York 048 & 060 Safety Controls, Compressor Protection, Low-Pressurelimit Switch, Freezestat

Page 29
LOW-PRESSURE LIMIT SWITCH

177820-YIM-A-0506

Should a high-pressure switch open three times within two hours of operation, the UCB will lock-out the com- pressor and flash a code (see Table 23).

LOW-PRESSURE LIMIT SWITCH

The low-pressure limit switch is not monitored during the initial 30 seconds of a cooling system's operation. For the following 30 seconds, the UCB will monitor the low-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 (closed during the 30-second monitor period described above), the UCB will monitor the low-pressure limit switch for any openings. If the low-pressure switch opens for greater than 5 seconds, the UCB will de-energize the compressor, initiate the ASCD, and stop the condenser fan.

If the call for cooling is still present at the conclusion of the ASCD, the UCB will re-energize the compressor.

Should a low-pressure switch open three times within one hour of operation, the UCB will lock-out the com- pressor and flash a code (see Table 23).

FREEZESTAT

During cooling operation, if a freezestat opens, the UCB will de-energize the compressor, initiate the ASCD, and stop the condenser fan. If the call for cool- ing is still present at the conclusion of the ASCD, the UCB will re-energize the compressor.

Should a freezestat open three times within two hours of operation, the UCB will lock-out the compressor and flash a code (see Table 23).

LOW AMBIENT COOLING

To 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 for cooling, the UCB will operate in the low ambient mode.

Low ambient mode operates the compressors in this manner: 10 minutes on, 5 minutes off. The indoor blower is operated throughout the cycle. The 5-minute off period is necessary to defrost the indoor coil.

Low ambient mode always begins with compressor operation. Compressor minimum run time may extend the minutes of compressor operation. The defrost cycle will begin immediately following the elapse of the mini- mum run time.

When operating in low ambient mode, the UCB will not lockout 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 the ASCD and the freezestat has closed, the unit will resume operation.

SAFETY CONTROLS

The unit control board monitors the following inputs for the cooling system:

1.A suction line freezestat to protect against low evaporator temperatures due to a low airflow or a low return air temperature, (opens at 26 ± 5 °F and resets 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 at 380 ± 10 psig and resets at 300 ± 10 psig).

3.A low-pressure switch to protect against loss of refrigerant charge, (opens at 7 ± 3 psig and resets at 22 ± 5 psig).

The above pressure switches are hard-soldered to the unit. The refrigeration system is monitored and con- trolled. On any fault, the system will be affected by any safety/preventive action.

The unit control board monitors the temperature limit switch of electric heat units.

COMPRESSOR PROTECTION

The compressor also has inherent (internal) protection. If there is an abnormal temperature rise in a compres- sor, the protector will open to shut down the compres- sor. The UCB incorporates features to minimize compressor wear and damage. An anti-short cycle delay (ASCD) is utilized to prevent operation of a com- pressor too soon after its previous run. Additionally, a minimum run time is imposed any time a compressor is energized.

Unitary Products Group

29

Image 29
Contents INSTALLATION MANUAL BCHCONTENTS SUNLINE SINGLE PACKAGE HEAT PUMPCOOLING SEQUENCE OF OPERATION TABLE OF CONTENTSSEQUENCE OF OPERATIONS OVERVIEW LIST OF TABLES LIST OF FIGURESGENERAL SAFETY CONSIDERATIONSINSPECTION REFERENCEINSTALLATION SAFETY INFORMATION INSTALLATIONPRODUCT NOMENCLATURE LIMITATIONSLOCATION TABLE 1 UNIT APPLICATION DATA BCHRIGGING AND HANDLING CLEARANCESCONDENSATE DRAIN DUCTWORKFIGURE 1 - RECOMMENDED DRAIN PIPING COMPRESSORS FIGURE 2 - COMPRESSOR RESTRAINING BRACKETFILTERS SERVICE ACCESSTYPICAL CONTROL WIRING TYPICAL POWER WIRINGFIGURE 3 - TYPICAL FIELD POWER & CONTROL WIRING COOLING / HEATING 24 VOLT THERMOSTATTABLE 2 CONTROL WIRE SIZES POWER AND CONTROL WIRINGOPTIONS/ACCESSORIES THERMOSTATECONOMIZER/MOTORIZED DAMPER AND RAIN HOOD TABLE 3 ELECTRIC HEATER CFM LIMITATIONSFIGURE 5 - HONEYWELL ECONOMIZER CONTROL W7212 FIGURE 4 - ENTHALPY SETPOINT ADJUSTMENTMINIMUM POSITION ADJUSTMENT ENTHALPY SET POINT ADJUSTMENTTABLE 6 BCH 6 POINT LOADS WEIGHT DISTRIBUTION TABLE 5 BCH 4 POINT LOADS WEIGHT DISTRIBUTIONFIGURE 6 - FOUR AND SIX POINT LOADING TABLE 4 CENTER OF GRAVITY ALL MODELSTABLE 7 PHYSICAL DATA TABLE 8 OPERATING WEIGHTS LBSCOMPRESSORS Unitary Products Group None Unitary Products Group TABLE 12 VOLTAGE LIMITATIONS1 TABLE 11 ELECTRIC HEAT CORRECTION FACTORSPOWER SUPPLY NOMINAL VOLTAGEDETAIL “B” FIGURE 8 - UNIT WITH ECONOMIZER RAINHOODDETAIL “A” FIGURE 11 - DISCONNECT/BLOWER ACCESS LOCATION FIGURE 10 - UNIT DIMENSIONS REAR VIEWTABLE 13 UTILITIES ENTRY TABLE 14 MINIMUM CLEARANCESUnitary Products Group Page Unitary Products Group Unitary Products Group TABLE 19 BELT DRIVE BLOWER MOTOR AND DRIVE DATA177820-YIM-A-0506 TABLE 20 STATIC RESISTANCES FIGURE 12 - BELT ADJUSTMENTPHASING 5.Afteradjusting,re-tightennutsAFIGURE 13 - PRESSURE DROP ACROSS COIL OPERATIONSEQUENCE OF OPERATIONS OVERVIEW COOLING SEQUENCE OF OPERATIONECONOMIZER SINGLE OR DUAL WITH POWER EXHAUST COOLING OPERATION ERRORSHIGH-PRESSURELIMIT SWITCH INTERMITTENT BLOWERCOMPRESSOR PROTECTION SAFETY CONTROLSLOW-PRESSURELIMIT SWITCH FREEZESTATSAFETY CONTROLS START-UPCOOLING TABLE 21 ELECTRIC HEAT LIMIT CONTROL SETTINGHEAT ANTICIPATOR SETPOINTS TABLE 22 ELECTRIC HEAT ANTICIPATOR SETPOINTSCOOLING TROUBLESHOOTING GUIDE TROUBLESHOOTINGOPERATING INSTRUCTIONS POST START CHECK LISTUnitary Products Group 177820-YIM-A-0506a.24 volts at the thermostat Y1 terminal NORMAL MAINTENANCE MAINTENANCEUNIT FLASH CODES TABLE 23 UNIT CONTROL BOARD FLASH CODESOUTDOOR COIL MOTORS177820-YIM-A-0506 Unitary Products Group5005 UnitaryNorman Products