
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wouldn't surprise me if copper industry wasn't involved in pushing those rules, though I don't know that they are as bad as the GFCI/AFCI manufacturers at pushing new requirements without good justification.
 
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