Chapter 7 - Maintenance

Mechanical ventilation systems need regular maintenance. Test emergency ventilation and alarm systems. Clean heaters and check gas jets and safety shut-off valves for proper operation. Motors and controls should be cleaned as necessary. Check all air inlets and fan housings for blockage. Check thermostat and controller calibration and settings. Because belt slippage causes blades to turn slower and deliver a proportionately smaller airflow, fan belt tension should be adjusted and worn belts replaced. Dust- and feather-covered fan blades, shutters and grills reduce exhaust fan output but 30-40%. Fan blades and shutters should be cleaned and lubricated every one to three months.

Fans that are not being used (for example, hot-weather fans during winter) should be sealed against unwanted infiltration with plastic or a simple top-hinged, manually-closed panel. Ensure that the fan housing is unsealed before the fan is put back into operation.

Recommended maintenance schedule

Every month

• Clean fan blades and shutters. Dirty fan shutters can decrease fan airflow up to 40%. Shut off power to thermostatically controlled fans before servicing them.
• Check fans with belt drives for proper tension and correct alignment. It too tight, belts may cause excessive bearing wear; if too loose, slippage reduces fan performance and wears the belt.
• During the heating season, remove dust from heater fins and filters, and check gas jets and safety shut-off valves for proper orientation.
• est emergency ventilation and alarm systems including standby generators.
• Clean heat exchanger (some manufacturers suggest cleaning more often).
• Make certain that shutters open and close freely. Apply graphite (not oil or grease) to fan shutter hinges.
• Check fan shutters during cold weather so they do not freeze open or shut.

Every 3 months

• Check gable and soffit air intakes for blockages.
• Clean motors and controls. Dirty thermostats do not sense temperature changes accurately or rapidly. Dust insulates fan motors and prevents proper cooling. If dust is allowed to build up, the motor can overheat.
• Clean dust accumulation from recirculation air ducts, if necessary.

Every 6 months

• Consider fan lubrication. Most ventilating fans have sealed bearings and do not require lubrication. Follow fan manufacturer’s recommendation for oil type and amount. Never over lubricate.
• Recalibrate thermostat, as needed.
• Clean guards and weather hoods.

Every year

• Clean and repaint chipped spots on fan housings and shutters to prevent further corrosion.
• During winter, disconnect the power supply and cover hot weather fans (not cold or mild weather fans) with plastic or an insulated panel on the warm (animal) side of the fan. Uncover in the spring.
• Check air inlets for debris and warping.
• Check plastic baffle curtains. They can become brittle with age and require replacement.
• Check attic insulation for signs of moisture and packing or removal by rodents.