Operating Sequence - York YCAQ10 Manual

Packaged liquid chillers air cooled – reciprocating hermetic

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Manual (100 pages)

Table Of Contents

Table of Contents

1. PANEL SWITCHES

A. Set the Return Chilled Water Temp. to the desired

temperature. (This will be leaving water temp.

setpoint if this option is utilized.)

B. Assure the Micro Logic Board jumpers/switches

are configured for the unit design and the system's

requirement. See pages 31 & 32.

2. Place the System Switch to the ON position. See the

OPERATING SEQUENCE for unit operation. The

compressor will start and a flow of liquid should be

noted in the liquid indicator. After several minutes of

operation, the bubbles should disappear and there

will be a solid column of liquid when the unit is oper-

ating normally. On start-up, foaming of the oil may

be evident in the compressor oil sight glass. After

the water temperature has been pulled down to op-

erating conditions, the oil should be clear. Normal

operation of the unit is evidenced by a hot discharge

line, clear oil in the compressor crankcase, solid liq-

uid refrigerant in the liquid indicator and usually no

more than 2 PSIG variation in suction pressure for

any given set of operating conditions.

Check direction of fan rotation. Air flow must be "up".

Allow the compressor to run for a short time, being

ready to stop it immediately if any unusual noise or

other adverse condition should develop. When start-

ing the compressor, always make sure the oil pump

is functioning properly. Compressor oil pressure must

be as described under "Oil Pressure Cutout" (See

Control Description).

Check the system operating parameters. Do this by

selecting various readouts such as pressure and tem-

perature. Compare these to test gauge readings.

CHECKING SUPERHEAT AND SUBCOOLING

The subcooling should always be checked when charg-

ing the system with refrigerant and/or before setting the

superheat.

When the refrigerant charge is correct, there will be no

bubbles in the liquid sight glass with the system operat-

ing under full load conditions, and there will be 10° to

15°F subcooled liquid leaving the condenser.

An overcharged system should be guarded against.

Evidences of overcharge are as follows:

a. If the system is overcharged, the discharge pres-

sure will be higher than normal. (Normal discharge

pressure can be found in refrigerant temperature/

pressure chart; use ambient temperature +30°F

for normal condensing temperatures.

b. The temperature of the liquid refrigerant out of the

condenser should not be more than 15°F less than

the condensing temperature. (The temperature

corresponding to the condensing pressure from

refrigerant temperature/pressure chart.)

YORK INTERNATIONAL

The subcooling temperature should be taken by record-

ing the temperature of the liquid line at the outlet of the

condenser and recording the liquid pressure at the liq-

uid service valve and converting it to a temperature from

temperature/pressure chart.

Example:

Liquid Line Pressure 260 PSIG converted to120°F

Minus Liquid Line Temperature Subcooling 105°F

Add refrigerant to the system to increase subcooling or

remove refrigerant to lower subcooling. After the

subcooling is set at 10-15°F the superheat should be

checked.

The superheat should be checked only after steady

operation of the chiller has been established, the leav-

ing chilled liquid has been pulled down to the required

temperature, and the unit is running fully loaded. Cor-

rect superheat setting is 8° - 12°F.

The superheat is the difference between the actual tempera-

ture of the returned refrigerant gas entering the compres-

sor and the temperature corresponding to the suction pres-

sure as shown in a standard pressure/temperature chart.

Example:

Suction Temperature

Minus Suction Pressure 60 PSIG

Converted to Superheat

The suction temperature should be taken 6" before the

compressor service valve, and the suction pressure is

taken at the compressor suction service valve.

Normally, the thermal expansion valve need not be ad-

justed in the field. If, however, an adjustment is to be

made, the expansion valve adjusting screw should be

turned not more than one turn at a time, allowing suffi-

cient time (approximately 20 min.) between adjustments

for the system and the thermal expansion valve to re-

spond and return to settled operation. Make sure that

expansion valve is not cycling by watching pressures

end temperatures curing the waiting period.

If the unit has been functioning satisfactorily during the

initial operating period it is ready for continuous operation.