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PRO
3
Top Mount Packaged Refrigeration System | Outdoor
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
satised
O O On O
On Box Temperature rises to -8.0° F On On On O
2° F Dierential, 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 2
minutes to freeze the coil.
On
Evaporator fans start after 2 min
delay
On On On O
TABLE 5 Model PTT | Low Temperature Models | EZY SETTING =1
SET POINT IS 10° F
These models are intended for freezer applications and require electric defrost.
3. Controllers