8
Control overview, Parameters and Theory of Operation
This unit is equipped with a sophisticated, microprocessor based, digital electronic control. All of the temperature and
defrost functions are controlled by use of a subset of a broad range of the control’s capabilities. Global Refrigeration has
preconfigured this control for optimal performance using the operating parameters listed below. It is highly recommended
that these parameters (other than set point temperature) be left at their Global Refrigeration factory settings. In the event
of a control failure, Global Refrigeration recommends that the replacement control be sourced from us, as our factory
replacement part will be preconfigured for the specific model required. In a service emergency, a Danfoss replacement
control of the same type and model can be used, but it must be installed as the original and programmed with the values
in the table below. All Danfoss parameters not shown are left at the Danfoss default values.
CAUTION: It is essential that control replacement is only done by trained service professionals; non- standard
program parameters may result in serious machine failures and may void the unit or compressor warranty.
Theory of operation: Danfoss controls for Global freezers are equipped with two temperature sensors; a cavity sensor
connected to the S4 input and a defrost sensor connected to the S5 input. It is configured for a time interval initiated /
temperature terminated defrost cycle.
The evaporator fan(s) are configured for continuous operation with the exception that they will de-energize via the
controller’s fan relay during defrost or by the door switch(s) if a door is opened. As temperature rises in the cabinet up to
the set point temperature plus the differential, the compressor control relay will energize, powering the compressor
contactor and the compressor will run. As the temperature falls to the set point, the control will de-energize the
compressor relay. After 8 hours of operation (or other interval specified in param. d03) the unit will initiate a defrost cycle .
Upon initiation of the of the defrost cycle, the compressor and evaporator fans will de-energize. The control will close the
defrost heater relay and the defrost heater will start heating the bottom of the evaporator coil. As frost melts away, the
temperature of the evaporator outlet tube, (where the defrost temperature sensor is located) will warm. When the defrost
sensor rises above it’s set point temperature of 35°F (param. d02) the defrost heaters will de-energize and the
compressor will be energized. If the defrost sensor fails to reach it’s stop temperature the control will invoke a timed
termination after 35minutes of defrost time (param. d04). Note that the evaporator fans will not resume operation at the
same time as the compressor. The evaporator fans will remain off for 15 minutes (param. d07) or until the defrost
sensor’s temperature declines to 10°F (d08); whichever comes first.
Parameter description.
Danfoss
ULG30BS
T30LSP
T30HSP
T30MSP
Units
Note: parameters not shown are left
Parameter
ULG50BC
T50LSP
T50HSQL
T50MSP
at their Danfoss factory default
Number
ULG80BC
T80LSP
T50HSQHP
T80MSP
T30LGP
settings
T50LGP
T80LGP
Differential
r01
7
7
7
7
°
F
Maximum Set Point setting
r02
+20
0
0
+50
°
F
Minimum Set Point setting
r03
- 20
- 30
- 40
+ 35
°
F
Temperature Units (°C/°F)
r05
F
F
F
F
Control Operating mode*
r12
1
1
1
1
0 = STOP, 1 = RUN, ‐1 = Manual
Defrost method
d01
1
1
1
0
0=None, 1= Electric, 2=Gas, 3 = BRINE
Defrost stop temperature
d02
38
38
38
38
°
F
Interval Between Defrost Cycles
d03
12
12
12
12
Hours
Maximum Length of Defrost Cycle
d04
35
35
35
35
Minutes
Delay for Fan Restart after Defrost
d07
15
15
15
15
Minutes
Fan (Re)start temperature
d08
10
10
10
10
°
F
Fan run during defrost 1 = yes, 0= NO
d09
0
0
0
0
Defrost sensor 0 = time, 1 = S5, 2=S4
d10
1
1
1
0
*
- This parameter must be set to 1 for control to function
