ECN Forum Forums Code Related Discussion NEC & other Code issues 4 conductor wire with 3 conductor plug

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

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

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

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)

Sorry for the confusion. Everything is single phase

The unused conductor needs to be bonded at both ends.

I have never heard of this can you name the code?
Bob

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).

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