Control and Operation
The Title 24 Standards require that the ventilation system have an override control which is readily accessible to the occupants. The “fan-on” switch on a typical thermostat controlling the HVAC system and the wall switch for an exhaust fan are both allowed as acceptable controls. The control must be “readily accessible”, e.g. it must be capable of being accessed quickly and easily without having to remove panels or doors. It can be as simple as a labeled wall switch by the electrical panel. It may be integrated in a labeled wall-mounted control or in the air moving device, but it cannot be buried in the insulation in the attic or the inside of the fan. The occupant must be able to modify the settings or override the system.
If intermittent fans are used, they must be controlled by a timer, and they must have an increased airflow rate to compensate for the off time. Time-of-day timers or duty cycle timers can be used to provide intermittent whole building ventilation. Manual crank timers cannot be used, since the system must operate automatically without intervention by the occupant. Some controls “look back” over a set time interval to see if the air handler has already operated for heating or cooling before it turns on the air handler for ventilation only operation.
(Excerpted from the CEC Title 24 Residential Compliance Manual)