Table 99: Cycling shutdown messages
Message Description
EVAPORATOR – LOW
PRESSURE
The evaporator pressure, as sensed by the Evaporator Transducer, has
decreased to the shutdown threshold. For water cooling applications,
the shutdown threshold is a fixed value. For Brine cooling applications,
the shutdown threshold varies according to the concentration of
the Brine solution. The Brine shutdown threshold is programmed at
the YORK Factory. It should not be changed by anyone other than a
qualified service technician following instructions in YORK YMC
2
Service
Manual, Form 160.84-M2.
Application Shutdown (psig) Restart (psig)
Water cooling 25.0 25.1
Brine cooling 6.0 to 25.0 as programmed +0.1> Shutdown threshold
The chiller will restart after the evaporator pressure increases to the
restart threshold. If this shutdown occurs 3 times in a 90 minute period,
an Evaporator-low pressure safety shutdown is initiated.
EXPANSION I/
O – SERIAL
COMMUNICATIONS
Valid communication between the microboard and the LTC I/O Board
have been disrupted for three consecutive attempts. The chiller will
automatically restart when valid communication is received.
ISOLATION VALVES -
NOT CLOSED
The optional brine freeze protection motorized isolation valves Close
output is energized > 40 seconds but the feedback from the valve limit
switch does not indicate it closed for 3 continuous seconds. This cycling
fault is released when the isolation valves closed input is energized.
LEAVING CHILLED
LIQUID – LOW
TEMPERATURE
The Leaving Chilled Liquid Temperature has decreased to the
programmed Shutdown Temperature Setpoint. If the chiller is
running when this occurs, a Soft Shutdown is performed. The chiller
will automatically restart when the temperature increases to the
programmed Restart Temperature Setpoint.
MBC – FAULT
CONTACTS OPEN
See MBC Shutdown – Requesting Fault Data message above. If
the control center’s microboard does not receive the cause of the MBC
fault over the serial link within 10 seconds after the fault contacts open
is recognized, it is assumed it is not forthcoming and that message is
replaced with this message.
MBC - LOW INPUT
VOLTAGE
Main DC supply voltage to the MBC decreased below 135 VDC
(150%-10%)
MBC – SERIAL
COMMUNICATIONS
This Cycling Shutdown is set when an invalid or no response is
received from the MBC to a Modbus command from the panel for
3 consecutive attempts with a 2 second timeout between attempts.
It shall be triggered by the Modbus communications task when its
fault conditions are met (thresholds of consecutive timeouts, ID
mismatches, checksum failures, or error packets). It is released when a
valid response is received.
103
YMC
2
Mod B with OptiView Control Center
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