Single Phase motor controled by 3 phase contactor

[ryguy1116]

I have a 120VAC 6amp non reversing motor to control.

I dont know how to wire it to a three pole contactor normally used for a 3phase motor. I have the correct size contactor from the manufacuture's data table for single phase use.(allen bradley 100-C09) Does this mean I only wire one pole? Do I jumper all three pole together?

I also dont know how to size an overload.

Is this the correct way to control a single phase motor in a comercial enviroment?

Thanks for the help.

 

[motorsdirect]

If this is a contactor and overload setup, the usual way is to run a line through two of the poles, so that the heaters in the overload unit work equally.
I.E: your inputs are labelled 1-3-5 and your outputs from the overload are labelled 2-4-6....you would put a link wire between terminals 3 & 6 ...then your supply wires would go to terminals 1 & 5 .....and your motor leads would go on terminals 2 & 4.
hope this helps

Jeff

http://www.motors-direct.co.uk

 

[DRWeig]

Hiya RYGuy,

Jeff gives good advice on wiring. From the amps, you're less than one horsepower and obviously automatically started. If for continuous duty, NEC 430-32(c) applies. You size your overload for 125% of nameplate FLA IF it has a service factor 1.15 or greater OR IF marked with a temperature rise not over 40 degrees C. Otherwise, size at 115% of nameplate FLA. Other exceptions might apply too -- IF your motor is thermally protected internally, or impedance protected against overload, you don't need separate overload relays and can leave the overload relay out of the circuit.

If you do need overloads, your local electical parts distributor probably has a chart from his supplier to choose the proper ones. Take in all the nameplate data, including FLA, service factor, and temperature rise.

Let us know what you wind up doing!!

Old Dave

 

[buzzp]

Just remember that the NEC OL settings are the maximum. NEMA MG generally suggests lower OL settings than the NEC. Ultimately, the manufacturer is the best source of this setting.
The NEC worries about safety (could care less if motor gets damaged) and NEMA worries about protecting the motor (with safety in mind as well).

 

[jraef]

If, on the other hand, it is just a contactor with no overload, it is perfectly OK to wire just one leg of the 120VAC through one pole of the contactor. You could leave the other contacts as "spares". It is not necessary to break the neutral since it is common to the ground anyway. There is however an advantage to wiring all 3 poles together in parallel. The contact material will last longer.

"Venditori de oleum-vipera non vigere excordis populi"

 

[DRWeig]

Thanks BuzzP, your comment on the MG standard is a good one. The NEC is more concerned with fire prevention than good practice to protect utilization equipment.

I hate learning new stuff at this age...

Old(er) Dave

 

[buzzp]

Anytime. Not many people understand that the NEC is the max settings, not necessarily the recommended settings.
Another big confusion is that "SF" applies to HP and not amp draw. If it is "SFA" or similar then amps is applicable. Just thought I would throw that out too.