Trane Tracer UC400 - Page 65

BAS-SVX48H-EN
65
Figure 23. Occupancy Categories
If the fan operates at a constant (single) speed, the UC400 Controller uses two (2) OA damper
position setpoints and two CO
2
setpoints (refer to the illustrations in the section, “CO
2
-Based
Demand Controlled Ventilation (DCV),” p. 47):
• With the fan operating, set the Design Minimum OA Damper Position setpoint so that in
brings in outdoor airflow equal to the V
ot-Design
value calculated in Step 1 (470 cfm in this
example).
• With the fan operating, set the DCV Minimum OA Damper Position setpoint so that in brings
in outdoor airflow equal to the V
ot-DCVmin
value calculated in Step 2 (120 cfm in this example).
• Set the CO
2
Design Setpoint equal to the CO
2space-Design
value calculated in Step 3 (1200 ppm
in this example).
• Set the CO
2
Minimum Setpoint equal to the CO
2space-DCVmin
value calculated in Step 4 (400
ppm in this example).
If the fan operates at multiple speeds (or with single-zone VAV control), the UC400 Controller
uses four OA damper position setpoints and two (2) CO
2
setpoints (refer to the illustrations in the
section, “CO
2
-Based Demand Controlled Ventilation (DCV),” p. 47):
• With the fan operating at maximum speed, set the Design Minimum OA Damper Position at
Maximum Fan Speed setpoint so that in brings in outdoor airflow equal to the V
ot-Design
value
calculated in Step 1 (470 cfm in this example).
• With the fan operating at maximum speed, set the DCV Minimum OA Damper Position at
Maximum Fan Speed setpoint so that in brings in outdoor airflow equal to the V
ot-DCVmin
value
calculated in Step 2 (120 cfm in this example).
• With the fan operating at minimum speed, set the Design Minimum OA Damper Position at
Minimum Fan Speed setpoint so that in brings in outdoor airflow equal to the V
ot-Design
value
calculated in Step 1 (470 cfm in this example).
• With the fan operating at minimum speed, set the DCV Minimum OA Damper Position at
Minimum Fan Speed setpoint so that in brings in outdoor airflow equal to the V
ot-DCVmin
value
calculated in Step 2 (120 cfm in this example).
• Set the CO
2
Design Setpoint equal to the CO
2space-Design
value calculated in Step 3 (1200 ppm
in this example).
• Set the CO
2
Minimum Setpoint equal to the CO
2space-DCVmin
value calculated in Step 4 (400
ppm in this example).
The best way to adjust the OA damper setpoints is to operate the fan as stated above, and then
use an airflow measurement hood (or other airflow measurement technique) to determine the
OA damper position (%) setpoint that corresponds to the required outdoor airflow (V
ot
).
However, if airflow measurement is not possible or practical, a less-accurate approach could be
to calculate the OA damper position (%) setpoint that by dividing the required outdoor airflow
(V
ot
) by the fan airflow at the corresponding speed. Since damper performance is not linear (%
change in damper position does not always equal the same % change in airflow passing through
SSeettttiinnggss ffoorr CCOO
22
--BBaasseedd DDeemmaanndd CCoonnttrroolllleedd VVeennttiillaattiioonn