LX Series Unit Ventilator Controller User's Guide
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using data from an enthalpy-calculating sensor
•
using humidity and temperature from sensor or network inputs to calculate
enthalpies
Outdoor Temperature
: If outdoor temperature is available, but not the enthalpy
and the economizer enable input, then free cooling occurs if the outdoor
temperature is below the maximum outdoor temperature. A deadband of 1.8 Fº
(1C°) space is used in this process.
Maximum outdoor temperature is set on the Heating-Cooling Configuration screen
or by modifying UCPTfreeCoolSetpoint.
Note:
If discharge air temperature or mixed air temperature is not available, the
Fresh_Air_Damper_Mod output commands the fresh air damper closed or
to the fixed minimum position, depending on the fan state input value and
occupancy mode. The damper opens fully only during an emergency purge.
When Free Cooling is Used
The Rooftop Unit Controller uses free cooling when the following conditions
occur:
•
The fan speeds 1, 2, or 3 are ON, or fan speed modulation is at the minimum
speed.
•
All heating outputs have been OFF for the minimum amount of time defined
by the Change Over Delay option on the Heating-Cooling Configuration
screen UCPTchngeOverDelay.
•
nviApplicMode must be set to HVAC_AUTO or HVAC_COOL.
•
The space temperature input data must be valid, or the UVC must be slaved to
another unit.
•
There must be a cooling demand. A cooling demand results from a comparison
between the space temperature and the active cooling setpoint.
Mechanical Cooling
The UVC turns the mechanical cooling outputs ON when all of the following
conditions occur:
•
The fan speeds 1, 2, or 3 are ON, or fan speed modulation is at the minimum
speed.
•
All heating outputs have been OFF for the minimum amount of time defined
by the Change Over Delay option on the Heating-Cooling Configuration
screen UCPTchngeOverDelay.
•
nviApplicMode must be set to HVAC_AUTO or HVAC_COOL.
•
The space temperature input data must be valid, or the Unit Ventilator
Controller must be slaved to another unit.
•
The outdoor temperature must be greater than the Minimum Outdoor
Temperature entered on the Heating-Cooling Configuration screen.