240 Volt Wiring


Old 08-05-04, 06:01 PM
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240 Volt Wiring

I'm replacing an electric hot water heater with a 240 volt only heater, not a 120/240 volt. There is a separate subpanel box which supplies power to only the heater by a triple pole 20amp breaker. The electric cable going to the heater has 4 wires: red, black, white and ground, while the heater has three wire leads and a ground screw. I connected the red/hot wire to one heater lead and the black/hot wire to the other two heater leads and grounded the ground as the heater installation instructions indicated. The instructions don't mention the white/neutral lead though, so can I just cap it off and electric tape it at the heater end since I don't need it?

The cable goes through a hot water heater timer between the subpanel and the heater and all 4 wires flow through it, but I don't think that impacts capping the white/neutral since 240 volts doesn't need it.

I just want to be sure I'm doing things right. Thanks for the help.
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Old 08-05-04, 06:43 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
The white wire is probably not a neutral. You say that the breaker is a triple pole breaker. This implies that the wiring is set up for timed operation. The water heater instructions should have wiring instructions for both timed and non-timed connection.

If your power company requires timed operation, then you will have to investigate the triple breaker to determine the two non-timed connections and then determine the proper wiring. In this case you need all the wirees in the cable.

If your power company does not require timed operation then you only need to use two of the poles on the breaker, but they must be the correct two, so that you get 240 volts and not 0 volts. In this case you do not need the extra wire in the cable.

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