Kilowatt Output; Remote Reset Of Alarms; Condenser Pump Control; Condenser Freeze Prevention - Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual

Kilowatt Output
-- An output is available on tile CCM
module [Terminal J8-1 (+) and J8-2 (-)1 to represent the power
consumption of the chiller Tile 4 to 20 mA signal generated by
the CCM module can be wired to the building automation or
energy management system to monitor the chiller's energy
consumption. Output is 2 mA with the chiller off. and it
varies linedy from 4 mA (representing 0% rated kilowatt
consumption) to 20 mA (representing 100% RATED LINE
KILOWATFS). The rated peak kilowatt consumption is
configured by the user in the VFD_CONF display screen by
the setting the RATED LINE KILOWATFS fiom the machine
electrical &tta nameplate.
Remote Reset of Alarms
-- A stan&u'd feature of the
PIC |II controls is the ability to reset a chiller in a shutdown
alarm state from a remote location. [f the condition which
caused the alarm has cleared the chiller can be placed back into
a normal CCN operating mode when the REMOTE RESET
OPTION (ICVC_PSWD menu) is set to ENABLE. A variety
of Career Comfort Network software systems including
ComfortVIEW
TM
or Network Sel-v'ice Tool
TM
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 rM module and reset the
fault displayed. Both methods would access the ICVC_PSWD
screen and fome the RESETALARM? point to YES to reset the
fault condition. [f the P[C III controls have determined that is
safe to start the chiller the CCN MODE? point (ICVC_PSWD
screen) can be forced to YES to place the chiller back into
norln;fl CCN operating mode. The only exceptions am the
following ahums that cannot be reset from a remote location:
Aimm/Alert STATE 100, 200, 201, 204, 206, 217-220,
233, 234, 247, and 259. To view alarm codes, refer to Trouble-
shooting Guide, Checking Display Messages, page 79. After
the alarm has been reset the PIC HI control will increment the
STARTS IN 12 HOURS counter by one upon restart. If the limit
of 8 starts in a 12-hour period is reached (Pmstart/Alert state
100), this must be reset at the local chiller control panel
(IeVC).
Condenser Pump Control
--
The chiller will moni-
tor the CONDENSER PRESSURE and may turn on the con-
denser pump if the condenser pressure becomes too high while
the compressor is shut down. The COND PRESS OVERRIDE
paralneter is used to determine this pressure point. COND
PRESS OVERRIDE is found in the SETUPI display screen,
which is accessed from the EQUIPMENT SERVICE table.
The default value is 125 psig (862 kPa).
If the CONDENSER PRESSURE is greater than or equal to
the COND PRESS OVERRIDE, and the ENTERING CON-
DENSER WATER temperature is less than 115 F (46 C), the
condenser pump will energize to try to decrease the pressure
and Alert 151 will be generated. The pump will turn off when
the condenser pressure is 3.5 psi (24.1 kPa) less than the
pressure override and the CONDENSER REFRIG TEMP is
within 3 ° F (1.7 ° C)of the ENTERING CONDENSER WATER
temperature.
Condenser Freeze Prevention -- This
control
_dgo-
rithm 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 fiom
freezing. The PIC III can perform this lhnction whenever the
chiller is not running excq)t when it is either actively in pump-
down or in pumpdown/lockout with the fieeze prevention
disabled.
When the chiller is off and CONDENSER REFRIG TEMP
is less than the CONDENSER FREEZE POINT, the
CONDENSER WATER PUMP will be energized (Alert State
154) Howevel, if the chiller is in pump down, and when it
entered pump down mode the CONDENSING REFRIG TEMP
was more than 5 ° F (2.7 ° C) above the CONDENSER
FREEZE POINT. the same low temperature condition will
generate Alarm State 244 trod the CONDENSER WATER
PUMP will be energized. In either case, the fault state will clem
and the pump will turn off when the CONDENSER REFRIG
TEMP is more than 5 ° F (2.7 ° C) above the CONDENSER
FREEZE POINT and the entering condenser water temperature
is greater than the CONDENSER FREEZE POINT. If the chill-
er is in Recycle Shutdown Mode when the condition occurs,
the controls will transition to a non-recycle shutdown.
Evaporator Freeze Protection
-- When the EVAP-
ORATOR REFRIG
TEMP is less than the EVAP REFRIG
TRIPPOINT plus the REFRIG OVERRIDE DELTA T (config-
urable fi_m 2 ° to 5 ° F or 1.1 ° to 2.8 ° C), Alert State 122 will be
displayed, and a capacity override will occm: (See Table 7.)
When the unit is running or in recycle, if the EVAPORATOR
REFRIG TEMP is equal to or less than the EVAP REFRIG
TRIPPOINT (33 ° F or 0.6 ° C for watek configurable for brine),
Protective Limit Alarm State 232 will be displayed, the unit
will shut down, and the CHILLED WATER PUMP will remgfin
on. The alarm will be clem'able when the leaving chilled water
temperature rises 5°F (2.8°C) above the CONTROL POINT.
When the unit is off, if the EVAPORATOR REFRIG TEMP
is less than the EVAP REFRIG TRIPPOINTplus 1° F (0.6 ° C),
Alarm State 243 will be generated and the CHILLED WATER
PUMP will be turned on. The _flmm can be reset when the
EVAPORATOR REFRIG TEMP rises 5 ° F (2.8 ° C) above the
EVAP REFRIG TRIPPOINT`
Tower Fan Relay Low and High
-- Low condens-
er water temperature can cause the chiller to shut down when
refrigerant temperature is low. The tower fan relays, located in
the stmter, am controlled by the PIC III to energize and deener-
gize as the pressure differential between cooler and condenser
vessels changes. This prevents low condenser water tempera-
turn and maximizes chiller efficiency. The tower fan relay can
only accomplish flris if the relay has been added to the cooling
tower temperature controllel:
TOWER FAN RELAY LOW is turned on whenever the
condenser water pump is running, flow is verified, ;rod the
difference between cooler and condenser pressure is more than
30 psid (207 kPad) for entering condenser water temperature
greater than 65 F (18.3 C).
TOWER FAN RELAY LOW is turned off when the condens-
er pump is off. flow is stopped, or the EVAP REFRIGERANT
TEMP is less than the EVAP REF OVERRIDE TEMP for
ENTERING CONDENSER WATER temperature less than
62 F (16.7 C), or the difference between the CONDENSER
PRESSURE and EVAPORATOR PRESSURE is less than
25 psi d (172.4 kPad) for ENTERING CONDENSER water less
than 80 F (27 C).
TOWER FAN RELAY HIGH is turned on whenever
the condenser water pump is running, flow is verified and
the difference between EVAPORATOR PRESSURE and
CONDENSER PRESSURE is more than 35 psid (241.3 kPa)
for ENTERING COND WATER temperature greater than the
TOWER FAN HIGH SETPOINT (SETPOINT menu, default
75 F [23.9 C]).
41