Grounded conductor permitted to be bare?

[Madeinoregon]

It seems common practice to use a bare conductor in a 3 wire cable as a grounded conductor for a dryer circuit in older homes. I understand that this is sort of grandfathered in, but I’m having trouble finding the code reference that permits this. Everything I find seems to be in reference to SE conductors which I take as different than SE cable used for branch circuit conductors. I am a journeyman wireman but have only done commercial/industrial work my entire career so residential/service work is out of my wheelhouse.

 

[Dennis Alwon]

It is not compliant anymore but here is the article

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.

 

[LarryFine]

Welcome to the forum.

Everything I find seems to be in reference to SE conductors which I take as different than SE cable used for branch circuit conductors.

No, they mean the same cable type as typical service cable, just smaller.

 

[Madeinoregon]

It isn’t compliant anymore? As in there was a change in the 2020 code cycle?

 

[Madeinoregon]

Welcome to the forum.

Thank you!

 

[infinity]

It's been non-compliant for many code cycles. For existing installations it can remain if the SE cable originates at the service not from a sub-panel.

 

[Madeinoregon]

Yes, that was my understanding. The existing installation is still compliant with the NEC’s exception.

 

[tortuga]

if your in Oregon See this thread:

3 wire stove grounding

A older house has a 3 wire cable (two hots and a ground/neutral) from a range going to a sub fed panel. Does the ground/neutral wire terminate on the neutral buss or the grounding buss? Personally I think it goes to the neutral buss because it has 120v neutral current from timer and other 120v...

forums.mikeholt.com

 

[kwired]

It isn’t compliant anymore? As in there was a change in the 2020 code cycle?

The change occurred back in 1996 NEC. Since then you only permitted to use a "three wire" circuit for existing applications, where conditions mentioned in the exception allow.

The ability to use a bare grounded conductor in this situation existed before then, but still was limited to type SE cable - as in the cable type covered in art 338, not service entrance conductors in general.

Why they allowed that but not a simple NM or UF cable with a bare EGC, IDK. pretty much the same electrically. Physically the SE cable has a concentric bare conductor that spirals around the insulated conductors along the length of the cable.

 

[Madeinoregon]

Thanks for your help everyone.

 

[LarryFine]

Why they allowed that but not a simple NM or UF cable with a bare EGC, IDK. pretty much the same electrically. Physically the SE cable has a concentric bare conductor that spirals around the insulated conductors along the length of the cable.

I believe the reason is the wrapped bare conductor assures that any metallic intrusion will contact the grounded wire first.

I've also seen 10-3 NM w/out ground run to dryers, and two paralleled 10-3 NMs run to ranges and ovens.

 

[kwired]

I believe the reason is the wrapped bare conductor assures that any metallic intrusion will contact the grounded wire first.

I've also seen 10-3 NM w/out ground run to dryers, and two paralleled 10-3 NMs run to ranges and ovens.

10-3 w/out ground (to a dryer) was specifically allowed. The grounded conductor needed to be insulated, unless it was a type SE cable.

paralleled 10-3 was in violation of other code sections, but insulated grounded conductor part of the installation was still required, unless it was a type SE cable.

 

[tortuga]

I believe the reason is the wrapped bare conductor assures that any metallic intrusion will contact the grounded wire first.

I've also seen 10-3 NM w/out ground run to dryers, and two paralleled 10-3 NMs run to ranges and ovens.

Yeah thats is actually more common here in older homes and in that case you have no controversy running a separate EGC.
I have seen 8/3 with no bare ground also to ranges.

I will add another option is you can get '240' volt nameplate ranges these days.
I have seen quite a few of those recently (they take a funny little 240V oven light bulb)
There is still a place to land a neutral from a 4 wire range cord but no white internal wire connected to the tap block.
So in theory you could use a NEMA 6-50 receptacle and cord (a 'welder' or 'kiln' receptacle) with the old 2 wire + bare SE cable.