110 off 220 Pump

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  #1  
Old 10-21-00, 11:09 AM
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I have a 220 Well pump that is fed by 3-wire 220 from the house, one hot, one neutral and ground. Thus, combined 220 arrives at my pump house and is wired directly to the pump. Is there any way to get 110 for occasional lighting in the shed without rerunning a different direct-burial wiring out there?
 
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  #2  
Old 10-21-00, 02:56 PM
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Hello, Doncon:

What you have at your pump is one wire with 110 vac, one wire with 110 vac, a common (neutral) and, hopefully a ground. The difference in potential between the two wires is 220 vac. In some circumstances (in older installations), the neutral and the ground are considered common. The new systems employ all four wires.

In your situation, you can tap one leg of the 220 vac line (which is 110 vac) and the neutral for a minimum service installation (your light). I would suggest that you not involve any heavy installations on this type of lash-up because it does bad things to the balance of power on your main circuit box.
But, a light is considered minimal impact and is, in most cases, an acceptable addition to the circuit.

One of Sparky's admirers,

Smokey
 
  #3  
Old 10-21-00, 08:34 PM
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Thanks for the info! The wiring from the special pump breaker box to the pump house is 12/2 + Ground, so the bare wire is carrying the neutral and there is no real ground. If I come off one side of the pump for a light-duty 110/120 circuit, should I put in a ground rod for additional safety? It's about a 100 ft. underground run.

 
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Old 10-21-00, 08:51 PM
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What you have is a 12/2wGrnd cable. This cable is alright to use for the 220 volt pump because no neutral is being used.

You must not use this cable for a 110 volt use.

Your conductors in this cable is two conductors that will read 120 volts to ground each. The black and white will read 220 volts between these two conductors.

You have no insulated neutral. You only have a bare grounding conductor. You must not use a bare grounding conductor for a grounded neutal. The return path for you lighting is a grounded conductor but it will carry current. No bare wire is allowed to be used as a current carrying conductor.

DO NOT USE THIS CABLE TO YOUR OUT BUILDING FOR BOTH 220 VOLT AND FOR A 120 VOLTS SYSTEM. If you used your bare wire for the return path of you 120 volt circuit you would be creating a major shock hazard.

Run a 10/3wGrnd UF cable buried 18" deep to your out building. This cable will have a black red white and bare wire in this cable. You then can install a small breaker panel and power your pump and lighting and receptacles in you outbuilding. Do not install a ground rod. Your grounding source will be the fourth wire in the 10/3wGrnd UF cable. This makes you panel in the outbuilding a sub panel and the neutrals and ground must be separated in the outbuilding because the outbuilding panel is a subpanel using the main building grounding source.

Good Luck

Wg
 
  #5  
Old 10-22-00, 11:04 AM
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take the advice of w-goodrich. You CANNOT use the existing wire arrangement to run a 110v circuit. My understanding is that currently you have 2 insulated wires and a bare ground wire going to your pump. This works fine for a 220v only application, but cannot be used for 110v because there is no neutral (white) wire present. Both insulated conductors supply power to your pump and no neutral wire is required for your pump operation. DO NOT use the bare ground wire for the heutral wire. Although it would work, you would be energizing the entire ground system in you house which would create a dangerous situation which could result in someone electrocuting themselves.The only option is to wire a sub-panel at your shed as outlined by w-goodrich. Not really a simple solution to a simple problem, but the only safe and proper way to solve it.
 
  #6  
Old 10-22-00, 12:32 PM
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Install a 220V receptical at the pump,
and use a 220 to 110 trasformer, else run
another cable to get 110.
 
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