3
74-3965
Disconnecting Airflow Pickup Tubes
Anytime the airflow pickup tubes are disconnected
from the controller, the controller should be powered
down. There is no chance of damage to the controller,
but if the controller is exposed to unusually high static
pressure (< 5.0 in. w.c.) when one pickup tube is
connected there is a very slight possibility that the
controllers sensing process will stop operating. Should
this condition be suspected, simply cycle power to the
controller. It is not possible for this condition to occur
under normal operation with both airflow pickup tubes
connected to the controller.
Flow Pickup Pressure Physical
Measurement
Physical measurement of the flow pickup pressure for
the purpose of testing is best done with an instrument
capable of displaying pressure to 0.01 ±0.005 in. w.c.
Though electronic gauges and sensors often offer the
necessary accuracy, their sensitivity can cause
problems in field applications.
RULES OF THUMB
Balancing Airflow Setpoint Guidelines
All VAV II controllers must be balanced for both
minimum and maximum airflow for highest accuracy. If
the controller’s final configuration is to be a constant
volume unit, a minimum airflow balance is
recommended. The following guidelines are
recommended for flow volume setpoints.
