I have a water heater that gets electricity from a dryer cord plugged into an outlet on the wall.

Water heater connected with dryer plug

I need to remove the outlet and replace it with permanent wiring and some form of quick disconnect.

Based on a conversation with my local inspector the best way he thought to get this done is to use the following:

  • 1 gang box extender (like this or this),
  • 2 pole 30 amp switch (example) mounted on the face of the extender
  • Connect one end of a whip (example) to the bottom of one of the 1/2" hubs/knock out
  • Connect whip to the top of the hot water heater

I am only able to find a few types of handy box extensions and they are all made of metal.

My existing box is non-metallic and so doesn't have a grounding screw.

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The extensions don't have spots to screw in a grounding screw as I guess they assume they are being screwed into a metal box that is grounded and so they expect to be grounded through the screws used to attach them.

How can I ground the extension so that I don't have an ungrounded metal handy box/junction box extension?

Ps, if you feel this is the wrong way to do this in the first place add a comment and I will ask a separate question more generally about the best way to go from a hot water heater hooked with with a dryer plug to something code compliant.

  • I take it the write-up is for a 422.16(A) violation? Also, what make/model is the water heater? Commented Apr 5, 2017 at 0:41
  • One more thing -- do you have fuses or circuit breakers in your panel? Commented Apr 5, 2017 at 0:43
  • @ThreePhaseEel I plan to purchase this hot water heater but haven't purchased it yet. I pulled the permit but haven't had an inspection yet so no code violation yet, hoping to avoid that by asking a lot of questions and taking my time. Commented Apr 5, 2017 at 0:47
  • @ThreePhaseEel Circuit breakers, no fuses. Commented Apr 5, 2017 at 0:47
  • 1
    @Harper The white and black are both hot as you thought (10AWG on a 30 amp breaker). The current water heater and the one I am looking at both turn on only one element at a time so you only get 4500 watts at any given time instead of 9000 watts. Commented Apr 5, 2017 at 1:49

1 Answer 1


Your inspector is right and wrong at the same time!

First off, the existing install is a violation of NEC 422.16(A), so your inspector was correct to point that out:

(A) General. Flexible cord shall be permitted (1) for the connection of appliances to facilitate their frequent interchange or to prevent the transmission of noise or vibration or (2) to facilitate the removal or disconnection of appliances that are fastened in place, where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance or repair and the appliance is intended or identified for flexible cord connection.

As to the proposed fix, however, your inspector is confused or working from an old Code edition, as the 2014 (and 2017 AFAIK) NEC do not require a disconnecting means for a hardwired appliance if the breaker can be locked off (an electrical supply house will be able to order in lockoff devices for any modern breaker type). This is 422.31(B) in the Code:

(B) Appliances Rated over 300 Volt-Amperes. For permanently connected appliances rated over 300 volt-amperes, the branch-circuit switch or circuit breaker shall be permitted to serve as the disconnecting means where the switch or circuit breaker is within sight from the appliance or is lockable in accordance with 110.25.

So, I'd simply take an ordinary single gang metal faceplate with a 1/2" KO in it and use that instead of faffing about with a box extension that needs grounding. (250.148 calls out metallic boxes, but not metallic faceplates on nonmetallic boxes...although it is still wise to attach a grounding pigtail to the faceplate in this case.)

  • 1
    Better to buy a faceplate with a knockout in it. Trying to get a hole in a plastic faceplate will be challenging, and may not be allowed by the inspector. Also, where appliances are not within sight of the breaker, it's useful to have a servicemen switch near the appliance. This is especially true for plumbing and HVAC appliances, as plumbers and HVAC techs might not know to lockout the breaker.
    – Tester101
    Commented Apr 5, 2017 at 1:04
  • 1
    When the inspector and I talked about what I planned on doing he mentioned that I didn't have to have a disconnecting means if the breaker panel was in sight of the unit. He didn't mention anything about being able to lock off the breaker. Regardless, I wanted to install a switch any way as a form of safety measure so if something goes wrong someone has an easily accessible means of turning off power right at the water heater. I will go research what breaker lock offs are. Thanks for your help Commented Apr 5, 2017 at 1:05
  • @Tester101 -- the only KOed faceplates I've met are metal (although there might be ones for ENT that'd work for LFNC too?) Commented Apr 5, 2017 at 1:06
  • @Tester101 I haven't seen any that weren't metal either, in which case I would need to find a way to ground a metal faceplate when I have a non-metalic box. Commented Apr 5, 2017 at 1:08
  • @ChrisMagnuson I can't find the code that requires a metal box cover to be grounded (other than when used with receptacles or switches). Though I could definitely be missing something.
    – Tester101
    Commented Apr 5, 2017 at 1:28

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