Airflow Balancing - Fxa/Fxk - Lennox ROOFTOP FLEXY FCA Series Installation Operating & Maintenance Manual

AIRFLOW BALANCING - FXA/FXK

AIRFLOW BALANCING - FXA/FXK AIRFLOW BALANCING - FXA/FXK AIRFLOW BALANCING - FXA/FXK AIRFLOW BALANCING - FXA/FXK
The FX* models are designed to operate with more complex
supply and extract ductwork systems. Without balancing there
are numerous risks :
- Fan motor overvoltage
- Significant flow variations depending on the position of
the dampers, which affects the building concerned,
especially when applied
to pressure balanced
systems.
To rectify this we have fitted an
equilizing grill on the fresh air
dampers. The grill can be
moved after unscrewing the
knurled nuts (1 - figure 14) and
operates as an adjustable
damper.
Before starting to adjust fully
open the equilising grills.
To equilise, proceed as follows
:
Example :
Zone
Technical specification
Recycled air without setting
Recycled air after setting b/b'
Fresh air before setting
Fresh air after setting grill a
Fresh air after setting grill b'
Figure 15
FX in "recycle air" position
Figure 16
FX in "fresh air" position
Page 24 - IOM / ROOF-TOP FLEXY™ Series
Grill b'
1
fresh air by pass
Figure 14
1
Pa 200
Pa 190
Pa 190
Pa 270
Pa 190
Pa 190
Supply air
A. Set the unit to the "recycle air" position (figure 15)
B. Measure the static pressure in the areas indicated 1/2/
3/4/5/6
C. Before proceeding further, check that the pressure
difference between zones 1 and 4 satisfies the static
pressure required.
If this is not the case, refer to the "AIR FLOW
BALANCING" section.
D. If the flow and the pressure are correct :
On grills "b" and "b'", bring the pressure at 5 to the
same level as 3 (the grills must be moved
simultaneously by the same amount).
E. Check that the power absorbed by the extract fan
motor is less than its rated power.
If the values are not the same, refer to the "AIR FLOW
BALANCING" section.
F. Switch the unit to "fresh air" (figure 16), and measure
the static pressure at 2/3/4/5/6.
G. Adjust grill "a" so that the value measured at 3 is the
same as the value at point B.
H. Finally check that the pressure at 5 is the same as the
pressure measured at point B. If not, slightly adjust the
grill "b" setting of the fresh air by-pass.
2 3
-230 -210
-230 -210
-80 -50
-230 -210
-230 -210
Extracted air
2 3
1
a
Fresh air
4 5
-180
-190 -70 -120
-190 -210 -240
-200 -220 -250
-200 -220 -250
-190 -210 -240
4 5
6
Discharge
b, b'
6