why receptical voltage suddenly only 15 volts?

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  #1  
Old 09-05-11, 12:57 PM
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Question why receptical voltage suddenly only 15 volts?

I've had a receptical in my garage working for 15 years and suddenly the voltage from it is only 15 volts!

From the black wire to ground is 115 volts.
From the white wire to ground is 115 volts.
From black to white is only 15 volts.

What has happened here?

Lance
 
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  #2  
Old 09-05-11, 02:18 PM
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From the white wire to ground is 115 volts
That is wrong. It should be ~0 volts. You need to inspect all the connections on the circuit, especially the neutrals. Check all receptacles, lights, switches, and junction boxes remove and inspect the inside of all wire nuts (or just replace them).
 
  #3  
Old 09-05-11, 03:41 PM
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Yup, sounds like a loose or disconnected wire somewhere.

As Ray said, you should get 120v between Hot and Neutral, 120v between Hot and Ground, and 0 between Neutral and Ground. (anywhere between 113-123v is fine)

When you get 15v or so using a digital multimeter, you're probably just measuring phantom voltage . You can ignore it.
 
  #4  
Old 09-05-11, 04:08 PM
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Question Whoa! More strange info!

Here's more info. My garage has a light, electric door opener, and a recepticle. They were all working for 15 years, then yesterday nothing works suddenly.

OK, so first I wanted to verify that the power coming into the garage was OK, so I disconnected all other wires from the supply power cable coming into the garage leaving me with the single white and black that bring power to the garage.

I measured 115v from the white to ground (I put the probe on the metal of the light switch box)

I then measured 0v from the black to that ground.

Isn't this reversed? Keep in mind this circuit was working for 15 years!

FYI: before disconnecting everything, the black coming into the garage went to a light switch and the white went to a cluster of 3 other whites all tied together.

What the heck has happened?

Lance
 
  #5  
Old 09-05-11, 04:29 PM
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It's possible the polarity has been reversed for the past 15 years. Everything would probably have worked, but that doesn't mean it was right or safe. I think I'd find the circuit to the garage where it connects to the main service panel in the house and start checking there for proper connections and voltages.
 
  #6  
Old 09-06-11, 06:07 PM
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Fixed!

Thanks all, I found and fixed the problem.

You were right in that the polarity is reversed. People amaze me.

Anyhow, I began to work back from the garage to the source to check each connection as suggested. As it turns out, the first marette connections on the garage roof had rotting electrical tape around them and just disintegrated as I twisted them to undo them.

I cleaned up the wires, made new connections and we have light!

Thanks.
Lance
 
  #7  
Old 09-06-11, 07:00 PM
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the first marette connections on the garage roof had rotting electrical tape around them and just disintegrated as I twisted them to undo them.

I cleaned up the wires, made new connections and we have light!
Was this a connection to the overhead feed to the garage or is this building wiring that should be in a junction box. Your description leads me to believe this was the garage connection to overhead wiring.
 
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