Economizer Troubleshooting - Carrier 48LC Series Controls, Start-Up, Operation And Troubleshooting

Economizer Troubleshooting

Use the SystemVut Display to view the economizer status. Check
the current alerts and faults and the alarm history for economizer
specific alerts or any relevant faults or alerts and correct those
issues. Use test mode to troubleshoot by ramping the economizer
up and down with and without the indoor fan and power exhaust
fan on. Inspect the mechanical economizer for actuator, gear, or
blade damage. Ensure the actuator is mounted with the correct
spring return (close damper when no power applied to unit).
Ensure there is a 500 ohm resister across the actuator as the
4- -20mA output signal must be converted to 2- -10V.
PROBLEM
Damper Does Not Move.
Economizer Operation is Limited
to Minimum Position.
Economizer Position is Less
Than Minimum Position.
Economizer Does Not Return
to Minimum Position.
Damper Does Not Close on
Power Loss.
Economizer is Not at Configured
Minimum Position
LEGEND
CCN --- Carrier Comfort Network
IAQ --- Indoor Air Quality
Table 17 – Economizer Service Analysis
POSSIBLE CAUSE
Indoor Fan is off.
Actuator is unplugged at motor or at
economizer board.
Unit is not configured for economizer.
Outdoor-air temperature is above economizer
high temperature lockout.
Outdoor-air temperature is below economizer low
temperature lockout.
Communication loss to economizer board.
Damper is jammed.
Minimum position is set incorrectly.
Outdoor-air temperature is above economizer
high temperature lockout.
Outdoor-air temperature is below economizer
low temperature lockout.
Enthalpy or differential dry bulb are preventing free
cooling.
Outdoor-air thermistor is faulty.
Low suction pressure problem with a compressor.
IAQ is controlling minimum damper position.
Unit is in Unoccupied mode.
Unit is operating under free cooling.
Damper is jammed or spring return is backwards.
Unit is operating under free cooling or a force is
applied to the commanded position.
R
The Economizer alerts can be summarized as a failure to modulate
the damper blades. This can be due to the actuator not being
properly connected to the damper, or because the actuator's
feedback signal is indicating that damper is not performing as
commanded. The mechanical disconnect diagnostic will run when
conditions are appropriate to determine proper air temperature
changes. This uses the OAT, RAT, and SAT to tell if the damper is
mixing the outdoor air with the return air. The other alerts inform
where the damper is stuck relative to the commanded position.
Check for proper thermostat connection.
Unit is not configured for continuous fan
operation and the thermostat is not calling for
heating or cooling.
Unit is in Unoccupied mode and there is no
call for heating or cooling.
Tripped circuit breaker.
No power to the unit.
Unit is off via CCN command.
Check wiring connections.
Configure unit for economizer per the
instructions.
Adjust the high temperature lockout setting
if it is incorrect, otherwise, economizer is
operating correctly.
Adjust the low temperature lockout setting
if it is incorrect, otherwise, economizer is
operating correctly.
Check wiring connections.
Identify the obstruction and safely remove.
Adjust minimum position setting.
Adjust the high temperature lockout setting
if it is incorrect, otherwise, economizer is
operating correctly.
Adjust the low temperature lockout setting if it is
incorrect, otherwise, economizer is operating
correctly.
Check enthalpy and return air compared to
outside air temperature.
Replace outdoor-air thermistor.
Economizer is operating correctly, identify
compressor problem.
Adjust the IAQ settings if incorrect,
otherwise, the economizer is operating correctly.
Adjust unit occupied schedule if incorrect,
otherwise, economizer is operating correctly.
Economizer is operating correctly.
Identify the obstruction and safely remove.
Economizer is operating correctly.
40
REMEDY