YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls
YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls
YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls
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SECTION 7 - OPERATION<br />
and these faults will be recorded as such under the<br />
HISTORY information stored at the instant of the primary<br />
fault. In some cases, this information may be<br />
valuable in troubleshooting the primary fault. An example<br />
of the “ALL FAULT” history message is shown<br />
on page 106 under the HISTORY key. When an “ALL<br />
FAULT” occurs, associated history information will<br />
not be stored. If an additional fault does not occur, the<br />
“ALL FAULTS” display will indicate NONE.<br />
In cases where a VSD fault occurs during the rampdown<br />
of a control panel fault (i.e.: low suction pressure,<br />
low water temp, etc.), the VSD fault will be stored as a<br />
new fault with the associated fault information stored<br />
at the instant the VSD fault occurred (i.e.: IGBT Gate<br />
Drive, Single Phase Input, VSD CT Plug, etc.). The<br />
control panel fault that occurred prior to the VSD fault<br />
will be stored with the associated complete data related<br />
to the fault as a numerically lower numbered history in<br />
the history buffers.<br />
High Discharge Pressure Cutout (Software)<br />
Fault<br />
The High Discharge Pressure Cutout is a software<br />
fault. A system will fault and shut down with a controlled<br />
ramped shutdown on high discharge pressure<br />
when the discharge pressure rises above 22.4 barg (325<br />
PSIG) for 0.5 seconds. The system will be allowed to<br />
restart when the discharge pressure falls to 20.3 barg<br />
(295 PSIG). The system will also be inhibited from<br />
starting if the pressure is above 20.3 barg (295 PSIG).<br />
The fault message for this safety is shown below:<br />
90<br />
SYS X YYYYYYYY HIGH DISCHARGE PRESSURE<br />
The X indicates the system and YYYYYYYY indicates<br />
the system is in a “FAULT” condition and will<br />
restart when the 120 second anti-recycle timer times<br />
out, or “LOCKOUT” and will not restart until the operator<br />
clears the fault using the keypad.<br />
High Discharge Pressure Cutout<br />
(HPCO) (Hardware) Fault<br />
The mechanical High Pressure Cutout protects the<br />
system from experiencing dangerously high discharge<br />
pressure. A system will fault and shut down immediately<br />
when the mechanical high pressure cutout contacts<br />
open. The fault will occur immediately and not<br />
wait 3 seconds, which is typical of most system faults.<br />
The HPCO is wired in series with the VSD Run Signal<br />
and will only be checked by the Chiller Control Board<br />
FORM 201.28-NM1.1<br />
ISSUE DATE: 8/29/2012<br />
when the system is running. The mechanical cutout<br />
opens at 23.2 barg ± 0.55 barg (337 PSIG ± 8 PSIG)<br />
and closes at 17.4 barg ± 0.69 barg (252 PSIG ± 10<br />
PSIG). The Status display fault message for this system<br />
is shown below:<br />
SYS X YYYYYYYY HPCO FAULT<br />
The X indicates the system and YYYYYYY indicates<br />
the system is in a “FAULT” condition and will restart<br />
when the 120 second anti-recycle timer times out or<br />
“LOCKOUT” and will not restart until the operator<br />
clears the fault using the keypad.<br />
Low Suction Pressure Cutout (Software) Fault<br />
The programmable Low Suction Pressure Cutout is<br />
a secondary back-up for the flow switch and protects<br />
against operation with low refrigerant charge, which<br />
helps protect the chiller from an evaporator freeze-up,<br />
should the system attempt to run with a low refrigerant<br />
charge. The Status display fault message for this cutout<br />
is shown below:<br />
SYS X YYYYYYYY LOW SUCTION PRESSURE<br />
The X indicates the system and YYYYYYY indicates<br />
the system is in a “FAULT” condition and will restart<br />
when the 120 second anti-recycle timer times out or<br />
“LOCKOUT” and will not restart until the operator<br />
clears the fault using the keypad. Typically, the cutout<br />
will be set at 1.65 barg (24 PSIG) for chilled water applications.<br />
The cutout is ignored for the first 30 seconds of system<br />
run time. During the next 3 minutes of run time the<br />
cutout point is linearly ramped from 10% of the cutout<br />
value up to the programmed cutout point. If at any time<br />
during the first 3 minutes of operation the suction pressure<br />
falls below the ramped cutout point, the system<br />
will shut down with a controlled ramped shutdown.<br />
The cutout pressure during operating periods of 30 seconds<br />
to 210 seconds is ramped and can be calculated<br />
by:<br />
(Programmed Cutout x Run Time) -1.2 PSIG<br />
Cutout =<br />
200<br />
After the first 3 minutes and 30 seconds of run time, if<br />
the suction pressure falls below the cutout as a result<br />
of a transient in the system, a transient timer is set at<br />
30 seconds and a linearly ramped cutout is set start-<br />
JOHNSON CONTROLS