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mode of operation can be enabled and disabled via Pre-Cool Enable Command. Pre-Cool is reported
via Heat Cool Mode Status when active. Ventilation air is not provided during Pre-Cool operation.
VVDA
VVDA equipment types, a transition from Unoccupied to Occupied mode or Off/Shutdown to Occupied,
if a valid space temperature input is above the Pre-Cool Setpoint + 1.5°F Pre-Cool Mode will initiate.
Symbio™ 700 operates in a discharge air control mode providing discharge air per Discharge Air
Cooling Setpoint Active until space temperature drops equal or below the Pre-Cool Setpoint. In this
cooling mode the outdoor air damper minimum position is 0%, but the controller will use compressor
and/or economizer cooling when suitable. VVDA units will modulate fan speed and manage to the duct
static pressure setpoint.
Pre-Cool mode can also be commanded via Heat Cool Mode Request. In this case, the Symbio 700
remains in Pre-Cool indefinitely until the commanded mode is removed. When space temperature is
equal or less than Pre-Cool Setpoint, cooling capacity is disabled but the supply fan continues to
circulate air until the Pre-Cool command is removed. Cooling capacity control will enable if space
temperature rises above Pre-Cool Setpoint + 1.5°F.
Space Temperature Control
Space temperature control units must be in Cool or Auto mode to allow Pre-Cool operation. A transition
from Unoccupied to Occupied mode, the controls will initiate Pre-Cool if a valid space temperature input
is above the Pre-Cool Setpoint + 1.5°F. The Symbio™ 700 operates in a space temperature control
mode controlling space temperature to the Pre-Cool Setpoint. The supply fan operates at maximum
speed. When 60 minutes expires or when space temperature is equal or below the Pre-Cool Setpoint,
Pre-Cool mode will terminate.
Pre-Cool mode can also be commanded via Heat Cool Mode Request from a building automation
system or external control. The Symbio 700 controller will continuously control space temperature to the
Pre-Cool setpoint until the mode is released or changed.
Night Purge
Night Purge mode is typically applied in building unoccupied periods when conditions are suitable for
economizer cooling; all other forms of cooling capacity are disabled. This mode is only supported via a
commanded Heat Cool Mode Request. The controller will not use local inputs and assume outdoor air is
suitable for economizing. The outdoor air damper minimum position setpoint will be overridden to 0%.
Night Purge operation is terminated when the Night Purge, Heat Cool Mode Request is removed.
VVDA
When active, the Symbio™ 700 operates in a discharge air control mode, modulating the outdoor air
damper to provide cooling capacity per Discharge Air Cooling Setpoint Active.
Space Temperature Control
Space temperature control equipment modulates the outdoor air damper to control space temperature
to the Space Temp Cooling Setpoint Status setpoint. If space temperature is greater than the space
cooling setpoint + 1.5°F the outdoor air damper will be at 100% with supply fan at maximum speed. If
space temperature is less than the space cooling setpoint -1.5°F the outdoor air damper will be closed
with supply fan at minimum speed. Constant volume units, the supply fan operates at 100% while Night
Purge is active.
Daytime Warm-up
Daytime Warm-up is a feature of VVDA units that can be Enabled, or Disabled. Daytime Warm-up is
available with any heat type installed. Daytime Warm-up is a mode used during building occupied
periods to recover a critical zone that is too cold. Ventilation air is provided while in Daytime Warm-up
mode.
When the Heat Cool Mode Request is Cool (the unit is providing cooling), if a valid space temperature is
3°F below the adjustable Daytime Warm-up Setpoint, daytime Warm-up operation initiates. The unit will
operate in a discharge air control mode delivering heating capacity per Discharge Air Heating Setpoint
Heat Cool Modes
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