# Article 250.140 Exceptions



## swimmer (Mar 19, 2011)

I wired in some electric ranges recently and I was surprised to see the neutral and ground wires crimped together on brand new ranges straight from the manufacturer. I called the local inspector and he cited Article 250.140. which I have copied at the bottom of this post for convenience.​

I want to make sure I understand the exceptions in this article as they apply to the wiring schemes that I regularly encounter. I have not included schemes involving SE cable. All example circuits below are dedicated to the range and are of sufficient ampacity.



Scheme 1: Existing non-metallic cable with a hot, neutral and no ground to serve a 120V appliance. ==> In this case, connect the crimped neutral / ground from the appliance to the neutral from the wall.


Scheme 2: Existing non-metallic cable with 2 hots, neutral and no ground to serve a 240V appliance. ==> In this case, connect the crimped neutral / ground from the appliance to the neutral from the wall.



Scheme 3: Existing flexible metallic conduit with 2 hots and no neutral. ==> Need to run a neutral. The exceptions to 250.140 do not apply because:

a. EGC is present (the flex itself if under 3')

b. There is no grounded conductor coming from the wall












The current 2011 NEC edition:
- 250.140 Frames of Ranges and Clothes Dryers.
- - Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be connected to the equipment grounding conductor in the manner specified by 250.134 or 250.138.
- - - _Exception: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor if all the following conditions are met. 
- - - - (1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system. 
- - - - (2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum. 
- - - - (3) The grounded 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. 
- - - - (4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment._


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## HARRY304E (Sep 15, 2010)

Swimmer,

Do you have a copy of the 2011 NEC Handbook?

There is a lot of commentary on 250.140 and 250.142 that will help you out.

I think that those appliances come through with the ground and neutral bonded together because they are assuming that the appliance will be hooked up on ac existing circuit from before the 1996 NEC. So it is up to us to remove that bonding jumper when we install a new circuit the complies with the Code from 1996 on.


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## Fibes (Feb 18, 2010)

Number 2 is the only scheme that would be applicable due to the bolded text below;



> Exception: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor *if all the following conditions are met.*


Note, the wording is for 120/240v appliances not 120 or 240v appliances



> (1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.


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## swimmer (Mar 19, 2011)

Fibes said:


> Note, the wording is for 120/240v appliances not 120 or 240v appliances



Thanks.


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## denny3992 (Jul 12, 2010)

I connected a new cooktop a mnth ago, 30a 240v 2 hots and grnd.

While moving some grnds around in the panel (after energizing the cooktop) i pulled the grnd off the bar in the panel and got lit up off the grnd.... I couldnt believe it.

Note: it wasnt a neutral and grnd it was a labeled as a egc!


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## swimmer (Mar 19, 2011)

denny3992 said:


> I connected a new cooktop a mnth ago, 30a 240v 2 hots and grnd.
> 
> While moving some grnds around in the panel (after energizing the cooktop) i pulled the grnd off the bar in the panel and got lit up off the grnd.... I couldnt believe it.
> 
> Note: it wasnt a neutral and grnd it was a labeled as a egc!


It sounds like the cooktop ground was connected to neutral in the cooktop. When you disconnected this same wire from the ground bar in the panel, it simply made a voltage divider between L1 and L2. I'm sure the chassis of the cooktop was at the same voltage that shocked you.


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## swimmer (Mar 19, 2011)

*Still confused on 250.140*

What type of house cabling or wiring is covered by the exception?
It sounds like it must be some sort of old non-metallic cabling.
For example, say the range outlet is fed by non-metallic 10/3 cable. Are they saying that NM 10/3 cables were once manufactured with BLK, RED, WHT and no GND?

If metallic conduit feeds the range outlet, and a ground wire is missing, then the conduit and metal boxes are equipment grounds and you screw a grounding wire into the outlet box that connects with the range ground wire.
And yes, I know about the 3' flex ground rule.


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## don_resqcapt19 (Jul 18, 2010)

swimmer said:


> I wired in some electric ranges recently and I was surprised to see the neutral and ground wires crimped together on brand new ranges straight from the manufacturer. ​_..._


Did you read the instructions? I don't do residential, but when I installed a new cook top at home a couple of years ago, it came like that, but instructions said to cut the bond when you install it on a circuit that has both a grounded and grounding conductor.


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## chicken steve (Mar 22, 2011)

1/2 the ranges and dryers in Vermont are run off seu , 2 wire 3 conductor using the bare as a noodle, w/ the bond @ the appliance

We've had calls where the HO will state s/he gets bit when having one hand on the dryer , other on the washer

Or having one hand on the range, other on the sink....

~CS~


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## swimmer (Mar 19, 2011)

don_resqcapt19 said:


> Did you read the instructions? I don't do residential, but when I installed a new cook top at home a couple of years ago, it came like that, but instructions said to cut the bond when you install it on a circuit that has both a grounded and grounding conductor.



Don, you are responding to the original post. My new question is: What type of house cabling complies with this exception? I've seen the service entrance cable that is described in condition 3 but I've never seen a cable with 3 insulated conductors with no ground. I'm counting flex and MC armor as ground.


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## Dennis Alwon (May 9, 2009)

swimmer said:


> Don, you are responding to the original post. My new question is: What type of house cabling complies with this exception? I've seen the service entrance cable that is described in condition 3 but I've never seen a cable with 3 insulated conductors with no ground. I'm counting flex and MC armor as ground.



In years past we wired ovens and dryers with 10/3 nm without ground. That was always a stock item since the ovens and dryers neutrals and ground were bonded together. For ranges we usually used SEU cable. Today, of course, we use 10/3 with ground and SER or NM for the ranges.

The ranges come bonded because of the old nstalls. It is up to the EC's to take the bond off the neutral.


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## swimmer (Mar 19, 2011)

Dennis Alwon said:


> 10/3 nm without ground.


Thanks Dennis. I had no idea such a cable ever existed, even in the past.


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