Bohn PRO3 - Refrigeration and Defrost Sequences; Model-Specific Sequences; Low Temp Model Operation (EZY=1)

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 o 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.
Status Compressor
Condenser
Fans
Evaporator
Fans
Defrost
Heaters
Notes
O
Display alternates “OFF”
and Room Temperature
O O O O
If unit shows “OFF”, depress the “^”
button and hold for three seconds.
On Automatic Defrost on start up O O O On
If coil temperature is below 65° F. If it
is above, defrost is not initiated. Drip
Time and Freeze Time are ignored.
On
Defrost Sensor reaches 65° F
and defrost is terminated
O O O O
On
Cooling cycle initiated -
Drip Time
O O O O
System Timer Begins/ 2 min
drip time
On
Drip Time of 2 minutes ends -
coil freeze begins
On On O O
Compressor starts and evaporator fans
delay for 2 minutes to freeze the coil.
On
Evaporator fans start after
2 min delay
On On On O
On
Box Temperature (-10.1° F) is
satisfied
O O On O
On
Box Temperature rises
to -8.0° F
On On On O
2° F Dierential, Minimum
Compressor O time is 4 minutes
On
Defrost Initiated
(Manually or 6 hour counter)
O O O On Electric Defrost
On
Cooling cycle initiated -
Drip Time
O O O O
System Timer Begins/ 2 min
drip time
On
Drip Time of 2 minutes ends -
coil freeze begins
On On O O
Compressor starts and evaporator fans
delay for 1 minute to freeze the coil.
On
Evaporator fans start after
1 min delay
On On On O
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.