Pre-Start
32
RT-SVX33E-EN
Verifying Proper Air Flow (Units with Belt
Drive Indoor Fan)
Much of the systems performance and reliability is closely
associated 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
adjustable motor sheave.
Before starting the SERVICE TEST, set the minimum
position setpoint for the economizer to 0 percent using the
setpoint potentiometer located on the Economizer Control
(ECA), if applicable.
ReliaTel Control
Using the Service Test Guide in
Table 7, p. 31
, 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.
With the fan operating properly, determine the total
system airflow (CFM) by;
1.
Measuring the actual RPM,
2. Measure the amperage at the supply fan contactor and
compare it with the full load amp (FLA) rating stamped
on the motor nameplate.
a. Calculate the theoretical BHP
Actual Motor Amps X Motor HP
Motor Nameplate Amps
b. Using the fan performance tables in the unit Service
Facts, plot the actual RPM (step 1) and the BHP (step
2a) to obtain the operating CFM.
3. If the required CFM is too low, (external static pressure
is high causing motor HP output to be below table
value),
a. Relieve supply and/or return duct static.
b. Change indoor fan speed and repeat steps 1 and 2.
•
To Increase Fan RPM; Loosen the pulley adjustment set
screw and turn sheave clockwise.
•
To Decrease Fan RPM; Loosen the pulley adjustment
set screw and turn sheave counterclockwise.
•
If the required CFM is too high, (external static
pressure is low causing motor HP output to be above
table value), change indoor fan speed and repeat steps
1 and 2.
•
To stop the SERVICE TEST, turn the main power
disconnect switch to the “Off” position or proceed to
the next component start-up procedure. Remove
electro mechanical test mode connections (if
applicable).
Return Air Smoke Detector
The return air smoke detector is designed to shut off the
unit if smoke is sensed in the return air stream. Sampling
the airflow entering the unit at the return air opening
performs this function.
In order for the smoke detector to properly sense smoke in
the return air stream, the air velocity entering the unit must
be between 500 and 4000 feet per minute. Equipment
covered in this manual will develop an airflow velocity that
falls within these limits over the entire airflow range
specified in the evaporator fan performance tables.
