View Full Version : wiring 3ph air compressor

10-05-2003, 04:33 PM
I recently picked up a 15hp 3ph kellog air compressor. It appears to be in nice shape. It has a 'control panel" with fuses and an hour meter.
I have 3 ph power at my place. How difficult/complex is it to wire this into the panel? Should i get an electrician?
I can get the specs on the motor today.
The circuit where the old compressor was attached (previous property owner took it) has 3 15amp breakers tied together.

10-05-2003, 04:36 PM
"3 15 amp breakers tied together"??? How, in series? In parallel? I think it's time for an electrician, you DON'T want to mess this up.

10-05-2003, 04:36 PM
Get a good electrician, not just a house wirer.

Where are you? If you are close to North georgia I can help. Otherwise feel welcome to email. Don't sound like they had it right at the last place. Usually ONE breaker, the control transformer provides 120 or 24 volt power for the controls, or.. in a worst case the controls are line voltage. (a switch can kill you quite dead)


10-05-2003, 05:38 PM

They most likely had a 3 pole common trip magnetic breaker. I would get a commercial electrician to get it done right. Electrical equipment can be exceptionally dangerous when mishandled and not wired to code. It can also screw your building insurance up when they find an illegal wiring job burned it to the ground.

Better safe than sorry my brother.

10-05-2003, 09:04 PM
Yeah I suspected it wasnt like wiring an house outlet!
I have an electrician friend from the local navy base, ill see if i can get him over. THanks for the offer IBEW, i am in connecticut

10-05-2003, 09:52 PM
I, as Ibew would be glad to help if I can. Some of the power and control wiring can get very interesting. An industrial / commercial electrician would probably be your best bet alright. Good luck!

10-05-2003, 11:12 PM
lol, sounds to me as though merf has a normal setup. 3 phase and "3 breakers tied together". Isn't the "tie" a dumbbell or pin through the handles? Thrud has it right if he means an I*I*T breaker.

15 amps for 15 hp on 220 3 phase sounds small to me, maybe the old setup was 440. Check to be sure, motor may need re-strapping, starter may need new coil and heaters to change the voltage (if the voltage is wrong).


10-06-2003, 07:06 AM
Since 1976, I don't ever remember hooking up a compressor to a 15 amp 3 pole breaker. Could be thou.

Some 20's 30's 40's and 50's yes... Inrush on a motor while starting is about 600%.. It just lasts a few milleseconds but that is enough to trip a wrong sized breaker.

The breaker is mainly short protection for the wire, device, the overload protection should be on the bottom of the contactor in the manner of thermal overloads. Usually they are time oriented elements that melt allowing a gear to turn or a heated bimetal switch to operate.

How to size a breaker for a motor, take the motor nameplate and multiply at least 1.5, most times that will be protective and work alright without tripping. Size the wire to the breaker current also, not the motor.

I know some people on this post will scoff, but 746 watts per hp with three phase giving a efficiency of "x" 1.3 . Phase convertors are not as efficient as NORMAL 3 phase power.

Do you think the phase convertor will work with the reduced efficiency? If you use one, run a idle motor also. 3 phase is the perfect power source. Balanced.. Much easier on generators.