Choosing the Right Pulley for Your Belt Drive Fan

By We re still here！ | Published: 2026-10-29

Category: Buying Guides

Select the correct pulley size for your belt drive fan using model prefixes. This guide covers 2.75-inch and 6-inch pulleys for whole house and drum fans.

Quick answer

Match your fan's model prefix to the correct pulley: 2.75 in. pulley for models starting with CX24BD, CX30BD, or BF48BD; 6 in. pulley for models starting with BF36BD, BF42BD, or BF48BD.

Why pulley size matters

Using the wrong pulley can cause belt slippage, vibration, or motor strain. Each pulley is designed for a specific range of fan diameters and motor shaft configurations. The 2.75 in. pulley attaches to the motor shaft via set screw, while the 6 in. pulley mounts to the bearing plate assembly shaft.

The trade-off between sizes

The 2.75 in. pulley is compact and works with smaller whole house fans (24 in. and 30 in.) and the 48 in. drum fan. The 6 in. pulley is larger and designed for 36 in. and 42 in. drum fans, offering a different mounting point. Both restore fan function but are not interchangeable.

Decision rules for pulley selection

Identify your fan model prefix: Locate the model number on the fan's nameplate. The first five characters (e.g., CX24BD, BF36BD) determine compatibility.
Match prefix to pulley: Use the 2.75 in. pulley for CX24BD, CX30BD, and BF48BD prefixes. Use the 6 in. pulley for BF36BD and BF42BD prefixes. Both pulleys work with BF48BD models, but the 2.75 in. pulley mounts to the motor shaft while the 6 in. pulley mounts to the bearing plate assembly.
Check mounting style: The 2.75 in. pulley uses a set screw to attach to the motor shaft. The 6 in. pulley uses a set screw to attach to the bearing plate assembly shaft. Confirm your fan's shaft type before ordering to ensure a proper fit.

Product facts

2.75 In. Pulley for Belt Drive 24 In. and 30 In. Whole House Fans and 48 In. Drum Fans: For use only with belt-driven 24 in. and 30 in. whole house fans and 48 in. drum fans. Compatible with fan models beginning in CX24BD, CX30BD, and BF48BD. If your fan model starts with CX24BD, CX30BD, or BF48BD, this 2.75 in. pulley is the correct replacement.
2.75 In. Pulley for Belt Drive 24 In. and 30 In. Whole House Fans and 48 In. Drum Fans
6 In. Pulley for Belt Drive Drum Fans: For use only with 36 in. and 42 in. drum fans. Compatible with fan models beginning in BF36BD, BF42BD, and BF48BD. Choose this 6 in. pulley when your fan model starts with BF36BD or BF42BD; it also works with BF48BD models.
6 In. Pulley for Belt Drive Drum Fans