The control module will operate economizer, run diag- nostics to monitor alarms/alerts at all times, and respond to CCN communications to perform any con®gured network POC (product outboard control) functions such as time/ outdoor-air temperature broadcast and global occupancy broad- cast. When the optional expansion I/O board is employed, it will: perform a periodic scan and maintain a database of ex- panded I/O points; perform Fire/Smoke control (power ex- haust required); if in Occupied mode, perform IAQ control and monitor the fan, ®lter, demand limit, and ®eld-applied status (with accessories).
If thermostats are used to energize the G input, the control module will turn on the indoor fan without delay and open the economizer dampers to minimum position. If thermo- stats are used to deenergize the G input, the control module will turn off the indoor fan without delay and close the econo- mizer dampers.
When cooling, G must be energized before cooling can operate. The control module determines if outdoor condi- tions are suitable for economizer cooling using the standard outdoor air thermistor. For the economizer to function for outside air cooling: the enthalpy must be below the enthalpy set point; the
When Y1 input is energized, the economizer will be modu- lated to maintain SAT at the de®ned set point. (The default is 55 F.) When SAT is above the set point, the economizer will be 100% open. When SAT is below the set point, the economizer will modulate between minimum and 100% open position. When Y2 is energized, the control module will turn on compressor 1 and continue to modulate the economizer as described above. If the Y2 remains energized and the SAT reading remains above the set point for 15 minutes, com- pressor 2 will turn on. If Y2 is deenergized at any time, only the last stage of compression that was energized will be turned off. If outdoor conditions are not suitable for economizer cool- ing, the economizer will go to minimum position and cycle compressors 1 and 2 based on demand from Y1 and Y2 re- spectively. The compressors will be locked out when the SAT temperature is too low (less than 40 F for compressor 1 and less than 45 F for compressor 2). After a compressor is locked out, it can restart after normal
The Time Guard function maintains a minimum off time of 5 minutes, a minimum on time of 10 seconds, and a minimum delay before starting the second compressor of 10 seconds.
When heating, the heat stages respond to the demand from W1 and W2 of the thermostat input. Heating and cooling will be mutually
COOLING, VARIABLE VOLUME UNITS Ð On power up, the control module will activate the initialization software. The initialization software reads DIP switch no. 1 position to determine CV or VAV operation. The initialization se- quence: clears all alarms and alerts;
The control module will determine if an interface (link- age) is active and if the unit will operate in a Digital Air Volume (DAV) mode. In a DAV system, the room terminals are equipped with microprocessor controls that give
commands to the base unit module. If a linkage is active, the control module will replace local comfort set points, space and return air temperatures, and occupancy status with the linkage data supplied.
The control module will determine occupancy status from Time Schedules (if programmed), Remote Occupied/ Unoccupied input, global occupancy schedules, or DAV. If temperature compensated start is active, the unit will be con- trolled as in the Occupied mode.
NOTE: The temperature compensated start is a period of time calculated to bring the unit on while in Unoccupied mode to reach the occupied set point when occupancy occurs.
The control module will set the appropriate operating mode and fan control. The control module will turn on the VFD if Occupied mode is evident. If in Unoccupied mode and a valid space temperature reading is available (either from a sensor or DAV), the control module will monitor SPT (space tem- perature) against unoccupied heat and cool set points. The control module will start the VFD whenever SPT is outside of the set points (Unoccupied Heat or Unoccupied Cool). The VFD may also be started by nighttime thermostat via remote Occupied/Unoccupied input or by a temperature com- pensated start algorithm. When the VFD is running in a nor- mal mode, the control module will start heating or cooling as required to maintain
When cooling, the control module will energize the power exhaust enable output to the external power exhaust control- ler (when power exhaust is used).
The control module will run continuous diagnostics for alarms/alerts; respond to CCN (Carrier Comfort Network) communications; perform any con®gured network POC (Prod- uct Outboard Control) functions such as time/outdoor air tem- perature broadcast and global broadcast; and perform Fire/ Smoke control.
HEATING, CONSTANT VOLUME (CV) UNITS Ð The control module is powered by 24 vac. If the unit is con- trolled with a room sensor, the fan will run continuously in the Occupied mode, with the
If the unit is controlled with a room sensor the fan will not run in the unoccupied mode. Upon a call for heat, the ®rst stage of heat is energized, the
HEATING, VARIABLE AIR VOLUME (VAV) UNITS Ð The control board is powered by 24 vac. When there is a call for heating (from Morning
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