How is the motor mounted, and what is the diameter of its body?

Does the motor have a face mounting or is it a belly band, which is wrapped around the motor body?

What is the motor’s horsepower and amp draw?

This information is normally stamped on the original motor. If the horsepower rating is not visible, matching the amperage draw of the motor will normally suffice.

What is the applied voltage?

Is the applied voltage 115 or 230 V? This obvious mistake can cause serious problems for the service technician.

What is the required rpm?

This must be matched very closely to the original motor. For example, if the original motor is rated at 1,075 rpm, the replacement motor must be rated at 1,075 or 1,050 rpm. An rpm rating of 1,725 or 3,450 cannot be used, as it will likely overload the motor.

What is the rotation of the original motor?

Determining the correct rotation of the motor is essential to the proper operation of the system. It is quite easy to get the rotation wrong. The rotation of a motor is normally stamped on the motor’s data plate. It will be stated as being either clockwise (CW) or counter-clockwise (CCW). How-ever, this rotation is based on how the motor is viewed — from the shaft end or lead end. To make it simpler, some manufacturers include the orientation with the stated rotation. For example, a motor stamped “CWLE” means its rotation is clockwise looking at the motor from the lead end of the motor; “CWSE” means clockwise rotation looking from the shaft end.

What are the shaft’s length and diameter?

Make sure the diameter of the shaft matches that of the original motor. The length of the shaft is also a concern. However, there is some play with that number as long as the shaft is not too short. A shaft that is too long can normally be cut down to fit, if needed.

What type of bearings does it have? Does it use a sleeve bearing or a ball bearing?

All of these questions can easily be answered by examining the original motor. Not matching any one of these specifications can potentially cause problems with the motor or the system in which it is used. It is usually best to bring the original motor to the supply house to match its replacement. This enables the counter person to assist in obtaining the correct replacement.

Once the replacement motor is installed, it is a good practice to measure the amp draw of the new motor and verify that it is operating within its amperage range. The motor should also be examined after approximately 2 hours of run time to ensure that there are no other problems. This may not be practical at times, but it should be done whenever possible.

Marchese is the owner of Coldtronics of Pittsburgh, PA. He can be reached at 412-734-4433; www.coldtronics.com (website); or joe@coldtronics.com (e-mail).

Publication date: 12/02/2002