Specifications

Demand Defrost

When “DINM” = “DEMD” and ‘DFPD’ is set to ‘0’, the controller will initiate a demand defrost. The controller will not

go to ‘DEFROST MODE’ until a heavy frost accumulation is in the evaporator coil. When frost is built up in the

evaporator, it will block the air flowing through the evaporator coil and reduce the heat transfer area. It will also

decrease the evaporating temperature, which, in turn, increases probability of frosting. A demand defrost scheme to

detect the frost build-up and the criteria to start defrost are programmed in the Master Controller. Unlike scheduled

defrost, the Master Controller 2.0 with demand defrost is really an energy saver. If no selection is made, the

controller will automatically select demand defrost when the power is applied to the controller. The defrost procedure

is the same as described for the scheduled defrost.

After selecting the demand defrost, if the elapsed time since the last defrost has been a selectable time (INTV)

from 8 hours (480) to 72 hours(4320), the Master Controller 2.0 will go into defrost to ensure a proper oil return.

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 setpoint times out, standard five minutes, or the fan cut-in sensor’s temperature (FDTP) TS1

goes below the FAN DELAY TEMPERATURE Setpoint . 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)