SECTION 7 - OPERATION
JOHNSON CONTROLS
127
Form 201.28-NM1.1
Issue date: 08/06/2021
7
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 following is the Status dis-
play fault message for this system:
SYS X YYYYYYYY HPCO FAULT
The X indicates the system and YYYYYYY 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
If the system attempts to run with a low refrigerant
charge, the programmable "Low Suction Pressure Cut-
out" protects the chiller from an evaporator freeze-up.
The cutout is ignored at the system start to allow ini-
tial programmable "Suction Pressure Startup Bypass
Time".
Immediately after the Suction Pressure Startup Bypass
Time has expired, the Suction Pressure Cutout is linear-
ly ramped to allow the programmed Suction Pressure
Startup ramp the Bypass Time, from 10% to 100% of
the programmed Suction Pressure Cutout, as explained
below.
If at any time during the ramp, the suction pressure
falls below the ramped Suction Pressure Cutout, the
system will shut down. If at any time after the ramp,
the suction pressure falls below the programmable Suc-
tion Pressure Cutout, the system will shut down. This
causes a lockout on the 3rd fault in 90 minutes.
Following is the system message, where X is the sys-
tem number.
Low suction pressure smart freeze fault
For R-134a and R-513A refrigeration sytem:
Suction Pressure Override Threshold =
Suction Pressure Cutout in psig + 1.7 psig
This safety fault is set when the Suction Pressure < pro-
grammable Suction Pressure Override Threshold, lon-
ger than the programmable Smart Freeze Timer.
SYS X YYYYYYYY LOW SUCTION PRESSURE
This safety fault is released when the Suction Pressure
>= Suction Pressure Override Threshold. This fault
causes a lockout on the 3
rd
fault in 90 minutes. The fol-
lowing is the system message, where X is the system
number.
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 following is the status display fault message for
this safety:
SYS X YYYYYYYY LOW MOTOR CURRENT
The X indicates the system and YYYYYYY 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 lubrica-
tion, 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 barg (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 following is the Status display fault mes-
sage for this safety:
SYS X YYYYYYYY HIGH DIFF OIL PRESSURE
The X indicates the system and YYYYYYY 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.
SYS X YYYYYYYY LOW SUCT PRES SMART FREEZE
