sequence of
Operation operation
Fan Mode Operation
For multiple fan speed applications, the TracerZN520 controller offers additional fan configuration flexibility. Separate default fan speeds for heating and cooling modes can be configured. The fan runs continuously for requested speeds (off, high, medium, or low). When the fan mode switch is in the Auto position or a hardwired fan mode input does not exist, the fan operates at the default configured speed. See Table 21 for default fan configuration for heat and cool mode. During unoccupied mode, the fan cycles between high speed and off with heating and cooling fan modes. If the requested speed is off, the fan always remains off.
During dehumidification, when the fan is on Auto, the fan speed can switch depending on the error. Fan speed increases as the space temperature rises above the active cooling setpoint.
Additional flexibility built into the control- ler allows you to enable or disable the local fan switch input. The fan mode request can be either hardwired or communicated to the controller. When both are present, the communicated request has priority over the hardwired input. See Tables 22, 23, and 24.
Table
| auto fan | fan speed |
| operation | default |
Heating | continuous | off |
|
| low |
|
| medium |
|
| high |
Cooling | continuous | off |
|
| low |
|
| medium |
|
| high |
Table
Communicated | Fan switch (local) | Fan operation |
fan speed input |
|
|
Off | Ignored | Off |
Low | Ignored | Low |
Medium | Ignored | Medium |
High | Ignored | High |
Auto | Off |
|
Low |
|
|
Medium |
|
|
High |
|
|
Auto | Off |
|
Low |
|
|
Medium
High
Auto (configured default, determined by heat/cool mode)
Table
| 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 | default | off/high | default | off/high |
| fan sp. |
| fan sp. |
|
Table
Communicated fan speed input | Fan operation |
Off | Off |
Low | Low |
Medium | Medium |
High | High |
Auto (or not present) | Auto (fan runs at |
| the default speed |
Continuous Fan Operation
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 unoccupied 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 communi- cated request, or the default fan speed (off).
If both a zone sensor module and communicated request exist, the commu- nicated request has priority.
Fan Cycling Operation
TracerZN520 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.
Fan Off Delay
When a heating output is controlled off, the Tracer ZN520 controller automatically holds the fan on for an additional 30 seconds. This
Table
Outdoor Air Temp. | Modulating Outdoor Air Damper |
|
| |
|
| occupied or occupied bypass | occupied standby | unoccupied |
none or invalid | open to occupied minimum position | open to occupied standby minimum position | closed | |
failed | open to occupied minimum position | open to occuied standby minimum position | closed | |
present and economizing feasible | economizing minimum postion to 100% | economizing between occupied standby | open & economizing when | |
|
|
| minimum position to 100% | unit is operating, closed |
|
|
|
| otherwise |
present & economizing not feasible | open to occupied minimum position | open to occupied standby minimum position | closed | |
55 |
