Specifications

59
JOHNSON CONTROLS
Form 201.28-NM1.EN.PED/CE (0211)
7
High Discharge Pressure Cutout
(HPCO) (Hardware) Fault
The mechanical High Pressure Cutout protects the
system from experiencing dangerously high discharge
pressure. A system will fault and shut down immediately
when the mechanical high pressure cutout contacts open.
The fault will occur immediately and not wait 3 seconds,
which is typical of most system faults. The HPCO is
wired in series with the VSD Run Signal and will only be
checked by the Chiller Control Board when the system
is running. The mechanical cutout opens at 23.2 barg ±
0.55 barg (337 PSIG ± 8 PSIG) and closes at 17.4 barg
± 0.69 barg (252 PSIG ± 10 PSIG). The Status display
fault message for this system is shown below:
SYS X FAULT: HPCO FAULT
The X indicates the system and FAULT indicates the
system is in a “FAULT” condition and will restart
when the 120 second anti-recycle timer times out or
“LOCKOUT” and will not restart until the operator
clears the fault using the keypad.
Low Suction Pressure Cutout (Software) Fault
The programmable Low Suction Pressure Cutout is
a secondary back-up for the flow switch and protects
against operation with low refrigerant charge, which
helps protect the chiller from an evaporator freeze-up,
should the system attempt to run with a low refrigerant
charge. The Status display fault message for this cut-out
is shown below:
SYS X FAULT: LOW SUCTION PRESSURE
The X indicates the system and FAULT indicates the
system is in a “FAULT” condition and will restart
when the 120 second anti-recycle timer times out or
“LOCKOUT” and will not restart until the operator clears
the fault using the keypad. Typically, the cutout will be
set at 1.65 barg (24 PSIG) for chilled water applications.
The cutout is ignored for the first 30 seconds of system
run time. During the next 3 minutes of run time the
cutout point is linearly ramped from 10% of the cutout
value up to the programmed cutout point. If at any
time during the first 3 minutes of operation the suction
pressure falls below the ramped cutout point, the system
will shut down with a controlled ramped shutdown.
The cutout pressure during operating periods of 30
seconds to 210 seconds is ramped and can be calculated
by:
(Programmed Cutout x Run Time) -1.2 PSIG
200
Cutout =
After the first 3 minutes and 30 seconds of run time, if
the suction pressure falls below the cutout as a result
of a transient in the system, a transient timer is set at
30 seconds and a linearly ramped cutout is set starting
at 10% of the programmed cutout. If over the next 30
seconds, the suction pressure does not stay above the
ramped cutout, which ramps between 10% of the cutout
and the programmed cutout over the 30 second period,
the system will fault on low suction pressure.
Low Motor Current Cutout Fault
The Motor Current Cutout shuts the system down with
a controlled ramped shutdown when the microprocessor
detects the absence of motor current (less than 10% FLA),
usually indicating that a compressor is not running. This
safety is ignored for the first 10 seconds of operation.
The status display fault message for this safety is shown
below:
SYS X FAULT: LOW MOTOR CURRENT
The X indicates the system and FAULT indicates the
system is in a “FAULT” condition and will restart
when the 120 second anti-recycle timer times out or
“LOCKOUT” and will not restart until the operator
clears the fault using the keypad.
High Differential Oil Pressure Cutout Fault
The High Differential Oil Pressure Cutout protects the
compressor from low oil flow and insufficient lubrication,
possibly from a dirty oil filter. A system will fault and
shut down with a controlled ramped shutdown when its
Discharge to Oil Differential Pressure rises above the
cutout of 4.48 barD (65 PSID). This safety is ignored for
the first 90 seconds of run time. This safety measures the
pressure differential between discharge and oil pressure,
which is the pressure drop across the oil filter. The Status
display fault message for this safety is shown below:
SYS X FAULT: HIGH DIFF OIL PRESSURE
The X indicates the system and FAULT indicates the
system is in a “FAULT” condition and will restart
when the 120 second anti-recycle timer times out or
“LOCKOUT” and will not restart until the operator
clears the fault using the keypad.