Hardwiring 230VAC Compressor Question

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 before proceeding.

*[I have copy of the NEC 2002 Codebook in case anyone needs to reference it].

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 panel: Blk/Red =209VAC Blk/Wht =120VAC Red/Wht =120VAC 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'.

Questions:

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 30amps 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 ground wire??? 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.

-N.

I have the current NEC codebook but am still perplexed. Thanks for any clarification.

Reply to
N.
Loading thread data ...

On Tue, 2 Dec 2003 10:10:12 -0800, N. wrote (in message ):

I have no knowledge of NYC local codes, but as far as the national code goes:

  1. Yes
  2. A double breaker is required. 30 Amp would be correct for #10 wire.
  3. The ground is through the shell of the BX cable. If your flex does not complete the grounding path a bonding wire must be installed. A copper lug in the panel is not necessary, I am unclear as to if the panel is your "Service entrance" or a subpanel. If a subpanel a lug is NOT allowed.
  4. Correct.

Roger in Vegas Worlds Greatest Impulse Buyer

Reply to
Roger Hull

Not quite. If it is a subpanel, bonding the grounded conductor and the grounding conductor is not allowed. It is common for a subpanel to have a ground bar bonded to the panel (the panel is required to be bonded to the grounding conductor, but that happens through the BX shell as pointed out in this case).

The NEC no longer allows the armor on some armored cables to be used as the grounding conductor. This typically applies to flexible metal conduit, but may also apply to BX armored cable. Check the book.

scott

Reply to
Scott Lurndal

On Tue, 2 Dec 2003 18:08:53 -0400, Scott Lurndal wrote (in message ):

Regarding service panels: The basement houses the 'Main Service Feed Panel' for the building. I live on the 4th floor, and I have a 'Breaker Panel' that is fed from that main panel: a Greenfield cable rises 4 floors and enters my 'Breaker Panel'...it is the ONLY panel in my living space. Nomenclature: does this 'Breaker Panel' generally qualify as a 'subpanel', or conversely, would a 'subpanel' be the nomenclature for any additional breaker panel installed along a new circuit I run downstream from my 'Breaker Panel'?

Yes, I had assumed the ground to be the shell of the BX cable...there is no 'ground bar' in my breaker panel. In my space, none of the receptacles have a ground wire .... I assume the BX cable itself to be the ground.

Regarding grounding the motor to the 'Breaker Panel': I was thinking the BX/Flexible Metal Conduit would suffice, but I had purchased a little copper screw/terminal to screw to the 'Breaker Panel" (refering to it as a 'lug' in my initial post). I'm still a little unclear as to general grounding/bonding practices, and was wondering if the BX was sufficient for the ground in my circuit, or if I would need to install a seperate green ground wire off the 'lug' from the 'Breaker Panel' and connect that to the motor.

When the electrical upgrade was made, the contractor installed a new receptacle and ran BX back to the 'Breaker Panel"...there is no seperate ground wire in this circuit, so, yes, I'm assuming the BX is functioning as the ground. What are the views on the best way for me to execute the ground for this motor circuit?

Thanks again.

-N.

Reply to
N.

Any breaker panel that is fed from another breaker panel is a subpanel. There is only one "Service entrance" panel and it is fed from the power company lines. The panel in your living quarters sounds like a subpanel and is fed from the service entrance somewhere else in the building. As to running an additional green wire from the motor to the panel, it is not necessary by code but will do no harm (Except to confuse the next occupant :)

Reply to
Roger Hull

BX is a lot different than Flexible Metal Conduit. Run the separate ground. When you install the lug in the subpanel scrape the paint off the back of the subpanel behind the lug.

Reply to
ATP

On Tue, 2 Dec 2003 22:16:38 -0400, ATP wrote (in message ):

Good idea. Thanks to all for the assistance.

I have one last question. As long as I'm running the circuit into the room the compressor is in, I figure I might as well throw in an additional 120VAC recep while I'm at it. This would be for running other shop stuff, likely when the compressor ISN'T running. What would be the simplest method? Can I branch off one of the 120VAC wires going to the compressor (either the red or black) either before or after it enters the compressor's switchbox, and then run it down to a standard dual 120VAC three prong wall receptacle Of course I would have to run a white neutral wire off the subpanel to complete the wiring to the recep.

I could always just run a completely seperate 120VAC wire and a white nuetral wire from the subpanel and put them on a dedicated breaker to provide juice to the recep. I just figure it would be easier to run both the 120VAC recep and the compressor motor off the same circuit.

Is that kosher? Thanks.

-N.

Reply to
-n.

On Tue, 2 Dec 2003 16:56:23 -0400, Roger Hull wrote (in message ):

Roger, what sort of purchases are we talking about to have won the title?

-N.

Reply to
-n.

Roger Hull wrote in news: snipped-for-privacy@nntp.velocitus.net:

If the panel you refer to is your service entrance, you *SHOULD* have a bare #6 min/#4 preferred BARE ground wire running from the terminal block which the white wire connects to a ground rod outside your building. This provides the earth ground. As for your installation: Typically, you will use a double breaker, 30A for #10 wire. Pull 3 wires, 1 red, 1 black and 1 bare from your panel to the disconnect box, and the same to your compressor. Red to one hot side, black to the other and ground to the ground lug on the compressor. The ground must also attach via screw, to the disconnect box (if using metal box) This bare ground should connect to the neutral/ground terminal strip in the service panel. In combination with the ground rod/#6/4 wire this provides a direct earth ground for the compressor.

Reply to
Anthony

On Wed, 3 Dec 2003 1:27:37 -0500, Anthony wrote (in message ):

The breaker panel in my residence does have a terminal block that the white nuetral wire connects to (the largest white wire that comes from the main service panel in the building's basement), and is also where all the white neutral wires for the various circuits in my residence also terminate (but no bare wires connect to it...indeed, there are no bare wires in my breaker panel). Are you suggesting that this terminal block is where I should connect the bare ground wire to (instead of just connecting to the panel itself)?

Thanks.

-N.

Reply to
-n.

No. You could accomplish the same thing by running a small feeder to a subpanel, but you cannot piggyback a receptacle load on a hot leg running to a piece of equipment. BTW, the hot legs are not really 120 VAC, that is the phase to neutral potential but you are using phase to phase and the phase to phase potential is what is important here. If you have 210V between phases you may have a 120/208 three phase service to the building, a single phase service would give you approximately 240 hot leg to hot leg, yet the legs would still be 120V to neutral. Calling them 120 V legs implies an additive relationship when you put them together which does not really exist, it only appears to exist in center tapped single phase systems because of the symmetry involved.

Reply to
ATP

-n. wrote in news: snipped-for-privacy@news.verizon.net:

Obviously this system is grounded through the conduit (not my preference, but ok) In this case, the metal flex conduit from the breaker panel to the disconnect box obviously serves as ground path. You will probably need a bonding wire (bare or green) from the ground lug on the compressor to the ground lug on the disconnect box (the actual box itself).

Reply to
Anthony

Especially because the wires going to the compressor will be protected by a 25 or 30 amp breaker. You want the 120 receptacle to be on a 15 or

20 amp breaker.
Reply to
Bob Engelhardt

RE: Subject

Some where in this thread, 209V was noted as a measured voltage.

If that data is in fact true, you may be getting two legs and a neutral of a

208Y/120V, 3 phase service.

If that is true, you will almost certainly burn up a 240V motor unless you also install a buck-boost transformer for the 240V motor.

BTW, 208Y/120V is quite common in commercial buildings.

Be a good idea to reconfirm your supply voltage.

Reply to
Lew Hodgett

Although 208/230 motors are pretty common, he should check the nameplate.

Reply to
ATP

On Wed, 03 Dec 2003 10:06:45 GMT, -n. put forth the notion that...

Never connect a ground wire to the neutral bus bar in a subpanel. Your ground has to connect to the can, preferably by using a ground lug bolted to the back of the panel.

Reply to
Checkmate

According to Ingersoll Rand (I am a dealer) you CANNOT run a compressor with a motor designed for 230v AC on a 208v circuit. IR sells a special 208v motor for those installations. You have to order it with the correct motor on it.

We've tried using the standard 230v motor and had problems with them overheating and shorting out. It will run for a while, but eventually the motor will fail.

We are seeing more and more 208v in our area instead of 230v. I'm not sure of the reason, but most newly constructed areas are being serviced with

208v.

Rick

Reply to
Rick

Rick, do you know what RPM motor I should be using on an older Ingersoll-Rand Type 30 Model 234C4?

Reply to
Jim Kovar

On Sat, 6 Dec 2003 08:24:57 -0600, Rick put forth the notion that...

It's a simple matter to get a 240/24 volt transformer, and wire it up in a boost configuration. This will turn 208 volts into 230.

Reply to
Checkmate

-n. wrote

You are nuts to get your electrical wiring information from this group. In the past some of the information I've seen posted is downright dangerous, a lot is just plain wrong, some misguided, some pertains to other jurisdictions or situations or is out of date, some makes no economic sense. A small part is good sound advice from knowledgable professionals who are up on current code. So how do you sort it out? Hire an electrician.

mike

Reply to
Mike

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