Trane IntelliPak SAHL Series Installation, Operation And Maintenance Manual page 24

General Information
The Exhaust Enable Target could be above or below the Active Building Design OA Minimum
Position Target Setpoint, based on the Active Exhaust Enable Setpoint being set above or below
the Building Design Minimum Position at 100% Fan Speed Command. Note that an Exhaust Enable
Setpoint of 0% will result in the same effect on Exhaust Fan control as on VAV applications with and
without Statitrac.
Occupied Cooling Operation
For normal cooling operation, cooling capacity will be staged or modulated in order to meet the
calculated discharge air target setpoint. If the current active cooling capacity is controlling the
discharge air within the deadband, no additional cooling capacity change will be requested. As the
Discharge Air Temperature rises above the deadband, the algorithm will request additional
capacity as required (additional compressors or economizer). As the Discharge Air Temperature
falls below the deadband, the algorithm will request a reduction in active capacity.
Default Economizer Operation
By default, the unit will be setup to optimize the minimum supply fan speed capability during
Economizer Only operation. If the economizer is able to meet the demand alone, due to desirable
ambient conditions, the supply fan speed will be allowed to increase above the minimum prior to
utilizing mechanical cooling if discharge air setpoint falls below the discharge air Lower Limit
(Cooling) setpoint.
Unoccupied Mode
In Unoccupied mode the unit will utilize setback setpoints, 0% Minimum OA Damper position, and
Auto Fan Mode operation as on normal CV units. The Supply Fan speed, and cooling and
modulating types of heat, will be controlled to the discharge air target setpoint as is done during
occupied periods. The Supply fan speed during staged heat control will be forced to 100% as on
normal CV units.
Occupied Heating Operation
Occupied heating operation has two separate control sequences; staged and modulated. All staged
heating types will drive the supply fan to maximum flow and stage heating to control to the Zone
Heating Setpoint. For units with Hydronic and Gas heat, modulated SZVAV Heating. On an initial
call for heating, the supply fan will drive to the minimum heating airflow. On an additional call for
heating, the heat will control in order to meet the calculated discharge air target setpoint. As the
load in the zone continues to request heat operation, the supply fan will ramp-up while the control
maintains the heating discharge air temperature. Heating can be configured for either the energy
saving SZVAV Heating solution as described above, or the traditional, less efficient CV Heating
solution.
Compressor (DX) Cooling
Compressor control and protection schemes will function identical to that of a traditional unit.
Normal compressor proving and disable input monitoring will remain in effect as well as normal
3-minute minimum on, off, and inter-stage timers. Also, all existing head pressure control schemes
will be in effect.
Cooling Sequence
If the control determines that there is a need for active cooling capacity in order to meet the
calculated discharge air target setpoint, once supply fan proving has been made, the unit will begin
to stage compressors accordingly. Note that the compressor staging order will be based on unit
configuration and compressor lead/lag status.
Once the discharge air target setpoint calculation has reached the Minimum Setpoint and
compressors are being utilized to meet the demand, as the discharge air target setpoint value
continues to calculate lower the algorithm will begin to ramp the supply fan speed up toward 100%.
Note that the supply fan speed will remain at the compressor stage's associated minimum value
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