Unit Start-Up
RT-SVX22M-EN
45
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.
•
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
SERVICETEST, 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
(7.5 - 10 Ton High Efficiency, 10 Ton
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 Table 10, p. 60,
momentarily jump across theTest 1 &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.
Once the supply fan has started, determine the total
system airflow (CFM)
1. Measure the DC voltage across harness test terminals.
Using the fan rpm table shown above, determine RPM
correlated to measured voltage.
2. 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/Decrease Fan RPM turn DA COOL_FAN
SPD on the RTOM clockwise/counter-clockwise.
3. 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.
•
Stop the SERVICE TEST, turn the main power
disconnect switch to the “Off” position and reconnect
Economizer 4-pin power connector if disconnected for
this procedure.
Proceed to the next component start-up procedure.
Table 10. RPM table
Potentiometer
Voltage
Motor RPM
Potentiometer
Voltage
Motor RPM
1.00
217
4.50
1061
1.25
279
4.75
1126
1.50
312
5.00
1191
1.75
362
5.25
1253
2.00
427
5.50
1315
2.25
479
5.75
1374
2.50
543
6.00
1432
2.75
605
6.25
1487
3.00
668
6.50
1539
3.25
732
6.75
1588
3.50
797
7.00
1633
3.75
863
7.25
1675
4.00
929
7.50
1700
4.25
995
Note:
Factory setting is 7.5V
