Controlling Loads; Compressor; Defrost; Control Of Evaporator Fans - Emerson Dixell XR75CX Series Installation And Operation Manual

3

Controlling Loads

3.1. Compressor

The regulation is performed according to the temperature
measured by the thermostat probe with a positive 
differential (HY) from the setpoint: if the temperature 
increases and reaches setpoint plus the differential, the
compressor is started and then turned OFF when the 
temperature reaches the setpoint value again
Figure 3-1 - Compressor Temperature Regulation
In case of a fault in the thermostat probe, the start and stop
of the compressor are timed through parameters Con and
CoF.

3.2. Defrost

Two defrost modes are available through the tdF 
parameter: defrost through electrical heater (tdF=EL) and
hot gas defrost (tdF=in).
• EdF=in, the defrost is made every idF time (the
standard method for the controller)
Other parameters are used to control defrost cycles: its
maximum duration (MdF) and two defrost modes: timed or
controlled by the evaporator's probe (P2P).
At the end of defrost dripping time is started, its 
duration is set in the Fdt parameter. With Fdt=0, the 
dripping time is disabled.
2 • XR75CX I&O Manual
3.3. Control of Evaporator
The fan control mode is selected by means of the FnC 
parameter:
• FnC = C_n: fans will switch ON and OFF with the
compressor and not run during defrost.
• FnC = O_n: fans will run even if the compressor is
OFF, and not run during defrost.
After defrost, there is a timed fan delay allowing for
.
drip time, set by means of the Fnd parameter.
• FnC = C_y: fans will switch ON and OFF with the
compressor and run during defrost.
• FnC = O_y: fans will run continuously during 
defrost also.
An additional parameter called FSt provides the 
setting of temperature, detected by the evaporator probe,
above which the fans are always OFF. This is used to make
sure that air is circulated only if this temperature is lower
than set in FSt.

3.3.1. Forced Activation of Fans

Managed by the Fct parameter, this function is 
designed to avoid short cycles of fans that could occur
when the controller is switched ON or after a defrost, when
the room air warms the evaporator.
How it works: If the temperature difference between the
evaporator probe and the room probe is higher than the Fct
parameter value, the fans will be switched ON. When Fct
= 0, the function will be 
disabled.
3.3.2. Cyclical Activation of the Fans
When FnC = C-n or C-y (fans are working in parallel with
the compressor), by means of the Fon and FoF parameters,
the fans can carry out ON and OFF cycles even if the 
compressor is switched OFF. When the compressor is
stopped, the fans will continue to work for the Fon time.
With Fon = 0, the fans always remain OFF when the 
compressor is OFF.
3.4. Light Relay
The functioning of the auxiliary relay (terminals 
1-2) can be set by the oA2 parameter, according to the kind
of application needed. Possible settings are as follows:
Fans
With Compressor Off
Configuration (PAR

oA2; Terminals 1-2)

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