144
YORK INTERNATIONAL
High Discharge Pressure Cutout:
The Discharge Pressure Safety prevents system pres-
sure from exceeding safe working limits. This safety is
a backup for the mechanical High Pressure Cutout in
each system. The Discharge Pressure Safety is program-
mable for a range of values below the system upper
limit (see Section 8.2 / Page 168, High Discharge Pres-
sure Cutout for more details).
High Discharge Temperature Cutout:
This safety protects the compressor rotors from dam-
age due to overheating, expansion, and breakdown of
the oil film seal between the rotors. It also protects
against excessive oil temperature in the discharge oil
separator.
For the first 4 seconds of operation discharge tempera-
ture is ignored. After 4 seconds of operation the com-
pressor will shut down if the discharge temperature ex-
ceeds 127°C (260°F).
High Oil Differential Pressure Cutout:
The High Oil Pressure Differential Safety protects the
compressors against loss of proper lubrication due to
oil return line blockage. The “differential oil pressure”
for this safety is computed by measuring discharge (oil
separator) pressure and subtracting oil pressure return-
ing to the compressor (Discharge - Oil = Oil PSID).
Under normal operation, the oil pressure differential
display will be less than 1.7 bar (25 PSID), typical 0.1
to 0.7 bar (2 - 10 PSID). If oil pressure at the compres-
sor drops due to filter blockage, the differential pres-
sure on the display will increase and when the maxi-
mum limit is reached the compressor will be shut down.
This safety is activated after 3 minutes of operation.
Oil pressure must be less than 4.4 bar (65 PSID) for
R22 models as long as the compressor continues to
run.
the customer are connected in series with the flow
switch(es). YCAS chillers have a single flow switch
wired to the control panel. If the flow switch opens, all
systems controlled by the panel it is connected to will
shut down and a NO RUN PERM (Permissive) mes-
sage will be displayed. Closing of the flow switch, when
flow is present, will cause the message to disappear
and auto-restart to occur.
Never bypass a flow switch. This will
cause damage to the chiller and void
any warranties.
2.6
SYSTEM FAULT (SAFETY) STATUS
MESSAGES
A System Fault will shut the affected system down
whenever a preset safety threshold is exceeded for 3
seconds. Automatic restart will occur after the first 2
shutdowns when the anti-recycle timer times out and
temperature demand exists. After any combination of
3 Manual Reset Safeties in a 90 minute time period, the
affected system will shut down and lock out on the last
fault. When one or more systems are shut down on one
of these safeties, a message will appear on the Status
display informing the operator of the problem.
The High Motor Current Safety is a
unique safety which will lock out a sys-
tem after only a single fault.
To reset a locked out system, turn the System Switch
for the affected system to the OFF position, then back
to the ON position (see Section 1.11, Fig. 63 for switch
locations).
Before returning a locked out system
to service, a thorough investigation of
the cause of the fault should be made.
Failure to repair the cause of the fault
while manually allowing repetitive re-
starts may cause further expensive
damage to the system.
S Y S
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H I G H
D S C H
P R E S
S Y S
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H I G H
D S C H
P R E S
S Y S
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H I G H
D S C H
T E M P
S Y S
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H I G H
D S C H
T E M P
S Y S
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H I G H
O I L
D I F F
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H I G H
O I L
D I F F
MicroPanel Contents
Summary of Contents for Millennium YCAS 0693
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