Carrier 69NT40-541-300, Operation And Service, Page: 84 / 152

T − 318 4 − 8
4.11 EMERGENCY BYPASS OPERATION
Operation by the refrigeration controller may be
overridden by use of the EMERGENCY BYPASS or by
use of the EMERGENCY DEFROST switch.
The EMERGENCY BYPASS switch functions to bypass
the controller in the event of controller failure. The
EMERGENCY DEFROST switch functions to bypass
the controller and place the unit in the defrost mode.
4.11.1 Emergency Bypass Operation
To place the unit in the emergency bypass mode, cut the
wire tie installed at the switch mounting (see Figure 2-6)
and place the EMERGENCY BYPASS switch in the
BYPASS position. This will in turn activate the
Emergency Bypass System (EBS) control module.
To operate the fans only, the MODE switch must be in
the FANS ONLY position and the EMERGENCY
BYPASS Switch must be in the ON position.
The EBS module uses the system’s safety devices (high
pressure switch, motor internal protectors, and heat
termination thermostat) to protect the system while in
Emergency Bypass Mode.
CAUTION
The unit will remain in the full cooling mode
as long as the emergency bypass switch is
in the BYPASS position and the MODE
SWITCH is in the FULL COOL position.
If the cargo is at risk of being damaged by
low temperatures, the operator must moni-
tor container temperature and manually
cycle operation as required to maintain
temperature within required limits.
In the ON position the EBS will be enabled. With the
MODE SWITCH in the FULL COOL MODE. The
following will occur simultaneously:
1. The EBS switch will enable EBS input.
2. The phase detection circuit will detect the phase
rotation and close to provide power to the compres-
sor contactor.
3. The condenser fan contact will close to energize the
condenser contactor and provide power to the con-
denser fan motor.
4. The evaporator fan contact will close to energize the
high speed evaporator contactor and provide power
to the evaporator fan motor.
5. The EBS electronic module will open the SMV to
100%.
To return the unit to normal operation, place the EBS
switch in the NORMAL OPERATION position. When
emergency operation is no longer required, re-install the
wire tie at the switch mounting.
4.11.2 Emergency Defrost Operation
To place the unit in the emergency defrost mode of
operation, cut the wire tie installed at the switch
mounting (see Figure 2-6) and place the switch in the
EMERGENCY DEFROST position.
NOTE
1. If the unit is in the emergency bypass
cooling mode, the emergency defrost
switch will override this mode and place the
unit in defrost.
2. The IN-RANGE LIGHT is de-energized
when in the emergency defrost mode.
The switch is a normally open four-pole switch, which is
placed in the EMERGENCY DEFROST position to:
a. De-energize the compressor, condenser fan and
evaporator fan contactors.
b. Illuminate the EMERGENCY DEFROST LIGHT.
c. Energize the heater contactor.
d. Illuminate the DEFROST LIGHT.
CAUTION
The unit will remain in the DEFROST mode
as long as the emergency defrost switch is
in the DEFROST position. To prevent cargo
damage, the operator must monitor con-
tainer temperature and manually cycle op-
eration as required to maintain temperature
within required limits.
To return the unit to normal operation, place the switch in
the NORMAL OPERATION position. When emergency
defrost is no longer required, re-install the wire tie at the
switch mounting.
4.12 ARCTIC MODE
With arctic mode enabled, if the ambient is colder than
-10.0 ° C there is a 30 − minute time delay at startup for
any of the components in the system, except for the
controller and the compressor crankcase heater (CCH),
which should be active at this point. In arctic mode, the
CCH is energized for 30 minutes to warm the oil in the
compressor and boil off any liquid refrigerant that may
be present in the crankcase.
If Pre-Trip is initiated during the 30 − minute time period,
Pre-Trip will be allowed to run normally. Once Pre-Trip is
over, the controller will revert to its normal control mode
logic.
If ambient is warmer than -10.0 ° C (14 ° F), the system
will run its normal startup logic.
Arctic mode is configurable by using the configuration
variable #29, refer to Table 3-4.
4.12.1 Crankcase Heater
When the crankcase heater is installed, it will be
operational whenever the compressor is off and there is
power to the unit. The heater is connected to a set of
normally closed auxiliary contacts on the compressor
contactor.