27
3.12.3 COMPONENT AIR-RESISTANCE DATA
CFM
[L/s]
1800
[850]
2200
[1038]
2600
[1227]
3000
[1416]
3400
[1605]
3800
[1793]
4200
[1982]
4600
[2171]
5000
[2360]
Electric Heater 20KW, 30KW
.060 [.015] .100 [.025] .140 [.034] .160 [.040] .230 [.057] .320 [.080] .410 [.102] .500 [.124] .600 [.150]
Mixing Box (R/A Damper Open)
.006 [.001] .008 [.002] .012 [.003] .024 [.006] .038 [.009] .053 [.013] .068 [.017] .080 [.020] .095 [.024]
Discharge Grille (Set Max. Open) .008 [.002] .011 [.003] .015 [.004] .020 [.005] .025 [.006] .031 [.008] .039 [.010] .046 [.012] .055 [.014]
Inlet Grille
.008 [.002] .010 [.002] .014 [.003] .020 [.005] .026 [.006] .032 [.008] .039 [.010] .049 [.012] .058 [.014]
Discharge Plenum
.02 [.005] .04 [.010] .05 [.012] .065 [.016] .085 [.021] .100 [.025] .120 [.030] .150 [.037] .180 [.045]
3.12.4 SELECTING THE PROPER BLOWER DRIVE & MOTOR SHEAVE SETTING
To select the proper blower drive, the following information is required.
• Target air-flow in CFM or L/s
• Total static pressure of the duct system in inches of water or kPa
• Component Resistance (See Section 3.12.3)
Add the total static pressure of the duct system to the component resistance to determine
the External Static Pressure (E.S.P.) that the air-handler must work against. Locate the
target CFM [L/s] row on the air-flow performance table and move to the right along that
row to the correct E.S.P. column. If the target CFM and E.S.P. are between the values
shown on the table, it will be necessary to interpolate between rows and lines.
There are heavy lines dividing blower drives from left to right with the “R” drive being
everything left of the first heavy line, “S” drive being for everything between the 1st and
2nd heavy lines, “T” drive being for everything between the 2nd and 3rd heavy lines, and
so forth.
Once the correct blower drive is determined, confirm the air-handler being installed has
the correct drive package or can be converted to the correct drive with field supplied
sheaves and belt(s). In some cases, a motor change is also required for field supplied
blower drives. See Section 3.12.5 for more details on field supplied blower drives.
Determine the correct blower RPM from the air-flow performance chart at the intersec-
tion of the target air-flow and E.S.P. Then refer to the Blower Package Data table to
determine the correct setting in turns open for the variable pitch motor sheave. The
variable pitch motor sheave can be adjusted in half turns to provide finer adjustments of
the blower RPM if needed. Adjust the variable pitch motor sheave to the correct setting
using the instructions found in Section 3.12.6.
3.12.5 FIELD SUPPLIED BLOWER DRIVES
For applications where the blower drive packages available from the factory cannot pro-
vide enough External Static Pressure (E.S.P.), the motor sheave and/or blower sheave
and the belt(s) can be changed to a factory authorized optional field supplied blower drive
that will extend the E.S.P. range of the air-handler. Please note that In some cases, a
higher horsepower motor may have to be substituted for the factory motor per the specifi-
cations in the Blower Package Data table. Factory authorized field supplied blower drive
specifications are provided in the Blower Package Data table and the air-flow perfor-
mance tables include data for the factory authorized field supplied blower drives.
IMPORTANT: Do not deviate from the specifications for the factory authorized
field supplied blower drive packages to assure the motor is not overloaded and to
assure that a known air-flow level can be achieved.
3.12.6 ADJUSTING THE VARIABLE PITCH MOTOR SHEAVE
The adjustable pitch sheave which is mounted on the motor shaft controls the fan
speed. To adjust the fan speed refer to figure at right, proceed as follows:
a. Loosen the set screw, item 1.
b. Rotate the adjustable sheave, item 2, to the desired position.
c. Lock the adjustable sheave in place by tightening the set screw, item 1.
NOTE: The adjustable sheave is not to be used to adjust belt tension.
WARNING
BEFORE MAKING FAN ADJUSTMENTS, BE SURE THE MAIN ELECTRICAL
DISCONNECT SWITCH IS IN THE “OFF” POSITION TO PREVENT POSSIBLE
INJURY DUE TO ACCIDENTAL OPERATION OF THE MOTOR.
!
