Honeywell AUTOMATIC CONTROL SI Edition User Manual

ENGINEERING MANUAL OF AUTOMATIC CONTROL
BUILDING AIRFLOW SYSTEM CONTROL APPLICATIONS
279
DAMPER
AXLE
AIRFLOW
PICKUP
INLET
SLEEVE
VAV BOX
M12214
Fig. 22. Airflow Pickup Station
for VAV Box Applications.
AIRFLOW MEASURING DEVICES
Various devices for measuring airflow are available. Figure 19
shows a flow measuring station that consists of:
— An air straightener section to eliminate swirl type
airflow and help normalize the velocity profile
— Total pressure sensors aligned into the air stream and
spaced on an equal area basis
— Static pressure sensors with ports perpendicular to the
airflow direction and positioned on an equal area basis
— Separate manifolds for static and total pressure averaging
The flow measuring station in Figure 19 uses a tube as an air
straightener (Fig. 20) with total and static pressure sensors at the
downstream end. These tubes are arranged on an equal area basis.
C2659
AIR
STRAIGHTENER
TOTAL
PRESSURE
SENSOR
STATIC
PRESSURE
SENSOR
MANIFOLD
ASSEMBLY
TOTAL PRESSURE
CONNECTION
STATIC
PRESSURE
CONNECTION
AIRFLOW
Fig. 19. Averaging Flow Measuring Station.
C2660
Electronic flow stations use the tube type construction with
thermal velocity sensors instead of static and total pressure
sensors. Other flow sensing arrangements use holes in round
tubing (Fig. 21A and 21B) or airfoil designs (Fig. 21C). It is
important to consult the manufacturer of each type of flow
station for specifications, calibration data, and application
information (location limitations within ducts).
Fig. 21. Miscellaneous Flow Sensing Arrangements.
Figure 22 illustrates illustrates an airflow pickup station
typically used in the primary air inlet to a VAV air terminal
unit. The pickup station consists of two tubes that measure
differential pressure. This measurement can be used in an
airflow calculation.
AIRFLOW
39.25 39.25
TOTAL PRESSURE
PORT
STATIC PRESSURE
PORTS
A. B.
C2661
AIR PROFILE
TOTAL
PRESSURE
STATIC
PRESSURE
FLOW
AIR PROFILE
NOTE: STATIC PRESSURE SIGNAL WILL BE LESS THAN ACTUAL
STATIC PRESSURE AND CANNOT BE USED FOR STATIC
PRESSURE CONTROL. AS DEPRESSION VARIES WITH
AIR VELOCITY, VELOCITY PRESSURE (VP=TP - SP) WILL
BE AMPLIFIED.
˚˚
TOTAL
PRESSURE
TUBE
STATIC
PRESSURE
TUBE
TOTAL
PRESSURE
TUBE
STATIC
PRESSURE
TUBE
(SEE NOTE)
C.
Fig. 20. Air Straighteners/Sensors and Manifolds.

Honeywell AUTOMATIC CONTROL SI Edition Specifications

General

Brand	Honeywell
Model	AUTOMATIC CONTROL SI Edition
Category	Control Systems
Language	English