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I have an old 30 amp outlet that I was planning to reuse. There isn't a connection for a ground, but since I am connecting to a metal box, I now have a connection between my neutral and ground. Should this cause a problem?

30 amp outlet

  • Can you name the new connector you are trying to replace this with? What is the load you will be serving? – Harper Mar 14 at 16:48
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In your other question I commented that due to your peculiar setup and grandfathering, you are forced to tie neutral and ground in your service panel here in the barn. (Normally you wouldn't).

Do not tie it anywhere else! Neutral is not ground!

Now, the socket in this picture is a NEMA 6-30. NEMA 6-30 has a ground and does not have or need a neutral. If that is the socket you want, you are all set. That would be used for water heaters, A/C units, compressors, machine tools and other equipment that runs on a 240V single-phase motor or resistor heating (such as a drying kiln).

This looks like all new work, and I assume that is MC cable. If that cable has a ground wire, you need to use it and not just depend on the metal sheath for a ground path.

Now, if you are installing a NEMA 10-30 (neutral not ground), stop. Do not use NEMA 10 for anything, it is obsolete and it is dangerous and illegal to install a new one. If you have a dryer that has an existing NEMA 10 cord/plug, then install a NEMA 14 receptacle (4-pin) which includes neutral and ground. Get the installation manual and follow the instructions for replacing the NEMA 10 cord with a NEMA 14 cord. (you need to remove the bootleg strap from the machine).

If you are installing a NEMA 14 (or 10) here, and you need neutral, look in that MC cable for a white and red wire. For neutral, you will need a cable that has black, white and red. If that is not present in the cable, then you need to replace the cable run. There is no way to retrofit neutral.

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By the way, in these drawings I show both hots as black. Because they are interchangeable, it doesn't matter if they're swapped. The wire is red in the cable mainly because that's how cables are made. In conduit, I would wire it with two blacks.

  • I've seen you mention the "In conduit, I would wire it with two blacks" remark - and similar - e.g., travelers two yellows (or red or whatever). If you have lots of colors available, wouldn't using two colors (e.g., black & red for the two hots here) make it easier to troubleshoot a flaky connection? Or does it end up as "if the connection seems flaky, unscrew/screw all wires in the circuit to play it safe" and therefore not matter? – manassehkatz Mar 12 at 13:52
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    @manassehkatz Good point, it doesn't cost anything more than another trip to get another spool of wire. However it hasn't slowed me down. Usually wire damage is at terminations. Especially so in metal conduit, wire damage enroute is rather unlikely unless the conduit itself is damaged. If so, that must be found or the replacement wires will also be damaged. The wire would need to be pulled anyway for inspection. – Harper Mar 12 at 14:52
  • The outlet was wired with the neutral going to ground. I was given 10-3/grd mc that I wired up. So I would not use the white wire and only use the green ground wire. I was curious because the 50 amp outlet has the labeling and terminals for all 4 wires. – Timothy Ryan Mar 14 at 13:39
  • @TimothyRyan that isn't uncommom when replacing dryer outlets with welder outlets. Are you saying you have a NEMA 14-50 that you want to hook up instead? What do you need to breaker it at? – Harper Mar 14 at 13:45
  • I have the nema 14-50 installed with 8g for the welder. The nema 6-30 ( is what it looks like) was the old plug in the barn. It had 12-2 wired to it and never had problems. I had 10-3 /grd to use, but I had only 3 connections on it unlike the nema 14-50 that has 4 connections on it. My error was using the neutral wire instead of the ground wire. Now my system ground and neutral are no longer connected. – Timothy Ryan Mar 14 at 18:23

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