Balancing; Variable Volume Venturi Valve - Price Antec Controls VENTURI VV Series Manual

BALANCING

The balancing process is required in the field to ensure that the valves are providing the necessary flow into and out of the
pressure-controlled space. The process involves measuring the airflow through the valve in the field, using third party calibrated
equipment and comparing it to the calibrated position feedback from the Venturi Valve.

Variable Volume Venturi Valve

There are two tools that are available in the Antec Controls system that will help adjust the calibrated position feedback from
the Venturi Valve, they are scale factor and offset.
NOTE: When using PACE or FHC controllers from Antec Controls, please refer to the appropriate manual for instructions on
adjusting the settings described below.
Scale Factor
Scale factor is a multiplication factor that is applied to the controller's electronic flow feedback. Its default value is 1.000, which
will not affect the flow feedback.
A scale factor greater than 1.000 will increase the flow feedback. A scale factor less than 1.000 will decrease the flow
feedback. To determine the scale factor required simply use the following formula.
NOTE: Scale factor is the recommended method of adjusting airflow readings.
Offset
Offset is an addition or subtraction in CFM, which is applied to the controller's electronic flow feedback. Its default value is 0
CFM, which will not affect the flow feedback.
Recommended Balancing Procedure
Below are the recommended steps to take when balancing Venturi Valves.
1. Check to make sure the pressure across the Venturi Valves is within the operating range of the valve.
Note: The minimum pressure drop will be indicated on the Specification label on the valve.
2. Depending on the balancer's process (which varies based on local requirements, balancer's test method, etc...), one of
the following will be required:
a. One airflow will be measured. Typically, the Max Scheduled airflow for the valve.
b. Two airflows will be measured. Typically, the Max Scheduled and Min Scheduled airflow for the valve.
3. In both cases, it is preferable to only use a scale factor to modify the flow feedback from the valve.
4. If two airflows are measured and using only the scale factor cannot satisfy the requirements, a combination of scale
factor and offset can be used.
Methods of adjusting the airflow for Variable Volume and Constant
Volume Venturi Valves are described below.
26 | VV – Manual | AntecControls.com
���������������� ���� ���������������� ���� ���� =
������������������������ = ������������ ���� ���������������� ���� �������� ���� �������� ���� ���� �������������������������������������������� − �������� ���� �������� ���� ������������ ���� �������� ���� �������� ���� ���� ��������������������������������
'
������������ ���� ���������������� ���� �������� ���� �������� ���� ���� ��������������������������������������������
'
�������� ���� ������������������������ ���� �������� ���� ���� ��������������������������������
Adjustments should only be made after the
differential pressure across the valve has
been checked to ensure it is within the
operating range of the valve.
CAUTION
VV