Unit Operation
Space Temperature ZN510 controls the space temperature according to the active space temperature, the active heating/cooling setpoint, and the space temperature control algorithm. The ZN510 controller receives the space temperature from either a wired zone sensor or as a communicated value. When neither a zone sensor nor communicated space temperature is present, the ZN510 controller generates a space temperature failure diagnostic.
Note:
The ZN510 controller cannot oper- ate without a valid space tempera- ture value (either hardwired or communicated).
The space temperature input can communicate timed override ON or CANCEL requests to the ZN510 controller. If the ON button is temporarily pressed, the zone sensor sends a signal to the controller. This signal is then interpreted as a timer override request which places the unit into occupied.
The controller uses the timed override request (while the zone is unoccupied) as a request to switch to the Occupied Bypass mode (occupied bypass). This Occupied Bypass mode lasts for the duration of the occupied bypass time, typically 120 minutes.
or
The controller’s Occupancy mode is determined from either a system level controller or another peer controller.
The CANCEL button cancels the timed override request and returned the unit to unoccupied mode. If the CANCEL button is temporarily
pressed, the zone sensor sends a signal to the controller. This signal is then interpreted as a timed override cancel which places the unit into unoccupied.
Local Setpoint
The local setpoint analog input is designed as the local (hardwired) setpoint input. This input cannot be used for any other function. The local input is a resistance input intended for use with Trane zone sensors.
If neither a hardwired nor communicated setpoint is present, the controller uses the stored default setpoints:
zOccupied setpoints:
In the occupied mode, the unit attempts to maintain the space temperature at the active occupied heating or cooling setpoint based on the measured space temperature, the active setpoint, and the proportional/ integral control algorithm.
zOccupied standby setpoints: In occupied standby mode, the controller uses the occupied standby cooling and heating setpoints. Because the occupied standby setpoints typically cover a wider range than the occupied setpoints, the ZN510 controller reduces the demand for heating and cooling the space. Also, the outdoor air damper is normally closed during occupied standby mode to further reduce the heating and cooling demands.
zUnoccupied setpoints:
In unoccupied mode, the unit attempts to maintain the space temperature at the stored unoc- cupied heating or cooling setpoint based on the measured
space temperature, the active setpoint, and the proportional/ integral control algorithm, regardless of the presence of a hardwired or communicated setpoint.
Once a valid setpoint is established (through the hardwired input or through communication) and when neither a local setpoint or communicated setpoint is present, the controller generates a setpoint failure diagnostic.
When a setpoint failure diagnostic occurs, the controller operates using the default heating and cooling setpoints. These setpoints are
The ZN510 controller uses the following validation sequence for the setpoints:
1.Check for a communicated setpoint. If present, validate this setpoint.
2.Check for a hardwired setpoint and validate the setpoint.
3.Use the default setpoint and validate this setpoint.
Fan Mode Input
The fan mode analog input (Fan) is designed to operate as the fan mode switch input. This input cannot be used for any other function. The fan switch on a Trane zone sensor generates the fan mode signal.
The ZN510 controller detects the unique resistance corresponding to each position of the fan switch. By measuring the resistance, the controller determines the requested fan mode.
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