BAS-SVX48H-EN
49
Figure 22. OA Damper Position Setpoints
• Based on the current fan speed, the controller calculates a Design Minimum OA Damper
Position setpoint ((AA)) using a straight proportional calculation (the upper line on the chart
above) between the Design Minimum OA Damper Position at Maximum Fan Speed ((11)) and
the Design Minimum OA Damper Position at Minimum Fan Speed ((22)).
• The UC400 Controller calculates a DCV Minimum OA Damper Position setpoint ((BB)) using a
straight proportional calculation (the lower line on the chart) between the DCV Minimum OA
Damper Position at Maximum Fan Speed ((33)) and the DCV Minimum OA Damper Position at
Minimum Fan Speed ((44)).
• When the CO
2
concentration in the zone is equal to, or higher than, the CO
2
Design Setpoint,
the OA damper is adjusted to the calculated Design Minimum OA Damper Position setpoint
((AA)) for the current fan speed.
• When the CO
2
concentration in the zone is equal to, or lower than, the CO
2
Minimum
Setpoint, the OA damper is adjusted to the calculated DCV Minimum OA Damper Position
setpoint ((BB)) for the current fan speed.
• When the CO
2
concentration in the zone is between the CO
2
Minimum Setpoint and the CO
2
Design Setpoint, the OA damper position is determined using a straight proportional
calculation between the calculated Design Minimum OA Damper Position ((AA)) and DCV
Minimum OA Damper Position ((BB)) setpoints for the current fan speed.
Refer to the section, “Settings for CO
2
-Based Demand Controlled Ventilation,” p. 63, for
instructions on calculating and adjusting the following setpoints used for DCV:
• Design minimum OA Damper position at maximum speed is one of the following depending
on Occupancy mode:
– Standby Minimum Position Setpoint.
– Economizer Minimum Position Setpoint Local.
• Design minimum OA Damper position at minimum speed is Occupied Low Fan Min Position
Setpoint.
• DCV minimum OA damper position at maximum fan speed is DCV Minimum Economizer
Position at Maximum Speed.
• DCV minimum OA damper position at minimum fan speed is DCV Minimum Economizer
Position at Minimum Speed.
DX Cooling Operation, 1 or 2 Circuits
The UC400 Controller supports 1- or 2-stage direct expansion (DX) cooling for space temperature
cooling. DX cooling function applies to cooling operation for a cooling-only unit and for a heat
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