Pre-Start
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 5, 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
36 | Packaged Heat Pump • |
