New Stove/range

[robertd]

In the 3 wire install, the requirement can be summarized as 'the combination EGC/neutral' must be suitable as a _neutral_ circuit conductor.

The bare wire in NM cable is _not_ considered suitable for this purpose.

The bare wire in SE cable _is_ considered suitable.

I don't know if this is a historical artifact, or if there is some requirements difference that makes the bare conductor in SE cable somehow better than the bare conductor in NM. I would note that the bare conductor in SE is regularly used as the neutral for a service.

(Or see the actual code posted at the same time I was writing this post....)
-Jon

I think the neutral on SE cable is larger then the ground on old NM cable, but I don't know if that's the reason.

 

[letgomywago]

I think the neutral on SE cable is larger then the ground on old NM cable, but I don't know if that's the reason.

Insulated white was allowed also at this time it had to do with the conductor in SE being considered insulated enough by the thicker jacket

 

[mtnelect]

Customer has existing 3-wire with copper SE cable(bare #8 wire for neutral). A new 4-wire run would be nearly impossible.

New stove says "grounded circuit is required." It doesn't give the usual diagram of a 3 vs 4 wire install options like I normally see.

Is a 3-wire circuit not a "grounded" circuit?

This might help to explain ...

 

[LarryFine]

This might help to explain ...

That's what I've been saying. The existing circuit may be used.

 

[kwired]

An existing 3-wire appliance circuit may remain. That's why the appliances are convertible.

OP is kind of saying appliance doesn't appear to be convertible, I think. Doesn't really say if he has three or four terminals either though.

 

[kwired]

I think the neutral on SE cable is larger then the ground on old NM cable, but I don't know if that's the reason.

It generally is. If used as service entrance it needs to carry unbalanced neutral current of the service. Usually only one size smaller than ungrounded conductors, until you get to about 1/0 and larger then usually two sizes smaller.

With NM cable you have a white conductor though usually same size as ungrounded, and the EGC is only sized per 250.122 and is presuming the OCPD will not be larger than ungrounded conductor ampacity.