System Fault (Safety) Status Messages - York YCAS0098EB Installation Operation & Maintenance

Micro Panel Contents
the chiller must be manually reset. See Section 8.2
(page 162).
Flow Switch Open:
S Y S # N O
S Y S # N O
Closure of the flow switch(es) 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(es).
YCAS 2 System chillers have a single flow switch wired
to the control panel. If the flow switch opens, all systems
will shut down and a NO RUN PERM (Permissive)
message 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
system 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, Page 128, Fig. 46
for switch locations).
138
R U N P E R M
R U N P E R M
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
restarts may cause further expensive
damage to the system.
High Discharge Pressure Cutout:
S Y S # H I G H
S Y S # H I G H
The Discharge Pressure Safety prevents system pressure
from exceeding safe working limits. This safety is a
backup for the mechanical High Pressure Cutout in each
system. The Discharge Pressure Safety is programmable
for a range of values below the system upper limit (see
Section 8.2 / Page 160, High Discharge Pressure Cutout
for more details).
High Discharge Temperature Cutout:
S Y S # H I G H
S Y S # H I G H
This safety protects the compressor rotors from damage
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 tem-
perature is ignored. After 4 seconds of operation the
compressor will shut down if the discharge temperature
exceeds 260°F (127°C).
High Oil Differential Pressure Cutout:
S Y S # H I G H
S Y S # H I G H
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 returning
to the compressor (Discharge - Oil = Oil PSID). Under
normal operation, the oil pressure differential display
will be less than 25 PSID (1.7 bar), typical 2 - 10 PSID
D S C H P R E S
D S C H P R E S
D S C H T E M P
D S C H T E M P
O I L D I F F
O I L D I F F
JOHNSON CONTROLS