Need help with new compressor

[Kurser04]

Two years ago my uncle passed and I acquired this air compressor with the intent of eventually using it in my garage. I just got some funds together and now have a new breaker box in the garage with the 220 needed.

My questions are:
1. How many amp 220 breaker should I use? At the store today the smallest one they had for my GE box was 20 amp. The motor is placarded 11amp.

2. Do I need a switch other than the pressure switch?

3. How many amp plug should I use? It has a 15 amp plug now.

4. This compressor hasn't ran in many years. My uncle was sick for a long time before he died. I don't know when he last used the compressor. Do I need to do anything before I turn it on?

 

[pattenp]

If running it at 240V and you can't find a 15A DP breaker I would just use the 20A DP breaker and #12 wire for the circuit and a 20A 240V 6-20 outlet and plug.

Edit: You don't need a separate switch. Make sure it turns by had and the pump has oil in it before putting power to it..
Do you have a Home Depot near you? I think they should have a GE 15A 2 pole.





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[Kurser04]

Thank you pattenp. I thought I might need to replace the plug with a 20amp and go that route. I was at Lowes last night and they didn't have a GE 15 amp 2 pole. I asked and they said it isn't even in their inventory. I'll try Home Depot also before I go with the 20 amp.

To be clear, I can use standard 12ga romex from the box to the outlet?

 

[Charles (in GA)]

Its a stationary compressor. Don't use a plug, just hardwire it to a disconnect.

OP needs to make doubly sure that the motor is currently set up for 240 and not 120v, since the motor can be run on either. Check all of the jumpers in the motor based on the placard on the motor to verify.

Charles

 

[Kurser04]

Thank you Charles. I think I will stick with the plug and receptacle though. It would be easier if I ever need to move the compressor. I will check the jumpers. I hadn't thought of that. I just assumed they were good.

 

[Charles (in GA)]

Well, using a plug and receptacle creates its own set of problems. You will have to use flex cord such as SOOW, which is fine stranded. The terminals on the pressure switch are probably designed for solid wire, the type of terminals where you shove a straight piece of wire under the edge of the screw and tighten the screw down. Now you are faced with attempting to wrap this fine stranded wire and the terminal screws and get it to stay put as you tighten it down, none of which the terminal is designed for. Other option will be to tin the wires at the ends.

Lots of code issues with plug and receptacle connection of motors over 1 hp. By using a receptacle, you are effectively creating a general purpose branch circuit.

430.42 Motors on General-Purpose Branch Circuits.
Overload protection for motors used on general-purpose
branch circuits as permitted in Article 210 shall be provided as specified in 430.42(A), (B), (C), or (D).

(A) Not over 1 Horsepower. One or more motors without individual overload protection shall be permitted to be connected to a general-purpose branch circuit only where the
installation complies with the limiting conditions specified in 430.32(B) and 430.32(D) and 430.53(A)(1) and (A)(2).

(B) Over 1 Horsepower. Motors of ratings larger than specified in 430.53(A) shall be permitted to be connected to general-purpose branch circuits only where each motor is protected by overload protection selected to protect the motor as specified in 430.32. Both the controller and the motor overload device shall be approved for group installation with the short-circuit and ground-fault protective device selected in accordance with 430.53.

(C) Cord-and-Plug-Connected. Where a motor is connected to a branch circuit by means of an attachment plug anda receptacle or a cord connector, and individual overload protection is omitted as provided in 430.42(A), the rating of the attachment plug and receptacle or cord connector shall not exceed 15 amperes at 125 volts or 250 volts. Where individual overload protection is required as provided in 430.42(B) for a
motor or motor-operated appliance that is attached to the branch circuit through an attachment plug and a receptacle or a cord connector, the overload device shall be an integral part of the motor or of the appliance. The rating of the attachment
plug and receptacle or the cord connector shall determine the rating of the circuit to which the motor may be connected, as provided in 210.21(B).

Looking at the pics of the motor, I cannot see where the motor has its own overload protection (usually a reset button on the end of the motor opposite the pulley, and the data plate usually says "Thermally Protected" or something like this.) If you have any concerns about following code for disconnect means, circuit protection, motor control (switch, starter, etc) then you will really want to consider hardwiring the motor to the circuit.

I might be overdoing this somewhat, but I'll bet the plug and receptacle stays connected for many years to come. Stuff like this doesn't get moved very often.

Charles

 

[Kurser04]

Do I need to use conduit from the disconnect to the pressure switch? Can I use standard 12ga romex?

 

[Norcal]

Do I need to use conduit from the disconnect to the pressure switch? Can I use standard 12ga romex?

Use flexible metal conduit (Greenfield) or liquid tight (my preferred) the non metallic version is inexpensive & easy to work with, NM cable "Romex®" ***** & is a poor way to do it, & solid conductors on vibrating equipment is not a good idea.


NM is required to be protected from physical damage so care must be taken in it's use.

 

[Kurser04]

Trying to find a 20amp disconnect on the Internet and having a hard time. If I shouldn't use NM wire what do I use?

 

[wyliesdiesels]

Trying to find a 20amp disconnect on the Internet and having a hard time. If I shouldn't use NM wire what do I use?

Use THHN.

And u wont find a disconnect rated for 20a.

Disconnects come in standard sizes 30a, 60a, 100a, 200a, & 400a.

U can use a disconnect rated higher than 20a just not lower.

 

[sberry]

Could use a cord too.

 

[pattenp]

Being only a 2HP motor I'd wire up a 6-20R outlet using 12/2 NM (Romex) and use 12/3 SJOOW cord with a 6-20P plug on the compressor and be done with it.

And I surely hope the motor is wired to be 240V since the plug on it currently is 240V.

 

[Kurser04]

I'm helping a friend do an annual on a plane this weekend, but hopefully I have some time in the evening to work on this compressor project. Thanks for all the help.