36
Alarms/Alerts —
Alarms and alerts are messages that
one or more faults have been detected. The alarms and alerts
indicate failures that cause the unit to shut down, terminate an
option (such as reset) or result in the use of a default value such
as a set point. Refer to the Troubleshooting section for more
information.
Up to 25 alarms/alerts can be displayed in currently active
alarms. Up to 50 alarms/alerts can be stored in the alarm histo-
ry. See Tables 25 and 26 to view and clear alarms.
When an alarm or alert is stored in the display and the
machine automatically resets, the alarm/alert is deleted. Codes
for safeties which do not automatically reset are not deleted
until the problem is corrected and the machine is reset. To clear
manual reset alarms from the CCP modules, press the reset
button located on the CCP board generating the alarm, for
5 seconds, (CCP1 for compressors A1 or B1, CCP2 for
compressors A2 or B2). Next, follow the example in Table 26
to clear the alarm from the Main Base Board (MBB) history.
Alarm relay usage alerts and alarms are configurable
in (CONFIGURATION MODE, SUB-MODE OPT2) to be
both one or the other or off paragraph.
Run Hours and Starts —
The HOUR and STRT sub-
modes under the Run Status mode contain items for number of
hours for each circuit and each compressor and the total
number of starts for each compressor. All items are password
protected, but can be changed if a replacement MBB is
installed.
Press
to make the current value flash. Use the arrow
keys to configure the correct value and press the
key
again. Record the current values from the MBB before remov-
ing the module or downloading new software.
Temperature Reset —
The control system is capable of
handling leaving-fluid temperature reset based on return cooler
fluid temperature. Because the change in temperature through
the cooler is a measure of the building load, the return tempera-
ture reset is in effect an average building load reset method.
The control system is also capable of temperature reset based
on outdoor-air temperature (OAT), space temperature (SPT), or
from an externally powered 4 to 20 mA signal. Accessory
sensors must be used for OAT and SPT reset (HH79NZ023 for
OAT and HH51BX006 for SPT). The Energy Management
Module (EMM) must be used for temperature reset using a 4 to
20 mA signal.
To use the return reset, four variables must be configured. In
the Configuration mode under the sub-mode RSET, items
CRST, CRT1, CRT2, and DGRC must be set properly. See
Tables 27 and 28 on page 37 for correct configuration.
To reset the return fluid temperature, the unit set point is
reset from full load based on the chilled fluid return tempera-
ture. The example uses a reset value of 10 degrees at full reset.
Full reset is at a 2-degree temperature difference across the
cooler and no reset would be at a 10 F difference across the
cooler. See Fig. 14-17 and Table 29.
Under normal operation, the chiller will maintain a constant
leaving fluid temperature approximately equal to the chilled
fluid set point. As the cooler load varies, the entering cooler
fluid will change in proportion to the load as shown in Fig. 14.
Usually the chiller size and leaving-fluid temperature set point
are selected based on a full-load condition. At part load, the
fluid temperature set point may be colder than required. If the
leaving fluid temperature was allowed to increase at part load,
the efficiency of the machine would increase.
Return temperature reset allows for the leaving temperature
set point to be reset upward as a function of the return fluid
temperature or, in effect, the building load.
Figure 14 is an example of no reset. Figures 15, 16, and 17
are examples of outdoor air, space and return water tempera-
ture resets.
Table 25 — Alarms Mode and Sub-Mode Directory
Table 26 — Example of Reading and Clearing Alarms
*Press
and
simultaneously to display expanded alarm description.
IMPORTANT: Do not clear the alarms without first
reviewing the full list and investigating and correcting
the cause of the alarms.
ENTER
ENTER
SUB-MODE
KEYPAD ENTRY
ITEM
ITEM EXPANSION
COMMENT
CRNT
AXXX or TXXX
CURRENTLY ACTIVE ALARMS
Alarms are shown as AXXX.
Alerts are shown as TXXX.
RCRN
YES/NO
RESET ALL CURRENT ALARMS
HIST
AXXX or TXXX
ALARM HISTORY
Alarms are shown as AXXX.
Alerts are shown as TXXX.
SUB-MODE
KEYPAD
ENTRY
ITEM
ITEM EXPANSION
COMMENT
CRNT
AXXX or TXXX
CURRENTLY ACTIVE ALARMS
ACTIVE ALARMS (AXXX) OR
ALERTS (TXXX) DISPLAYED.*
CRNT
RCRN
NO
Use to clear active alarms/alerts
NO
NO Flashes
YES
Select YES
NO
Alarms/alerts clear, YES changes to NO
ENTER
ENTER
ENTER
ENTER
ESCAPE
ENTER
ENTER
ENTER
ESCAPE