Nmd vs nmb

[tortuga]

NMD is an interesting type of Romex. It looks like they allow a smaller equipment grounding conductor for 12 awg and 10 awg sizes and require a larger one on 6 awg.
It looks like it is available with 10-2 WG with a red and black so you dont have to use all that tape when running 240V circuits.
They used to allow the one size smaller equipment grounding conductor here. Are there any peer reviewed studies that show the NMD is equally or less safe than NMB?
At what distance does there become a difference between 14awg and 12awg equipment grounding conductor for tripping a 20A breaker?
Are there any local codes that allow it in the US?

NMD90 specifications

NMD at home depot

 

[raider1]

I could be wrong, but it appears this cable is only designed to comply with the Canadian Electrical code and not the NEC.

This product is listed on Southwire's website under Canadian building wiring.

I could see alot of problems with trying to use this NM cable where the EGC's are sized too small to comply with 250.122.

Chris

 

[LarryFine]

It looks like it is available with 10-2 WG with a red and black so you dont have to use all that tape when running 240V circuits.

That would be great for DC, too.

 

[iwire]

That would be great for DC, too.

Only if your talking ungrounded DC. Grounded DC systems must use white and another color other than green. If you have a DC system that is negative grounded the negative will be white and the positive may well be black.

With PV systems gaining popularity this is something electricians have to adjust to or they will end up redoing work, damaging equipment or worse ........ get injured or killed.

 

[tortuga]

Here in the Pacific Northwest it is common to use electric heat as in Canada so that is probably why they have the red and black for straight 240V loads. Would be a much cleaner install if we had something like that here. I also like how they have a blue outer skin for AFCI circuits and a red skin for 240V circuits.

I could see alot of problems with trying to use this NM cable where the EGC's are sized too small to comply with 250.122.

Yes is does not meet 250.122 and I am questioning why 250.122 was changed?
I see allot of older NM that has a 16 awg equipment grounding conductor.
I think 14 awg is a good minimun size for 15 and 20A circuits, similar to how in the NEC 10 is a allowed size for 30-90 amp circuits. However I also like how the Canadian code specs 8 AWG on 60-90A circuits.

The most available fault current on the end of a 110' 20A a residential branch circuit is typicaly what 4,000A or 200% the rating of the breaker? The max legnth is typically 110 feet otherwise you would be above 5% VD on the branch circuit (up to 8% total). So what is the time difference to blow a typical circuit breaker using a 14awg vs a 12awg?
or .3377Ω VS .2123Ω ?

 

[iwire]

Here in the Pacific Northwest it is common to use electric heat as in Canada so that is probably why they have the red and black for straight 240V loads. Would be a much cleaner install if we had something like that here. I also like how they have a blue outer skin for AFCI circuits and a red skin for 240V circuits.

I would rather use tape then stock different colors of NM for 208 or 240 circuits.