How to check 240V ground and neutral wires are wired properly?

Question

Edit: Never mind. I found a 24 amp charger with a 10-30 plug for only slightly more $ than the 14-40 charger I was planning on getting, so I'm going to leave the outlet as-is.

I turned of the 30A breaker and used my non-contact voltage tester to make sure these wasn't any voltage at the outlet. When I pulled the cover plate off the NEMA 10-30 dryer outlet in my garage (built in 1994) in preparation for replacing it with a NEMA 14-50 outlet so I can plug in a EV charger (drawing 24 Amps), I was happy to see that there were 4 wires coming into the box. I was surprised, however, to see that the bare copper (ground) wire was connected to the neutral terminal of the outlet, while the white (neutral?) wire was not connected to anything. While the dryer has been working fine for 30 years, from what I've read, that is not up to code, even prior to 1996. Since that seems wrong, I'm concerned what else could be screwed up (specifically is the white wire really the neutral), and want to test things before I install the NEMA 1450 outlet.

With the breaker still off, I verified that there is continuity between the bare copper wire and a nearby water pipe (for the washing machine), so I think that means it is a good ground wire, but I don't know how to test that the white wire is a good neutral.

My question are:

1. Am I correct that the existing wiring connection the ground wire to the outlets neutral connection is not up to code?
2. Is testing continuity between the bare copper wire and a nearby water pipe a correct way to test that it is a good ground wire?
3. How can I test that the white wire is a good neutral?

Answer 1

STOP!

Based on more comments that "an electrician said". DO NOT HIRE THAT ELECTRICIAN! You can't install a 14-50 receptacle on a 30A circuit. Period. Full. Stop. You either put in a 40A or 50A circuit (both are OK with a 14-50) or you put in a modern 30A 14-30 receptacle. And then you get an appropriate plug/cord to match. Tesla has those cords/plugs readily available for their mobile chargers. Other brands might or might not. Or switch to hardwired. BUT YOU CAN'T USE 14-50 RECEPTACLE WITH A 30A CIRCUIT!.

• You can't put a 14-50 receptacle on a 30A circuit. A 14-50 can only be on a 40A or 50A circuit. The only way you can do that is you replace the circuit breaker with a 40A or 50A breaker and replace the cable because it is 99.99999% guaranteed that the existing cable is only 10 AWG.

• 10-30 is long obsolete. Your setup is a typical "don't know what we're doing swap between a good 14-30 and a bad 10-30 because we got a dryer with a 3-wire cord".

The right thing to do here is:

• Replace the 10-30 receptacle with a properly wired 14-30 receptacle.
• If you are planning to still use the dryer, replace the 3-wire cord and 10-30 plug with a 4-wire cord and 14-30 plug and remove the neutral/ground bond from the dryer.

Depending on the type of EVSE (a.k.a., "charger") that you have, you may want to seriously consider hardwiring instead of a receptacle.

Answer 2

Am I correct that the existing wiring connection the ground wire to the outlets neutral connection is not up to code?

Not to code. You are correct.

Is testing continuity between the bare copper wire and a nearby water pipe a correct way to test that it is a good ground wire?

No. All current applied to a good ground wire should go to ground. Continuity testing with a grounded wire is at best unreliable.

How can I test that the white wire is a good neutral?

A simple voltage test between hot and neutral is typical.

Answer 3

Check for continuity from the neutral wire to ground, you should get continuity since ground and neutral are connected at service entrance.

then disconnect the neutral wire at the panel and test again. The continuity should go away. If it doesn't you have a dodgy cross connection between neutral and ground or you have not identified the correct neutral wire.

Answer 4

The best way to test continuity of the white would be to test line voltage wires to the white, then disconnect the white in the panel and re-test hoping that no voltage is measured.

Using a 14-50r on a 30A circuit has been debated several times here on SE, but there is no arbitor to end discussion. The NEC has two separate paragraphs, where the wording is distinctly different:

210.21(B) Receptacles. (1) Single Receptacle on an Individual Branch Circuit A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

(3) Receptacle Ratings. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall not be less than the values listed in Table 210.21(B)(3), or, where rated higher than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating.

To me it seems a 50A receptacle is not less than 30A, but my interpretation is without authority, the Code says:

90.4 Enforcement.(B) Interpretations.The authority having jurisdiction for enforcement of the Code has the responsibility for making interpretations of the rules, for deciding on the approval of equipment and materials, and for granting the special permission contemplated in a number of the rules.

You could call you local Electrical Inspector, most have published office hours at beginning of shift.