Building Management Systems - Page 20

The VariTrac II comfort control system provides individual temperature control to each comfort zone in a building while using the same single zone air conditioning unit. The VariTrac II also varies the flow of supply air to each zone, providing the heating and cooling capacity required to match the load in each specific zone.

ICS Capability

The VariTrac II Central Control Panel (CCP) interfaces with the Tracker or Tracer building management system. It provides control, monitoring, and diagnostics of the individual VariTrac dampers, CCP, and corresponding HVAC unit.

Software Capabilities

The VariTrac II CCP scans the zone UCMs to determine the deviations from setpoint, length of deviation, time from last heat or cool changeover, and number of zones requiring heating or cooling.Based on this information, the CCP selects the system heat or cool mode and stages of capacity. The CCP also monitors the system air temperature to ensure that high and low temperature limits are maintained.

The CCP monitors system air velocity or static pressure and VariTrac damper position to control duct air pressure, and to maintain proper air velocity through the HVAC unit.

Group Control of Zones

All VariTrac UCM zone dampers on a system can be designated as a member of one of four groups. All group members respond together to group commands such as timed override, time of day control, air flow control overrides, and ventilation settings.

Occupied/Unoccupied Mode

The Tracker or Tracer provides time of day control for the VariTrac II zone groups. Each group on a VariTrac system can be individually scheduled, enabling greater scheduling flexibility of each HVAC system. When any group is in the occupied mode, the associated HVAC unit operates in the occupied mode.

The system can provide multiple on/off time periods per day for each of the seven weekdays. It also can provide:

• Holiday schedules and multiple holiday dates
• Exception day schedules
• Automatic daylight saving time
• Optimal start by group

Setpoint Control

The system allows the operator to control setpoints for all VariTrac zone UCMS, Setpoint control includes occupied and unoccupied heating and cooling setpoints, and air volume minimum and maximum setpoints. If desired, use a setpoint control mounted on the zone sensor. The setpoint knob can be enabled and disabled via the Tracer or Tracker system, The operating range of the setpoint knob can be limited to maintain system stability while still allowing for occupant comfort control.

After Hours Override

Use either a space-mounted override button, or the Tracker or Tracer system to temporarily provide override from the unoccupied to the occupied mode. The system can also specify the length of the override period. An override for a specific zone becomes an override for its group. The associated HVAC unit operates in the occupied mode for the duration of the override period.

Group Control

The Tracker or Tracer system enables access to overrides by group. This allows the operator to manually control the groups occupied/unoccupied mode, damper position override, and VAV terminal unit heater and fan mode if available. It also provides for operation of a ventilation cycle when the HVAC unit is in a zero energy state. This provides greater zone ventilation capability without affecting comfort.

System Status

The current operating status of the VariTrac system can be accessed through the Tracker or Tracer system. The operator can view a service summary of the entire VariTrac system at a glance, a more detailed view of each zone, or the current operating status of the HVAC unit.

Alarming and Alarm Log

The Tracker or Tracer system has the capability of monitoring VariTrac for system and zone alarms. Such things as sensor failure or communication loss can be monitored. Custom alarms are also available. The system retains a list of past alarms in an alarm log for operator review. If a Trane Voyager Rooftop is attached to the VariTrac system, Voyager alarms can be monitored.