Maersk Container Industry Star Cool SCI-20 User Manual

14 of 116 pages
6.9 Evaporator fan
The evaporator fan function ensures correct fan speed (high or low). The function is active in the
automatic mode.
This function has 2 modes:
1. Normal
Low speed in Frozen mode or if the following three conditions are set:
- Tset is more than or equal to 0°C (32°F)
- No fresh air exchange
- Dehumidication is turned o or humidity setpoint below 65%
Otherwise high speed.
2. Economy
The fans run at a constant low speed. Exception: Tret > Tsup + 8°C (14°F) then high speed,
until Tret > Tsup + 3°C (5°F) is reached.
Economy mode is switched on by the operator.
6.10 Defrost function
The defrost function ensures regular evaporator defrosting. The function is active in Automatic mode.
Defrost initiation
• On demand defrost, meaning defrost function will start when needed.
Defrosting interval
• The on demand defrost system is constantly monitoring the evaporator temperatures in order
to prevent the evaporator blocking up with ice. If the system registers that the evaporator has
become blocked up with ice, an on-demand defrost will be initiated.
• The minimum time between defrosts is 2½ hours depending on the operation mode.
The actual defrost execution is carried out using combinations of air defrost, hot gas, and electrical
heaters and uses 4 modes:
1. Wait
In Wait mode the time is refreshed for the next defrost provided that the following conditions are
satised:
- Compressor is running
- T0 is less than T0min.
Wait mode termination can be due to:
- Calculated ice amount in the evaporator is above critical level (on-demand defrost)
- Defrosting action initiated manually (manual defrost initiation)
2. Initialize
Wait until the condenser temperature is above 50°C (122°F), however no more than 300 sec.
3. Execute
In this mode the actual evaporator defrosting takes place. A defrost start event is made in
the trip log. Cooling system termination results in compressor initiation, only ramp up mode is
executed. Evaporator fan is stopped. Evaporator heating elements are turned on. Compressor
runs at a constant frequency at 83% of full speed. Expansion valve control is deactivated. Hot
gas valve is used to heat the evaporator from the inside with the hot gas from the compressor.
Evaporator defrosting terminates when evaporator temperature (Tevap), is above defrost termi-
nation temperature for 2 min. or upon elapse of max. defrost time. A defrost stop event is made
in the datalog with the current interval and Tevap temperature.
4. Terminate
Terminate mode is dividable into two parts:
- Evaporator re-freezing preventing remaining water drops on evaporator from blowing into
the container upon evaporator fan initiation.
- Termination ensuring low evaporator fan speed to prevent shock boiling and to ensure that
the temperature controller takes over in a controlled way. After termination, the unit continues
normal operation again with the same setpoint temperature as before defrost start.

Maersk Container Industry Star Cool SCI-20 Specifications

General

Brand	Maersk Container Industry
Model	Star Cool SCI-20
Category	Refrigerator
Language	English