Dryer receptacle

[Will Wire]

I did a service call recently involving a Dryer circuit and receptacle. The branch circuit cable supplying the outlet box is a 10-3 NM with ground. The conductors in this cable are 10 gauge black, white, and red, and a 14 gauge equipment grounding conductor. The house was built in the 1960’s. NEC 250.140 exception states that the grounded conductor can be used to ground the frame if an equipment grounding conductor is not present in the outlet or junction box. Since an equipment grounding conductor is present in the box is a 4 wire receptacle code compliant even though the equipment grounding conductor is undersized? This falls between NEC 250.122 (A) and 250.140 Exception. Thank you-Trent

 

[jumper]

Yes, it is compliant since the cable is grandfathered. Full sized grounds for 14,12, and 10 were not required until 1968 IIRC.

 

[al hildenbrand]

. . . is a 4 wire receptacle code compliant even though the equipment grounding conductor is undersized?

This is an interesting question, to me. As you describe the existing installation of the 10/3 reduced size EGC, it sounds like the 10/3 branch circuit was installed correctly to the Code of it's day, which means the reduced size EGC was an acceptable means of bonding to the Grounding Electrode System.

But, the changing of the receptacle from a three wire crows foot, to a modern four wire, is a modification of the original install. Because of this, I believe the local AHJ has a stake in "acceptance" that it would be prudent to check with.

In my opinion, the #14 EGC in will work perfectly as a low impedance fault clearing path for a typical residential clothes dryer application in a stand alone single family dwelling.