York YCAS0295EB, Installation Operation & Maintenance

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133 YORK INTERNATIONAL
FORM 201.19-NM7 (804)
S Y S # C U R R L I M I T I N G
S Y S # C U R R L I M I T I N G
S Y S # S U C T L I M I T I N G
S Y S # S U C T L I M I T I N G
ning of the chiller is not economical compared to the
use of “free” cooling techniques (see also Section 8.2
/ Low Ambient Temperature Cutout [page 162]). The
fault will clear when ambient temperature rises 2°F
(1°C) above the cut-out.
High Ambient Temperature Cutout:
The High Ambient Temperature Safety protects the
chiller from running in ambients above 130°F (54°C)
where potential malfunction of system mechanical and
electrical components may result. The High Ambient
Cutout is programmable and can be set for lower limit
values if required (see also Section 8.2 / High Ambient
Temperature Cutout [page 162]). The fault will clear
when ambient temperature drops 2°F (1°C) below the
cut-out.
Low Leaving Chilled Liquid Temperature Cutout:
The Low Liquid Temperature Safety assures that the
evaporator is not damaged from freezing due to im-
prop er ly set control points. It also attempts to protect
the chiller from freezing, if the fl ow switch should fail.
However, the fl ow switch should always be regarded
as the primary safety. Whenever the chilled liquid
temperature drops below the programmable cutout, the
chiller will shut down (see also Section 8.2 / Leaving
Water Temperature Cut out, page 162). The chiller fault
will clear when tem per a ture rises 4°F (2°C) above the
cut-out and cooling de mand exists.
115VAC Under Voltage Cut-Out:
The Under Voltage Safety assures that the system is
not operated at voltages where malfunction of the mi-
cro pro ces sor could result in system damage. When ev er
the microprocessor senses an on-board control power
supply failure while a compressor is running, the chill er
is shut down. The microprocessor circuitry is capable of
operating at voltages 10% below the nominal 115VAC
supply to the panel. Auto-restart of the chill er oc-
curs after a 2 minute start-up timer has elapsed from
the time when power is reapplied, if the AUTO RE-
START ON POWER FAILURE is enabled. Otherwise
the chill er must be manually reset. See Section 8.2
(page 164).
2.5 UNIT FAULT STATUS MESSAGES
A Unit Fault will shut the entire chiller down when a
preset safety threshold is exceeded. The chiller will
au to mat i cal ly restart after the condition causing the
shut down clears. Restart will occur only after anti-re-
cy cle timers are satisfi ed and cooling demand requires
ad di tion al cooling. A reset hysteresis is built into each
safe ty so repetitive faulting and clearing will not occur
in a short time period.
Continuous monitoring by the microprocessor assures
that instantaneous reaction results. When the chiller is
shut down on one of these safeties, a message will ap-
pear on the Status display informing the operator of the
problem as shown in the text that follows.
Any time that a Unit Fault occurs, the shutdown will be
logged into the HISTORY BUFFER.
Low Ambient Temperature Cutout:
The Low Ambient Temperature Safety prevents the
chill er from running in very low temperatures which
could cause damage due to low system pressures. This
feature is programmable and can also be used to shut
down the chiller at a temperature where continued run-
U N I T F A U L T
L O W A M B I E N T T E M P
U N I T F A U L T
H I G H A M B I E N T T E M P
U N I T F A U L T
L O W L I Q U I D T E M P
U N I T F A U L T
1 1 5 V A C U N D E R V O L T A G E
Compressor Motor Current Limiting:
The Motor Current Limiting message indicates that a
compressor motor current has reached a pro gram ma ble
threshold or a BAS current limit threshold, and the
system is being unloaded to as sure that motor current
does not be come ex ces sive ly high caus ing a fault.
See
Anticipatory Unloading Controls Page 155 for detailed
operation.
Suction Temperature Limiting:
This message indicates that saturated suc tion tem per a ture
on a system has dropped to 24°F (-4.4°C) in the
water cooling mode and that any further temperature
reduction could cause some ic ing of the evaporator
tubes. Saturated suction tem per a ture is computed by the
micro by con vert ing suction pres sure to temperature.
See Anticipatory unloading controls page 155 for
deatailed operation. Suction limiting is not active in
the glycol mode.
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