Variable Volume Fan Space Temperature Control (Szvav/Vvzt); Supply Fan Control - Trane SYMBIO 700 Troubleshooting Manual

Variable Volume Fan Space Temperature Control (SZVAV/VVZT)

Similar to the Reliatel control system, the Symbio 700 includes a Single Zone VAV (VVZT) control
sequence.
When configured for VVZT control, this sequence is only applicable when the following are true;
otherwise, the CVZT sequence is leveraged:
Occupancy Status = Occupied
Supply Fan Configuration Status = Continuous
Discharge Air Temperature sensor is not in an Alarm state
The unit is operating under a cooling demand (SZVAV heating is not applicable with staged heat on initial
launch of Symbio 700 for Odyssey)
The sequence is PI-based (proportional, integral) and strives to maintain space temperature within 1F of
the Active Cooling and Heating setpoints.
When Space Temperature Active > Space Temp Cooling Setpoint Status, the algorithm will begin
calculating a need for Cooling capacity to be energized. A discharge air temperature setpoint will be
calculated lower in order to determine proper compressor staging needs.
When Space Temperature Active < Space Temp Cooling Setpoint Status, the algorithm will begin
calculating a reduction in need for Cooling capacity to be energized. A discharge air temperature
setpoint will be calculated higher in order to determine proper compressor staging needs.
Different from the CVZT sequence, compressors will be staged to maintain the discharge air
temperature at the Discharge Air Temperature Setpoint Active setpoint.

Supply Fan Control

In order 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 will remain 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 will be controlled at maximum
.
speed
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