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4 conductor wire with 3 conductor plug #83735
02/18/03 11:25 AM
02/18/03 11:25 AM
R
rayb  Offline OP
Junior Member
Joined: Feb 2003
Posts: 7
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

2017 / 2014 NEC & Related Books and Study Guides
Re: 4 conductor wire with 3 conductor plug #83736
02/18/03 02:30 PM
02/18/03 02:30 PM
L
Len_B  Offline
Member
Joined: Jan 2003
Posts: 53
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

Re: 4 conductor wire with 3 conductor plug #83737
02/18/03 02:48 PM
02/18/03 02:48 PM
R
rayb  Offline OP
Junior Member
Joined: Feb 2003
Posts: 7
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

Re: 4 conductor wire with 3 conductor plug #83738
02/18/03 04:41 PM
02/18/03 04:41 PM
C
CDN_ELECTRICIAN  Offline
Member
Joined: Jan 2003
Posts: 73
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)

Re: 4 conductor wire with 3 conductor plug #83739
02/18/03 04:58 PM
02/18/03 04:58 PM
R
rayb  Offline OP
Junior Member
Joined: Feb 2003
Posts: 7
Carlisle, MA USA
Sorry for the confusion. Everything is single phase

Re: 4 conductor wire with 3 conductor plug #83740
02/18/03 06:16 PM
02/18/03 06:16 PM
T
txsparky  Offline
Member
Joined: May 2001
Posts: 552
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
Re: 4 conductor wire with 3 conductor plug #83741
02/18/03 06:27 PM
02/18/03 06:27 PM
S
sparky806  Offline
Member
Joined: Dec 2002
Posts: 59
Shawnee, KS, USA
The unused conductor needs to be bonded at both ends.

Re: 4 conductor wire with 3 conductor plug #83742
02/18/03 06:38 PM
02/18/03 06:38 PM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
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
Re: 4 conductor wire with 3 conductor plug #83743
02/23/03 04:04 PM
02/23/03 04:04 PM
H
Hutch  Offline
Member
Joined: May 2002
Posts: 381
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).

Re: 4 conductor wire with 3 conductor plug #83744
02/23/03 08:35 PM
02/23/03 08:35 PM
R
rayb  Offline OP
Junior Member
Joined: Feb 2003
Posts: 7
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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