Single Zone Vav - Cooling; Cool - Trane Symbio 700 Controller Application Manual

space temperature and discharge air temperature sensor are required input. If the discharge air
temperature input becomes invalid, the control automatically reverts to Single Loop Space Temperature
Control. Symbio™ 700 operates in Single Loop Space Temperature Control in heating modes when
staged gas heat and staged electric heat are configured.
Single Zone VAV is a control method of space temperature control that operates the supply fan at the
lowest allowed for the cooling capacity required to satisfy the load in the space. As cooling capacity
increases, the supply fan speed will increase accordingly until it reaches 100% of its allowed range of
operation.
When there is no demand for heating or cooling the supply fan operates at the minimum speed setting
while providing ventilation according to occupancy setpoints, see the following figure. Alternately, the
supply fan can be setup to cycle off when there is no demand for heating or cooling via Supply Fan
Configuration Command setting.
Figure 7. Supply fan sequence of operation
Single Zone VAV — Cooling

Cool

When there is a space cooling demand, DX cooling will initialize and increase to satisfy space
temperature. The supply fan will continue to operate at a low, fixed speed at low cooling capacities until
the cooling capacity requires additional airflow to keep compressor operation optimal. The supply fan
speed will increase as the demand for cooling capacity increases. The minimum supply fan speed is
calculated by DX cooling capacity. As the space requires additional cooling capacity, Space
Temperature Control will calculate a lower discharge air temperature setpoint increasing DX cooling
which in turn increases the supply fan speed. Cooling capacity and supply fan speed both can increase
to 100%.
If the unit discharge air temperature reduces to the Discharge Air Temperature Minimum Cool Limit
setting or DX cooling reaches 100% capacity, cooling capacity increases will hold while the supply fan
speed will continue to increase to 100% or modulate to manage space comfort cooling.
ACC-APG002A-EN
Space Temperature Control
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