Safety Shutdown Messages - York YST Operation Manual

SECTION 2 - OPTIVIEW CONTROL CENTER INTRODUCTION
" proximity probe – low Supply voltage"
This message indicates the +24VDC power supply
voltage to the Proximity Probe has decreased to
+19.0VDC. This is below the minimum level required
for reliable operation. The chiller will automatically
restart when the voltage increases to >19.7VDC.

SafeTY ShuTdoWn MeSSageS

"Watchdog – Software reboot"
The Microboard's software Watchdog initiated a Mi-
croprocessor reset because it detected that a portion of
the chiller operating Program was not being executed.
The result of this reset is a Safety shutdown and re-ini-
tialization of the Program. This is generally indicative
of a severe electrical power disturbance or impending
Microboard failure. The chiller can be started after the
START/STOP switch is placed in the STOP-RESET
(O) position.
" internal error – Cannot Create Task"
A program execution error occurred in providing re-
quested task handle.
" internal error – no Timer handles available"
A program execution error occurred in providing
requested timer handle.
"Control panel – power failure"
A Control Power failure has occurred. If the power fail-
ure duration was less than 6 minutes, the remainder of
the "System Coastdown" is performed upon restoration
of power. The chiller can be started after the START/
STOP control switch is placed in the STOP-RESET
(O) position. This message can indicate a Cycling (au-
to-restart after power failure) or Safety (manual restart
after power failure) shutdown, depending upon Control
Center configuration. It indicates a Cycling shutdown
when displayed in orange characters; Safety shutdown
when displayed in red characters. The Control center is
configured for auto-restart or manual restart after pow-
er failure by a qualified Service Technician following
instructions in YORK Service Manual 160.67-M3.
"evaporator – low pressure"
The evaporator pressure, as sensed by the Evapora-
tor Transducer, has decreased to the Safety shutdown
threshold. For water cooling applications, the safety
shutdown threshold is a fixed value for the respective
140
refrigerant. For Brine cooling applications, the safety
shutdown threshold varies according to the concentra-
tion of the Brine solution. The Brine shutdown thresh-
old is programmed at the YORK Factory. It should not
be changed by anyone other than a qualified Service
Technician following instructions in YORK Service
Manual 160.67-M3. The chiller can be started after the
evaporator pressure increases to the restart threshold
and the START/STOP control switch is placed in the
STOP-RESET (O) position.
ShuTdoWn
Water Cooling -
R22
- R134a
Brine Cooling - 25.0 to 54.3
R22 as programmed
6.0 to 25.0
- R134a
as programmed
" evaporator – low pressure - Smart freeze"
Smart Freeze protection is activated and has shut-
down the chiller because the evaporator temperature
has been below the Smart Freeze threshold for greater
than the allowable number of seconds. If the Evapora-
tor Refrigerant Temperature sensor is Enabled, (using
procedure in Service Manual 160.67-M3), this param-
eter is used as the evaporator refrigerant temperature
and the freeze threshold is 32.8°F. If this sensor is not
enabled, the evaporator refrigerant temperature used is
the Evaporator Saturation Temperature, derived from
the Evaporator Pressure Transducer and the freeze
threshold is 34.0°F.
The total count is incremented once for every sec-
ond the evaporator refrigerant temperature is below
the freeze threshold (but is never decremented below
zero). The number of seconds it will take the chilled
liquid to freeze is based on how far the evaporator re-
frigerant temperature is below the freeze threshold as
follows:
# seconds to freezing = (4053.7) / (freeze thresh-
old – evap. refrigerant temp.)
Smart Freeze is activated only if the feature has been
Enabled by a Service technician and the Leaving
Chilled Liquid temperature Setpoint is <38.0°F.
FORM 160.67-O1
ISSUE DATE: 4/1/2015
reSTarT (pSig)
(pSig)
54.3 54.4
25.0 25.1
+0.1 >
Shutdown
threshold
+0.1 >
Shutdown
threshold
JOHNSON CONTROLS