LX Series Unit Ventilator Controller User's Guide
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Fresh_Air_Damper_Mod
If the damper is controlled with the Fresh_Air_Damper_Mod output, then the
damper is controlled in one of three ways:
•
Demand Control Ventilation (DCV)
: If DCV is used, the damper is closed
when the CO
2
level is lower than the CO
2
concentration level set on the
General Settings menu of the UVC configuration wizard. As the CO
2
level
rises above this point, the damper modulates to reduce the CO
2
level while
maintaining the mixed air temperature or supply air temperature above the low
limits setpoint. The controller uses DCV whenever an input is configured as a
CO
2
sensor.
•
Return, Outdoor, and Mixed Air Temperatures
: If the damper is controlled
by comparing return, outdoor, and mixed air temperatures, the fresh air damper
is set so that the amount of fresh air is slightly greater than or equal to the
minimum amount of fresh air expressed as a percentage of the total air volume.
To use return and mixed air temperatures, select Air Volume in the Fresh Air
Minimum input.
•
Minimum Fresh Air Position
: If there is no CO
2
sensor and damper position
chosen on the General Settings menu, then the Fresh_Air_Damper_Mod
output uses the minimum fresh air position set on the General settings tab of
the Unit Ventilation Controller configuration wizard. If the discharge and
mixed air temperatures are not available, the damper is always fully closed or
in the minimum position set by Fresh Air Minimum Input.
Humidity Control
The UVC maintains the humidity level at the humidity setpoint that you enter on
the General Settings menu. The humidity setpoint is stored in
UCPThumidityLevelSetpoint. The fan speeds one, two, or three must be ON for
humidity control to function.
Humidification and dehumidification outputs have a minimum ON/OFF time. This
value is also entered on the General Settings menu.
You can perform humidity control using a PID loop. Enter the PID loop parameters
on the PID screen of the Rooftop Unit Controller configuration wizard. For a
description of PID loop control, see
section.
The UV Controller maintains the humidity level at the humidity setpoint by the
following methods:
•
switching ON or OFF the HUMIDIFIER_ON_OFF or
DEHUMIDIFIER_ON_OFF
•
modulating the HUMIDIFER_MOD or DEHUMIDIFIER_MOD outputs
When you select any cooling output, it unlocks the Dehumidifying Settings. To
dehumidify with a cooling coil, you must enter a minimum cooling override value
and the fan speed override value. Dehumidification is more efficient if the air goes
through the cooling coil slowly.
