Exhaust control

fan configuration. The controller can be configured to auto, to a specific fan speed, or to off. If both a communicated and hard-wired value (fan- speed switch) is present, the communicated value has priority.

Note:

In occupied mode, The Tracer ZN521 zone controller requires continuous fan operation because of cascade zone control. In unoccupied mode, the fan cycles.

When the controller receives a communicated auto signal (or the associ- ated fan-speed switch is set to AUTO with no communicated value present), the fan will operate in the auto mode. In the auto mode, the fan will operate according to the fan default (configurable using the Rover service tool). The fan speed can be configured to default to auto, a specific speed, or off for both heating and cooling operation.

Configured as auto and with multiple speeds available, the fan will auto- matically switch speeds depending on the difference between the zone temperature and the active zone temperature setpoint. The fan speed will increase as the difference increases and decrease as the difference decreases.

When the controller receives a communicated fan-speed signal (high, medium, low) or the associated fan-speed switch is set to a specific fan speed, the fan will run continuously at the desired fan speed during occu- pied, occupied standby, and occupied bypass operation. During unoccu- pied operation, the fan will cycle between off and high regardless of the communicated fan-speed signal or fan-speed switch setting (unless either of these is off, which will control the fan off).

The fan will turn off when the controller receives a communicated off sig- nal, when the fan-speed switch is set to OFF, when specific diagnostics are generated, or when the default fan speed is set to off and the fan is oper- ating in the auto mode.

The ability to enable or disable the controller’s associated fan speed switch is configurable.

Exhaust control

Exhaust control is accomplished by a single-speed exhaust fan or a two- position exhaust damper. BOP2 controls this function. To enable exhaust control, configure the controller by selecting Exhaust Fan/Damper Present and by selecting the number of fan speeds as either One or Two.

The exhaust function is coordinated with the supply fan and outdoor/ return air dampers as follows:

•The exhaust output is energized only when the supply fan is operat- ing and the outdoor air damper position (%) is greater than or equal to the Exhaust Fan/Damper Enable Setpoint (configurable using the Rover service tool).