York ZF180 Installation Manual

Also see for ZF 180 Series: Technical guide Installation manual Instruction manual Technical guide Installation manual

Contents

5168276-XIM-B-0216Johnson Controls Unitary Products 37Sequence Of OperationCooling Sequence Of OperationNOTE: For more in-depth sequence of operation of theSimplicity® SE control please refer to LIT-12011950 onwww.upgnet.com under Product Center \ EquipmentCatalog \ Commercial Products \ Zoning Systems andControls.For ZF units, a "Y1" call for the first stage of cooling is passed tothe Unit Control Board (UCB) which then determines whetherthe requested operation is available and if so, whichcomponents to energize. With a "Y1" call for first stage coolingthe UCB will determine if a first stage cooling output is valid aslong as all safeties and time-delays allow a C1 output forcooling. The C1 relay on the UCB will close and send 24 voltsto the M1 relay starting the first stage compressor and alsoenergizing M4 relay starting the associated condenser fans.During any call for fan or cooling the FAN output on the UCBwill energize the M3 relay starting the supply fan.If a Y2 call is present it is passed to the Unit Control Board(UCB) which then determines whether the requested operationis available and if so, which components to energize. With a"Y2" call for first stage cooling the UCB will determine if asecond stage cooling output is valid as long as all safeties andtime-delays allow a C2 output for cooling. The C2 relay on theUCB will close and send 24v to the M2 relay starting the secondstage compressor also energizing M6 relay starting theassociated condenser fans. During any call for fan or coolingthe FAN output on the UCB will energize the M3 relay startingthe supply fan.Continuous BlowerBy setting the room thermostat fan switch to "ON," the supplyair blower will operate continuously.Intermittent BlowerWith the room thermostat fan switch set to "AUTO" and thesystem switch set to either the "AUTO" or "HEAT" settings, theblower is energized whenever a cooling or heating operation isrequested. The blower is energized after any specified delayassociated with the operation.When energized, the indoor blower has a minimum run time of30 seconds. Additionally, the indoor blower has a delay of 10seconds between operations.No Outdoor Air OptionsWhen the thermostat calls for the first stage of cooling, the low-voltage control circuit from “R” to “Y1” and “G” is completed.The UCB energizes the economizer (if installed and free coolingis available) or the first available compressor * and thecondenser fans. For first stage cooling, compressor #1 isenergized. If compressor #1 is unavailable, compressor #2 isenergized. After completing the specified fan on delay forcooling, the UCB will energize the blower motor.When the thermostat calls for the second stage of cooling, thelow-voltage control circuit from “R” to “Y2” is completed.Compressor #2 is energized, provided it has not been lockedout, and condenser fan motor #1, and condenser fan motor #2remain energized. (If the ambient temperature is above 60ºF.)To be available, a compressor must not be locked-out due to ahigh or low-pressure switch or freezestat trip and the Anti-Short Cycle Delay (ASCD) must have elapsed.These units utilize a lead-lag feature that results in an equalamount of run hours on all compressors, thereby extending thelife of the compressors. This feature works as follows: If thethermostat requires for more than one stage of cooling, thecurrently off compressor with the least number of run hours willbe the next to be energized. When the thermostat requiresfewer stages of cooling, the currently running compressor withthe most run hours will be the first to be de-energized.Economizer With Single Enthalpy SensorWhen the room thermostat calls for “first-stage” cooling, the lowvoltage control circuit from “R” to “G” and “Y1” is completed.The UCB energizes the blower motor (if the fan switch on theroom thermostat is set in the “AUTO” position) and drives theeconomizer dampers from fully closed to their minimumposition. If the enthalpy of the outdoor air is below the set pointof the enthalpy controller (previously determined), “Y1”energizes the economizer. The dampers will modulate tomaintain a constant supply air temperature as monitored by thedischarge air sensor. If the outdoor air enthalpy is above the setpoint, “Y1” energizes compressor #1.When the thermostat calls for “second-stage” cooling, the lowvoltage control circuit from “R” to “Y2” is completed. The UCBenergizes the first available compressor. If the enthalpy of theoutdoor air is below the set point of the enthalpy controller (i.e.first stage has energized the economizer), “Y2” will energizecompressor #1. If the outdoor air is above the set point, “Y2” willenergize compressor #2. If Y2 brings on compressor #1 andthis condition remains for more than 20 minutes, thencompressor #2 will be energized until the thermostat issatisfied.Once the thermostat has been satisfied, it will de-energize “Y1”and “Y2”. If the compressors have satisfied their minimum runtimes, the compressors and condenser fans are de-energized.Otherwise, the unit operates each cooling system until theminimum run times for the compressors have been completed.Upon the final compressor de-energizing, the blower is stoppedfollowing the elapse of the fan off delay for cooling, and theeconomizer damper goes to the closed position. If the unit is incontinuous fan operation, the economizer damper goes to theminimum 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.