York YVAA Installation Operation & Maintenance page 115

Form 201.47-ICOM1
Issue date: 17/11/2022
High discharge pressure cutout (software)
fault
The High Discharge Pressure Cutout is a software fault.
A system will fault and shut down with a controlled
ramped shutdown on high discharge pressure when the
discharge pressure rises above 22.4 barg (325 psig) for
0.5 seconds. The system will be allowed to restart when
the discharge pressure falls to 20.3 barg (295 psig). The
system will also be inhibited from starting if the pres-
sure is above 20.3 barg (295 psig). The following is the
fault message for this safety:
SYS X YYYYYYYY HIGH DISCHARGE PRESSURE
The X indicates the system and YYYYYYYY in-
dicates the system is in a FAULT condition and will
restart when the 120 second anti-recycle timer times
out, or LOCKOUT and does not restart until the
operator clears the fault using the keypad.
High discharge pressure cutout (HPCO)
(hardware) fault
The mechanical high pressure cutout protects the sys-
tem from experiencing dangerously high discharge
pressure. A system will fault and shut down immediate-
ly when the mechanical high pressure cutout contacts
open. The fault occurs immediately and does not wait 3
seconds, which is common in 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 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 initial
programmable Suction Pressure Startup Bypass Time.
JOHNSON CONTROLS
Immediately after the Suction Pressure Startup By-
pass Time has expired, the Suction Pressure Cutout
is linearly 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
Suction 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.
SYS X YYYYYYYY LOW SUCTION PRESSURE
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 <
programmable Suction Pressure Override Threshold,
longer than the programmable Smart Freeze Timer.
This safety fault is released when the Suction Pressure
>= Suction Pressure Override Threshold. This fault
causes a lockout on the 3
rd
lowing is the system message, where X is the system
number.
SYS X YYYYYYYY LOW SUCT PRES SMART FREEZE
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
SECTION 7 - OPERATION
fault in 90 minutes. The fol-
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