3 prong 240


  #1  
Old 01-13-04, 08:59 PM
MAGGAST1
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3 prong 240

I've got a machine that has a three prong 240 plug. From left to right, facing the back of the plug, it has green, white, and black. The green goes to chassis on the machine. The white and black go to a breaker on the machine and then to a manifold bar of sorts. Is this correct? should I wire a circuit for this with two hot leads and a ground, or two hot leads with a neutral? The machine is large, but portable, on wheels and there is nothing elso to ground it with.
 
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Old 01-13-04, 10:39 PM
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What you see inside the breaker box is correct.
Hook the black & white to the breaker and the green to the ground bar inside the breaker panel and you should be OK. Don't connect anything to the neutral.
 
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Old 01-14-04, 12:43 AM
georgekopf
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Good Question

I'm installing a 240 volt receptacle for a wet-dry vac. It uses the NEMA 6-15R configuration (that's two horizontal slots and a rounded slot). My books all say that the three wire hookup is standard but that the new code requires a 4 wire hookup. I think that as of 1996, 240 volt receptacles require a seperate ground and neutral wires. The funny thing is that I wasn't able to find a receptacle at Home Depot with more than 3 poles (2 hot and 1 ground). I'm going to stop by an electrical supply shop tomorrow and I'll let you know what I find out.

Good Luck.
 
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Old 01-14-04, 07:45 AM
MAGGAST1
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Thanks Jughead,
One more thing. The breaker box I referred to is on the load side. That is, on the machine itself. The plug is one with 3 prongs, 2 on a slant and the middle is verticle or straight. What I want to do is wire a receptacle. Shouls I pull 3 wires, two hot leads and the ground?
Thanks
 
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Old 01-14-04, 08:13 AM
M
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georgekopf - you are correct in that the code does not allow conductor sharing of the neutral and grounding functions. However, your 6-15 application is for two hots and an equipment ground - there is no neutral, therefore only 3-wires with a 3-prong plug and receptacle are required.

The code change you refer to was created to disallow 3-wire receptacles and cords for ranges and dryers on new installations. Dryers and ranges have 110 volt functions (motors, lights, etc.) and have in the past utilized a 3-wire system (except in mobile homes where they've always been 4-wire) where one wire served not only as a safety ground, but as a current carrying conductor as well. Safety grounds are not allowed to carry current except in the event of a fault, so the code change was created to address the issue.
 
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Old 01-14-04, 08:21 AM
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Maggast1, it sounds like you have a 6-50P and will need a 6-50R or standard 3-wire "range" receptacle. In almost all cases, the number of prongs on a plug will match the number of conductors required for the circuit. 3 prongs = 3 conductors. The only instance where the prongs and circuit conductors wouldn't match would be if the ground wire terminated onto the housing of a metal plug which is very rare.
 
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Old 01-14-04, 08:33 AM
MAGGAST1
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Mcjunk,
Thanks, it is a range plug. Do I run 2 hot leads to the receptacle and no common?
 
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Old 01-14-04, 08:41 AM
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What exactly is this "machine"? As I think we have now established, this machine needs no neutral (aka common).
 
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Old 01-14-04, 09:35 AM
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You would only need the neutral if the device also used 120 volts inside. Otherwise you only need two hots and a ground. If you are putting in a receptacle you only need to pull three wires, two hots and a ground.
 
  #10  
Old 01-14-04, 09:52 AM
MAGGAST1
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Thanks!
The machine is a custom built parts washer for hospital application. It has a compressor and heat as well as cooling elements. The company that built it no longer exists.
 
 

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