Wiring 240V Receptacle /w 12-2

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  #1  
Old 09-12-05, 03:06 PM
_raptor_z_
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Wiring 240V Receptacle /w 12-2

I am wiring a receptace for a dust collector in my garage that has a 240V 2HP electric motor. When I wired the supplied switch, the motor had only three wires, the black, white and ground. This was the same case where the switch wires connected to the motor, and also on the end where I installed the plug.

When I went to wire the receptable, it appears that I need to run both the black and the white from the subpanel as hot (one to each breaker on the 240V circuit) along with a ground. However, I am used to 120V wiring where there is a neutral wire present.

I asked at a large retailer how this could work and was told that since the two feeds on the 240V circuit are out of phase with each other, that they alternate acting as the neutral while the other wire is hot. Is this true?

If so, can I wire the receptable with 12-2 ? (the 240V draw on this motor is 12 A) Are both spade connectors wired hot?

Thanks.
 
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  #2  
Old 09-12-05, 03:08 PM
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The answer is "yes" to every single one of your assumptions and questions. Your dust collector needs no neutral, and both the black and white will be hot.
 
  #3  
Old 09-12-05, 03:11 PM
_raptor_z_
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Originally Posted by John Nelson
The answer is "yes" to every single one of your assumptions and questions. Your dust collector needs no neutral, and both the black and white will be hot.
Wow, thank you for such a quick response!
 
  #4  
Old 09-12-05, 07:47 PM
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Since the white is hot, does he need to mark it with black electrical tape on each end so that someone who owns this home in the future won't confuse the white with a neutral?
 
  #5  
Old 09-12-05, 07:51 PM
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Yes, he should mark each end of the white wire. A black magic marker is generally preferred to electrical tape, since the tape seems to want to fall off.
 
  #6  
Old 09-12-05, 07:53 PM
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Technically the white wire should be marked with black. However, anyone who thinks a white wire attached to a breaker, or attached to a 240 volt receptacle is a neutral should not be looking inside the panel or inside the receptacle.
 
  #7  
Old 09-12-05, 09:22 PM
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Originally Posted by racraft
Technically the white wire should be marked with black. However, anyone who thinks a white wire attached to a breaker, or attached to a 240 volt receptacle is a neutral should not be looking inside the panel or inside the receptacle.

I have seen in service changes where the white wire was not marked and it got put onto the neutral bar instead of the breaker. Yes I know that it should be marked when being removed from the breaker but it happens. Plus with all the DIYers NEC wants to make sure nobody gets hurt thinking this white wire is a neutral.
 
  #8  
Old 09-13-05, 10:04 AM
CLUE
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Coupled Breakers

On the subject of 220v, I have two 1,700 Watt-220 volt heaters on a 2/12 w ground wire. The breaker is 2-20apms coupled together. Does that mean I have a 40 amp breaker and if so, can I add a third heater?
 
  #9  
Old 09-13-05, 10:12 AM
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No, it's a 20-amp breaker, and no, you cannot add a third heater.
 
  #10  
Old 09-13-05, 10:15 AM
CLUE
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But I could reduce the heater sizes and add a third as long as I use only 80% of the available watttage, right?
 
  #11  
Old 09-13-05, 10:59 AM
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Sure, but that's a lot of effort and expense for a trivial gain.
 
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