Carrier 48FC Series Controls, Start-up, Operation And Troubleshooting

Also see for 48FC 04: Installation instructions

Carrier 48FC Series Controls, Start-up, Operation And Troubleshooting Manual pdf 37 page image

37Economizer TroubleshootingUse the SystemVut Display to view the economizer status. Checkthe current alerts and faults and the alarm history for economizerspecific alerts or any relevant faults or alerts and correct thoseissues. Use test mode to troubleshoot by ramping the economizerup and down with and without the indoor fan and power exhaustfan on. Inspect the mechanical economizer for actuator, gear, orblade damage. Ensure the actuator is mounted with the correctspring return (close damper when no power applied to unit).Ensure there is a 500 ohm resister across the actuator as the4--20mA output signal must be converted to 2--10V.Feedback from the actuator is a 2 to 10 volt feedback. If thefeedback does not reach 2 volts when commanded to 0% a negativetrim (ECO FEEDBACK TRIM in the Service Calibration menu) canbe put on the feedback to stop Economizer alarms occurring at 0%. Ifthis done the max damper position (ECON MAX POS in theEconomizer Settings menu) must be set less than 100% to preventEconomizer alarms at 100% since the trimmed value will not reach100% at 10 Volts. Both signals can be measured with a meter onthe signal and feedback wires J7 pins 4 and 3 respectively andreferenced to ground J7 pin 8 while the values can be displayed onthe local display.The Economizer alerts can be summarized as a failure to modulatethe damper blades. This can be due to the actuator not beingproperly connected to the damper, or because the actuator’sfeedback signal is indicating that damper is not performing ascommanded. The mechanical disconnect diagnostic will run whenconditions are appropriate to determine proper air temperaturechanges. This uses the OAT, RAT, and SAT to tell if the damper ismixing the outdoor air with the return air. The other alerts informwhere the damper is stuck relative to the commanded position.Table 16 – Economizer Service AnalysisPROBLEM POSSIBLE CAUSE REMEDYDamper Does Not Move. Indoor Fan is off. Check for proper thermostat connection.Unit is not configured for continuous fanoperation and the thermostat is not calling forheating or cooling.Unit is in Unoccupied mode and there is nocall for heating or cooling.Tripped circuit breaker.No power to the unit.Unit is off via CCN command.Actuator is unplugged at motor or ateconomizer board. Check wiring connections.Unit is not configured for economizer. Configure unit for economizer per theinstructions.Outdoor-air temperature is above economizerhigh temperature lockout. Adjust the high temperature lockout settingif it is incorrect, otherwise, economizer isoperating correctly.Outdoor-air temperature is below economizer lowtemperature lockout. Adjust the low temperature lockout settingif it is incorrect, otherwise, economizer isoperating correctly.Communication loss to economizer board. Check wiring connections.Damper is jammed. Identify the obstruction and safely remove.Economizer Operation is Limitedto Minimum Position.Minimum position is set incorrectly. Adjust minimum position setting.Outdoor-air temperature is above economizerhigh temperature lockout. Adjust the high temperature lockout settingif it is incorrect, otherwise, economizer isoperating correctly.Outdoor-air temperature is below economizerlow temperature lockout. Adjust the low temperature lockout setting if it isincorrect, otherwise, economizer is operatingcorrectly.Enthalpy or differential dry bulb are preventing freecooling. Check enthalpy and return air compared tooutside air temperature.Outdoor-air thermistor is faulty. Replace outdoor-air thermistor.Low suction pressure problem with a compressor. Economizer is operating correctly, identifycompressor problem.Economizer Position is LessThan Minimum Position.IAQ is controlling minimum damper position. Adjust the IAQ settings if incorrect,otherwise, the economizer is operating correctly.Unit is in Unoccupied mode. Adjust unit occupied schedule if incorrect,otherwise, economizer is operating correctly.Economizer Does Not Returnto Minimum Position. Unit is operating under free cooling. Economizer is operating correctly.Damper Does Not Close onPower Loss. Damper is jammed or spring return is backwards. Identify the obstruction and safely remove.Economizer is Not at ConfiguredMinimum Position Unit is operating under free cooling or a force isapplied to the commanded position. Economizer is operating correctly.LEGENDCCN --- Carrier Comfort NetworkRIAQ --- Indoor Air Quality