Electric Water Heater Wiring

Hey Guys-

I’m replacing my gas water heater with an electric one. I was surprised to read from multiple sources, including the manufacturer diagram, to use only a 10/2 conductor and connect the neutral to the 30 amp double-pole breaker to get the 240 volts. And of course, put a piece of black tape around it to indicate its hot. But I thought it was a violation now to use the white conductor as an ungrounded conductor?


How else would you get 240v?

You are identifying the white as an ungrounded conductor by marking it with black tape in the panel.

In a cable assembly it is still code compliant to re-identify the white as a hot conductor. In conduit you would need to use the proper colors for the hots.

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With a 10/3 conductor. But there’s no neutral connection on the water heater just a ground. So if you use a 10/3 what do you do with the neutral?

So if running the conductor from the disconnect box to the WH in a conduit, you would need to use 10/3? But again, what do you do with the white neutral since the WH only has 2 hots and a ground?

Two hots and a ground in any form (within reason).

If you use 10/3 the black and red are the hots, the white or bare is the ground.

Simply snip off the excess wire–or pull it all the way out of the cable–or wrap it in a jar of jelly–anything you want to do with it, so long as you have the three wires.

You would just use 2 blacks and a green.

Using 10-3 would be a waste of materials. It could be used. The white would just be unused.

The bare would be the ground, not the white. Grounding conductors need to follow the color convention required by Article 250.

I found this on the iNACHI electrical course under the 240 Volt termination section:

"Since adoption of the 1996 NEC, all 240V circuits are required to be 4-conductor assemblies carrying:

  • two 120V ungrounded (hot) conductors;
  • one grounded (neutral) conductor; and
  • one equipment grounding conductor."

Any thoughts on that?

Also, why doesn’t an electric water heater use a neutral?

That info is only dealing with circuits used for ranges and dryers that are actually 120/240v loads. It would help if it were clarified that it was talking about a 120/240 circuit.

A straight 240v load like a heat pump, AC compressor or a water heater do not require a neutral so 2 hots and a grounding means are all that is needed.

Thanks Jim. Why don’t those appliances (heat pumps, ACs, electric water heaters) utilize a neutral though? How do their uses of electricity differ from other appliances, like a stove, that are 240V but do use a neutral?

Because they operate at 240 volts. The neutral would only be needed if something were operating at 120 volts.

Items like timers, dryer motors and lights are all 120 volt and need the neutral. Water heaters, AC compressors do not have anything that needs a neutral.

Kenny you better take the electrical course before Nick sends you an email…!!

Thanks David. That was one of the first courses I took when becoming a member and have referred back to it several times.

The NACHI course and the other electrical books I’ve read all indicate that electricity seeks to complete a continuous circuit. Supply through the hot (ungrounded) conductor, to the fixture where it completes a task, and then back through the neutral (grounded) conductor.

I’m sorry if it’s a dumb question. But again, if 120V fixtures need the neutral path to allow current back to the panel why don’t 240V fixtures? Or am I just thinking about it wrong?

To simplify; Straight 240v circuits use the hot leg as the return path from the other leg.

Not a dumb question, I just would not try to figure it out by asking here.
There are too many wrong answers that turn up a rule-of-thumb.

You should study it all again till you fully understand it.

Having a related application to go along with training make all the world of difference in understanding.

AC current thru the hot and neutral wires actually switches from positive to negative rapidly. But if you look at a particular point in time you could have the following …

Hot Wire (Leg-A) - Positive
Hot Wire (Leg-B) - Negitive
Neutral Wire - Negative

For a 240V circuit current is flowing from Leg-A to Leg-B

For a 120V circuit current is flowing from Leg-A to the Neutral

Maybe that might help … :wink:

This picture of the out put from an transformer might help

single phase.gif

Thank you and yes, those help out a lot. I can’t say that I fully understand it yet, but it answers my question as to why the neutral isn’t needed.