Hello, I have dryer hookup question. I purchased a new dryer, and I hired an electrician to replace the old 1950’s three wire outlet with a four wire outlet. He recommended not replacing the existing wiring, and that the conduit that runs from the outlet to the panel could be used as the ground, so there was no need to run a separate ground wire.

When he connected the new four wire dryer cord to the appliance, he attached the green ground wire to the metal frame along with the yellow/green wire. Now comes the question, should the yellow green wire be attached to the frame as well, or should it be connected to the Neutral post? There is no ground wire going from the outlet to the panel, so this configuration seems correct. What do you guys think?

SOunds correct to me. Yellow/green is a common identifier for the ground wire, and the whole purpose of the 4-prong receptacle is so that you do NOT connect the ground to the neutral.

I hope he tested the integrity of that conduit as a grounding path.

Greg,
Integrity of the conduit for an effective ground fault current path has always been my concern. so I always try to install an additional EGC.

How do you test the integrity of the conduit?

I would use my Ecos tester. That verifies < 1 ohm under a load.

Thank you for the help. I’ll ask him if he tested the integrity of that conduit as a grounding path. If the answer is no, I’ll ask him to run an additional EGC to be safe. This site is a great resource.
Thanks again

I’m going to add a ground wire, but I have a ground wire size question. The dryer feed is a 10/3. Can I use a 12 wire as a ground, or do I need to use a 10?

How about calling the guy you hired back, and asking him to do it?

That sounds like a plan.

Circuits with OCPD at 30 Amps will require #10 grounding conductors unless the raceway/EMT is suitable.

I have a problem with any test that occurs on the actual continuity of a given run of conduit, especially when it is going to be used as an essential conductor that could be asked to carry large currents, under fault conditions.
Reason I say that is, because that test only gives a "snap-shot" of the condition of that conduit run at that given time, not 1 or 5 years down the track.
This resistance will change over time.
I would never fail to run a new (seperate) ground back to the supplying panel.

Me thinks he is the guy he hired.

Nah. can't be, A-line. After all, this is a professional site, not one catering to the DIY

The thread does bring up one sore point: second-guessing a professional. Every job has it's unique set of circumstances, and only the pro on the scene is really in a position to make the judgement calls.

I suspect the OP was simply confused by the change in type of cord and receptacle. While this is all old news to us, to the consumer it won't register until they replace that dryer or range - and that can be in another 20 years!

There might be a 'business,' or 'customer service' lesson in this, and that is: to the customer, four prongs means four wires; if at all possible, maybe we ought to humor the guy, and at least install a pigtail.

On a related note... how would you handle an old style 10/3 NM with reduced equipment-grounding conductor when upgrading from three-wire to four-wire dryer receptacle?
Would you run a new 10/3 NM branch circuit with a full size equipment-grounding conductor or use the existing 10/3 NM, keeping in mind that the new 4-wire receptacle has terminals rated for #10 to #4 AWG wire.

I know I’ve connected the old 14/2 and 12/2 NM with reduced grounding conductors to the grounding terminals of 15A 3-wire duplex receptacles during replacement before, without really thinking about how the minimum size wire rating on the device terminals is #14 AWG.
I guess in actuality, a pigtail could be used to comply here.

table 250.122 gives the minimum size EGC I would upgrade the wire to comply with code.