220 run

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  #1  
Old 07-05-04, 11:54 AM
Valk1500
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220V run to garage?

I would like to install a 220V, 70' new run in my home for a 110, 15 Amp 5hp air comprssor that I am converting to 220V, 7.5 amps per leg. I plan to use 10/3 romex, my confusion is, do you use the fourth conductor (ground conductor)? If you do I guess you cap off the white nuetral on both ends?

I'm not familiar with the the grounded/ungrounded theory on this. I presume this is grounded since you could use the ground wire to nuetral which effectively is the same as ground?

For a plug, do I just use a 2pole, 3wire 6-15 p/r, or should you use a 3pole, 3wire 10-20 p/r?


Thanks for any help.
 

Last edited by Valk1500; 07-05-04 at 12:46 PM. Reason: correction in wording
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  #2  
Old 07-05-04, 01:16 PM
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Attached or detached garage? It makes a big difference.

If you don't need a neutral (and you don't), then run 10/2, not 10/3. If you already wasted your money on 10/3, then yes, cap off the white wire at each end.

Never use a grounding wire as a neutral (except in pre-1996 ranges and clothes dryers).
 
  #3  
Old 07-05-04, 06:53 PM
Valk1500
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220V run to garage?

This is an attached garage, in a one story 1995 home. I have not purchased anything for the project yet.

Ok, if I use 10/2 romex would'nt I be using the third uninsulated conductor (center wire) which is the ground wire wraped in paper as a neutral? Or is this wire not concidered to be a neutral but defined as a ground and is ok to use it in this application?

Sorry for my being a confused student electrician. Help...

John, I'm lost by your previous post you said:

Never use a grounding wire as a neutral (except in pre-1996 ranges and clothes dryers).
 
  #4  
Old 07-05-04, 07:02 PM
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I know this may be difficult to accept, but you do not need a neutral. The compressor has no place to hook one up, and does not require one for operation.

The white and black will be the hot conductors, and the bare will be the grounding conductor (i.e., carries no current except if there is a fault).
 
  #5  
Old 07-05-04, 07:25 PM
Valk1500
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220V run to garage?

Ok, that is the same as what this 125/250V drawing at the bottom shows:

http://www.leviton.com/sections/techsupp/diagrams2.htm

So, when you run the wire in the attic, should you run it under the insulation like it is now along the interior ceiling framing or can you run it up along the framing of the roof to avoid digging in insulation but paying the price in a longer wire run? Is there a correct way?
 

Last edited by Valk1500; 07-05-04 at 07:27 PM. Reason: spelling
  #6  
Old 07-05-04, 07:41 PM
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No. I don't see any diagram on that whole web page that matches this situation. All of those diagrams are 3-wire, some with grounding and some without. They all have a "W" connection. You have a 2-wire with grounding. That's not on this page. Does your compressor have a plug on it? If so, does it look like any of those in the picture?

When running wire in the attic, you must run it stapled to the side of framing members. If it must cross framing members, you must install a 2x4 and staple the cable to the side of the 2x4 "guard strip". You can either run it under the framing, or up high if you want. Either way, it must be protected from physical damage from somebody roaming around up there. The exact rules depend on whether the attic has a permanent ladder or stairs.
 
  #7  
Old 07-05-04, 08:12 PM
Valk1500
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The compressor still has a standard 3 prong 120V plug on it. I need to change it to a 6-15p or 6-20p when I convert the motor to 220V.
 
  #8  
Old 07-05-04, 09:34 PM
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Nema 6

Originally Posted by Valk1500
Ok, that is the same as what this 125/250V drawing at the bottom shows:

http://www.leviton.com/sections/techsupp/diagrams2.htm

So, when you run the wire in the attic, should you run it under the insulation like it is now along the interior ceiling framing or can you run it up along the framing of the roof to avoid digging in insulation but paying the price in a longer wire run? Is there a correct way?
I think this is the type of wiring you want:<br>
<img src="http://phil.ipal.org/electric/nema-06-wiring.gif">
 
  #9  
Old 07-21-04, 07:30 PM
Valk1500
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220V run to garage?

The house has a folding ladder that folds into the ceiling, so what rule do you go by to run the romex in this case?
 
  #10  
Old 07-21-04, 07:50 PM
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Guard boards for all wiring.
 
  #11  
Old 07-22-04, 07:55 PM
Valk1500
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15 Amp draw 230volt Compressor

Do I use a 15 amp breaker for a 230volt compressor that draws 15 amps, or should you use a bigger breaker?
 
  #12  
Old 07-22-04, 08:24 PM
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Originally Posted by Valk1500
Do I use a 15 amp breaker for a 230volt compressor that draws 15 amps, or should you use a bigger breaker?
Is that the 5 HP compressor you first posted about? 5 HP is a lot of power and I would think it would draw even more than 15 amps at 120 volts. Can you get the nameplate ratings on it (HP, watts, volts, amps, whatever it says). It can draw a lot more when it first starts, varying depending on the present line pressure it is compressing against. But it seems to me you need something more than 15 amps. I think it might need 20 amps. And of course the wiring needs to be 12/2 or better.
 
  #13  
Old 07-23-04, 04:39 AM
Valk1500
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I went to a bigger compressor 230volt 15 Amp, dont have it yet.

With the bigger tank I will have less motor run time, cycling the motor less.

http://www.harborfreight.com/cpi/cta...emnumber=32357
 
  #14  
Old 07-23-04, 04:53 AM
mgb
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You need a 2-pole 20 amp breaker.
 
  #15  
Old 07-23-04, 06:33 PM
Valk1500
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6-20 receptical

Do I use a 20amp outlet also?
 
  #16  
Old 08-20-04, 06:58 PM
Valk1500
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220V run to garage?

Ok, that was a lot of work, and it sure would be better to do in the winter! Must have been 120 degrees up there...

Anyway the run (hard part) is done just need to tack it all down.

Thanks for the help. Compressor runs like a champ.
 
  #17  
Old 08-20-04, 09:12 PM
Homer Simpson
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Points to consider

Valk,

Some points to consider. I guess the 110 wasn't a reference to voltage.
Any motor over 1500 watts runs more economically on 220V.

I don't know without looking these things up, what a 5hp motor need in term
of conductor size for the length of run to and from and overcurrent protection.

But, when you run a conductor in a hot attic you may have to derate the
ambient capacity of the wire in the tables and go to a larger wire. Heat and
electricity don't go together well. The hotter the wire the more current flow
is reqired, the more current flow the hotter the wire get. A cycle. Some attics get to 145 deg
and hotter depending on roof covering. Just some thoughts. Say goodbye, Homer. Goodbye
 
  #18  
Old 08-21-04, 07:52 PM
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The compressor referred to is not a 7hp, or even a 5hp motor. It is one of those "max developed" horsepower ratings. A true 5hp motor draws well more than 14 amps, which is what the Harbor freight site states for this unit. The only correct way to wire this unit is to use the actual amperage input (14 amps).

"Any motor over 1500 watts runs more economically on 220V."
Homer, can you explain this one to me?
 
  #19  
Old 08-24-04, 03:54 AM
rlrct
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Bump ...

"Any motor over 1500 watts runs more economically on 220V."

Homer - I'd be interested in why this is true, too. Motor theory isn't one of my strong points.
 
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