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Sequence of Operation
operating in heating mode the heat speed set
cannot be lower than Speed Set 4.
4. To stop the SERVICE TEST, turn the main power
disconnect switch to the "Off" position or proceed to
the next component start-up procedure.
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 16, p.
51, momentarily jump across the Test 1 and
Test 2 terminals on LTB1 one time to start the Minimum
Ventilation Test.
Electromechanical Control:
Guide perform the proper test mode connections.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 (ReliaTel™/Electromechanical):
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 using (Actual Motor
Amps/ Motor Nameplate Amps) X Motor HP.
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.
62
Using the Service Test
•
To stop the SERVICE TEST, turn the main power
disconnect switch to the "Off" position or proceed to
the next component start-up procedure.
Units with Direct Drive Indoor Fan -
Electromechanical Control
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 adjusting the output voltage from the
MMC/ECM board to the direct drive fan. 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™ Units with Direct Drive Indoor
Fan
Note: 10 tons standard efficiency, 6 (074) to 10 tons high
efficiency and optional on 7.5 (092) to 8.5 tons
standard efficiency
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 adjusting the voltage from the RTOM
indoor fan speed output to the direct drive plenum fan. If
installed, before starting the SERVICE TEST disable the
economizer by disconnecting the 4 pin power connector
located at the base of the Economizer Control (ECA).
Using the service test guide in
momentarily jump across the Test 1 and Test 2 terminals
on LTB1. Repeat process until Service Test Mode is at Cool
2 (2-Steps of Cooling Applications Only) or Cool 3 (3-Steps
of Cooling applications). The indoor motor shall be
operating @ 100%, to verify turn DA COOL_FAN SPD
potentiometer full clockwise, voltage should read ~7.5 Vdc
across harness test terminals. The Unit schematic
illustrates location for measuring the indoor motor speed
voltage.
Table 22. Direct drive plenum fan settings (rpm vs.
voltage)
Potentiometer Voltage
1
1.25
1.5
1.75
2
2.25
2.5
2.75
3
3.25
3.5
Table 16, p.
51,
Motor RPM
N/A
N/A
N/A
N/A
N/A
325
402
465
544
630
716
RT-SVX21AC-EN
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Troubleshooting
