550.13-N10Y
Unitary Products Group
12
®
3.
The tension on the belt should be adjusted for a deflec-
tion of 3/16” per foot of belt span with an applied force of
2 to 3 pounds. This adjustment is made by moving the
blower motor mounting plate. Refer to Figure 14. Turn-
ing the adjustment bolt (B) moves the motor mounting
plate up or down. Two hex nuts (A have to be loosened
to move the mounting plate and retighten after the
mounting plate has been moved to the proper position.
NOTE: Never loosen the two nuts (C) (shown in Fig. 14)
4.
All pulleys are factory aligned.
5.
All supply air motor pulleys are factory set at 3 “turns
open”.
After the supply air blower motor is operating, adjust the
resistances in both the supply and the return duct system to
balance the air distribution throughout the conditioned space.
The job specification may require that this balancing be done
by someone other than the equipment installer.
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 position per-
pendicular to the air flow so that velocity pressure will not
affect the static pressure reading.
3.
Using an inclined manometer, determine the pressure
drop across a dry indoor coil. Since moisture on the coil
may vary greatly, measuring the pressure drop across a
wet coil under field conditions would be inaccurate. To
assure a dry coil, the system should be de-activated
while the test is being run.
TABLE 6: SUPPLY AIR BLOWER MOTOR PULLEY
ADJUSTMENT
TURNS
OPEN
DRIVE RANGE
625-810 RPM
827-986 RPM
5
625
827
4
662
859
3
699
891
2
736
923
1
773
955
0
810
986
FIGURE 14 : TYPICAL MOTOR MOUNTING
ASSEMBLY
M O T O R
M O U N T
B
C ( D O N O T L O O S E N )
M O T O R
A
