Honeywell W7750A Continuous Unoccupied Mode, Occupancy Mode and Manual Override Arbitration

EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

	RESET
	NOT ASSIGNED
	(LED OFF)
PRESS FOR LESS		BYPASS
	PRESS FOR ONE
THAN ONE SECOND		TIMEOUT
	TO FOUR SECONDS

BYPASS OCCUPIED

PRESS FOR LESS THAN ONE SECOND

(LED ON)

PRESS FOR FOUR

TO SEVEN SECONDS

UNOCCUPIED

(LED BLINK)

PRESS FOR MORE THAN SEVEN SECONDS

M8483A

Fig. 45. LED and Bypass pushbutton operation.

STANDBY MODE (StatusOcySen)

The digital input for an occupancy sensor (usually a motion detector or possibly a time clock) provides the controller with a means to enter an energy-saving Standby mode whenever people are not in the room. Standby mode occurs when the scheduled occupancy is Occupied, and the occupancy sensor detects no people currently in the room (digital input contacts Closed means people are in the room, and contacts Open means the room is Unoccupied). When in Standby mode, the Excel 10 W7750 Controller uses the Standby Cooling Setpoint for cooling (CoolStbySpt), or the Standby Heating Setpoint for Heating (HeatStbySpt) as the Actual Space Temperature Setpoint. The occupancy sensor signal can also be a network input from another LONWORKS Bus device, so that no physical sensor is required at the receiving W7750 Controller.

IMPORTANT

When the W7750 Controller is in Standby mode, the economizer minimum position setting is not observed. This means the fresh air dampers will go fully closed if there is no call for cooling.

CONTINUOUS UNOCCUPIED MODE

This mode is entered when a wall module is configured with a Bypass pushbutton that was pressed for four to seven seconds causing the wall module LED/LCD to blink. This mode can also be entered via a network command (ManualOcc set to Unoccupied). If the controller is in this mode, it reverts to the Unoccupied setpoints for temperature control, and the economizer does not observe its minimum position setting. The controller remains in this mode indefinitely until the Bypass pushbutton is pressed to exit the mode or a network command is sent to clear the mode. A configuration parameter is available to disable wall-module initiation of Continuous Unoccupied mode (OvrdType).

OCCUPANCY MODE AND MANUAL OVERRIDE ARBITRATION

The W7750 has multiple sources for occupancy schedule information and, therefore, it employs an arbitration scheme to determine the current actual mode. Time-of-day (TOD) schedule status comes from two sources, a configured digital input for OccTimeClock or the DestSchedOcc network input received from a central control. If the digital input source is configured, it has highest priority and determines the Occupancy mode. This digital input is either ON (shorted = occupied), OFF (open = unoccupied), or not active (not configured); otherwise, the status is determined by the DestSchedOcc input from the network source. The DestSchedOcc has three possible states, occupied, unoccupied or standby.

Manual Override Status can be derived from three sources and governed by two selectable arbitration schemes. The two schemes are:

•Network Wins or Last-in Wins, as set in OvrdPriority.

The three sources of manual override status are: DestManOcc - Has possible states: Occupied,

Unoccupied, Bypass, Standby and Not Assigned (not active). This input source has the highest priority in determining manual override status for a Network Wins arbitration scheme, and in the event there is more than one source change at a time in the Last-in Wins arbitration scheme. Here, bypass initiates a self-timed bypass of the control unit and expires upon completion of the defined timed period. The controller then treats the bypass status of this input as Not Assigned until the next change in status.

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