T_C-IOM-2A30
Verifying Proper Air Flow
(Units with Belt Drive Indoor Fan)
Much of the systems performance and reliability is closely as-
sociated with, and dependent upon having the proper airflow
supplied both to the space that is being conditioned and across
the evaporator coil.
The indoor fan speed is changed by opening or closing the ad-
justable motor sheave.
Before starting the SERVICE TEST, set the minimum position
setpoint for the economizer to 0 percent using the setpoint po-
tentiometer located on the Economizer Control (ECA), if appli-
cable.
ReliaTel Control
Using the Service Test Guide in Table 6, momentarily jump
across the Test 1 & Test 2 terminals on LTB1 one time to start
the Minimum Ventilation Test.
Once the supply fan has started, check for proper rotation. The
direction of rotation is indicated by an arrow on the fan housing.
Use the following procedure to determine the proper adjust-
ment of the evaporator fan for a specific application.
1. With the fan operating properly, determine the total system
airflow CFM (m
3
/h) by;
a. Measuring the actual RPM,
b. Measure the amperage at the supply fan contactor and
compare it with the full load amp (FLA) rating stamped
on the motor nameplate.
c. Calculate the theoretical BHP (KW)
Actual Motor Amps X Motor HP (KW)
Motor Nameplate Amps
d. Using the fan performance tables in the unit Service
Facts, plot the actual RPM (step 1) and the theoretical
BHP (KW) (step 2c) to obtain the operating Air Flow.
2. If the required Air Flow is too low, (external static pressure is
high causing motor HP (KW) output to be below table
value), perform one or both of the following.
a. Relieve supply and/or return duct static.
b. Change indoor fan speed and repeat steps 1.a and
1.b.
3. If the required CFM is too high, (external static pressure is
low causing motor HP output to be above table value), per-
form one or both of the following:
Pre - Start
a. Relieve supply and/or return duct static.
b. Change indoor fan speed and repeat steps 1.a and
1.b.
To Increase Fan RPM; Loosen the pulley adjustment set
screw and close the sheave by moving the two halves
closer together.
To Decrease Fan RPM; Loosen the pulley adjustment set
screw and open the sheave by moving the two halves far-
ther apart..
4. To stop the SERVICE TEST, turn the main power discon-
nect switch to the “Off” position or proceed to the next com-
ponent start-up procedure.
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