70
YORK INTERNATIONAL
The superheat is the difference between the actual tem-
perature of the returned refrigerant gas entering the com-
pressor and the temperature corresponding to the suc-
tion pressure as shown in a standard pressure/tempera-
ture chart.
Example:
Suction Temperature
44°F (6.7°C)
Minus Suction Pressure 60 PSIG (413.4 kPAG)
Converted to Temperature
–34°F (1.1°C)
Superheat
10°F (5.6°C)
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 15 minutes) between adjust-
ments for the system and the thermal expansion valve
to respond and return to settled operation.
If the unit has been functioning satisfactorily during the
initial operating period, it is ready for continuous opera-
tion.
OPERATING SEQUENCE
(ALSO SEE COMPRESSOR CAPACITY CONTROL)
NOTE: The operating sequence described below relates
to operation after power has been applied on a
hot water start (such as start-up commissioning).
On compressor start-ups, internal timers limit
minimum time between compressor starts to 1
minute, time between compressor start and load-
ing to 2 min., and time between optional stages
of loading to 2 min. which may make the chiller
initially appear to deviate from normal operation
described on Pages 62-65.
1. For the system compressors to run, all Manual Re-
set Cutouts must be reset, the Flow Switch must be
closed, and any remote cycling contacts must be
closed.
2. As long as power is applied, the Crankcase Heat-
ers will be on and stay on as long as the compres-
sors are not running.
3. When the System Power Switch is applied, the unit
will start a 2 minute start-up timer.
4. At the end of the 2 minute timer, the 10 minute anti-
DUAL CIRCUIT UNITS
recycle timer will start at T = 0. At this time the Micro
Board will check all system conditions. If no safe-
ties are tripped and cooling demand is present, the
lead compressor will start (unloaded). If a safety is
tripped or no cooling demand is present, the timer
will stay at T = 0 until proper conditions exist. Coin-
cident with the start of the lead compressor, the as-
sociated liquid line solenoid will open after pump-
down to 13 PSI over Suction Pressure Cut-out is
completed.
5. T = 4 sec. The motor current of the lead compres-
sor must be > 24% FLA and < 115% FLA. Oil pres-
sure must > 10 PSID (68.9 kPaD). If these condi-
tions are not met, the lead compressor shuts down.
6. T = 30 sec. At this time the oil pressure of the lead
compressor must be a minimum of 25 PSID (172.2
kPaD) and suction pressure must be 80% cutout.
7. T = 60 sec. If cooling demand requires and no safe-
ties are tripped, the lag compressor starts (unloaded)
and its liquid line solenoid opens after pumpdown to
13 PSI over Suction Pressure Cut-out is completed.
8. T = 64 sec. The motor current of the lag compres-
sor must be >24% FLA and < 115% FLA. Oil pres-
sure must be >10 PSID (68.9 kPaD). If these condi-
tions are not met, the lag compressor shuts down.
9.
T = 90 sec. The oil pressure of the lag compres-
sor must be a minimum of 25 PSID (172.2 kPaD).
Suction pressure of the lag compressor must be 80%
cutout.
10. T = 2 min. The lead compressor will load if cool-
ing demand requires.
11. T = 3 min. The lag compressor will load if cooling
demand requires.
12. T = 4 min. The lead compressor’s suction pres-
sure must be cut-out (cut-out = 44 PSIG) (303 kPa).
At the same time, the oil pressure of the lead
compressor must be 20 PSID (137.8 kPaD).
13. T = 5 min. The lag compressor’s suction pressure
must be > cut-out (cut-out = 44 PSIG ) (303 kPaD).
At the same time, the oil pressure of the lag com-
pressor must be > 20 PSID (137.8 kPaD).
14. T = 10 min. The anti-recycle timer times out. This
places the timer at T = 0 position. The compressors
will run as long as cooling demand exists.
Содержание YCAG18
Страница 11: ...YORK INTERNATIONAL 11 FORM 150 40 NM25 SINGLE CIRCUIT UNITS LD01712 ELEMENTARY DIAGRAM FIG 4 CONTINUED...
Страница 12: ...12 YORK INTERNATIONAL SINGLE CIRCUIT UNITS FIG 4 CONTINUED LD01713 CONNECTION DIAGRAM ELECTRICAL BOX...
Страница 43: ...YORK INTERNATIONAL 43 FORM 150 40 NM25 DUAL CIRCUIT UNITS FIG 29 CONTINUED ELEMENTARY DIAGRAM LD01716...
Страница 44: ...44 YORK INTERNATIONAL DUAL CIRCUIT UNITS FIG 29 CONTINUED CONNECTION DIAGRAM ELECTRICAL BOX LD01717...
Страница 99: ...YORK INTERNATIONAL 99 FORM 150 40 NM25...
