York SUNLINE DCG Series Installation Manual

Contents

York SUNLINE DCG Series Installation Manual Manual pdf 41 page image

290699-YIM-B-0607Unitary Products Group 41HIGH-PRESSURE LIMIT SWITCHDuring cooling operation, if a high-pressure limit switchopens, the UCB will de-energize the compressor, ini-tiate the ASCD (Anti-short cycle delay), and, stop thecondenser fan. If the call for cooling is still present atthe conclusion of the ASCD, the UCB will re-energizethe compressor.Should a high-pressure switch open three times withintwo hours of operation, the UCB will lock-out the com-pressor and flash a code (see Table 32).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 compressor,initiate the ASCD, and stop the condenser fan.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 thecompressor, initiate the ASCD, and stop the condenserfan.If the call for cooling is still present at the conclusion ofthe ASCD, the UCB will re-energize the compressor.Should a low-pressure switch open three times withinone hour of operation, the UCB will lock-out the com-pressor and flash a code (Table 32).FREEZESTATDuring cooling operation, if a freezestat opens, theUCB will de-energize the compressor, initiate theASCD, and stop the condenser fan. If the call for cool-ing is still present at the conclusion of the ASCD, theUCB will re-energize the compressor.Should a freezestat open three times within two hoursof operation, the UCB will lock-out the compressor andflash a code (Table 32).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 45ºF. 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 compressor due to a freezestat trip. How-ever, a freezestat trip will de-energize the compressor.If the call for cooling is still present at the end of theASCD and the freezestat has closed, the unit willresume operation.SAFETY CONTROLSThe unit control board monitors the following inputs forthe cooling system:1. A suction line freezestat to protect against lowevaporator temperatures due to a low airflow or alow return air temperature, (opens at 26 ± 5 °F andresets at 38 ± 5°F).2. A high-pressure switch to protect against exces-sive discharge pressures due to a blocked con-denser coil or a condenser motor failure, (opens at380 ± 10 psig and resets at 300 ± 10 psig).3. A low-pressure switch to protect against loss ofrefrigerant charge, (opens at 22 ± 5 psig and resetsat 45 ± 5 psig).The above pressure switches are hard-soldered to theunit. The refrigeration system is monitored and con-trolled. On any fault, the system will be affected by anysafety/preventive action.The unit control board monitors the temperature limitswitch of electric heat units and the temperature limitswitch and the gas valve of gas furnace units.COMPRESSOR PROTECTIONThe compressor also has inherent (internal) protection.If there is an abnormal temperature rise in a compres-