York SUNLINE MagnaDRY DR180 Installation Manual

Also see for SUNLINE MagnaDRY DR 180: Submittal data sheet Installation manual

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York SUNLINE MagnaDRY DR180 Installation Manual Manual pdf 55 page image

127915-YIM-A-0405Unitary Products Group 55MOTORIZED OUTDOOR AIR DAMPERS -This system operation is the same as the units with nooutdoor air options with one exception. When the "R" to"G" circuit is complete, the motorized damper drivesopen to a position set by the thumbwheel on thedamper motor. When the "R" to "G" circuit is opened,the damper spring returns fully closed.COOLING OPERATION ERRORSEach cooling system is monitored for operation outsideof the intended parameters. Errors are handled asdescribed below. All system errors override minimumrun times for compressors.HIGH-PRESSURE LIMIT SWITCHDuring cooling operation, if a high-pressure limit switchopens, the UCB will de-energize the associated com-pressor, initiate the ASCD (Anti-short cycle delay), and,if the other compressor is idle, stop the condenserfans. If the call for cooling is still present at the conclu-sion of the ASCD, the UCB will re-energize the haltedcompressor.Should a high-pressure switch open three times withintwo hours of operation, the UCB will lock-out the asso-ciated compressor and flash a code (see Table 33). Ifthe other compressor is inactive, the condenser fanswill be de-energized.LOW-PRESSURE LIMIT SWITCHThe low-pressure limit switch is not monitored duringthe initial 30 seconds of a cooling system's operation.For the following 30 seconds, the UCB will monitor thelow-pressure switch to ensure it closes. If the low-pres-sure switch fails to close after the 30-second monitor-ing phase, the UCB will de-energize the associatedcompressor, initiate the ASCD, and, if the other com-pressor is idle, stop the condenser fans.Once the low-pressure switch has been proven (closedduring the 30-second monitor period described above),the UCB will monitor the low-pressure limit switch forany openings. If the low-pressure switch opens forgreater than 5 seconds, the UCB will de-energize theassociated compressor, initiate the ASCD, and, if theother compressor is idle, stop the condenser fans.If the call for cooling is still present at the conclusion ofthe ASCD, the UCB will re-energize the halted com-pressor.Should a low-pressure switch open three times withinone hour of operation, the UCB will lock-out the associ-ated compressor and flash a code (Table 33). If theother compressor is inactive, the condenser fans willbe de-energized.FREEZESTATDuring cooling operation, if a freezestat opens, theUCB will de-energize the associated compressor, ini-tiate the ASCD, and, if the other compressor is idle,stop the condenser fans. If the call for cooling is stillpresent at the conclusion of the ASCD, the UCB will re-energize the halted compressor.Should a freezestat open three times within two hoursof operation, the UCB will lock-out the associated com-pressor and flash a code (Table 33). If the other com-pressor is inactive, the condenser fans will be de-energized.LOW AMBIENT COOLINGTo determine when to operate in low ambient mode,the UCB has a pair of terminals connected to a temper-ature-activated switch set at 30ºF. When the low ambi-ent switch is closed and the thermostat is calling forcooling, the UCB will operate in the low ambient mode.Low ambient mode operates the compressors in thismanner: 10 minutes on, 5 minutes off. The indoorblower is operated throughout the cycle. The 5-minuteoff period is necessary to defrost the indoor coil.Low ambient mode always begins with compressoroperation. Compressor minimum run time may extendthe minutes of compressor operation. The defrost cyclewill begin immediately following the elapse of the mini-mum run time.When operating in low ambient mode, the UCB will notlockout the compressors due to a freezestat trip. How-ever, a freezestat trip will de-energize the associatedcompressor. If the call for cooling is still present at theend of the ASCD and the freezestat has closed, theunit will resume operation.SAFETY CONTROLSThe unit control board monitors the following inputs foreach cooling system:1. A suction line freezestat to protect against lowevaporator temperatures due to a low airflow or a