Finally (!) after a two year wait, my building received hookup of the
second leg of an electrical service upgrade (delay was due to asbestos
contamination issues)...I now have 220VAC availible. Time to hookup my
5HP/80 gallon IR compressor!
I have a question regarding grounding that I need to be clear on
*[I have copy of the NEC 2002 Codebook in case anyone needs to
Here's the hardware configuration:
-Compressor Motor: 5HP/230VAC/ 1 Phase/ 22.5 FLA
-Electrical Service Panel:
We have BX metal cable in this building which is the local NYC code.
The breaker panel in my place has as the main feed a metal Greenfield
conduit entering it: the Greenfield carries three wires,
white/red/blk. There is NO green ground wire anywhere in this panel.
Red connects to one side of the breaker terminal. Black connects to
the other side of the breaker terminal. White goes to a seperate
non-breaker terminal, and I am assuming the white is thus neutral.
Here are the voltage meter readings I get when testing at the breaker
Wht/Service Panel = 0.29 VAC
Blk/ Service Panel = 120VAC
Red/ Service Panel = 120VAC
I intend to run BX cable from the service panel to an enclosed metal
switchbox: and then a short length of Liquid Tite Flexible Metal
Conduit from the switchbox to the compressor motor. I am using 10guage
wire for the circuit. Total length of the circuit from panel to motor
is approx. 20'.
1) Will a 230VAC single phase motor run OK on 210VAC service?
2) I need either a Duplex Breaker, or 2 Single Breakers to control the
circuit. What should each pole of the breaker be rated at? Is 25 or
correct? Do I need any special 'motor type breaker'?
3)The motor has terminals for 2 wires and 1 ground wire. From my
understanding I can run the Red (120VAC) & Blk (120VAC) from the
breaker panel to the switchbox, and then from the switchbox onto the
motor to their respective terminals. However, what do I use as a
Can I put a copper grounding screw/lug into the service panel box and
run a green ground wire off of that and use it as my ground?
4) There is no need to utilize the white wire in this circuit, correct
(unless I decide to place a 120VAC outlet somewhere on the circuit?
Thanks a bunch.
I have the current NEC codebook but am still perplexed.
Thanks for any clarification.