66389-BIM-C-1208
30
Johnson Controls Unitary Products
CHECKING AIR QUANTITY
METHOD ONE
1.
Remove the dot plugs from the duct panel (for location of
the dot plugs see Figure 9).
2.
Insert eight-inches of 1/4 inch metal tubing into the air-
flow on both sides of the indoor coil.
NOTE:
The tubes must be inserted and held in a position
perpendicular to the air flow so that velocity pres-
sure will not affect the static pressure readings.
3.
Use an Inclined Manometer or Magnehelic to determine
the pressure drop across a dry evaporator coil. Since the
moisture on an evaporator coil can vary greatly, measur-
ing the pressure drop across a wet coil under field condi-
tions could be inaccurate. To assure a dry coil, the
compressors should be de-activated while the test is
being run.
NOTE:
De-energize the compressors before taking any test
measurements to assure a dry evaporator coil.
4.
The CFM through the unit with clean 2 inch filters can be
determined from the pressure drop indicated by the
manometer by referring to Figure 25.
5.
To adjust Measured CFM to Required CFM, see ’SUP-
PLY AIR DRIVE ADJUSTMENT’.
6.
After adjustments have been completed, remove the
tubes and replace the dot plugs.
7.
Tighten blower pulley and motor sheave set screws after
any adjustments. Re-check set screws after 10-12 hrs.
run time is recommended.
.
METHOD TWO
1.
Drill two 5/16 inch holes, one in the return air duct as
close to the inlet of the unit as possible, and another in
the supply air duct as close to the outlet of the unit as
possible.
2.
Insert eight inches of 1/4 inch metal tubing into the air-
flow of both return and supply air ducts of the unit.
NOTE:
The tubes must be inserted and held in position per-
pendicular to the airflow so that velocity pressure
will not affect the static pressure readings.
3.
Use an Inclined Manometer or Magnehelic to determine
the pressure drop across the unit. This is the External
Static Pressure (ESP).
4.
Select the indoor blower specifications for the unit from
Table 19, 3 or 5 H.P. Motor.
5.
Determine the number of turns the variable pitch motor
sheave is open.
6.
Select the correct blower performance table for the unit
from Tables 15 - 18.
7.
Determine the unit Measured CFM from the Blower Per-
formance Table, External Static Pressure and number of
turns the variable pitch motor sheave is open.
8.
To adjust Measured CFM to Required CFM, see ’SUP-
PLY AIR DRIVE ADJUSTMENT’.
9.
After adjustments have been completed, remove the
tubes and seal holes.
10. Tighten blower pulley and motor sheave set screws after
any adjustments. Re-check set screws after 10-12 hrs.
run time is recommended.
NOTE:
With the addition of field installed accessories
repeat this procedure.
Failure to properly adjust the total system air quan-
tity can result in extensive blower damage.
Failure to properly adjust the total system air quan-
tity can result in extensive blower damage.