Why are the conductors in 6/2 and 8/2 NM-B black and white?

S

skorpioskorpio

Member
Location
Georgia
Occupation
Engineer
I've always wondered what the logic was to making the default colors of larger gauge 2 conductor NM-B black and white? The only time I can see this being useful is if you were running a 120V only sub panel, which is pretty much never, or running a 30 or 50A 120V receptacles, which personally have never actually seen one in person. In almost all cases 6/2, 8/2, and for the most part even 10/2 will be used almost exclusively for 240V circuits, so why do the manufactures color code it for 120V?

...and on a related note, I've also always wondered why alternatively coded NM-B, in general, isn't a thing, regardless of gauge. I mean if you go to the trouble of making both 12/2/2 and 12/4, and 14/2/2 and 14/4 which are basically the same cables with 2 different color codes, why not just make a handful of alternate NM-B and MC /2 and /3 cables like Red/Black for 240V, Red/White and Blue/White and Red/White/Blue for alternates for 120V? Seems like this would be a win/win for manufactures as it would increase the number of variants contractors stock on the truck, with very little additional investment on their part, since they are making the components that would make up these products already. Not even suggesting they get crazy with it, just the most common color combinations that are used all the time in pipe and flex of black, red and sometimes blue. This would just largely eliminate the need to ever have to re-identify conductors for 240V or switch travelers.

Sorry, just seems like a really obvious product that just doesn't exist.
 
As far as having a pile of different cables on the truck, I always wanted less inventory not more. On another note, if I was inside a job and it was a quarter mile (actually just outside) to the truck I would certainly pull a roll of tape out of my tool bag before going to get another roll of cable.
 
ptonsparky said:
Pure conjecture.
White is cheaper than a color and that could make all the difference to the bean counters.
Click to expand...
hmm, I doubt that is it, if it was I don't see how we would have ended up with all the new outer jacket colors on NM-B, seems like the manufactures would have resisted that more if that was the case. Also there isn't a cost difference between white THHN and any other color and that's basically what is in NM-B particularly in the larger gauges.
 
skorpioskorpio said:
In almost all cases 6/2, 8/2, and for the most part even 10/2 will be used almost exclusively for 240V circuits, so why do the manufactures color code it for 120V?
Click to expand...
I agree, it makes little sense because the white is almost always re-identifed in the larger 2-wire cables. In Canada they make black and red cables.

p_1000108211.jpg


 
roger said:
As far as having a pile of different cables on the truck, I always wanted less inventory not more. On another note, if I was inside a job and it was a quarter mile (actually just outside) to the truck I would certainly pull a roll of tape out of my tool bag before going to get another roll of cable.
Click to expand...
Well fair enough, but just because it exists doesn't mean you'd have to use it, not unless it became codified. But more to the point, if you were doing a job where everything was pipe and flex, would you only run black and white so you didn't have to have more spools on the truck?

And on the subject of codified, as more and more AFCIs and GFCIs are being required where white neutral wires commonly land on breakers, or PoN buses I personally just think we're quickly getting to the point where no load carrying white (or grey) wire should ever land on a breaker, re-identified or not. This is already the case if running THHN smaller than #4. I just think that multi-conductor cables shouldn't get a pass on that rule. I mean how many panels have you opened where there are white load wires on breakers that have NOT been re-identified? Or in boxes? Or on 240V receptacles? So while you may be diligent about marking re-purposed neutrals, a whole lot of guys are not.
 
30 amp RVs are 120v 😉

But does as Tom said, it really does come down to money. Not that white is cheaper than red, but it's cheaper to make only white than it is to make one version with white and a different version with a red.

And they can't make it with only red because it's a violation to re-identify a continuous red wire as a grounded conductor if needed - nec 200.6(A)

All in all, sometimes it's just better to keep doing things the way they've always been done
 
skorpioskorpio said:
I personally just think we're quickly getting to the point where no load carrying white (or grey) wire should ever land on a breaker, re-identified or not.
Click to expand...
Anyone who opens a panel cover and doesn't know what a white conductor that is landed on a multipole breaker is has no business being in there.


skorpioskorpio said:
This is already the case if running THHN smaller than #4.
Click to expand...
If you're running conductors in a raceway regardless of size a white conductor cannot be re-identifed as an ungrounded conductor.
 
With SEU cable the 2 hot conductors are black and black with a red traces. I don't see why 8/2 or 6/2 have a white conductor. In canada you can buy 2 wire NM with no neutral for any size wire, but as @roger stated that just means another cable to have to carry in the vehicle.
 
Another vote for money... every color combination you make (black/white, black/red, black/slate, etc) entails another SKU that must be manufactured, stocked, maintained, included in advertising media (even if it's just another row on the available options table), etc. Likewise the guys in the trucks don't want to stock multiple combinations when it's faster and easier to twirl a couple rounds of phase tape to re-identify a non-neutral conductor than to run back and forth to collect, set up, pull, and tear down the "correct" color group.
 
infinity said:
Anyone who opens a panel cover and doesn't know what a white conductor that is landed on a multipole breaker is has no business being in there.



If you're running conductors in a raceway regardless of size a white conductor cannot be re-identifed as an ungrounded conductor.
Click to expand...
Maybe so, but it should never be the case that an unidentified white is in a panel carrying load, or for that matter nowhere should there ever be a non-re-identified white conductor terminated to anything carrying load.

And this is exactly my point NM and MC are effectively encapsulated raceways, they are not classified that way, but that is what they are. But once the outer covering is removed they are free conductors like any other, but they are given an exemption in the code because they are a manufactured multi-conductor assembly. My point is simply why should they be exempt?
 
skorpioskorpio said:
My point is simply why should they be exempt?
Click to expand...
My guess is that like a lot of things in the NEC it's merely tradition or because we've always done it that way. To your point I agree that for a 2-wire NM cable in sizes above #10 there should be two conductors with colors not designated as a grounded conductor.
 
ModbusMan said:
Another vote for money... every color combination you make (black/white, black/red, black/slate, etc) entails another SKU that must be manufactured, stocked, maintained, included in advertising media (even if it's just another row on the available options table), etc. Likewise the guys in the trucks don't want to stock multiple combinations when it's faster and easier to twirl a couple rounds of phase tape to re-identify a non-neutral conductor than to run back and forth to collect, set up, pull, and tear down the "correct" color group.
Click to expand...
It really doesn't take all that many combinations to do 4 colors, and the same manufactures already typically do at least 8 common colors of at least 5 common gauges of THHN on a multitude of different spool sizes, not to mention all sorts of other specialty wire and cable. But more to the point, if there existed 6/2 through 10/2 with red/black conductors as well as with the current black white, at a price that was the same or very near, which roll would you keep on YOUR truck?
 
skorpioskorpio said:
I mean how many panels have you opened where there are white load wires on breakers that have NOT been re-identified? Or in boxes? Or on 240V receptacles? So while you may be diligent about marking re-purposed neutrals, a whole lot of guys are not.
Click to expand...
I come from the times when reidentifying
was not not required and IMO it's only there for the inexperienced. If I see a white or gray connected as a hot conductor I know what it is
 
BTW, AFC makes all kinds of different color combinations and the sheath has bands to show what they are
 
roger said:
I come from the times when reidentifying
was not not required and IMO it's only there for the inexperienced. If I see a white or gray connected as a hot conductor I know what it is
Click to expand...
Me too. The re-identification nonsense was simply to dumb it down for people who have no business doing electrical work. If you pulled out a wall switch and there are only two conductors in the cable you know that the white is the hot leg. Same with a multi-pole circuit breaker.
 
roger said:
I come from the times when reidentifying
was not not required and IMO it's only there for the inexperienced. If I see a white or gray connected as a hot conductor I know what it is
Click to expand...
I on the other hand came from doing commercial work in Chicago where this was just never ever a thing. Get out of that environment and into Romexland and it's absolutely everywhere. Make sure you have a fresh battery in your non-contact tester.
 
You must log in or register to reply here.
Top