Wiring Air Compressor

[OldracerJones]

I'm trying to wire up my Sears Air Compressor. It's a 240V, single phase with a white, black and green wire coming out of the motor going to the pressure switch box. (See photo 1)

My circuit breaker box (sub-panel) has a 50 amp circuit breaker that is not being used. it's a double pole with white, black and bare copper wires. The bare copper goes to the bus bar and the white and black each come out one side of the breaker (see photo 2).

My compressor is two feet away from the brekaer box so I should not need a disconnect as i can just use the breaker.

I think I need to connect the white from the breaker to the white connector above the white from the motor and the black from the breaker to the black connector above the black wire from the motor. The ground would ground to the screw on the case in the pressure switch box. I would need to mark the white with black tape to show it was hot.

Does this sound right? Can't find any diagrams for any of the Sears stuff.

 

[nkachur]

Everything sounds right. Definately cover up the white wires with red / black.

 

[duude]

I'm trying to wire up my Sears Air Compressor. It's a 240V, single phase with a white, black and green wire coming out of the motor going to the pressure switch box. (See photo 1)

My circuit breaker box (sub-panel) has a 50 amp circuit breaker that is not being used. it's a double pole with white, black and bare copper wires. The bare copper goes to the bus bar and the white and black each come out one side of the breaker (see photo 2).

My compressor is two feet away from the brekaer box so I should not need a disconnect as i can just use the breaker.

I think I need to connect the white from the breaker to the white connector above the white from the motor and the black from the breaker to the black connector above the black wire from the motor. The ground would ground to the screw on the case in the pressure switch box. I would need to mark the white with black tape to show it was hot.

Does this sound right? Can't find any diagrams for any of the Sears stuff.

Where are the black and white coming from the breaker feeding now? Or is it being back fed from the load side of the 50a breaker? Ultimately you will connect the 2 legs from the 2 pole breaker to the two hot inputs of the motor via the switch and tie the ground down to the system ground. Not sure of teh code where you live, but it may be fine to use the panel as a disconnect if it is in sight/reach. It is a good idea to tape the white w/bkl tape.

 

[OldracerJones]

The circuit was for a hot tub that is no longer there? I'm going to disconnect them, put new wires in and run to the compressor.

 

[Tom in Seattle]

While you are disconnecting the hot tub wiring you should change the breaker to the correct size. I doubt the compressor needs a 50A circuit. If you do leave the 50A breaker in place you'll need to run 6/2 wire. I think that's special order at the big box stores. You may only need 12/2 and a 20A breaker.

Also, since you say this is a subpanel the neutral and ground wires MUST go to separate buses, otherwise you'll have neutral current flowing back to the main panel through the ground wires. The panel bonding screw should NOT be attached. You may need to add another bus bar for the grounds.

 

[OldracerJones]

Hooked it up and it is working great. 10/2 wire didn't get warm at all during 30 minute warm up run. I did not change the breaker, is it critical to do so?

 

[nkachur]

The breaker is designed to protect all downstream components for the circuit. If the breaker will not trip on the circuit being overloaded / shorted the downstream components could overheat to the point that a fire develops. It is in your best interest to have a breaker that is rated for the circuit that you are protecting.

 

[OldracerJones]

Thanks for the help. Changed the breaker to a 30 amp, no problems on start up.