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wired for constant speed/constant volume
operation.
Single Zone VAV Supply Fan
Supply fan operation is selectable between
“Auto” and “On”. The supply fan will either
cycle with cooling/heating operation (Auto)
or operate continuously (On). The setting is
selectable for both occupied and unoccupied
modes of operation.
As the space temperature deviates ½ of the
space temperature deadband above the space
cooling setpoint the supply fan will be
activated and operate at the cooling
minimum speed. As the space temperature
increases the supply fan will increase in
speed to the cooling maximum speed
delivering more cool air. As the space
temperature decreases toward the cooling
space temperature setpoint the supply fan
will decrease in speed delivering less cool
air. As the space temperature reaches the
cooling space temperature setpoint the
supply fan will operate at cooling minimum
speed.
As the space temperature achieves the
cooling space temperature setpoint minus ½
of the space temperature deadband the
supply fan is de-activated (Auto) or operates
at the cooling minimum speed (On).
As the space temperature deviates ½ of the
space temperature deadband below the space
heating setpoint the supply fan will be
activated and operate at the heating
minimum speed. As the space temperature
decreases the supply fan will increase in
speed to the heating maximum speed
delivering more hot air. As the space
temperature increases toward the heating
space temperature setpoint the supply fan
will decrease in speed delivering less hot air.
As the space temperature reaches the heating
space temperature setpoint the supply fan
will operate at heating minimum speed.
As the space temperature achieves the
heating space temperature setpoint plus ½ of
the space temperature the supply fan is de-
activated (Auto) or operates at the cooling
minimum speed (On).
During the dehumidification mode of
operation the supply fan will operate at the
constant dehumidification speed.
Economizer
If the space temperature deviates ½ of the
space temperature deadband above the space
cooling setpoint and the outside air
temperature is below the economizer enable
temperature setpoint, the unit will use
outside air to cool the space.
If the controller is enabled for enthalpy
controlled economizer the outside air
enthalpy must be below 25 Btu/lb before the
economizer will be activated.
For constant volume systems if the outside
air temperature is below 50°F the
economizer will modulate to maintain 55°F
supply air temperature.
For single zone VAV systems if the outside
air temperature is below the cooling supply
air temperature setpoint the economizer will
modulate to maintain the cooling supply air
temperature setpoint.
Minimum damper position setpoint,
compressor low limit setpoint and low
supply air temperature setpoint are required.
The economizer control is used only for
occupied cooling.
If the economizer control does not satisfy
the space within three concurrent
compressor stage delays mechanical cooling
will be activated.
Dehumidification
When the space relative humidity rises
above the space relativity humidity setpoint,
the cooling stages will be activated and
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