Wiring an Air Compressor

Hi Guys,
Below is a message I posted on the metalworking newsgroup. I am hoping the
soemone can help me with the wiring to the motor, magnetic starter and
pressure switch.
My sincerest thanks for the help.
I got my hands on a 1972 80 gallon 2 stage compressor. The pump is a Quincy
model 325 13. I understand that this is the compressor on their QR series
machines. It is in great shape, has a 5 HP Single Phase Motor and a
magnetic starter. All the wiring has been removed.
Here are some questions I hope you can help me with:
What order does the unit get wired in? Is it line voltage to - pressure
switch to magnetic starter to motor?
What kind of oil should I use?
It is missing the air filter assembly, where can I purchase a new one?
Where would I get repacement drive belts?
My sincerest thanks.
Reply to
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I have no clue to you exact unit. Typically Line 1 will land at the top of the starter and splice off to the pressure switch. From the pressure switch it comes back to the 120 volt coil,,,, I AM guessing. Coil could be 220 volt. Line 2 would also land on the top of the starter. Be sure to ground all metal surfaces. Some where near the unit there should be a safety disconnect switch, in series where may be an on-off switch.
Oil type should be stated on the unit.
Belts are easy, measure the width, depth, and length and go to a real parts house. IF there are several belts make sure that your buying matched belts if your planning on having this running for long periods of time.
Reply to
I am hoping the
starter and
You really do need a diagram, and the right sized over-load heaters with the magnetic starter... ' those are amperage rated and should be sized about 5% over the max amperage rating for the motor on the exact voltage you will be running it on...all that should be on the name plate..you will need to know if you have 208, 220 or 230 volts.
take the motor info with you to an electrical wholesaler that sells the public... ask for a cheap magnetic starter with heaters rated for it, the miniature ones are the cheapest....and coil voltage to match the motor voltage. the magnetic starter is going to cost you... 150 dollars or more.
the mag starter will come with wiring instructions...put the pressure switch in series with the coil... the motor power goes into the top of the mag starter and out the front or bottom depending on which you get.
but without the diagram for the mag starter you will be in trouble.
You could also skip the mag starter entirely and wire one hot line through the pressure switch to motor and the other to the other motor lead.
the switch has to be rated for the amp draw of the motor... 5 hp single phase might be a little heavy for your switch..a heavy amp rated pressure switch will probably cost you 75 dollars.
In your application a mag starter is not completely necessary. Buy or borrow a clamp around type amp meter so you can verify the full load amperage when the motor is running... if its within range its probably wired right.
Protect the motor with a fused disconnect if you want...use dual element time delay fuses, sized 10% over the FLA rating of the motor (running amps).
good luck with your business
Phil Scott
pump is a Quincy
their QR series
Motor and a
to - pressure
a new one?
Reply to
Phil Scott
My sincerest thanks for your help. Are there any disadvantages to wiring the compressor without a magnetic starter?
Thanks again.
Reply to
disadvantages to wiring
You lose over load heater protection for the motor..but with fuzed disconnect added you get the same protection.
Myself Id just size the breaker a little tight and forget about it...its a fairly slight burn out the motor risk over time... if you check the amps on start up and those are in range you will be good until after a 10,000 hours of run time on the motor... then as its windings go south overload heaters might work... you would still need a new motor though..and 5hp single phase motors can cost a lot.
If your application is not requiring all that high of volume of air..say for occasional use only, the tank will handle any surge demands you could go to a vastly cheaper 2 hp motor...then cut the motor pulley size diameter in half.
The compressor would last forever that way. Make sure you pulley is small enough that you dont exceed full load amps on the motor.
your current pressure switch will probably handle one leg of the motor feed..
Mag starters are used primarily for large single phase (yours) and all three phase motors (sometimes without over loads, relying the circuit breakers, a bad idea).
Ye welcome... I needed the distraction from my current brain twisting project... I gots the numberin' all screwed up... Sensor #1 feeds input #9 and outputs to output #3... not smart. ... but thats how it all mish mashed together..
Phil Scott
need to
motor... 5
Reply to
Phil Scott
PS if you go to a 2 hp motor make sure its a high torque model made for compressor use..... if you are going to use the thing much spend the extra 50 bucks and upgrade to a heavier duty motor (not higher HP, just heavier duty rated.) then Id buy the new half diameter pulley for it at the same time so it fits the shaft, an adjustable pulley would be the hot set up....and if you get it from Granger (dont buy dayton brand btw) get one of their ultra slick adjustable bases for it..that way you keep the belts tight no problem. Get a GE motor, or a US motor... the new off breed chinese ones can be real dicy...and though many say dayton is fine... 40 years in the business proves to me otherwise.
Phil Scott
Reply to
Phil Scott

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