Evaporator Fan Operation; Failure Action; Generator Protection; Compressor High Temperature Protection - Carrier PrimeLINE 69NT40-561-200 Operation And Service Manual

Defrost Timer
If CnF23 is configured to "SAv" (save), then the value of the defrost interval timer will be saved at power down and
restored at power up. This option prevents short power interruptions from resetting an almost expired defrost inter-
val, and possibly delaying a needed defrost cycle. If the save option is not selected the defrost timer will re-initiate
and begin recounting.
If CnF11 is model number configured to OFF the operator will be allowed to choose "OFF" as a defrost interval
option.
If CnF64 is configured in the operator will be allowed to choose "PuLS" as a defrost interval option. For units oper-
ating with "PuLS" selected, defrost interval is determined by the unit temperature set point and the Evap Fan Puls-
ing Temp setting on the Trip Settings screen. When the unit temperature set point is equal to or less than the
Evaporator Fan Pulsing Temperature Setting, the defrost interval is set to 6 hours. Otherwise, the defrost interval is
determined using the Automatic Defrost Interval Determination logic. In either case, "PuLS" remains displayed in
this function select code.
If any Auto Pretrip sequence is initiated, the Defrost Interval setting will be set to 'AUTO' unless CnF49 (OEM
Reset) is set to "Custom" AND CnF64 (Evaporator Fan Pulsing Logic) configuration variable is set to IN, in which
case the Defrost Interval setting on the Trip Settings screen will be set to "Pulse".
If defrost does not terminate correctly and temperature reaches the set point of the Heat Termination Thermostat
(HTT) 54°C (130°F), the HTT will open to de-energize the heaters (AL059 & AL060). If the HTT does not open and
termination does not occur within two hours, the controller will terminate defrost. AL060 will be activated to inform
of a possible DTS failure.
Protection Modes of Operation
4.3.23

Evaporator Fan Operation

Opening of an evaporator fan internal protector will shut down the unit.
4.3.24

Failure Action

Function code Cd29 may be operator set to select the action the controller will take upon a system failure. The fac-
tory default is full system shutdown. Refer to
4.3.25

Generator Protection

Function codes Cd31 (Stagger Start, Offset Time) and Cd32 (Current Limit) may be operator set to control the start
up sequence of multiple units and operating current draw. The factory default allows on demand starting (no delay)
of units and normal current draw. Refer to
4.3.26

Compressor High Temperature Protection

The controller continuously monitors compressor discharge pressure and temperature, and suction pressure. If
discharge pressure or temperature rises above the allowed limit or suction pressure falls below the allowed limit,
the compressor will be cycled off and on every 3 minutes. Condenser and evaporator fans will continue to operate
during the compressor off cycle.
If high compressor dome temperature occurs, as measured by the CPDS, the controller will allow additional refrig-
erant to be released into the system in order to provide cooling to the evaporator coil and compressor dome. The
controller is alerted to high compressor dome temperatures via the CPDS when ambient temperature is greater
than 43.3°C (110°F), return air temperature is less than -17.5°C (0.5°F) and the compressor discharge temperature
is greater than 117.7°C (244°F).
Dome temperature control logic will disengage when return air temperature and ambient temperature return to
allowed limits or when the compressor turns off.
4.3.27

Compressor Low Pressure Protection

If the suction pressure low limit is triggered, the DUV will energize to raise the suction pressure.
4.3.28

Perishable Mode - System Pressure Regulation

In Perishable mode, system pressures may need to be regulated at ambient temperatures of 20°C (68°F) and
below. Once below this ambient temperature, the condenser fan may cycle on and off based on limits imposed for
discharge pressure. For extremely cold ambient temperatures, -18°C (0°F), heater cycling may occur within normal
system operation based on discharge pressure limits.
Table 4–6.
Table 4–6.
4–13 T-362