Need 120 & 240 volts on 3 wires, Need Master Electrician!

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  #1  
Old 04-03-07, 11:31 AM
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Need 120 & 240 volts on 3 wires, Need Master Electrician!

I have 3 wires (black, black, white) running underground to a pump house. Currently, it is running 240 volt service. (hot 120, hot 120, neutral). I need 120 volts to run a small appliance, so I figured I could get a recepticle, and use one of the blacks as a hot, and the neutral white. I get 120 volts on my tester, but when I connect my appliance, it trips the breaker. Can you do this? What could I be doing wrong?
 
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  #2  
Old 04-03-07, 12:21 PM
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Is there a breaker panel in the pump house or do the underground feeders connect directly to the pump?

> when I connect my appliance

What is the appliance?

> it trips the breaker.

Where is the breaker and what is the amperage rating on the breaker (15,20,30) ?

> Can you do this?

Maybe.
 
  #3  
Old 04-03-07, 12:44 PM
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Is this perhaps a GFCI breaker?

I suspect that it is a GFCI breaker and that the white wire is connected to the neutral or ground bar instead of to the breaker.

Another issue. IS there a ground in this scheme at all? You need a ground to connect up a receptacle.
 
  #4  
Old 04-03-07, 12:50 PM
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Is the wire in conduit? What Size? Is there a bare or green wire also?
 
  #5  
Old 04-03-07, 01:42 PM
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You don't have a ground. You can't connect a three prong receptacle.
Or perhaps you don't have neutral and this is a GFCI double pole. This would definitely cause a GFCI trip.

You can't do what you are attempting. This is most likely a 240 volt only circuit.
 
  #6  
Old 04-03-07, 04:39 PM
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As I said in my initial post, there are only 3 wires, (2 black, 1 white).

The blacks are connected to 2-30amp breakers, but the breaker switches are connected together. The white is connected to the neutral bar. The lines then go underground via plastic conduit to the pump house. They then connect to a second breaker box, also rated at 30 amps, then it connects directly to an irrigation pump. It doesn't look like GFCI, it looks like standard 240 breakers.

I realize there won't be a ground, but it doesn't matter becuase my appliance is only a 2 prong anyway. The "appliance" is a 120v water softner, that uses a 300 ma DC adapter. So it doesn't need alot of power.

I should add that the 120 recepticle I added works fine if the pump is not running. And the pump works if the 120 is not being used. If I turn on both at the same time, that is when it makes a wierd noise and trips the breaker.

The question I'm asking is:

Can I tap one of the 2 black wires, and use the neutral to create a 120 recepticle?
 
  #7  
Old 04-03-07, 04:47 PM
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The next step would be a volt meter on each line to check the voltage as it is running. Then a current clamp to measure the current.
 
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Old 04-03-07, 06:06 PM
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Absoffthewake wrote: "... They then connect to a second breaker box, also rated at 30 amps, then it connects directly to an irrigation pump."

OK so just to be clear in addition to the two breakers in the house you have two breakers in the pump house also? If so then your best course of action is to wire the outlet to a new breaker in the pump house subpanel.

The experts though will need to know some info about the p/h subpanel. Does it have a separate neutral and ground bar? Is the neutral bar isolated from the subpanel? Is there a ground rod. Is there any metallic path such as a steel water pipe to the house?
 
  #9  
Old 04-03-07, 06:55 PM
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This is ALL moot. He either has no neutral or no ground. IMO they used a white as a ground (not legal or correct).
This pump is a 240v load, so there is only two hots and a ground. A ground rod out there WILL NOT provide a ground.

To the OP: DO NOT install a 120v receptacle off this feed. No matter how you do it it will be illegal an unsafe.

The only way to make it work IS if this run is in conduit as was asked previously and you can pull in another conductor.

DO NOT run this the way you have it. You are messing around with this when you really do not know what you are doing. Best case you will burn something out. Worst case you will get killed.
 
  #10  
Old 04-04-07, 01:12 AM
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You have a 30 amp circuit feeding the pump house. No, you cannot just tap these conductors to serve a 15 or 20 amp receptacle.

If the “30 amp breaker box” in the pump house is a service rated panel, and has the space for an additional single pole breaker, you can do this if the combined load does not exceed 30 amps. If the “breaker box” is just a disconnect you can get a service rated panelboard for +/- $20.00. It can be a 50, 60 or even a 100 amp panel, it just has to be at least 30 amps.

The feeder serving the pump house can be 3 wire if, there are no other metallic paths between the two structures. This includes water or gas piping, phone or other low voltage wiring even a fence could be an issue. If there are no other metallic paths you could have 2 hot and a neutral feeding the panel in the pump house (no ground). The neutral buss would be bonded to the panel in the pump house and you will need a Grounding Electrode System (GES) at the pump house. The Grounding Electrode Conductor (GEC) and the Equipment Grounding Conductor (EGC), for the circuits in the pump house, will originate from the same neutral/ground buss in this panelboard.

Ideally (even if there are no other metallic paths) the pump house would be fed with 4 wires, 2 hot, a neutral and an EGC. The EGC must be green or bare. With a 4 wire feeder the neutral buss is not bonded to the panel (in the pump house) and a separate ground bar will be bonded to the panel. The GEC, the feeder EGC and the EGC for the pump house circuits will terminate to the ground buss and any neutral conductors would terminate at the neutral buss.

In any case we need to know if the panel where the feeder originates is a main panel or a sub panel. Is there a meter and disconnect on the Power Company’s pole? If so there is a chance the “main” panel for the house is actually a “sub” panel and we would need to know how the white wire to the pump house is connected.

There are many other details that need to be considered. A $ 10.00 book called “WIRING SIMPLFIED” (available at most home improvement centers) will go a long way in covering those details and explaining terminology.
 
  #11  
Old 04-04-07, 04:56 AM
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Juhl's reply is another option, and the ONLY way to do it with what you have.

I seriously doubt the panel in the well house is acceptable. I'd bet it was simply a fused (breakered) disconnect. It would have to be replaced with a 4, 6, 8, etc, space panel.

This being said, from the gist of the questions this is NOT something I would recommend the OP do himself.
 
  #12  
Old 04-04-07, 01:39 PM
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Another option would be to get a small 240V to 120V transformer, or find a comatible transformer supply that works off of 240V, and has a 240V prong configuration.
 
  #13  
Old 04-11-07, 06:05 PM
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Thanks for your help!
 
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