3.1.7.2Frozen Range Below
For set points below
a.Operation in the conventional mode (Code 33 OFF)
The return air probe is used for control and is so indicated by the LED on the display board.
The Frozen temperature range is not sensitive to minor temperature changes. The method of temperature control employed in this range takes advantage of this fact to greatly improve the energy efficiency of the unit. Temperature control in the Frozen range at or below
If the return air temperature in the container drops 0.2_C (0.4_F) below the set point temperature, the compressor is cycled off. When the temperature is greater than 0.2_C (0.4_F) above the set point and the three minute time delay has been met, the compressor will restart. The unit will always operate at full capacity, with both the suction modulation (SMV) and suction solenoid (SSV) valves fully open unless suction solenoid override or current limiting is activated. See section 2.10 for explanation of suction solenoid override.
To prevent on/off cycling of the compressor from occurring, a three minute compressor off time must be satisfied before the compressor will restart. Under a condition of rapidly changing return air temperature, the time delay may allow the return air temperature to rise slightly more than 0.2_C (0.4_F) above the set point temperature before the compressor can restart.
b. Operation in the economy mode (Code 34 OFF)
The economy mode is deactivated by setting function code Cd34 to the “OFF” status. Economy mode has no active display indicator to show that it is enabled, so a manual display of function code Cd34 must be performed to enable the user to see its current status. A second way to deactivate economy mode is to change the set point. Once economy mode is deactivated, the system will return to normal control mode operations.
In order to achieve economy mode frozen operation, a frozen set point temperature must be selected PRIOR to activating economy mode. When economy mode frozen is active, the system will perform normal frozen mode operations except that the entire refrigeration system,
excluding the Controller, will be turned off when the control temperature is less than or equal to the set point - 2_C, (i.e., the set point is set at
c. Operation in the bulb mode (Code 35 OFF)
The unit will not run in bulb mode if a frozen range set point is selected. As described in section 3.1.7.1.d., if a frozen set point is selected, dehumidification is deactivated and the temperature above which DTS must go during defrost resets to 25.6_C (78_F).
3.2 PRE-TRIP DIAGNOSTICS
CAUTION
NOTE
When
a.Starting and Terminating
NOTE
Prior to starting tests, verify that Controller function codes Cd04, Cd05, Cd06 and Cd07 are operational. Otherwise, tests may fail incorrectly. All alarms must be rectified and cleared.
A
