22
7
6
0.625 - 0.675 in. W.C.
Start-Up - Direct Gas
Start-Up
Step 3 Set the Burner Air Pressure
Differential
With all access panels in place, the fan running and
discharging 70°F air, connect a U-Tube manometer to
the outer sensing probes (see figure #42) and
measure the static pressure across the burner.
The proper static pressure should be between 0.625
and 0.675 inches wc. If needed, evenly adjust the
baffles above and below the burner, keeping the
burner centered in the opening until the required
pressure is obtained. See figure #41.
Outer Sensing Probes
U-Tube
Manometer
Adjustable
Top Baffle
Air Flow
Burner
Adjustable
Bottom Baffle
IMPORTANT!
Proper air velocity over the burner is critical on direct fired gas units. If the air velocity is not within
the unit specifications, the unit will not operate efficiently, may have sporadic shutdowns and may
produce excessive carbon monoxide (CO) or other gases.
NOTE!
To increase the static pressure decrease the
opening. To decrease the static pressure
increase the opening.
IMPORTANT!
This process may need to be repeated until the
proper pressure is achieved. This adjustment
will change the air quantity delivered by the unit
and therefore the air quantity delivered should be
rechecked. Refer to the blower start-up section.
NOTE!
When required pressure is obtained be sure to
reconnect the outer sensing probes.
NOTE!
The pressure drop was set at the factory and may
not need adjustment.
Figure 41.
Burner and Baffles
Figure 42.
Measuring the Pressure Drop