System ground and system neutral

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  #1  
Old 08-31-06, 06:06 AM
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System ground and system neutral

I resently wired up a 3 prong 220 receptical from a 4 wire source. The welder had no means for equipment ground and was not wired for it. It was a new welder with a 3 wire cord.
The receptical I used for 3 wire system and the wire feeding it was 4 wire bx cable. I attached the ground to the metal box
and the system neutral to the 3rd screw on the receptical
and the 2 hots leads to their respective screws. It all works fine
but I came across something that I dont understand.
First off the circuit is fed by a sub panel with a separate neutral and ground terminal buss . When I started to install the receptical into the gounded metal box a small visual spark on
was noted. I measured the voltage between the ground and the box and read zero but yet the spark was constantly produced when I started to install the receptical. I somehow think its a potential difference between the ground and neutral is creating
the spark but why can't it be read with a meter? It cant be felt with your bare hands either.

Larry
 
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  #2  
Old 08-31-06, 06:12 AM
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Larry,

You wired things wrong. Your welder needs a ground, not a neutral. A welder is a strsight 240 volt device. As such it needs two hot wires and a GROUND wire, not a neutral wire. Cap the neutral in the receptacle box and do not use it.
 
  #3  
Old 08-31-06, 08:52 AM
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I agree with Racraft. Just to verify, what is this welder's make/model? What are the numbers found on the receptacle and plug?
 
  #4  
Old 08-31-06, 09:14 AM
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Thanks guys.

Your absolutely right. I bet I have wired hundreds of 3 wire 220 recepticals correctly but this time I guess I went brain dead. It was the first 4 wire supply for a 3 wire device. Thank you so much guys for keeping my wires straight.

Larry
 
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