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common when the unit is economizing and bringing in
large quantities of outside air.
Space Static Pressure Control with
Statitrac
TM
Statitrac
TM
is an option. Space static pressure control
operation will become active when the supply fan is On
and proven, the outdoor air damper position is greater
than the relief enable position setpoint and a valid
space static pressure value is greater than the active
space static pressure setpoint plus half the deadband.
When the activation conditions have been met, the unit
will start the relief fan and control relief damper and
fan speed to maintain the space static pressure
setpoint. Once the relief fan operation is proven, the
fan will modulate to track the relief damper position.
Space pressure control operation terminates when the
relief damper is closed and the space static pressure is
below setpoint minus half the deadband, or space
static pressure is within deadband for 30 minutes.
Space Static Pressure Control without
Statitrac
TM
If Statitrac
TM
is not installed, or the space static
pressure sensor has failed, space static pressure
control without Statitrac
TM
becomes active. The relief
damper will track to the outdoor air damper position
and the relief fan speed will track to the relief damper
position when the supply fan is proven On and the
outdoor air damper position is greater than the relief
enable position setpoint.
Space static pressure control operation will be
terminated whenever any of the activation conditions
are not true, when the outdoor air damper is fully
closed or when the outdoor air damper is less than the
relief enable point minus 10%.
If the relief fan or damper is in failure, the relief fan will
be commanded Off and the relief damper will be
commanded Closed.
Discharge Air Temperature
Control
Discharge Air Temperature Control uses available
heating and cooling capacity to deliver the required
temperature at the discharge of the unit. A discharge
air temperature sensor is required for operation.
In cooling modes, the control uses cooling sources to
deliver air temperature as required by the Discharge
Air Cooling Setpoint. In heating modes, the control
uses heat sources to deliver air temperature as
required by the Discharge Air Heating Setpoint.
Primary heat is never used in conjunction with
mechanical cooling.
Multi Zone-VAV and Constant
Volume - Discharge
Temperature Units
These unit types provide Discharge Air Temperature
Control in all heat, cool, and occupancy modes of
operation. The typical operating mode is Cooling
delivering conditioned air to multiple zones of a
building. Multi Zone-VAV units have duct work to
supply VAV terminal units. The VAV units modulate to
control space comfort.
These units also change over to provide heat (when
installed). A building automation system or VAV Box
Relay Output can be used when the heat source
requires full airflow. See Heat Types for more
information. A valid space temperature input must be
provided to perform heating modes such as Daytime
Warm Up and Morning Warm Up (when enabled).
Supply Air Tempering
Supply Air Tempering is a function of discharge air
control Cool mode when DX cooling is off and the
outdoor air damper is at minimum position. This
function is typically required when outdoor air intake
percentage is high and the outdoor air temperature is
low. If discharge air temperature falls below the
Discharge Air Cooling Setpoint, the control will temper
(warm up) the discharge air by initiating heating
capacity. Cool – Tempering is displayed on the user
interface Operating Mode screen when this function is
active. The control will transition back to normal
cooling when heat capacity is no longer required.
Supply Air Tempering is disabled by default.
Multi Zone-VAV equipment allows supply air
tempering when equipped with Modulating Gas, Ultra
Modulating Gas, and SCR Electric Heat. Constant
Volume – Discharge Air Temperature equipment allow
all forms of heating to provide supply air tempering.
Changeover Input
Multi Zone-VAV and Constant Volume Discharge
Temperature units configured with heat include a
binary Changeover Input. An open input requests
discharge air cooling operation. A closed input will
change over to discharge air heating. This local input is
arbitrated with building management Heat Cool Mode
Request commands to determine the active mode of
operation.
VAV Box Relay Output
This binary output is provided by the controller to be
optionally wired to VAV units in a Multi Zone-VAV
system to coordinate system changeover to full airflow
heating. The binary output is de-energized when the
controller is operating in cooling modes. The binary
output energizes when the heat type installed requires
full airflow. See Maximum Heat for more details.
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