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If after the 5 minute period the saturated suction tem-
perature is above 28°F (-2°C), the compressor is al-
lowed to reload, if required, to maintain leaving chilled
water. Otherwise, the microprocessor will reset the 5
minute timer and start the process again. To assure that
leaving chilled water requirements are satisfied while
one compressor is under suction temperature limiting
control, the microprocessor will start or load other
compressor(s) as necessary.
3.5 UNIT FAULT STATUS MESSAGES
Unit faults will shut the entire chiller down when a
pre-set safety threshold is exceeded. The chiller will
automatically restart after the condition causing the
shutdown clears. Restart will occur only after anti-re-
cycle timers are satisfied and cooling demand requires
additional cooling. A reset hysteresis is built into each
safety to prevent repetitive faulting and clearing.
Continuous monitoring by the microprocessor assures
that instantaneous reactions result. When the chiller is
shutdown on one of these safeties, a message will ap-
pear on the 'STATUS' display informing the operator
of the problem. When a unit fault occurs, the shutdown
will be logged into the 'History Buffer'.
Low Ambient Temperature Cutout:
This cutout protects the chiller from running in very
low temperatures which could cause damage due to low
system pressures.
U N I T
L O W
A M B I E N T
This cutout is programmable and can also be used to
shutdown the chiller at a temperature where continued
running of the chiller is not economical compared to
the use of "free" cooling techniques.
The fault will clear when ambient temperature rises
2°F (1°C) above the cutout.
High Ambient Temperature Cutout:
U N I T
H I G H
A M B I E N T
This cutout protects the chiller from running in ambi-
ents above 130°F (54°C) where potential malfunction
of system mechanical and electrical components may
result.
YORK INTERNATIONAL
F A U L T
T E M P
F A U L T
T E M P
The cutout is programmable and can be set for lower
limit values if required.
The fault will clear when ambient temperature drops
30°F (1°C) below the cutout.
Low Leaving Chilled Liquid Temperature Cutout:
This cutout assures that the evaporator is not damaged
from freezing due to improperly set control points. It
also attempts to protect the chiller from freezing, if the
flow switch should fail.
U N I T
L O W
L I Q U I D
Whenever the chilled liquid temperature drops below
the programmable cutout, the chiller will shutdown.
The chiller fault will clear when temperature rises 36°F
(2°C) above the cutout and a cooling demand exists.
115VAC Under Voltage Cutout:
This cutout assures that the system is not operated at
voltages where malfunction of the microprocessor could
result in system damage.
U N I T
L O W
L I Q U I D
Whenever the microprocessor senses an on-board con-
trol power supply failure while a compressor is run-
ning, the chiller is shutdown. The microprocessor cir-
cuitry is capable of operating at voltages 10% below
the nominal 115VAC supply to the panel.
Auto-restart of the chiller occurs after a 2 minute start-
up timer has elapsed from the time when power is re-
applied, if the automatic restart on power failure is en-
abled. Otherwise the chiller must be manually reset.
Flow Switch Open:
Closure of the flow switch is monitored to check that
flow is present in the evaporator when a compressor is
running. Any external cycling devices fitted by the cus-
tomer are connected in series with the flow switch.
S Y S
#
N O
S Y S
#
N O
If the flow switch opens, all systems will shutdown
and a 'NO RUN PERM' (Permissive) message will
be displayed.
FORM 201.25-NM1 (302)
F A U L T
T E M P
F A U L T
T E M P
R U N
P E R M
R U N
P E R M
43
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