Posted sachin on June 14, 2019
We received a call today about this so here’s some quick thoughts (as in NOT EXHAUSTIVE) for roof or wall exhaust fan belt replacement:
- Identify belt length and type
- Measure center to center on pulleys (aka sheaves)
- Measure outside diameter of each pulley
- Measure the width of pulley gap where belt enters
- Typically the belts are V type, with either an A or B width
- If low HP type fans, usually A
- If high HP, usually B
- Count number of grooves (usually one or two) – this tells you how many belts are needed
- Buy the belts LOL (if you want the best set it and forget it solution, click here to give us some details and we’ll quote you what we use)
- Put the new belts on starting on the smallest pulley and rolling on to larger
- Check tension by twisting the belt at the center point – proper tension is typically a half turn at the center distance between pulleys (this is not technically spot on but tends to be very close and avoids needing a belt tension measuring device in a pinch – for less critical equipment like this it works fine)
- If tension is too tight or too loose, adjust at the motor mount (should have a way to adjust distance) NOTE: if you use our belt solution above you won’t need to do this!
- Re-check belt tension after the fan has run for a few weeks as the belts tend to stretch during break-in. NOTE: if you use our belt solution above you won’t need to do this!
Things to avoid:
- Disconnect and lockout the power before you touch anything!
- Belt over-tightening – leads to premature bearing and belt failure
- Belt under-tightening – leads to loss of power transfer along with a premature belt and pulley failure
- Pulley/Sheave misalignment – check 3 planes with a straight edge/string/laser