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#83735 - 02/18/03 08:25 AM 4 conductor wire with 3 conductor plug
rayb Offline
Junior Member

Registered: 02/18/03
Posts: 7
Loc: Carlisle, MA USA
Hi All,

Sorry to waste nandwidth but I have been unable to find an answer to this. I am hooking up some 230V woodworking machines and have 2 questions:

1) The NEC implies that each motor over 1HP needs its own protected circuit - Is that true for a 'one user shop' i.e. can I have my frequently used 2HP dust collector and my infrequently used 2hp jointer on the same 220v circuit?

2) When wiring the 220v only machines - The machines have 3 conductor plugs - I pulled 10/3 wire - what do I do with the unused conductor - do I just tie it off at the machine, connect it at the box, not connect it ???

TIA

Ray Bahr

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#83736 - 02/18/03 11:30 AM Re: 4 conductor wire with 3 conductor plug
Len_B Offline
Member

Registered: 01/19/03
Posts: 56
Loc: New Hampshire
rayb,

As long as the motors have internal thermal overload protection you may install them on the same circuit (assumes 2 x 2hp = 24amps, which is 80% of 30 amp breaker protecting #10awg conductors)
My recommendation would be to install 30amp receptacles, and cord and plug connect the tools.(no one piece of equipment may draw more than 80% of cicuit capacity)
The unused conductor should be wirenutted and/or securely taped at both ends.

Len

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#83737 - 02/18/03 11:48 AM Re: 4 conductor wire with 3 conductor plug
rayb Offline
Junior Member

Registered: 02/18/03
Posts: 7
Loc: Carlisle, MA USA
Thanks Len,

So, I will pull a 10/3 circuit for my DC and Jointer with a 30A breaker, and I will wire nut/tie off the unused wire.

Ray Bahr

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#83738 - 02/18/03 01:41 PM Re: 4 conductor wire with 3 conductor plug
CDN_ELECTRICIAN Offline
Member

Registered: 01/22/03
Posts: 75
Loc: Concord,Ontario,Canada
I believe to answer your question properly you have to identify the Hp of each motor and # of phases for each.

You imply one is single phase and the other three phase?

If so you cannot use a 3 pole breaker to protect a 2 pole load (breaker may not see full fault and trip)

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#83739 - 02/18/03 01:58 PM Re: 4 conductor wire with 3 conductor plug
rayb Offline
Junior Member

Registered: 02/18/03
Posts: 7
Loc: Carlisle, MA USA
Sorry for the confusion. Everything is single phase

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#83740 - 02/18/03 03:16 PM Re: 4 conductor wire with 3 conductor plug
txsparky Offline
Member

Registered: 05/25/01
Posts: 578
Loc: Magnolia,.Texas U.S.A.
 Quote:
I pulled 10/3 wire - what do I do with the unused conductor -(first post)

{2nd post}So, I will pull a 10/3 circuit
_________________________
Donnie

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#83741 - 02/18/03 03:27 PM Re: 4 conductor wire with 3 conductor plug
sparky806 Offline
Member

Registered: 12/07/02
Posts: 59
Loc: Shawnee, KS, USA
The unused conductor needs to be bonded at both ends.

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#83742 - 02/18/03 03:38 PM Re: 4 conductor wire with 3 conductor plug
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
 Quote:
The unused conductor needs to be bonded at both ends.


I have never heard of this can you name the code?
Bob
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#83743 - 02/23/03 01:04 PM Re: 4 conductor wire with 3 conductor plug
Hutch Offline
Member

Registered: 05/27/02
Posts: 383
Loc: South Oxfordshire, UK
Sorry, I may have missed something here but if these are 240V circuits only and not 120/240V ones, why not use 10-2 instead. Casual enquiry shows a cost saving of around 30%. Paint or tape the exposed white wire black (200-7 Exception 1).

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#83744 - 02/23/03 05:35 PM Re: 4 conductor wire with 3 conductor plug
rayb Offline
Junior Member

Registered: 02/18/03
Posts: 7
Loc: Carlisle, MA USA
Actually for 2 reasons:

1) I have the 12-3 wire.
2) If I ever move things around and decide to run 120/240v circuits I will just need to hook up the 'spare' wire.

Ray Bahr

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