Water – How to ground a junction box extension when using a non-metallic box

groundingwater-heater

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.

Best Answer

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.)

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