Tracer® ZN.520
Continuous Fan Operation
Fan Cycling
Operation
Fan Off Delay
|
| Heating | Cooling | ||
| Fan mode | Occ. | Unocc. | Occ. | Unocc. |
Off | Off | Off | Off | Off | |
Low | Low | Off/High | Low | Off/High | |
Medium | Med | Off/High | Med | Off/High | |
High | High | Off/High | High | Off/High | |
Auto (continuous) | Default Off/High | Default | Off/High | ||
|
| fan sp. | fan sp. |
| |
During occupied and occupied standby modes, the fan normally is on. For multiple speed fan applications, the fan normally operates at the selected or default speed (off, high, medium, or low). When fan mode is auto, the fan operates at the default fan speed.
During unoccupied mode, the controller controls the fan off. While unoccupied, the controller heats and cools to maintain the unoccu- pied heating and cooling setpoints. In unoccupied mode, the fan is controlled on high speed only with heating or cooling.
The unit fan is always off during occupied, occupied standby, and unoccupied modes when the unit is off due to a diagnostic or when the unit is in the off mode due to the local zone sensor module, a communicated request, or the default fan speed (off).
If both a zone sensor module and communicated request exist, the communicated request has priority.
Tracer® ZN.520 does not support fan cycling in occupied mode. The fan cycles between high speed and off in the unoccupied mode only. The controller’s cascade control algorithm requires continuous fan operation in the occupied mode.
When a heating output is controlled off, the Tracer® ZN.520 controller automatically holds the fan on for an additional 30 seconds. This 30- second delay gives the fan time to blow off any residual heat from the heating source, such as a steam coil. When the unit is heating, the fan off delay is normally applied to control the fan; otherwise, the fan off delay does not apply.
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