YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls

SECTION 7 - OPERATION
and these faults will be recorded as such under the
HISTORY information stored at the instant of the primary
fault. In some cases, this information may be
valuable in troubleshooting the primary fault. An example
of the “ALL FAULT” history message is shown
on page 106 under the HISTORY key. When an “ALL
FAULT” occurs, associated history information will
not be stored. If an additional fault does not occur, the
“ALL FAULTS” display will indicate NONE.
In cases where a VSD fault occurs during the rampdown
of a control panel fault (i.e.: low suction pressure,
low water temp, etc.), the VSD fault will be stored as a
new fault with the associated fault information stored
at the instant the VSD fault occurred (i.e.: IGBT Gate
Drive, Single Phase Input, VSD CT Plug, etc.). The
control panel fault that occurred prior to the VSD fault
will be stored with the associated complete data related
to the fault as a numerically lower numbered history in
the history buffers.
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 pressure is above 20.3 barg (295 PSIG).
The fault message for this safety is shown below:
90
SYS X YYYYYYYY HIGH DISCHARGE PRESSURE
The X indicates the system and YYYYYYYY 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 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
FORM 201.28-NM1.1
ISSUE DATE: 8/29/2012
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 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
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 cutout
is shown below:
SYS X YYYYYYYY LOW SUCTION 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. 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
Cutout =
200
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 start-
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