York D*SC360 Installation Instructions Manual

Contents

York D*SC360 Installation Instructions Manual Manual pdf 14 page image

2. Turn the minimum outside air adjuster to the 0% outside airposition. All outside air damper blades should be fullyclosed. The linkage connecting the outside air and thereturn air dampers must move freely.3. Return the minimum outside air adjuster to the 100%outside air position and check for complete freedom oflinkage movement as the return air dampers close.4. Set the minimum outside air adjuster for the minimumventilation requirement of the job.HEATING SYSTEMTwo different types of heat are offered as factory-mountedoptions. Refer to the appropriate instruction for information onthe heating system.• 530.25-N1.1 - Gas-Fired Heating Option• 530.25-N1.9 - Electric Heating OptionCOOLING SYSTEMThese units have nominal cooling capacities of 30 and 40 tons.The DSC360 units have one semi-hermetic compressor. Twocooling stages are accomplished by unloading the compressor.The DSC480 unit has two semi-hermetic compressors. Twocooling stages are accomplished by cycling the individualcompressors.Normal sequence of operation is as follows:1. Power is supplied to the unit through the disconnect switch.The switch can be field installed or factory-installed as anoption.2. As soon as power is supplied to the unit, the compressorcrankcase heaters 1TH (and 2TH) will be energized.CAUTION: Do not attempt to start the compressors withoutat least 8 hours of crankcase heat or compres-sor damage will occur.3. The system switch on the room thermostat or the statuspanel must be in the AUTO or COOL position to completethe circuit between the terminals 119 and 103/RC.4. On demand of the room thermostat for cooling, contact TC1closes and energizes 1R coil.5. An internal connection in the thermostat or status panelenergizes 7R coil. 7R contact closes energizing 3M coil. 3Mcontacts close, starting the supply air fan motor. After anadequate air flow is established, 5 LP closes to energize6R coil. 6R contact closes in the compressor control circuit.NOTE: The above operation is for intermittent fan operation.For continuous operation, the fan switch on the roomthermostat or the status panel should be manuallyclosed to energize 7R.6. Relay contact 1R closes and energizes 1M coil, whichstarts the No. 1 compressor. At the same time, 4M coil isenergized to start the condenser fans.7. If the room temperature continues to rise, contact TC2closes and energizes 2R coil.8. On DSC480 units the 2R contacts close, energizing the 2Mcoil which starts the No. 2 compressor or on DSC360 unitsthe 2R contacts close de-energizing the compressorunloading solenoid which loads the compressor.9. The compressor short cycle time and low voltage protectionis part of the solid state compressor protection module. Itprevents a compressor from starting unless it has been offfor five minutes. It also monitors the voltage of the 120 voltcontrol circuit and will shut down the compressor if the 120volt control voltage drops below 85 æ4.5 volts.10. To maintain sufficient head pressure during low ambientoperation, condenser fans No. 1 and No. 2 will bede-energized by 1TH. Condenser fans No. 3 and 4 will bede-energized by 2TH (see Table 6).EXHAUST AIR SYSTEMThe exhaust air fans are energized by manually closing a circuitbetween terminals 60 and 64 of terminal block 2TB orautomatically by an end switch on the economizer dampermotor. As the economizer damper opens, it closes the endswitch on the damper motor and turns on the exhaust air fans.The degree of blade opening at which the exhaust fans areenergized can be adjusted by the following procedure.1. Use the black scale plate as an indicator of motor positionfor switch operation.2. Loosen the thumb nut and the cam locking screws.3. Set the operational and differential cams.4. Check switch adjustment by moving the adjuster 2RH tomove the motor. Switch should click when desired makeand break points are lined up with index mark and theexhaust fan should start and stop.WARNING: 120 volt power is connected to the switch.5. Tighten thumb nut.530.25-N3Y14 Unitary Products Group