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Related to Grounding a 3-prong dryer plug, but with a small twist.

I have a NEMA 10-30 that runs back to my main panel. Since we had a leak in the laundry room, I'm having to open the wall. I'd like to ground this, but I have a subpanel across the room that would be easy to reach (100 amp panel, 60A breaker with 4-4-4-6 aluminum feeder). Can I ground to this subpanel, or do I need to run 10 gauge ground the 100ft or so back to the main panel?

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  • Option 3 - Run a new 10/3 cable to go with your new 14-30 receptacle to the subpanel. No effect on overall usage, so only real concern is whether that will oversubscribe the 60A panel, which depends on what you have in it. What else is in the subpanel? Is that 4/4/4/6 copper or aluminum? What size feed breaker in the main panel?
    – manassehkatz-Moving 2 Codidact
    Commented May 28 at 19:39
  • @manassehkatz-Moving2Codidact Aluminum feeder. 100A panel on a 60A breaker. With a point-of-use water heater (14A) and a coffee maker (11A) in the kitchen that could push that box close to its limit really fast.
    – Machavity
    Commented May 28 at 20:03
  • Coffee maker is almost certainly 120V. If the water heater is 120V and the loads are on opposite legs then you actually have 65A rated wire (so you could upbreaker to 70A and promise to use only 65A) which would give you: 30A (dryer including derate) + 14A (largest of other loads) = 44A leaving 21A to spare. If the 14A heater is 240V then you are up 55A (30A + 14A + 11A) with ~ 10A to spare, which isn't much.
    – manassehkatz-Moving 2 Codidact
    Commented May 28 at 20:19
  • This will be decided by the retrofit ground rules at 250.130(C).
    – Harper - Reinstate Monica
    Commented May 29 at 1:21
  • The change was made in 2014 and I don't think any further changes to it have been made, and sadly it does say "branch circuit" so a sub-panel that's fed from the main panel and as a ground running back to the main does not qualify, as that's a feeder. electricallicenserenewal.com/… There are other options (besides all the way to the main panel) depending on the layout of your GEC and grounding system
    – Ecnerwal
    Commented May 30 at 15:40

1 Answer 1

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A retrofitted ground must come from the same panel as the power. You need to find an outlet or attachment point with a ground fed directly from the main panel or to run new power from the subpanel. I'm not a code expert but I think this applies to your situation, is, a retrofit ground is allowed but not from a different panel.

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    This seems like an absurd situation to be worried about. If some future person really manages to hook up a three-wire dryer using the retrofit ground wire as neutral (either by switching the receptacle back to a 10-30 or deliberately mis-wiring a 14-30 cord) they’re committing a major code violation and their #1 concern should be the possibility of electrifying the entire dryer chassis.
    – nobody
    Commented May 28 at 20:43
  • Meh. If some later occupant (after the OP leaves) does something that dumb, they deserve what they get.
    – nobody
    Commented May 29 at 0:56
  • @nobody - point (finally) taken and all my related comments removed.
    – jay613
    Commented May 30 at 16:12
  • @Ecnerwal likewise.
    – jay613
    Commented May 30 at 16:12

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