York YCAL0080SC, YCAL0014SC manual Unit Safeties

S Y S	1	H I G H	D S C H	P R E S
S Y S	2	H I G H	D S C H	P R E S

The Discharge Pressure Cutout is a software cutout in the microprocessor and is backed-up by a mechanical high pressure cutout switch located in the refrigerant circuit. It assures that the system pressure does not exceed safe working limits. The system will shutdown when the programmable cutout is exceeded and will be allowed to restart when the discharge pressure falls below the cutout. Discharge transducers must be in- stalled for this function to operate.

S Y S	1	L O W	S U C T	P R E S S
S Y S	2	L O W	S U C T	P R E S S

The Suction Pressure Cutout is a software cutout that protects the chiller from an evaporator freeze-up should the system attempt to run with a low refrigerant charge or a restriction in the refrigerant circuit.

At system start, the cutout is set to 10% of programmed value. During the next 3 minutes the cutout point is ramped up to the programmed cutout point. If at any time during this 3 minutes the suction pressure falls below the ramped cutout point, the system will stop. This cutout is ignored for the first 90 seconds of sys- tem run time to avoid nuisance shutdowns, especially on units that utilize a low pressure switch in place of the suction pressure transducer.

After the first 3 minutes, if the suction pressure falls below the programmed cutout setting, a “transient pro- tection routine” is activated. This sets the cutout at 10%

FORM 150.62-NM1

of the programmed value and ramps up the cutout over the next 30 seconds. If at any time during this 30 sec- onds the suction pressure falls below the ramped cut- out, the system will stop. This transient protection scheme only works if the suction pressure transducer is installed. When using the mechanical LP switch, the operating points of the LP switch are: opens at 23 PSIG +/- 5 PSIG (1.59 barg +/- .34 barg), and closes at 35 PSIG +/- 5 PSIG (2.62 barg +/- .34 barg).

S Y S	1	M P	/ H P C O	F A U L T
S Y S	2	M P	/ H P C O	F A U L T

The Motor Protector/Mechanical High Pressure Cutout protect the compressor motor from overheating or the system from experiencing dangerously high discharge pressure. This fault condition is present when CR1 (SYS 1) or CR2 (SYS 2) relays de-energize due to the HP switch or the motor protector opening. This causes the respec- tive CR contacts to open causing 0 VDC to be read on the inputs to the microboard. The fault condition is cleared when a 30 VDC signal is restored to the input.

The internal motor protector opens at 185°F - 248°F (85°C - 120°C) and auto resets. The mechanical HP switch opens at 405 PSIG +/- 10 PSIG (27.92 barg +/-

.69 barg) and closes at 330 PSIG +/- 25 PSIG (22.75 barg +/- 1.72 barg).

UNIT SAFETIES

Unit safeties are faults that cause all running compres- sors to be shut down. Unit faults are auto reset faults in that the unit will be allowed to restart automatically after the fault condition is no longer present.

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YORK INTERNATIONAL 63