Protection Modes Of Operation; Evaporator Fan Operation; Failure Action; Generator Protection - Carrier Transicold 69NT40-561-001 Operation And Service Manual

If controller function code CnF33 is configured to snap freeze, the controller will sequence to this operation. The
snap freeze consists of running the compressor without the evaporator fans in operation for a period of 4 minutes
at 100% capacity. When the snap freeze is completed, defrost is terminated.
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 interval,
and possibly delaying a needed defrost cycle.
CnF11 determines whether the operator will be allowed to chose "OFF" as a defrost interval option.
CnF64 determines whether the operator will be allowed to choose "PuLS" as a defrost interval option. For units
operating with "PuLS" selected, defrost interval is determined by the unit temperature setpoint and the Evaporator
Fan Pulsing Temperature Setting (Cd60). When the unit temperature setpoint is equal to or less than the Evapora-
tor Fan Pulsing Temperature Setting, the defrost interval is set to 6 hours. Otherwise, the defrost interval is deter-
mined using the Automatic Defrost Interval Determination logic. In either case, "PuLS" remains displayed in this
function select code.
After a new Defrost Interval is selected, the previously selected Interval is used until the next defrost termination,
the next time the DTT contacts are OPEN, or the next time power to the control is interrupted. If the previous value
or the new value is "OFF", the newly selected value will be used immediately.
If any Auto Pretrip sequence is initiated, Cd27 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 Cd27 will be set to
"PuLS".
4.4

Protection Modes of Operation

4.4.1

Evaporator Fan Operation

Opening of an evaporator fan internal protector will shut down the unit.
4.4.2

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. See
4.4.3

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. See
4.4.4

Compressor High Temperature, Low Pressure 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, return air temperature is less than -17.5°C and the compressor discharge temperature is greater than
117.7°C.
Dome temperature control logic will disengage when return air temperature and ambient temperature return to
allowed limits or when the compressor turns off.
If the suction pressure low limit is triggered, the DUV will energize to raise the suction pressure.
4.4.5

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.
T-340
Table 4–5, Controller Function Codes.
Table 4–5, Controller Function Codes.
4–14