12
Manual Defrost
The controller allows manually-initiated defrost when needed. The manual defrost will be disabled if the
evaporator inlet sensor detects the temperature higher than the defrost termination temperature. Operation of
the manual defrost will be discussed in a later section.
COIL DRAIN MODE (DRAN)
The controller automatically goes into COIL DRAIN whenever a defrost is terminated. The controller stays in
this mode for the preprogrammed ‘DRIP TIME’. When this time is completed the controller opens the
expansion valve and goes into FAN DELAY mode (FNDL).
While in COIL DRAIN MODE, the four-digit display on the controller will show ‘DRAN’ for five seconds,
‘RMTP’ for three seconds, and the numerical display of the room temperature for three seconds. The four-digit
display on controllers without an air temperature sensor will show ‘DRAN’.
FAN DELAY MODE (FNDL)
The controller will pull down the temperature of the evaporator without the fans on until one of the following
occurs: The FAN DELAY TIME of five minutes times out or the fan cut-in sensor’s temperature (FDTP) TS1
goes below the FAN DELAY TEMPERATURE of 30 Deg F. The controller will then go into COOL mode.
While in FAN DELAY MODE, the four-digit display will be ‘FNDL’ for three seconds, ‘FDTP’ for three
seconds, and the numerical display of the temperature reading from sensor TS1 for three seconds.
SAFETY MODE
When an alarm occurs, such as a sensor failure or a communication alarm, the controller will go into ‘SAFETY
MODE’. SAFETY MODE provides minimum refrigeration to the refrigerated room before the corrective action is
taken and the alarm is cleared. The system will do the following in Safety Mode:
• Pressure transducer alarm (PRSA)
o Cool mode
Valve open for the minimum compressor run time
Valve closed for the minimum compressor off time
Keep doing above cycle until alarm goes away
Ignores maximum pressure control mode
• Outlet sensor alarm (STSA)
o Cool mode
Valve open for the minimum compressor run time
Close valve for the minimum compressor off time
Keep doing above cycle until alarm goes away.
o Fan delay mode
Lets fan delay time out (five minutes)
o Defrost Mode
If this alarm and defrost term temp sensor alarm, reverse cycel defrost will last only
three minutes with valve open;
If this alarm and defrost term temp sensor alarm, electric defrost will last only ten
minutes with valve closed.
• Room temp sensor alarm (ATSA)
o Cool Mode
Run on superheat control for the minimum compressor run time
Close valve for the minimum compressor off time
Keep doing above cycle until alarm goes away.
• Low superheat alarm (LOSH)
o Close valve and wait for alarm to go away.
• High Room Temperature Alarm (HITA)
The ‘high room temperature alarm’ occurs when the room temperature is above the preprogrammed
‘HIGH TEMPERATURE ALARM’ for a preprogrammed number of minutes. The alarm is cleared when
the room temperature is less than the ‘HIGH TEMPERATURE ALARM’ set point.
• Low Room Temperature Alarm (LOTA)
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