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5.15 - Kilowatt output
An output is available on the CCM module [Terminal J8-1
(+) and J8- (–)] to represent the power consumption of
the chiller. The 4 to 0 mA signal generated by the CCM
module can be wired to the building automation or energy
management system to monitor the chiller’s energy con-
sumption. Output is mA with the chiller off, and it varies
linearly from 4 mA (representing 0% rated kilowatt con-
sumption) to 0 mA (representing 100%
RATED LINE
KILOWATTS
). The rated peak kilowatt consumption is
configured by the user in the VFD_CONF display screen
by setting the
RATED LINE KILOWATTS
from the
machine electrical data nameplate.
5.16 - Remote reset of alarms
A standard feature of the PIC III controls is the ability to
reset a chiller in a shutdown alarm state from a remote
location. If the condition which caused the alarm has cleared
the chiller, the chiller can be placed back into a normal CCN
operating mode when the
REMOTE RESET OPTION
(ICVC_PWD menu) is set to ENABLE. A variety of Carrier
Comfort Network software systems including ComfortVIEW
or Network Service Tool can access the PIC III controls
and reset the displayed alarm. Third party software from
building automation systems (BAS) or energy management
systems (EMS) can also access the PIC III controls through
a Carrier DataLINK module and reset the fault displayed.
Both methods would access the ICVC_PWD screen and
force the
RESET ALARM?
point to YES to reset the fault
condition. If the PIC III and controls have determined that it
is safe to start the chiller, the
CCN MODE?
point (ICVC_
PWD screen) can be forced to YES to place the chiller back
into normal CCN operating mode. The only exceptions are
the following alarms that cannot be reset from a remote
location: Alarm/Alert STATE 100, 00, 01, 04, 06, 17-0,
33, 34, 47, and 59. To view alarm codes, refer to Trouble-
shooting Guide, Checking Display Messages, page 54. After
the alarm has been reset, the PIC III control will increment
the
STARTS IN 12 HOURS
counter by one upon restart. If
the limit of 8 starts in a 1-hour period is reached (Prestart/
Alert state 100), this must be reset at the local chiller control
panel (ICVC).
5.17 - Condenser pump control
The chiller will monitor the
CONDENSER PRESSURE
and may turn on the condenser pump if the condenser
pressure becomes too high while the compressor is shut
down. The
COND PRESS OVERRIDE
parameter is used to
determine this pressure point.
COND PRESS OVERRIDE
is found in the SETUP1 display screen, which is accessed
from the EQUIPMENT SERVICE table. The default
value is 86 kPa.
If the
CONDENSER PRESSURE
is greater than or equal
to the
COND PRESS OVERRIDE
, and the
ENTERING
CONDENSER WATER
temperature is less than 46°C, the
condenser pump will energise to try to decrease the pressure
and Alert 151 will be generated. The pump turns off when the
condenser pressure is 4.1 kPa less than the pressure over-
ride and the
CONDENSER REFRIG TEMP
is within 1.7 K
of the
ENTERING CONDENSER WATER
temperature.
5.18 - Condenser freeze prevention
This control algorithm helps prevent condenser tube freeze-
up by energizing the condenser pump relay. The PIC III
controls the pump and, by starting it, helps to prevent the
water in the condenser from freezing. The PIC III can
perform this function whenever the chiller is not running
except when it is either actively in pumpdown or in
pumpdown/lockout with the freeze prevention disabled.
When the chiller is off and
CONDENSER REFRIG TEMP
is less than the
CONDENSER FREEZE POINT
, the
CONDENSER WATER PUMP
will be energised (Alert
State 154). However, if the chiller is in pumpdown, and when
it entered pumpdown mode, the
CONDENSING REFRIG
TEMP
was more than .7 K above the
CONDENSER
FREEZE POINT
, the same low temperature condition will
generate Alarm State 44 and the
CONDENSER WATER
PUMP
will be energised. In either case, the fault state will
clear and the pump will turn off when the
CONDENSER
REFRIG TEMP
is more than .7 K above the
CONDENSER
FREEZE POINT
and the entering condenser water tempe-
rature is greater than the
CONDENSER FREEZE POINT
.
If the chiller is in Recycle Shutdown Mode when the condi-
tion occurs, the controls will transition to a non-recycle
shutdown.
5.19 - Evaporator freeze protection
When the
EVAPORATOR REFRIG TEMP
is less than the
EVAP REFRIG TRIPPOINT
plus the
REFRIG OVER-
RIDE DELTA T
(configurable from 1.1 to .8 K, Alert State
1 will be displayed, and a capacity override will occur.
(See Table 6.)
When the unit is running or in recycle, if the
EVAPORATOR
REFRIG TEMP
is equal to or less than the
EVAP REFRIG
TRIPPOINT
(0.6°C for water, configurable for brine),
Protective Limit Alarm State 3 will be displayed, the
unit will shut down, and the CHILLED WATER PUMP
will remain on. The alarm will be clearable when the leaving
chilled water temperature rises .8 K above the
CONTROL
POINT
.
When the unit is off, if the
EVAPORATOR REFRIG TEMP
is less than the
EVAP REFRIG TRIPPOINT
plus 0.6 K,
Alarm State 43 will be generated and the CHILLED
WATER PUMP will be turned on. The alarm can be reset
when the
EVAPORATOR REFRIG TEMP
rises .8 K above
the
EVAP REFRIG TRIPPOINT.
5.20 - Tower fan relay low and high
Low condenser water temperature can cause the chiller to
shut down when refrigerant temperature is low. The tower
fan relays, located in the VFD, are controlled by the PIC III
to energise and deenergise as the pressure differential
between cooler and condenser vessels changes. This prevents
low condenser water temperature and maximises chiller
efficiency. The tower fan relay can only accomplish this if
the relay has been added to the cooling tower temperature
controller.
