Oven 3 wire question

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
People get this confused all the time. A neutral, or grounded conductor is allowed to serve as the EGC in some cases. But the EGC has NEVER been allowed to serve as the grounded conductor. So in the OP's case, there is no neutral, or grounded conductor, and can't be legally used to connect the stove/oven. Having said that, I've seen lot's of XX-2 w/ground being used for dryers, stoves, ovens, etc., but that isn't correct or allowed.
 

Knuckle Dragger

Master Electrician Electrical Contractor 01752
Location
Marlborough, Massachusetts USA
Occupation
Electrical Contractor
I've installed tons of ranges & ovens covering most brands. All of them have instructions for 3 and 4-wire. Never saw one that said you must run a 4-wire circuit if you only have a 3 wire.
I said you may.
Me neither. Just throwing it (check out the specs) out there for him to look into for himself.
Have a great day!
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
My question is, what is the difference between a bare stranded wire in an SE cable and a bare copper wire in an 8-2 romex cable ? Why is SE allowed but not NM cable ? Thank you
SE cable is used, among other uses, as service entrance wire. The bare conductor is the grounded/neutral conductor. NM cable isn't service entrance cable. The bare conductor is the EGC. The white conductor can be used as a grounded/neutral conductor or an ungrounded conductor if re-identified. In a nutshell, SE bare = grounded/neutral, NM (Romex) bare conductor = EGC. See my post #22 for more info.
 

mtnelect

HVAC Contractor
Location
Southern California
Occupation
Contractor
Section 250-140 (Section 250-60 in the 1996
NEC® and previous editions of the NEC®) now
applies only to existing branch-circuit installations.
For those installations wired according to the rules of
Section 250-60 prior to the 1996 NEC,® the required
appliance grounding was accomplished by the small
copper bonding strap furnished by the appliance
manufacturer that connected between the neutral terminal
and the metal frame of the appliance.

This method was used only in older homes prior to NEC 1996.
 

norcal

Senior Member
Section 250-140 (Section 250-60 in the 1996
NEC® and previous editions of the NEC®) now
applies only to existing branch-circuit installations.
For those installations wired according to the rules of
Section 250-60 prior to the 1996 NEC,® the required
appliance grounding was accomplished by the small
copper bonding strap furnished by the appliance
manufacturer that connected between the neutral terminal
and the metal frame of the appliance.

This method was used only in older homes prior to NEC 1996.
Prior to the adoption of the 1996 NEC which can lag by a number of years.
 
SE cable is used, among other uses, as service entrance wire. The bare conductor is the grounded/neutral conductor. NM cable isn't service entrance cable. The bare conductor is the EGC. The white conductor can be used as a grounded/neutral conductor or an ungrounded conductor if re-identified. In a nutshell, SE bare = grounded/neutral, NM (Romex) bare conductor = EGC. See my post #22 for more info.
thank you for your time, you all have helped me many times. I'm not trying to drag this question on. But I wonder why SE is ok by NEC and NM is not....it seems like a bare wire is a bare wire...whichever cable it is in. Is it because SE usually wraps around the other conductors in the sheath to affect inductance or something like that ? Just curious, and thank you again for showing me the NEC references.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
thank you for your time, you all have helped me many times. I'm not trying to drag this question on. But I wonder why SE is ok by NEC and NM is not.
I think the bare conductor in NM is strictly sized per 250.122 the bare conductor in SE cable might be typically larger.

The question we should all be asking is why in the world is any electric cooking appliance still using a neutral to power what a light and a clock?
They certainly never use the neutral for the cooking load.
 

norcal

Senior Member
I think the bare conductor in NM is strictly sized per 250.122 the bare conductor in SE cable might be typically larger.

The question we should all be asking is why in the world is any electric cooking appliance still using a neutral to power what a light and a clock?
They certainly never use the neutral for the cooking load.
The motor, timer, and drum light if present, in a dryer are all 120V, sometimes I wonder if we had 240V instead of 120V as the normal voltage how much better off we would have been.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The third wire in your existing branch circuit is a grounded conductor, not an equipment grounding conductor.

Mark
The 3rd wire in older dryers was an EGC. With the advent of digital displays in new dryers a neutral is needed. Hooking up the EGC and using it as a neutral is a Code violation.

That said, something that has been a gripe of mine for many years is - if manufacturers have digital displays and/or on-board PC boards that need 120V to operate, why don't they install a small step-down transformer and allow a 10/2 or 8/2 NM (in your case) cable to be installed or re-used ? Answer - because they want to increase sales. Adding a $5.00 part plus labor and R&D will put their prices over the edge. So, their answer is - have your electrician run the proper cable and pay him an exorbitant amount of money to do it. :-(
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The third wire in old dryers was a neutral for the dryer motor.
I'll take yours and Little Bills word for it. Seems to me that a bare wire (i.e. that of an SE cable) would be (or should have been) a Code violation. Maybe the CMP's at the time thought it would be OK because the jacket of the SE cable would suffice as insulation and that it had to originate from the main breaker panel.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
I think it's entirely historical reasons, with little or no technical basis.

Cheers, Wayne
Allot of the old 3 wire SE cable ranges I see around here are 8-8-8 SE cable. ( the bare braid equals #8)
So the bare neutral is full size, just like ungrounded 'NM' of the 40's -50's - 60's era is 8/3 neutral is full size.
Companies still make copper SE cable today, and it still has a larger bare conductor than table 250.122 would require for a EGC:

SE_cable.png

https://www.cerrowire.com/wp-content/uploads/2019/11/Cerrowire_SEU_copper_sheet_210412.pdf

And here is NM:


NM-B.png
Grounded NM cable when it first came out in the early 60's would only have had to comply with what 250.122 was then table 250-95, and a #12 bare would have been allowed for a 40 amp circuit

So the SE cable bare was always designed to be a neutral, NM bare never was.
 

kwired

Electron manager
Location
NE Nebraska
I think the bare conductor in NM is strictly sized per 250.122 the bare conductor in SE cable might be typically larger.

The question we should all be asking is why in the world is any electric cooking appliance still using a neutral to power what a light and a clock?
They certainly never use the neutral for the cooking load.
Though when dealing with a dryer, you can run 10-3 no ground, but can't run 10-2/WG even though all conductors are 10 AWG in either case, and probably would be with SE cable if you can find any. Have seen old SE cable in sizes that small but all were from ~1950 or earlier.

With a range circuit many cases there is nothing wrong with 6 AWG ungrounded conductors and 10 AWG grounded conductor either - if say you were running conductors in raceway.

I'm not certain they have a real justified reason for some the requirements here, but at same time it all comes down to allowing something that once was allowed to remain for existing installs, new installs the grounded conductor needs to be white (or gray) and EGC needs to be a separate conductor that is bare, green or green with yellow stripes, or can also be a qualifying metallic wiring method as the EGC.
 
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