035-16626-000-E-0103
Unitary Products Group
13
To check the supply air CFM after the initial balancing
has completed”
1. Drill two 5/16” holes in the side panel as shown in
Figure 15.
2. Insert at lest 6” of 1/4” tubing into each of these
holes for sufficient penetration into the air flow on
both sides of the indoor coil.
NOTE: The tubes must be inserted and held in a posi-
tion perpendicular to the air flow so that veloc-
ity pressure will not affect the static pressure
reading.
3. Using an inclined manometer, determine the pres-
sure drop across a dry indoor coil. Since moisture
on the coil may vary greatly, measuring the pres-
sure drop across a wet coil under field conditions
would be inaccurate. To assure a dry coil, the heat
pump system should be de-activated while the test
is being run.
4. Knowing the pressure drop across a dry coil the
actual CFM through the unit can be determined
from the curve in Figure 16.
If the CFM is above or below the specified value, the
supply air motor pulley may have to be re-adjusted.
After one hour of operation, check the belt and pulleys
for tightness and alignment.
After readings have been obtained remove the tubes
and seal up the drilled holes in the side panel. Dot
plugs (5/16” - P/N 029-13880-000) are available
through Source One Parts ordering procedures.
NOTE: Shut down the heat pump system before tak-
ing any test measurements to assure a dry
indoor coil.
FIGURE 14 - TYPICAL MOTOR MOUNTING
ASSEMBLY
B
A
(DO NOT LOOSEN)
MOTOR
MOTOR MOUNT
C
FIGURE 15 - HOLE LOCATIONS FOR PRESSURE
DROP READINGS
FIGURE 16 - CFM VS PRESSURE DROP
5 / 1 6 "
H O L E
5 / 1 6 "
H O L E
1 8 "
7 "
2 2 "
1 0 "
E V A P O R A T O R
C O I L
F I L T E R S
C O I L S E C T I O N
0.1
0.2
0.3
0.4
0.5
4800
5600
6400
7200
8000
8800
9600
SUPPLY AIR CFM
PRESSURE
DROP
(I
W
G)
FEH180
FEH240
