250.122 (b) Increased in size

[iwire]

ok, i understand. Is there a code reference for that

I believe that would be 250.122(B).

 

[bfrosty]

Say for the sake we're considering this an old installation, wouldn't you be violating the condition to have either SE cable or an insulated grounded conductor anyway?

Since you're essentially running a new circuit, and having a new installation for the dryer, wouldn't you need to have a 4 wire installation?

If I ran a new circuit agreed. If the BC was there and it is an old dryer brought in with lets say new home purchase? Just playing devils advocate (or NEC advocate as it may be), but Iwire probably is correct in his assumption of put the 40 Amp breaker in. The Handbook uses the (VD or any other reason) in the comments.

 

[BigJohn20]

If I ran a new circuit agreed. If the BC was there and it is an old dryer brought in with lets say new home purchase? Just playing devils advocate (or NEC advocate as it may be), but Iwire probably is correct in his assumption of put the 40 Amp breaker in. The Handbook uses the (VD or any other reason) in the comments.

But if we look at 250.140, which specifically addresses existing branch circuits regarding range frames and dryer frames, it allows the 3-wire circuit to only be used if the grounded conductor is insulated or part of SE, along with meeting the other parts of 250.140.

I'm not specifically talking about going from the 30 -> 40, but having a circuit wired with 8-2 NM-B that is supposed to be a dryer circuit.

 

[bfrosty]

Agreed, but there were instances where NM was used.

Prior to the 1996 Code, use of the grounded circuit conductor as a grounding conductor was permitted for all installations. In many instances, the wiring method was service-entrance cable with an uninsulated neutral conductor covered by the cable jacket. Where Type SE cable was used to supply ranges and dryers, the branch circuit was required to originate at the service equipment to avoid neutral current from downstream panelboards on metal objects, such as pipes or ducts.

Not saying I agree, but it happened.

 

[roger]

Prior to the 1996 Code, use of the grounded circuit conductor as a grounding conductor was permitted for all installations.

Not true, 250-57 required an EGC, article section 250-60 only allowed using the grounded conductor for ranges and dryers and only if certain conditions were met.

Roger

 

[hurk27]

I hate to say this but you are daisy chaining, violations as you go, installing a 40 amp breaker, to allow the #10 EGC in the 8/2 will now create the requirement, of a 40 amp dryer receptacle (dont think you will find one), the 40 amp dryer receptacle will require a 40 amp dryer cord, a 40 amp dryer cord will require a 40 amp dryer????

why not just install the proper 10/3 4-wire circuit and be done with it?:roll:

 

[bfrosty]

Roger,

The quote w/regards to the 99 code came from the NEC handbook. I'll defer to them...

 

[bfrosty]

I hate to say this but you are daisy chaining, violations as you go, installing a 40 amp breaker, to allow the #10 EGC in the 8/2 will now create the requirement, of a 40 amp dryer receptacle (don't think you will find one), the 40 amp dryer receptacle will require a 40 amp dryer cord, a 40 amp dryer cord will require a 40 amp dryer????

why not just install the proper 10/3 4-wire circuit and be done with it?:roll:

It was hypothetical, use cook top, or insert equipment here instead. The point was to test the 250.122 b. I have already conceded and fallen on my sword.

 

[roger]

Roger,

The quote w/regards to the 99 code came from the NEC handbook. I'll defer to them...

I see, that commentary is specific to 250.140 and is not covering "all installations" across the board, it is only addressing the frames of Ranges and Dryers.

Roger

 

[shermansfather]

I assume the intent of the code is to ensure the clearing of ground faults. Perhaps rather than introduce a more complicated set of EGC tables 250.122(b) fit the bill.
If you used just 250.122 with say a 2,000 ft run, 60A OCP, 40A Intended Load, #1 Cu used to keep voltage drop to 5%: A ground fault at the far end wouldn't trip OCP.

2,000 ft #10 = 2 ohm + 2,000 ft.#1 = .125, Total 2.125 ohm at 120V = 56 Amperes

It could happen.
I know 50A 120V load is pretty strange, Just looking for a worst case scenario.

 

[LarryFine]

I'm not specifically talking about going from the 30 -> 40, but having a circuit wired with 8-2 NM-B that is supposed to be a dryer circuit.

Agreed, but there were instances where NM was used.

Prior to the 1996 Code, use of the grounded circuit conductor as a grounding conductor was permitted for all installations.

Yes, but if NM was used, the neutral had to be insulated. That's been required for decades.