York Predator Z series Installation Instructions Manual

Contents

5370596-YIM-C-0518Johnson Controls Ducted Systems 45OperationCooling Operation• With a demand for first stage cooling either from athermostat or space sensor, the low-voltage control circuitto "C1" and "G" is completed. For first stage cooling, thecompressor is energized and the 1st stage operates (67%capacity). The UCB will energize the VFD equippedblower motor at low speed as set in the SmartEquipment™ control. When the thermostat calls for thesecond stage of cooling, the low-voltage control circuit to"C2" is completed. The control board energizes the 2ndstage of the compressor (100% capacity). If there is aninitial call for both stages of cooling, the UCB will delayenergizing the 2nd stage of the compressor by 30seconds in order to avoid a power rush. Once thethermostat has been satisfied, it will de-energize C1 andC2. If the compressor has satisfied the minimum run time(3 min default), the compressors and condenser fans arede-energized. Otherwise, the unit operates until theminimum run has been completed. Upon the compressorde-energizing, the blower is stopped following the elapseof the fan off delay for cooling.• To be available, a compressor must not be locked-out dueto a high or low-pressure switch or freezestat trip and theAnti- Short Cycle Delay (5 min default) must haveelapsed.Free Cooling Operation with Economizer• With a demand for first stage cooling either from athermostat or space sensor and the outside air is suitablefor free cooling, the dampers will be modulated tomaintain supply air temperature to within +/- 1 degree ofthe Free Cooling SAT Upper Setpoint. If the output to theeconomizer actuator is at 10 vdc and the supply airtemperature cannot be controlled to within 5 degrees ofthe Free Cooling SAT Upper Setpoint, one compressorwill be energized. The economizer will then be modulatedto maintain supply air temperature to within +/- 1 degreeof the Free Cooling SAT Upper Setpoint.• If a demand for second stage cooling occurs and theeconomizer is already modulating to maintain the supplyair temperature to the Cooling SAT Upper Setpoint, thesetpoint will be changed to the Free Cooling SAT LowerSetpoint. Any compressors that are energized will remainenergized and the economizer dampers will be modulatedto maintain supply air temperature to within +/- 1 degreeof the Cooling SAT Lower Setpoint. If the output to theeconomizer actuator is at 10 vdc and the supply airtemperature cannot be controlled to within 5 degrees ofthe Cooling SAT Lower Setpoint, compressor stage 2 willbe energized. The economizer will then be modulated tomaintain supply air temperature to within +/- 1 degree ofthe Cooling SAT Lower Setpoint.• If the output to the economizer actuator is at minimumposition and the supply air temperature drops more than 5degrees below the current economizer SAT setpoint, thehighest stage compressor will be de-energized as long asthe minimum run time has elapsed.Economizer With Single Enthalpy SensorWhen the room thermostat calls for cooling, the low voltagecontrol circuit from “R” to “G” and “Y1” is completed. The UCBenergizes the blower motor (if the fan switch on the roomthermostat is set in the “AUTO” position) and drives theeconomizer dampers from fully closed to their minimum position.If the enthalpy of the outdoor air is below the setpoint of theenthalpy controller (previously determined), “Y1” energizes theeconomizer. The dampers will modulate to maintain a constantsupply air temperature as monitored by the discharge air sensor.If the outdoor air enthalpy is above the setpoint, “Y1” energizesthe compressor and condenser fan motor only.Once the thermostat has been satisfied, it will de-energize “Y1”. Ifthe compressor has satisfied its minimum run time, thecompressor and condenser fan are de-energized. Otherwise, theunit operates the cooling system until the minimum run times forthe compressor has been completed. After the compressor de-energizes, the blower is stopped following the elapse of the fanoff delay for cooling, and the economizer damper goes to theclosed position. If the unit is in continues fan operation theeconomizer damper goes to the min. position.Economizer With Dual Enthalpy SensorsThe operation with the dual enthalpy sensors is identical to thesingle sensor except that a second enthalpy sensor is mountedin the return air. This return air sensor allows the economizer tochoose between outdoor air and return air, whichever has thelowest enthalpy value, to provide maximum operatingefficiency.Economizer With Power ExhaustA unit equipped with an economizer (single or dual enthalpy)and a power exhaust operates as specified above with oneaddition. The power exhaust motor is energized 45 secondsafter the actuator position exceeds the exhaust fan set point onthe economizer control. As always, the "R" to "G" connectionprovides minimum position but does not provide power exhaustoperation.Motorized Outdoor Air DampersThis system operation is the same as the units with no outdoorair options with one exception. When the "R" to "G" circuit iscomplete, the motorized damper drives open to a position setby the thumbwheel on the damper motor. When the "R" to "G"circuit is opened, the damper spring returns fully closed.Cooling Operation ErrorsEach cooling system is monitored for operation outside of theintended parameters. Errors are handled as described below. Allsystem errors override minimum run times for compressors.NOTE: The following components are needed to access thecontrol points in the Smart Equipment™ control.