analog to digital converter . . . . . . . . . . . . . . . 4 - UPGNet

351579-YTS-B-0608TROUBLESHOOTING A MILLENNIUM ®Simplicity ® CONTROLSTATUS LED CHARTThe Status LED mounted on the controller PC board will flashspecified flash patterns to indicate rooftop unit status. See Table14.Table 14: Status Led ChartFlash CodesDescriptionOn Steady Control Failure1 Flash (Not Applicable)2 Flashes Control waiting ASCDOFFNo Power or Control FailureFlash Times:• Off: The power is Off, or the control has failed• On 250ms Off 250ms: The Control is operating but anAlarm is active.• (The Number of the Alarm will be displayed on the characterdisplay.)• On one second, Off one second: This will be the "HeatBeat"; The Control is operating normally with no Alarms.• On Steady: The Control has Failed• Two flashes On, then two seconds Off: The Control iswaiting for an ASCD Timer to finish.FAILURE MODES AND DEFAULT OPERATIONERROR HISTORIESError data storage: The control will store the latest five errors in aFIFO manner in EEPROM, for later display. It will store statusinformation ("active" vs. "inactive") for all error types to providefor situations when an error snapshot is triggered by multipleerrors occurring at the same time. As the control collects errors, itwill overwrite the oldest error after the history buffer becomes full.Errors that are entered into the error history buffer:• Compressor locked out on safety chain trip• Supply fan failure• Heating SAT failure• Cooling SAT failure• SAT,RAT,OAT,IAQ, ST, or RH failure• Duct static or Bldg. Pressure sensor failure• Dirty Filter alarm• High duct static alarm• Hot Water Coil Freeze alarm• External alarm input• Bad Air Proving SwitchSENSOR FAILURES AND DEFAULT OPERATIONA failure of SAT RAT, OAT, IAQ, Space Temperature, or an outsideor return air Relative Humidity sensor will generate a commonerror. A failure of the Duct Static or Building Pressure sensor willgenerate another common error. The errors will be indicated by aStatus LED (see Status LED Chart earlier in this chapter). Theerrors will be written to the Error History Buffer. In networkedapplication, the error flag will be readable by the network. The errorindication of a sensor failure will continue until the problem iscorrected and will automatically terminate when the sensor isagain detected as reliable. If the unit is shut down as a result of asensor failure, the alarm must be reset (after the sensor problemhas been corrected) by resetting the controller (power cycle, orreset command issued by the Palm Pilot Configuration Tool).SAT SENSORCV operation: If the SAT sensor fails, the Economizer,excessive SAT control and predicted SAT drop checking will bedisabled. The Control will then continue a "limp along" operationunder zone thermostat, or zone sensor control. For VAVoperation the unit will be shut down.RAT SENSORIf the RAT sensor fails, Morning Warm Up mode and VAVOccupied Heating are disabled. For Economizer Loadingfunction, the control will default to estimated RAT of 75 °F (forthis function only).OAT SENSORUnits without Economizer: If there is no Economizer, thecontrol will lockout Cooling on an OAT sensor failure. This isbecause the controller can not determine when cooling needsto be locked out at low OAT to prevent damage to compressors.Heating operation will continue normally.Units with Economizer: All Economizer Operation will bedisabled. This is because OAT sensor is the most essential sensorin determining availability of free cooling. Even if the unit isequipped with Outside RH sensor and controller could calculateOutdoor Enthalpy, the OAT sensor is still essential in thatcalculation. The Economizer will only modulate to the MinimumPosition when the Fan is operating and the control is Occupied.OUTSIDE AIR RELATIVE HUMIDITY SENSORIf the OAH sensor fails, the control will only use the OAT sensorto decide if Free Cooling is available. The control will selfconfigureto Outside Temperature Method (see alsoEconomizer Operation section earlier in this document).RETURN AIR RELATIVE HUMIDITY SENSORThe control will self-configure to Outside Enthalpy Operation.SPACE TEMPERATURE SENSORCV operation with a zone sensor: When this sensor fails thecontrol will see if it has a RAT sensor. If it has a RAT sensor, thecontrol will use it as a backup and continue temperature controlJohnson Controls Unitary Products 43