Dryer Circuit

[electricman2]

Still not sure why that is wrong but if it was SE it would be OK. :-?

Me neither. I just replaced the receptacle and told HO his dryer is back in business.:smile:

 

[LarryFine]

I'm thinking he meant 8/2. I haven't seen 3 wire SE....but I have led a sheltered life.

Maybe so. :smile:

Like rubber cord, the neutral/ground is counted in SE cable.

 

[hardworkingstiff]

Like rubber cord, the neutral/ground is counted in SE cable.

Right, an 8/3 SE cable has a black, black/red tracer, and the strands of neutral/ground wrapped around the black and black/red conductors (at least back in the '70s).

So why was it OK to use the 8/3 SE (Al.), but the 10/2 (Cu.) romex was dangerous?

 

[charlie]

The oldest Code I have handy is 1990 and the requirement then was an INSULATED grounded conductor unless SE cable was used.
I realize that requirement was often over-looked, but the 10/2 wg would have been a violation in 1990.

If I am not mistaken, an insulated neutral was always required except for SE cable. Also, the SE cable could not originate from any other panelboard than the main service equipment because of the separation of the grounds and neutrals.

 

[mdshunk]

If I am not mistaken, an insulated neutral was always required except for SE cable. Also, the SE cable could not originate from any other panelboard than the main service equipment because of the separation of the grounds and neutrals.

Yup.

250-60(c) [1987 NEC]
The grounded circuit conductor is insulated; or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.

 

[iwire]

250-60(c) [1987 NEC]
The grounded circuit conductor is insulated; or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.

Yes, but the question remains ..... why?

Why is it OK for SE but not NM?:-?

 

[mdshunk]

Yes, but the question remains ..... why?

In the wise words of some Madison Avenue employee:

"Why ask why?" :grin:

If I was to guess, I'd say that it relates to having bare conductor, being used as a neutral, potentially loosely touching the can of a subpanel.

 

[LarryFine]

Yes, but the question remains ..... why?

Why is it OK for SE but not NM?:-?

I'll take a stab at it.

It could be that, when the rule was made, NM cables contained undersized EGC's (i.e., the ones with EGC's), which would not be protected by the branch-circuit OPD.

As for the only-from-the-main-panel rule, it's a dilemma we face when we render a main panel into a sub-panel: where do we land an SE's neutral doing double duty?

We're supposed to replace a cable, receptacle, and cord being used this way, but on the occasion we don't, the bare conductor is connected as a neutral, not as an EGC.

What's the point? I don't know. Except that an SE cable's bare conductor is clearly designed and approved for use as a current-carrying conductor; an NM's is not.