What is the Difference Between a 42 and 48 Frame Direct Drive FHP Motor? | Regal Rexnord

There are many rated dimensions for each frame rating. However, only two of these ratings commonly apply to FHP direct drive motors.

The two dimensions that commonly apply to 42 and 48 frame FHP direct drive motors are the “U” dimension (shaft diameter) and the “BD” dimension (the width or diameter of the motor.)

Common 42 frame FHP direct drive motor dimensions include:

• Motor = Approximately 5” diameter
• Shaft = 3/8” diameter

Common 48 frame FHP direct drive motor dimensions include:

• Motor = Approximately 5½” diameter
• Shaft = 1/2” diameter

You may also have noticed that some frame ratings are followed by a letter. This is the NEMA frame suffix. The letter “Y” denotes that the motor has a special mounting type, also referred to as a non-NEMA standard mount.

The standard mounting type for NEMA rated motors is a welded rigid base. Any motor that does not use this type of mount could be listed with the suffix “Y”.

Identifying the motor frame size, shaft dimensions and mounting type are important when replacing motors. Some of this information may be provided in the frame rating on the motor rating plate.

However, most of this information must be either measured or visually confirmed to select a replacement motor that not only operates properly but also mechanically fits the application.

And that’s a wrap on this segment of Motor Minute technical tips. Remember that we provide motor training and product information in multiple formats including videos, literature, podcasts, articles, of course Motor Minute technical tips and classroom education both online and face to face. All of this industry leading training is available at no charge to HVAC professionals at regalmmu.com. Thank you for taking the time to build your motor knowledge.