Carrier 50KC04-06 Service And Maintenance Instructions

53Set system selector switch at HEAT position and set thermostatat a setting above room temperature. Set fan at AUTO position.First stage of thermostat energizes the first-stage electric heaterelements; second stage energizes second-stage electric heaterelements, if installed. Check heating effects at air supplygrille(s).If electric heaters do not energize, reset limit switch (located onevaporator-fan scroll) by pressing button located between ter-minals on the switch.To shut off unit - set system selector switch at OFF position.Resetting thermostat at a position below room temperaturetemporarily shuts unit off until space temperature falls belowthermostat setting.Ventilation (Continuous Fan)Set fan and system selector switches at ON and OFF positions,respectively. Evaporator fan operates continuously to provideconstant air circulation.START-UP, PREMIERLINK CONTROLSFor details on operating 50KC**04-06 units equipped with thefactory-installed PremierLink controller option, refer to thePREMIERLINK Retrofit Rooftop Controller Version 3.x In-stallation, Start-up and Configuration Instructions.Refer to PremierLink Retrofit Rooftop Controller Version 3.xInstallation, Start-up, and Configuration Instructions for fulldiscussion on configuring the PremierLink control system.START-UP, RTU-OPEN CONTROLFor details on operating 50KC**04-06 units equipped with thefactory-installed RTU Open Controller option, refer to the Fac-tory-Installed Option RTU Open Multi-Protocol ControllerControls, Start-Up, Operation, and Troubleshooting manual.OPERATING SEQUENCEBase Unit ControlsCooling - Units without EconomizerWhen thermostat calls for cooling, terminals G and Y1 are en-ergized. The indoor-fan contactor (IFC) and compressor con-tactor are energized and indoor-fan motor, compressor, andoutdoor fan starts. The outdoor fan motor runs continuouslywhile unit is cooling.Heating - Units without EconomizerWhen the thermostat calls for heating, terminal W1 will be en-ergized with 24-v. The IFC and heater contactor no. 1 (HC1)are energized.Cooling, Unit with EconoMi$er IVFor Occupied mode operation of EconoMi$er IV, there must bea 24-v signal at terminals TR and N (provided through PL6-3from the unit’s IFC coil). Removing the signal at N places theEconoMi$er IV control in Unoccupied mode.During Occupied mode operation, indoor fan operation will beaccompanied by economizer dampers moving to MinimumPosition set point for ventilation. If indoor fan is off, damperswill close. During Unoccupied mode operation, dampers willremain closed unless a Cooling (by free cooling) or DCV de-mand is received.Integrated EconoMi$er IV operation on 50KC single compres-sor model requires a 2-stage thermostat (Y1 and Y2 switches).When free cooling using outside air is not available, the unitcooling sequence will be controlled directly by the space ther-mostat as described above in “Cooling - Units without econo-mizer”. Outside air damper position will be closed or MinimumPosition as determined by occupancy mode and fan signal.When free cooling is available as determined by the appropri-ate changeover command (dry bulb, outdoor enthalpy, differen-tial dry bulb or differential enthalpy), a call for cooling (Y1closes at the thermostat) will cause the economizer control tomodulate the dampers open and closed to maintain the unitsupply air temperature at 50°F to 55°F. Compressor will notrun.During free cooling operation, a supply air temperature (SAT)above 50°F will cause the dampers to modulate between Mini-mum Position set point and 100% open. With SAT from 50°Fto 45°F, the dampers will maintain at the Minimum Positionsetting. With SAT below 45°F, the outside air dampers will beclosed. When SAT rises to 48°F, the dampers will re-open toMinimum Position setting.Should 100% outside air not be capable of satisfying the spacetemperature, space temperature will rise until Y2 is closed. Theeconomizer control will call for compressor operation. Damp-ers will modulate to maintain SAT at 50°F to 55°F concurrentwith compressor operation. The Low Ambient Lockout Ther-mostat will block compressor operation with economizer oper-ation below 42°F outside air temperature.When space temperature demand is satisfied (thermostat Y1opens), the dampers will return to Minimum Damper positionif indoor fan is running or fully closed if fan is off.If accessory power exhaust is installed, the power exhaust fanmotors will be energized by the economizer control as thedampers open above the PE-On set point and will be de-ener-gized as the dampers close below the PE-On set point.Damper movement from full closed to full open (or vice versa)will take between 11/ 2 and 2 1/2 minutes.Heating, Unit with EconoMi$er IVDuring Occupied mode operation, indoor fan operation will beaccompanied by economizer dampers moving to Minimum Po-sition set point for ventilation. If indoor fan is off, dampers willclose. During Unoccupied mode operation, dampers will re-main closed unless a DCV demand is received.When the room temperature calls for heat (W1 closes), theheating controls are energized as described in “Heating - Unitswithout economizer”.Demand Controlled VentilationIf a field-installed sensor is connected to the EconoMi$er IVcontrol, a Demand Controlled Ventilation strategy will operateautomatically. As the level in the space increases above the setpoint (on the EconoMi$er IV controller), the minimum posi-tion of the dampers will be increased proportionally, until theMaximum Ventilation setting is reached. As the space level de-creases because of the increase in fresh air, the outdoor-damperwill follow the higher demand condition from the DCV modeor from the free-cooling mode.DCV operation is available in Occupied and Unoccupied peri-ods with EconoMi$er IV. However, a control modification willbe required on the 50KC unit to implement the Unoccupied pe-riod function.WARNINGELECTRICAL OPERATION HAZARDFailure to follow this warning could result in personal injuryor death.The unit must be electrically grounded in accordance withlocal codes and NEC ANSI/NFPA 70 (American NationalStandards Institute/National Fire Protection Association.)