Lifebreath CLEAN AIR FURNACE 60ELE - Manual (Page 9)

9
For general balancing it is sufficient to move the Pitot tube
around in the duct and take an average or typical reading.
Repeat this procedure in the other (supply or return) duct.
(Fig. B.). Determine which duct has the highest airflow
(highest reading on the gauge). Then damper that airflow
back to match the lower reading from the duct. The flows
should now be balanced.
Actual airflow can be determined from the gauge reading.
The value read on the gauge is called velocity pressure.
The Pitot tube comes with a chart that will give the air flow
velocity based on the velocity pressure indicated by the
gauge. This velocity will be either feet per minute or
metres per second. To determine the actual airflow, the
velocity is multiplied by the cross sectional area of the
duct being measured.
This is an example for determing 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"ч12] 2 ) ч 4
= 0.2 square feet
The airflow is then 640 ft./min x 0.2 square feet = 128cfm
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 multi-
ple readings as outlined in the literature supplied with the
Pitot tube.
Figure A:
Pitot Tube Air Flow Balancing Kit
c/w magnetic gauge, Pitot tube, hose and carry case.
PART NO. 99-167
Figure B:
Pitot Tube and Gauge
Note: For best results keep Pitot tube
well away from dampers.
Pitot Tube
Figure C:
Placement of the Pitot Tube
Note: For best results, keep Pitot tube well away from dampers and
motor turbulence.
Figure D
*Note: All dampers & fittings must be covered with insulation and sealed with tape
Installation