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1
3
2
CW
COM CCW
HIGH
LOW
HIGH PRESSURE TAP ON BOX FLOW RING
or FLOW SENSOR
LOW PRESSURE TAP ON BOX FLOW RING
or FLOW SENSOR
¼” OD TUBING
VELOCITY SENSOR / TUBING CONNECTIONS
INTERNAL TUBING FROM BOARD
VELOCITY SENSOR TO EXTERNAL
PRESSURE TAPS FACTORY INSTALLED
CONNECTING THE VELOCITY SENSOR
The VAV / VVR uses an on-board differential pressure sensor for monitoring of air flow and velocity of the box
discharge to the conditioned space. On the VAV, the sensor is connected with flexible tubing to external taps on the
lower edge of the enclosure marked “HIGH” and “LOW”. On the VVR, the tubing is connected directly to the velocity
sensor at the top of the VVR controller board.
IMPORTANT:
When connecting tubing directly to the on-board velocity sensor, the lower
(closest to the board) connection is the “LOW” pressure, and the upper
connection is the “HIGH”.
NOTE:
On the VAV assembly, the external taps accept a 1/4" OD tubing.
On the VVR retrofit board, the sensor taps are 3/8" OD.
Figure 17 shows the connection to the box flow ring (see box manufacturers installation manual) or the SSS series
flow sensor, which is provided for older boxes without a flow ring, or damper blade only type installations.
Figure 17: Typical VAV Velocity Sensor Tubing Connections
NOTE:
See Appendix 2 for box constant values for major manufacturers
