Basic Documentation

DIFFERENTIAL
PRESSURE
INCHES
of
WATER
0.020
0.019
0.018
0.017
0.016
0.015
0.014
0.013
0.012
0.011
0.010
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0.000
ROOM DIFFERENTIAL AIRFLOW - CFM
0.1 Ft
2
0.2 Ft
2
0.3 Ft
2
0.4 Ft
2
0.5 Ft
2
0.6 Ft
2
0.75 Ft
2
1.0 Ft
2
1.5 Ft
2
ROOM LEAKAGE AREA CURVES
0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400
Figure 3
. Room Differential Airflow vs. Differential Pressure for Various Room Leakage Areas.
Maintaining Room Pressurization
with Volumetric Airflow Tracking
Airflow tracking can maintain the desired room
pressurization polarity (positive or negative) for both
constant air volume (CAV) as well as variable air
volume (VAV) ventilation systems. Figure 4 shows
an airflow tracking control configuration for a VAV
chemical laboratory room ventilation system.
SUPPLY AIR
TERMINAL
ROOM
CONTROLLER
FUME HOOD
EXHAUSTS
ROOM
GENERAL
EXHAUST
CFM
CFM
CFM
CFM
Figure 4. Airflow Tracking Control Arrangement for a VAV Laboratory Room.
Volumetric airflow tracking is based upon measuring
and controlling room airflows. Figure 4 shows the
essential
components of a volumetric airflow tracking
control configuration for a VAV chemical laboratory
Page 4 of 8 Siemens Industry, Inc.
Document No. 149-977