Bohn PRO3 Installation And Operation Manual page 9

REFRIGERATION/DEFROST SEQUENCE OF OPERATION
The sequence of operation varies depending on the model that has been installed. The three basic models are Low
Temperature, Medium Temperature, and High Temperature models. The particular model can be determined by the
seventh digit of the model number. See Tables 1-3 for details and settings.
Control of the refrigeration and defrost system is provided by the Carel controller along with a space (box) temperature
sensor and a coil (defrost) temperature sensor. The controller will control on and off switching for the compressor,
condenser fan motor(s) (cycles with the compressor), evaporator fan motor(s) and electric defrost heaters for
electric defrost.
The Carel controller is pre-programmed for all three applications. This is done with the use of the parameter list.
The parameter list can be changed by entering the Carel Controller and changing the "EZY" setting. See page 15.
TABLE 2: OUTDOOR MODELS | LOW TEMPERATURE MODELS | EZY SETTING=1
SET POINT IS -10° F
These models are intended for freezer applications and require electric defrost.
Status
Display alternates "OFF"
Off
and Room Temperature
On Automatic Defrost on start up
Defrost Sensor reaches 65° F
On
and defrost is terminated
Cooling cycle initiated -
On
Drip Time
Drip Time of 2 minutes ends -
On
coil freeze begins
Evaporator fans start after
On
2 min delay
Box Temperature (-10.1° F) is
On
satisfied
Box Temperature rises
On
to -8.0° F
Defrost Initiated
On
(Manually or 6 hour counter)
Cooling cycle initiated -
On
Drip Time
Drip Time of 2 minutes ends -
On
coil freeze begins
Evaporator fans start after
On
1 min delay
Condenser
Compressor
Fans
Off Off
Off Off
Off Off
Off Off
On On
On On
Off Off
On On
Off Off
Off Off
On On
On On
Evaporator Defrost
Fans Heaters
If unit shows "OFF", depress the "^"
Off Off
button and hold for three seconds.
If coil temperature is below 65° F. If it
Off On is above, defrost is not initiated. Drip
Time and Freeze Time are ignored.
Off Off
System Timer Begins/ 2 min
Off Off
drip time
Compressor starts and evaporator fans
Off Off
delay for 2 minutes to freeze the coil.
On Off
On Off
2° F Differential, Minimum
On Off
Compressor Off time is 4 minutes
Off On Electric Defrost
System Timer Begins/ 2 min
Off Off
drip time
Compressor starts and evaporator fans
Off Off
delay for 1 minute to freeze the coil.
On Off
Notes
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