York D*SC360 Installation Instructions Manual

Contents

York D*SC360 Installation Instructions Manual Manual pdf 13 page image

ELECTRO-MECHANICAL CONTROLSThe operation of these units can be divided into four systems.1. Economizer System (optional)2. Heating System (optional)3. Cooling System4. Exhaust Air (optional)ECONOMIZER SYSTEMThe Economizer System consists of:1. Outdoor and return air dampers.2. Damper Actuator (Spring Return).3. Enthalpy Control - 5TH.4. Mixed Air Controller - 1RH.5. Minimum outside air adjuster (potentiometer) - 2RH.The Economizer System provides the first stage of coolingwhenever the outside air is cool and dry enough to satisfy theinternal cooling demand. The outside and the return airdampers are mechanically linked and are modulated by thespring return damper actuator. As the outside air dampers areopened by the damper actuator, the return air dampers areclosed.When the enthalpy control (5TH) senses outside airtemperatures per Table 5, the outside air dampers close to theirminimum position. The minimum position of the outside airdampers is determined by the set point of the minimum outsideair adjuster (2RH) located in the terminal box of the dampermotor.The enthalpy control (5TH) is factory set. It senses bothtemperature and humidity and varies its setting so as to limitthe introduction of outside air. As noted in Table 5, the controlwill not allow outside air to enter the unit during high humidityconditions except at a lower outside temperature. During dryconditions, air is introduced at a higher ambient.The outside and the return air dampers are controlled by aproportional type, mixed-air controller (1RH) which senses thetemperature of the air leaving the evaporator coil. The damperscan modulate anywhere from their minimum outside positionto 100% open in attempting to maintain the temperature settingof 1RH. If the indoor space temperature rises, TC2 will closeand the No. 1 compressor will be energized through the 5Rrelay contacts to provide second stage cooling.DAMPER LINKAGE ADJUSTMENTAfter power has been supplied to the unit, the outside andreturn air dampers should be checked to make sure theyoperate freely and close tightly. It may be necessary to readjustthe linkage between the damper motor and the blades due toloosening in shipment.Readjust linkage as follows:1. Turn the minimum outside air adjuster to the 100% outsideair position. All return air damper blades should be fullyclosed. Be sure that the spring-return damper actuator hascompleted its stroke (stopped running). If not, loosen thedrive rod bolt and let the damper motor drive the crankarmuntil the motor stops running. Retighten the drive rod boltto secure the drive rod.ECONOMIZER RAIN HOOD OPTIONThe outdoor and return air dampers, the spring-return damperactuator, the linkage, the enthalpy changeover control, themixed air temperature control and the minimum positionpotentiometer with manual auto switch are factory mounted aspart of the economizer option. The rain hood is shipped in aseparate package and must be assembled to the unit per theassemby instructions in Form 530.25-N1.4.CAUTION: Never operate the unit without installing the hood ormoisture will be drawn into the unit.FIXED OUTSIDE AIR RAIN HOODThe fixed outdoor air damper with a manual adjustment arm isfactory mounted on all units without the economizer operation.The rain hood is shipped in a separate package and must beassembled to the unit per the assembly instructions in Form530.25-N1.3.CAUTION: Never operate the unit without installing the hood ormoisture will be drawn into the unit.EXHAUST AIR RAIN HOOD OPTIONThe barometric exhaust dampers, the powered propeller ex-haust fan and the damper motor end switch are factory installedand wired as part of the exhaust air option. The rain hood isshipped in a separate package and must be assembled to theunit per the assembly instructions in Form 530.25-N1.2.NOTE: The exhaust hood for the DSC480 is shipped in twopackages.CAUTION: Never operate the unit without installing the hood ormoisture will be drawn into the unit.OPERATIONOUTDOOR DRYBULB TEMP. ÉF% RELATIVEHUMIDITY62 8067 6071 4073 2074 10TABLE 5 - ENTHALPY CONTROL (SET POINT "B")530.25-N3YUnitary Products Group 13