Air Compressor wiring help

[cncjerry]

I just got a new to me speedaire compressor and tank and I need some help wiring the motor and pressure switch. This is the motor and pressure switch I plan on buying
motor
switch
Here is my problem the motor has a capacitor start and run on it so I don’t need a motor starter the motor draws 19.5 amps @ 240 volts the pressure switch can only handle 2hp @ 240 volts so it looks like I need to wire in a relay and I don’t know what type of relay to buy anyone have any suggestions a link would be helpful.

 

[PAToyota]

I'd get a pressure switch that handles the capacity of the motor.

 

[cncjerry]

I'd get a pressure switch that handles the capacity of the motor.

I wish it were that easy i cant seem to find one big enough i think i found my solution i got a good deal on a 3ph coil motor starter and i can use only two of the starter legs then a 110 leg for the pressure switch to activate the coil of the stater.

 

[PAToyota]

Hmmm... Here is what I have on mine: http://ecatalog.squared.com/catalog/173/html/sections/20/17320013.html#1013485

But looking through the specs they don't have any for over 3hp on 220V (as you said).

I'll take a look at the part number on the one on my 5hp compressor (Quincy - came with the switch) and get back to you.

 

[wilbilt]

I would just use the starter you have, and use the pressure switch to control it.

 

[TNToy]

It'll be interesting to see how much the mfg's have been over-stating the size of their motors.

If a "5HP Compressor" can use a switch that's only rated to a 2HP load, well...

 

[Charles (in GA)]

I just got a new to me speedaire compressor and tank and I need some help wiring the motor and pressure switch. This is the motor and pressure switch I plan on buying
motor
switch
Here is my problem the motor has a capacitor start and run on it so I don’t need a motor starter the motor draws 19.5 amps @ 240 volts the pressure switch can only handle 2hp @ 240 volts so it looks like I need to wire in a relay and I don’t know what type of relay to buy anyone have any suggestions a link would be helpful.

This is exactly why you need a motor starter. Virtually all five horse and up compressors use a motor starter and a small pressure switch that controls the starter (which isn't anything more than a relay with a thermal limiter in it also.)

The compressor should have had one made on it.

Charles

 

[Charles (in GA)]

It'll be interesting to see how much the mfg's have been over-stating the size of their motors.

If a "5HP Compressor" can use a switch that's only rated to a 2HP load, well...

If they are packaged together (which he DID NOT say was the case) it is because they expected you to use a motor starter (bought as an option) to control the motor and the pressure is only expected to control the starter.

19+ amps is a true 5 hp motor.

Charles

 

[W-Cummins]

Yes as Charles sugested, run a correctly sized motor starter for that size motor. You will want a contactor/starter that has a 240V coil on it, other wise you will need a control transformer to run the coil @ 120V or I guess you could run a 4 wire circuit to the compressor). If you do other wise your just asking for problems with it.

I don't know if I would use the motor you have listed in the link. The motor is a strange (for 5 hp) framed motor (56h) and may or may not fit your tank/base or the pulley sheves. If your compressor was a true 5 hp model it probably had a 184 frame motor on it and you will want to replace it with another 184 framed motor.

William.....

 

[cncjerry]

Thanks for all the replies the motor I listed was just for an example it is probably not the motor I will buy. I am going to use the motor starter I posted previously it has a 120 volt coil contactor in it I should be able to run a line from one leg of the 220 to the pressure switch then from the pressure switch to the contactor coil.

 

[cncjerry]

Ok I finally got around finishing this project and I can’t quite seem to figure out the wiring for the starter. The one I am using is a take off from a 3ph 10hp air compressor it is a Siemens 3tf44 I kept all the wiring the same from the 3ph except I ran the wire from T1 to L2 exactly as shown in the first pic now my problem comes in with the way the switch is wired when I apply power I am getting 120 volts to all four leads to the switch so I figure that can’t be right the first pic is the way it is currently wired will what I have drawn in the second pic work?
The most information I could find was taken from this site How to wire a motor starter
pic1

pic2


Thanks Jerry