A lot of packaged roof top units are using Regal Beloit’s X-13 E.C.M. motor to raise the overall efficiency of the equipment and to improve the S.E.E.R. ratings on the units. These are used primarily on small packaged units under 5 tons.
Some of these small units are 3-phase units but the only component in the unit that is 3-phase is the compressor. All other components, including the X-13 motor are 208/230 single phase.
As you are all aware of — 208/230 3-phase comes in 2 “varieties”. In most areas of the country, when you check each incoming power leg to ground, you read 110/110/110 volts and 220 across each pair. BUT — in some areas the power has a wild or stinger leg so when your read each leg to ground you get 110/110/220 volts but still read 220 volts across each pair.
The power supply with the wild or stinger leg can cause some operating problems with the X-13 motor. Since the motor is a “constant torque” E.C.M. motor, both power legs to the motor must be the same. If the motor is connected to the wild or stinger leg, the motor will not function properly. It may “hunt” or it may not run at all.
The solution to this occurring is to move the wild or stinger leg of the power so the motor is not attached to it. The motor has to be attached to the same voltage to ground on each connection of the motor. Of course you will need to verify the compressor rotation if you have a scroll compressor, and, if it is running backwards, you can change any of the 2 non-wild or stinger legs to correct. You can also just change any 2 leads at the compressor since this is the only 3-phase component in the unit in most cases.
So, if you have a unit with an X-13 motor and the motor won’t run or is causing erratic operation of the motor, verify if you have the wild or stinger leg in your power supply, and if you do, make sure the motor is not connected to it.
If this does not correct the problem, then you will need to do additional diagnostic as to why the motor isn’t running but this should be the first thing to check, and it will solve a lot of problems with the X-13 motor.
Attached is a diagram showing the proper power wiring to an X-13 motor.