Fan Belt Length Calculator
Here’s a comprehensive table summarizing all you need to know about calculating fan belt length:
| Aspect | Details |
|---|---|
| Formula | Belt Length = 2C + [1.57 x (D1 + D2)] + 1-in. 2 |
| Variables | C = Distance between centers of motor and fan shafts D1 = Diameter of small pulley D2 = Diameter of large pulley 2 |
| Measurement Method | Use a cloth measuring tape or thin string to measure around the outside of the belt 3 |
| Adjustment for Belt Type | For A Belts (1/2″ width): Subtract 2 inches from outside measurement For B Belts (5/8″ width): Subtract 3 inches from outside measurement 3 |
| Alternative Method | If belt can’t be removed, use string to measure around existing belt on fan, then measure string length 4 |
| Important Note | Belt model numbers often differ from actual outside circumference 4 |
| Common Belt Types | A (1/2″ width), B (5/8″ width), Z (3/8″ width) 3 |
| Cogged Belts | Indicated by ‘X’ suffix (e.g., AX, BX) – allows fitting at tighter angles 1 |
| Wedge Belts | Indicated by ‘SP’ prefix (e.g., SPA, SPB) 1 |
| Measurement Precision | Round up to the next available belt size if exact length not available 2 |
| Additional Check | Inspect motor mount for adjustment range if exact size unavailable 2 |
Remember to also check the belt’s cross-section (width and height) to ensure you’re selecting the correct type of belt5. When replacing belts, it’s a good practice to inspect other components like the motor mount, fan, and housing to ensure they’re in good working order