The two most common causes of industrial fans not operating efficiently are:
The below chart lists several common industrial fan operational concerns and a variety of potential causes of these problems.
| Insufficient Air Flow | Duct elbows near fan inlet or outlet |
| Restricted fan inlet or outlet | |
| Impeller rotating in wrong direction | |
| Fan speed lower than design | |
| System resistance higher than design | |
| Dampers shut | |
| Faulty ductwork | |
| Dirty or clogged filters and/or coils | |
| Inlet or outlet screens clogged |
| Excessive Air Flow | System resistance less than design |
| Fan speed too high | |
| Filters not in place | |
| Registers or grilles not installed | |
| Improper damper adjustment |
| Excessive Power Draw | Fan speed higher than design |
| Gas density higher than design | |
| Impeller rotating in wrong direction | |
| Static pressure less than anticipated | |
| Fan size or type not appropriate for application |
| Overheating Bearings | Excessive amount of lubricant |
| Contaminated lubricant | |
| Old lubricant |
| Excessive Vibration | Accumulated material on impeller |
| Worn or corroded impeller | |
| Bent shaft | |
| Impeller or pulleys loose on shaft | |
| Motor out of balance | |
| Impeller out of balance | |
| Pulleys eccentric or out of balance | |
| Bearing or drive misalignment | |
| Mismatched belts | |
| Belts too loose or too tight | |
| Loose or worn bearings | |
| Loose bearing bolts | |
| Loose fan mounting bolts | |
| Weak or resonant foundation | |
| Foundation unlevel | |
| Structures not cross braced | |
| Fan operating in unstable system condition | |
| Worn coupling |
| Inoperative Fan | Blown fuse |
| Broken belts | |
| Loose pulley | |
| Motor too small | |
| Wrong voltage |
