York YCUL0045E, Installation Operation & Maintenance

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JOHNSON CONTROLS
60
FORM 150.63-NM8 (1020)
UNIT CONTROLS
S Y S 1 H I G H D S C H P R E S
S Y S 2 H I G H D S C H P R E S
S Y S 1 L O W S U C T P R E S S
S Y S 2 L O W S U C T P R E S S
The PUMPING DOWN message indicates that a com-
pressor in the respective system is presently in the pro-
cess of pumping the system down. When pumpdown is
initiated on shutdown, the liquid line solenoid or EEV
will close and a compressor will continue to run. When
the suction pressure decreases to the suction pressure
cutout setpoint or runs for 180 seconds, whichever
comes first, the compressor will cycle off.
FAULT STATUS MESSAGES
Safeties are divided into two categories – system
safeties and unit safeties. System safeties are faults
that cause the individual system to be shut down. Unit
safeties are faults that cause all running compressors
to be shut down. Following are display messages and
explanations.
SYSTEM SAFETIES:
System safeties are faults that cause individual systems
to be shut down if a safety threshold is exceeded for 3
seconds. They are auto reset faults in that the system
will be allowed to restart automatically after the fault
condition is no longer present. However, if 3 faults on
the same system occur within 90 minutes, that system
will be locked out on the last fault. This condition is then
a manual reset. The system switch (under OPTIONS
key) must be turned off and then back on to clear the
lockout fault.
The Discharge Pressure Cutout is a software cutout in
the microprocessor and is backed-up by a mechanical
high pressure cutout switch located in the refrigerant
circuit. It assures that the system pressure does not
exceed safe working limits. The system will shutdown
when the programmable cutout is exceeded and will be
allowed to restart when the discharge pressure falls 40
PSIG below the cutout. Discharge transducers must be
installed for this function to operate.
The Suction Pressure Cutout is a software cutout that
helps protect the chiller from a coil freeze-up should the
system attempt to run with a low refrigerant charge or a
restriction in the refrigerant circuit.
Repeated starts after resetting a low suc -
tion pressure fault will cause evaporator
freeze-up. Whenever a system locks out
on this safety, immediate steps should
be taken to identify the cause.
At system start, the cutout is set to 10% of programmed
value. During the next 3 minutes the cutout point is
ramped up to the programmed cutout point. If at any
time during this 3 minutes the suction pressure falls
below the ramped cutout point, the system will stop. This
cutout is ignored for the first 30 seconds of system run
time to avoid nuisance shutdowns, especially on units
that utilize a low pressure switch in place of the suction
pressure transducer.
After the first 3 minutes, if the suction pressure falls
below the programmed cutout setting, a “transient
protection routine” is activated. This sets the cutout at
10% of the programmed value and ramps up the cutout
over the next 30 seconds. If at any time during this 30
seconds the suction pressure falls below the ramped
cutout, the system will stop. This transient protection
scheme only works if the suction pressure transducer
is installed. When using the mechanical LP switch, the
operating points of the LP switch are: opens at 23 PSIG
+/- 5 PSIG (1.59 barg +/- .34 barg), and closes at 35
PSIG +/- 5 PSIG (2.62 barg +/- .34 barg).
The Motor Protector/Mechanical High Pressure Cutout
protects the compressor motor from overheating or the
system from experiencing dangerously high discharge
pressure. This fault condition is present when CR1 (SYS
1) or CR2 (SYS 2) relays de-energize due to the HP switch
or motor protector opening. This causes the respective
CR contacts to open applying 0VDC on the input to the
I/O Board. The fault condition is cleared when a 30VDC
signal is restored to the input.
S Y S 1 P U M P I N G D O W N
S Y S 2 P U M P I N G D O W N
S Y S 1 M P / H P C O I N H I B
S Y S 2 M P / H P C O I N H I B