Condenser Freeze Prevention; Tower Fan Relay Low And High; Auto. Restart After Power Failure; Water/Brine Reset - Carrier 19XR Start-Up, Operation And Maintenance Instructions Manual

energize to try to decrease the pressure. The pump will
turn off when the condenser pressure is 3.5 psi (24.1 kPa)
less than the pressure override or when the condenser re-
frigerant temperature (CONDENSER REFRIG TEMP) is within
3° F (1.7° C) of the entering condenser water temperature
(ENTERING CONDENSER WATER).
Condenser Freeze Prevention —
algorithm helps prevent condenser tube freeze-up by ener-
gizing the condenser pump relay. The PIC II controls the
pump and, by starting it, helps to prevent the water in the
condenser from freezing. The PIC II can perform this func-
tion 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 CONDENSER REFRIG TEMP is less than
or equal to the CONDENSER FREEZE POINT, the
CONDENSER WATER PUMP is energized until the
CONDENSER REFRIG TEMP is greater than the CON-
DENSER FREEZE POINT plus 5° F (2.7° C) and the
ENTERING CONDENSER WATER TEMPERATURE is less
than or equal to the CONDENSER FREEZE POINT. An alarm
is generated if the chiller is in PUMPDOWN mode and the
pump is energized. An alert is generated if the chiller is not
in PUMPDOWN mode and the pump is energized. If the
chiller is in RECYCLE SHUTDOWN mode, the mode will
transition to a non-recycle shutdown.
Tower Fan Relay Low and High —
water temperature can cause the chiller to shut down when
refrigerant temperature is low. The tower fan relays, located
in the starter, are controlled by the PIC II to energize and
deenergize as the pressure differential between cooler and
condenser vessels changes. This prevents low condenser wa-
ter temperature and maximizes chiller efficiency. The tower
fan relay can only accomplish this if the relay has been added
to the cooling tower temperature controller.
The tower fan relay low is turned on whenever the con-
denser water pump is running, flow is verified, and the dif-
ference between cooler and condenser pressure is more than
30 psid (207 kPad) for entering condenser water tempera-
ture greater than 65 F (18.3 C).
The tower fan relay low is turned off when the condenser
pump is off, flow is stopped, or the cooler refrigerant tem-
perature is less than the override temperature for ENTER-
ING CONDENSER WATER temperature less than 62 F
(16.7 C), or the differential pressure is less than 25 psid
(172.4 kPad) for entering condenser water less than
80 F (27 C).
The tower fan relay high is turned on whenever the con-
denser water pump is running, flow is verified and the dif-
ference between cooler and condenser pressure is more than
35 psid (241.3 kPa) for entering condenser water tempera-
ture greater than the TOWER FAN HIGH SETPOINT (SET-
POINT menu, default 75 F [23.9 C]).
The tower fan relay high is turned off when the condenser
pump is off, flow is stopped, or the cooler refrigerant tem-
perature is less than the override temperature and ENTER-
ING CONDENSER WATER is less than 70 F (21.1 C), or the
difference between cooler and condenser pressure is less than
28 Psid (193 kPa), or ENTERING CONDENSER WATER tem-
perature is less than TOWER FAN HIGH SETPOINT minus
3 F (−16.1 C).
The TOWER FAN RELAY LOW and HIGH parameter is
accessed from the STARTUP screen.
IMPORTANT: A field-supplied water temperature con-
trol system for condenser water should be installed.
The system should maintain the leaving condenser
water temperature at a temperature that is 20° F
(11° C) above the leaving chilled water temperature.
The tower fan relay control is not a substitute for a
condenser water temperature control. When used with
a water temperature control system, the tower fan relay
control can be used to help prevent low condenser
water temperatures.
This control
Auto. Restart After Power Failure —
may be enabled or disabled and may be viewed or modified
on the OPTIONS screen, which is accessed from the EQUIP-
MENT CONFIGURATION table. If the AUTO. RESTART
option is enabled, the chiller will start up automatically after
a power failure has occurred (after a single cycle dropout;
low, high, or loss of voltage; and the power is within ± 10%
of normal). The 15- and 3-minute inhibit timers are ignored
during this type of start-up.
When power is restored after the power failure and if the
compressor had been running, the oil pump will energize for
one minute before energizing the cooler pump. AUTO.
RESTART will then continue like a normal start-up.
If power to the CVC module has been off for more than
3 hours or the timeclock has been set for the first time, start
the compressor with the slowest temperature-based ramp load
rate possible in order to minimize oil foaming.
The oil pump is energized occasionally during the time
Low condenser
the oil is being brought up to proper temperature in order to
eliminate refrigerant that has migrated to the oil sump dur-
ing the power failure. The pump turns on for 60 seconds at
the end of every 30-minute period until the chiller is started.
Water/Brine Reset —
brine reset are available and can be viewed or modified on
the TEMP_CTL screen, which is accessed from the EQUIP-
MENT SERVICE table.
The CVC default screen indicates when the chilled water
reset is active. RESET TEMPERATURE on the MAIN-
STAT screen indicates the amount of reset. The CONTROL
POINT will be determined by adding the RESET
TEMPERATURE to the SETPOINT.
To activate a reset type, access the TEMP_CTL screen and
input all configuration information for that reset type. Then,
input the reset type number (1, 2, or 3) in the SELECT/
ENABLE RESET TYPE input line.
RESET TYPE 1: 4 to 20 mA (0 to 5 vdc) TEMPERATURE
RESET — Reset Type 1 is an automatic chilled water tem-
perature reset based on a remote temperature sensor input
configured for either an externally powered 4 to 20 mA or a
0 to 5 vcd signal. Reset Type 1 permits up to ±30 F (±16 C)
of automatic reset to the chilled water set point.
The auto, chilled water reset is hardwired to terminals
J5-3 (−) and J5-4 (+) on the CCM. Switch setting number 2
on SW2 will determine the type of input signal. With the
switch set at the ON position the input is configured for an
externally powered 4 to 20 mA signal. With the switch in the
OFF position the input is configured for an external
0 to 5 vdc signal.
RESET TYPE 2: REMOTE TEMPERATURE RESET — Re-
set Type 2 is an automatic chilled water temperature reset
based on a remote temperature sensor input signal. Reset Type
2 permits ± 30° F (± 16° C) of automatic reset to the set
point based on a temperature sensor wired to the CCM mod-
ule (see wiring diagrams or certified drawings). The tem-
perature sensor must be wired to terminal J4-13 and J4-14.
To configure Reset Type 2, enter the temperature of
the remote sensor at the point where no temperature reset
will occur (REMOTE TEMP [NO RESET]). Next, enter the
temperature at which the full amount of reset will occur
37
This option
Three types of chilled water or