Carrier 48TCA04---A12 Service And Maintenance Instructions

73When Y2 is energized, the economizer will be modulatedto control to a lower supply air setpoint SASP= SATLO2+ 3_F If the SAT > SASP + 5_F it will close theeconomizer to minimum position for 3 minutes, reset theintegrator for the economizer, then start modulating theeconomizer to maintain the SASP after the stage two hasbeen on for 90 seconds. This provides protection for thecompressor against flooded starts and allow refrigerantflow to stabilize before modulating the economizer again.By using return air across the evaporator coil just after thecompressor has started allows for increased refrigerantflow rates providing better oil return of any oil washed outduring compressor start--up.Routine No. 3: If the OAT > 68_F and the enthalpy is lowand the OAT < SPT then the economizer will open to100% and compressors 1 and 2 will be cycled based onY1 and Y2 inputs respectively. If any of these conditionsare not met the economizer will go to minimum position.If there is no call for heating or cooling, the economizer,if available, will maintain the SASP at 70_F.Heating — For gas or electric heat, HS1 and HS2 outputswill follow W1 and W2 inputs respectively. The fan willalso be turned on if it is configured for electric heat.Heating may also be energized when an IAQ sensorinstalled and has overridden the minimum economizerdamper position. If the OAT < 55_F and an IAQ sensor isinstalled and the IAQ minimum position > minimumdamper position causing the SAT to decrease below theSPT -- 10_F, then the heat stages will be cycled to temperthe SAT to maintain a temperature between the SPT andthe SPT + 10_F.Auxiliary Relay configured for Exhaust Fan — If theAuxiliary Relay is configured for exhaust fan (AUXOUT= 1) in the CONFIG configuration table and ContinuousPower Exhaust (MODPE) is enable in the SERVICEconfiguration table then the output (HS3) will beenergized whenever the G input is on. If the MODPE isdisabled then output will be energized based on the PowerExhaust Setpoint (PES) in the SETPOINT table.Indoor Air Quality — If the optional indoor air quality(IAQI) sensor is installed, the PremierLink controller willmaintain indoor air quality within the space at theuser--configured differential setpoint (IAQD) in theCONFIG configuration table. The setpoint is thedifference between the IAQI and an optional outdoor airquality sensor (OAQ). If the OAQ is not present then afixed value of 400 ppm is used. The actual space IAQsetpoint (IAQS) is calculated as follows:IAQS = IAQD + OAQ (OAQ = 400 ppm if not present)As air quality within the space changes, the minimumposition of the economizer damper will be changed alsothus allowing more or less outdoor air into the spacedepending on the relationship of the IAQI to the IAQS.The IAQ algorithm runs every 30 seconds and calculatesIAQ minimum position value using a PID loop on theIAQI deviation from the IAQS. The IAQ minimumposition is then compared against the user configuredminimum position (MDP) and the greatest value becomesthe final minimum damper position (IQMP). If thecalculated IAQ Minimum Position is greater than the IAQmaximum damper position (IAQMAXP) decision in theSERVICE configuration table, then it will be clamped toIAQMAXP value.If IAQ is configured for low priority, the positioning ofthe economizer damper can be overridden by comfortrequirements. If the SAT < SASP --8_F and both stages ofheat are on for more then 4 minutes or the SAT > SASP +5_F and both stages of cooling on for more then 4 minutesthen the IAQ minimum damper position will become 0and the IQMP = MDP. IAQ mode will resume when theSAT > SASP --8_F in heating or the SAT < SASP + 5_F incooling.If the PremierLink controller is configured for 1 stage ofheat and cool or is only using a single stage thermostatinput, this function will not work as it requires the bothY1 and Y2 or W1 and W2 inputs to be active. In thisapplication, it is recommended that the user configureIAQ priority for high.If IAQ is configured for high priority and the OAT < 55_Fand the SAT < (SPT --10_F), the algorithm will enable theheat stages to maintain the SAT between the SPT and theSPT + 10_F.CCN SENSOR MODE — When the PremierLinkcontroller is configured for CCN control, it will controlthe compressor, economizer and heating outputs based itsown space temperature input and setpoints or thosereceived from Linkage. An optional CO2 IAQ sensormounted in the space or received through communicationscan also influence the economizer and heating outputs.The PremierLink controller does not have a hardwareclock so it must have another device on the CCNcommunication bus broadcasting time. The controller willmaintain its own time once it has received time as long asit has power and will send a request for time once aminute until it receives time when it has lost power andpower is restored. The controller will control tounoccupied setpoints until it has received a valid time.The controller must have valid time in order to performany broadcast function, follow an occupancy schedule,perform IAQ pre--occupancy purge and many otherfunctions as well. The following sections describe theoperation for the functions of the PremierLink controller.Indoor Fan — The indoor fan will be turned on wheneverany one of the following conditions are met:S If the PremierLink controller is in the occupied mode andASHRAE 90.1 Supply Fan is configured for Yes in theCONFIG table. This will be determined by its owninternal occupancy schedule if it is programmed tofollow its local schedule or broadcast its local schedule asa global schedule, or following a global schedulebroadcast by another device.S If PremierLink controller is in the occupied mode andASHRAE 90.1 Supply Fan is configured for No and thereis a heat or cool demand (fan auto mode)48TC