Why do some 240 volt devices need no neutral?

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Old 04-17-06, 01:41 PM
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Question Why do some 240 volt devices need no neutral?

Why do devices like water heaters and well pump pressure switches not need a neutral conductor?

My well house has a 10-2 with ground UF feeder, and a "leg" has been pulled at the pressure switch to provide for a 120 V outlet for a water softener timer. I am rebuilding the well house and would like to wire this properly, but I am lacking the proper concept here.

Any general advice would be greatly appreciated.

Thanks for your time.

--scottf
 
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Old 04-17-06, 02:04 PM
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Originally Posted by scottf
Why do devices like water heaters and well pump pressure switches not need a neutral conductor?
Because they use 240V only and do not use 120V.
A neutral is used only to get 120V.


> My well house has a 10-2 with ground UF feeder, and a "leg" has been pulled
> at the pressure switch to provide for a 120V outlet for a water softener timer.

A bootleg.


> I am rebuilding the well house and would like to wire this properly,
> but I am lacking the proper concept here.

You need 10/3+ground cable and a subpanel and so forth (unless the well house is attached to your house, in which case, you need two separate circuits).
 
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Old 04-17-06, 02:05 PM
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Your setup is very unsafe and dangerous.

Electricity makes a complete path from the source through your device and back to the source.

With a typical 120 volt load one portion of that path is along the hot wire. The other portion of the path is along the neutral, or return, wire.

With a straight 240 volt load, the other hot wire is used as the return path, so no neutral is needed. This is because the current on each hot leg is identical, so there is no unbalanced current.

With a combination 120/240 load, the neutral is needed for the portion of the load that is unbalanced.

In your case, you need a sub panel at the well house, fed with either three conductors and no ground or fed with four conductors which would include a ground.
 
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Old 04-17-06, 08:04 PM
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Originally Posted by scottf
Why do devices like water heaters and well pump pressure switches not need a neutral conductor?

My well house has a 10-2 with ground UF feeder, and a "leg" has been pulled at the pressure switch to provide for a 120 V outlet for a water softener timer. I am rebuilding the well house and would like to wire this properly, but I am lacking the proper concept here.

Any general advice would be greatly appreciated.

Thanks for your time.

--scottf
..because there's no light bulb.

Your 10/2 that was robbed of a leg to make an outlet is a violation of the NEC.
 
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Old 04-18-06, 07:34 PM
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More about the "why" of center-tapped transformers ...

http://www.newton.dep.anl.gov/askasc...9/eng99316.htm
 
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Old 04-18-06, 11:47 PM
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in laymens terms, take the water soft off that circuit and run new wire to it on a separate circuit.
 
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Old 04-19-06, 12:35 AM
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> take the water soft off that circuit and run new wire to it on
> a separate circuit.

Is it your view that these circuits can be earth-grounded to the well casing, underground metal water pipe, or a made electrode?
 
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