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WARNING
Hazardous Voltage!
Failure to disconnect power before servicing could
result in death or serious injury.
Disconnect all electric power, including remote
disconnects before servicing. Follow proper lockout/
tagout procedures to ensure the power can not be
inadvertently energized. Verify that no power is
present with a voltmeter.
3. Interchange any two of the field connected main power
wires at the unit terminal block or the factory mounted
disconnect switch.
Note: Interchanging "Load" side power wires at the fan
contactors will only affect the individual fan
rotation. Ensure that the voltage phase
sequence at the main terminal block or the
factory mounted disconnect switch is ABC as
outlined in the
"Unit Startup_Electrical
Phasing," p. 92
System Airflow Measurements
Variable Air Volume Systems
1. Ensure that the "System" selection switch at the remote
panel is in the Off position.
2. Close the disconnect switch or circuit protector switch
that provides the supply power to the unit terminal block
or the unit mounted disconnect switch.
WARNING
Hazardous Voltage!
Failure to disconnect power before servicing could
result in death or serious injury.
Disconnect all electric power, including remote
disconnects before servicing. Follow proper lockout/
tagout procedures to ensure the power can not be
inadvertently energized. Verify that no power is
present with a voltmeter.
Important: HIGH VOLTAGE IS PRESENT AT TERMINAL
BLOCK OR UNIT DISCONNECT SWITCH.
3. Turn the 115 volt control circuit switch and the 24 volt
control circuit switch to the On position.
4. Navigate to Supply Fan Manual Overrides. The supply
fan speed will be adjusted through the user interface.
With the unit in Stop, tap the Manual Override button
for the Supply Fan. Set the Fan Speed to 100%.
RT-SVX073A-EN
section.
WARNING
Live Electrical Components!
Failure to follow all electrical safety precautions when
exposed to live electrical components could result in
death or serious injury.
When it is necessary to work with live electrical
components, have a qualified licensed electrician or
other individual who has been properly trained in
handling live electrical components perform these
tasks.
5. With the VFD at 100% and the supply fan operating at
full airflow capability, measure the amperage at the
supply fan contactors. If the amperage exceeds the
motor nameplate value, the static pressure is less than
design and the airflow is too high. If the amperage is
below the motor nameplate value, static pressure may
be too high and CFM may be too low. To determine the
actual CFM (± 5%):
a. Measure the actual fan RPM
b.
c. Plot this data onto the appropriate Fan
Performance Curve (see Performance Data).
Where the two points intersect, read straight down
to the CFM line. Use this data to assist in
calculating a new fan drive if the CFM is not at
design specifications.
d. An alternate method with less accuracy is to
measure the static pressure drop across the
evaporator coil. This can be accomplished by
completing the following steps:
•
Drill a small hole through the unit casing on
each side of the coil.
Important: Coil damage can occur if care is not
taken when drilling holes in this
area.
•
Measure the difference between the pressures
at both locations.
•
Plot this value onto the appropriate pressure
drop curve (see Fan Performance Data). Use
the data in Component Static Pressure Drops to
assist in calculating a new fan drive if the CFM
is not at design specifications.
•
Plug the holes after the proper CFM has been
established.
6. Press the STOP key at the user interface in the unit
control panel to stop the fan operation.
Unit Startup
95
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