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Figure 6. Multi-speed fan sequence of operation
Single Zone Variable Air Volume
When configured for VVZT (also known as SZVAV) control, the sequence is only applicable when
the following are true; otherwise, the CVZT sequence is leveraged:
• When Occupancy Status is Occupied and
• When Supply Fan Configuration Status is Continuous and
• When Discharge Air Temperature sensor is not in an Alarm state and
• The unit is operating under a cooling demand (VVZT heating is not applicable with staged
heat 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 calculates
a need for cooling capacity to be energized. A discharge air temperature setpoint calculates
lower to determine proper compressor staging needs. The minimum value of this calculated
setpoint for temperature control can be adjusted by the Discharge Air Temperature Minimum
Cool Limit setpoint.
When Space Temperature Active < Space Temp Cooling Setpoint status, the algorithm calculates
a reduction in need for cooling capacity to be energized. A discharge air temperature setpoint
calculates higher to determine proper compressor staging needs. The maximum value of this
calculated setpoint for temperature control can be adjusted by the Discharge Air Temperature
Maximum Cool Limit setpoint.
Different from the CVZT sequence, compressors are staged to maintain the discharge air
temperature at the Discharge Air Temperature Setpoint Active setpoint.
VVZT DAT Control Mode
With the Symbio 700 VVZT control sequence, the end user can choose to use the internally
derived Discharge Air Temperature Setpoint Active or to override the value with their own.
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