Lifebreath 60DHWDF(T) 用户手册

This is an example for determining the airflow in
a 6" duct. The Pitot tube reading was 0.025
inches of water. From the chart, this is 640 feet 
per minute.

The 6" duct has a cross sectional area of:

= 

[

3.14 x (6"÷12)

2

]

÷4

= 0.2 square feet

The airflow is then: 
640 ft./min. x 0.2 square feet  = 128 cfm

For your convenience, the cross sectional area
of some common round duct is listed below:
DUCT DIAM. (inches)   CROSS SECTION AREA (sq. ft.)

5.0

.14

6.0

.20

7.0

.27

The accuracy of the airflow reading will be 
affected by how close to any elbows or bends
the readings are taken. Accuracy can be
increased by taking an average of multiple 
readings as outlined in the literature supplied
with the Pitot tube.

BUILT-IN 

BALANCING 

DAMPERS

OUTSIDE

HOOD

INSULATED PIPE

WITH  VAPOUR 

BARRIER

26

Push and turn with slotted 
screwdriver. Damper 
automatically locks when 
pressure is released.

When connecting ductwork 
to the collar, take note where
screws are located. Screws 
should be located no further 
than 1/2” from outside edge 
of collar, so as not to impede 
operation of the damper.

1/2”