Trane Symbio 700 Application Manual page 18

S S p p a a c c e e T T e e m m p p e e r r a a t t u u r r e e C C o o n n t t r r o o l l S S e e q q u u e e n n c c e e o o f f O O p p e e r r a a t t i i o o n n
If the VVZT DAT Control Mode – Active point is set to "Auto", the VVZT control algorithm will use
the internally derived Discharge Air Temperature Setpoint Active, as described above, for all
cooling capacity output control.
If the VVZT DAT Control Mode – Active point is set to "Manual", the VVZT control algorithm will
use the Discharge Air Cooling Setpoint (Target) – Active as upper limit for the Discharge Air
Temperature Setpoint calculation. Typically this is set to a low value (i.e 50-55F) to drive longer
compressor runtimes. When this override is active, if the space temperature is 2° F below the
Space Temp Cooling Setpoint Status value or 1° F above the Space Temp Heating Setpoint
Status value, the controller will pause the override sequence until the space temperature
recovers to above the Space Temp Cooling Setpoint status.
Supply Fan Control
For the VVZT control sequence to be active, the Supply Fan Configuration Status must be ON/
Continuous.
The fan speed is continuously variable on VVZT systems. The fan remains at minimum speed
(based on active compressor stages) until the space demand requires additional airflow.
All heating is accomplished with the CVZT control sequence, and the fan is controlled at
maximum speed.
Figure 7. Supply fan sequence of operation
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