Emerson XR72CX User Manual

Digital controller with defrost and fans management

The regulation is performed according
to the temperature measured by the
thermostat probe with a positive
differential from the set point: if the
temperature increases and reaches set
point plus differential the compressor is
started and then turned off when the
temperature reaches the set point value
again.

Time

Temper.

Compr.

SET

ON

LED

MODE

FUNCTION

ON

Compressor enabled

Flashing

Anti-short cycle delay enabled

ON

Defrost enabled

Flashing

Drip time in progress

ON

Fans enabled

Flashing

Fans delay after defrost in progress.

ON

An alarm is occurring

ON

Continuous cycle is running

ON

Energy saving enabled

°C/°F

ON

Measurement unit

°C/°F

Flashing

Programming phase

1. Push and immediately release the SET key: the display will show the

Set point value;

2. Push and immediately release the SET key or wait for 5 seconds to

XR72CX

1. GENERAL WARNING

1.1 PLEASE READ BEFORE USING THIS MANUAL

 This manual is part of the product and should be kept near the instrument for easy and quick reference.
 The instrument shall not be used for purposes different from those described hereunder. It cannot be

used as a safety device.

 Check the application limits before proceeding.
 Dixell Srl reserves the right to change the composition of its products, even without notice, ensuring the

same and unchanged functionality.

3.4.2 Cyclical activation of the fans with compressor off.

When Fnc = c-n or c-Y (fans in parallel to 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 go on working for the Fon time. With Fon =0 the fans remain always
off, when the compressor is off.

4. FRONT PANEL COMMANDS

1.2

 Check the supply voltage is correct before connecting the instrument.
 Do not expose to water or moisture: use the controller only within the operating limits avoiding sudden

 Warning: disconnect all electrical connections before any kind of maintenance.
 Fit the probe where it is not accessible by the End User. The instrument must not be opened.
 In case of failure or faulty operation send the instrument back to the distributor or to “Dixell S.r.l.” (see

 Consider the maximum current which can be applied to each relay (see Technical Data).
 Ensure that the wires for probes, loads and the power supply are separated and far enough from each

 In case of applications in industrial environments, the use of mains filters (our mod. FT1) in parallel with

SAFETY PRECAUTIONS

temperature changes with high atmospheric humidity to prevent formation of condensation

address) with a detailed description of the fault.

other, without crossing or intertwining.

inductive loads could be useful.

2. GENERAL DESCRIPTION

Model XR72CX, format 32 x 74 mm, is microprocessor based controller, suitable for applications on
medium or low temperature ventilated refrigerating units. It has four relay outputs to control
compressor 1, compressor 2, fan and defrost, which can be either electrical or reverse cycle (hot
gas). It is also provided with up to four NTC or PTC probe inputs, the first one for temperature
control, the second one, to be located onto the evaporator, to control the defrost termination
temperature and to managed the fan. The digital input can operate as third temperature probe. The
fourth one, to connect to the HOT KEY terminals is used to signal the condenser temperature alarm
or to display a temperature.
The HOT KEY output allows to connect the unit, by means of the external module XJ485-CX, to a
network line ModBUS-RTU compatible such as the Dixell monitoring units of X-WEB family. It
allows to program the controller by means the HOT KEY programming keyboard.
The instrument is fully configurable through special parameters that can be easily programmed
through the keyboard.

3. CONTROLLING LOADS

3.1 COMPRESSOR

: To display target set point; in programming mode it selects a parameter or confirm an

operation.

(DEF) To start a manual defrost

(UP): To see the max. stored temperature; in programming mode it browses the parameter

codes or increases the displayed value.

(DOWN) To see the min stored temperature; in programming mode it browses the parameter

codes or decreases the displayed value.

To switch the instrument off, if onF = oFF.

Not used.

KEY COMBINATIONS:

+

+ To enter in programming mode.
+ To return to the room temperature display.

To lock & unlock the keyboard.



4.1 USE OF LEDS

Each LED function is described in the following table.

In case of fault in the thermostat probe the start and stop of the compressor are timed through

parameters “COn” and “COF”.

ND

3.2 2

COMPRESSOR MANAGEMENT – XR72C ONLY

The relay of the second compressor is activated in parallel with the relay of the first compressor, with
a possible delay set in the AC1 parameter. Both the compressors are switched off at the same time.

3.3 DEFROST

Two defrost modes are available through the “tdF” parameter: defrost through electrical heater (tdF
= EL) and hot gas defrost (tdF = in). Other parameters are used to control the interval between

defrost cycles (IdF), its maximum length (MdF) and two defrost modes: timed or controlled by the
evaporator’s probe (P2P).
At the end of defrost dripping time is started, its length is set in the FSt parameter. With FSt =0 the
dripping time is disabled.

3.4 CONTROL OF EVAPORATOR FANS

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 also during defrost

An additional parameter “FSt” provides the setting of temperature, detected by the evaporator probe,

above which the fans are always OFF. This is used to make sure circulation of air only if his
temperature is lower than set in “FSt”.

3.4.1 Forced activation of fans

This function managed by the Fct parameter is designed to avoid short cycles of fans, that could
happen when the controller is switched on or after a defrost, when the room air warms the
evaporator. Functioning: if the difference of temperature between the evaporator and the room
probes is more than the value of the Fct parameter, the fans are switched on. With Fct=0 the function
is disabled.

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5. MAX & MIN TEMPERATURE MEMORIZATION

5.1 HOW TO SEE THE MIN TEMPERATURE

1. Press and release the n key.

2. The “Lo” message will be displayed followed by the minimum temperature recorded.

3. By pressing the n key again or by waiting 5s the normal display will be restored.

5.2 HOW TO SEE THE MAX TEMPERATURE

1. Press and release the o key.

2. The “Hi” message will be displayed followed by the maximum temperature recorded.

3. By pressing the o key again or by waiting 5s the normal display will be restored.

5.3 HOW TO RESET THE MAX AND MIN TEMPERATURE RECORDED

1. Hold press the SET key for more than 3s, while the max. or min temperature is displayed. (rSt

message will be displayed)

2. To confirm the operation the “rSt” message starts blinking and the normal temperature will be

displayed.

6. MAIN FUNCTIONS

6.1 HOW TO SEE THE SETPOINT

display the probe value again.

6.2 HOW TO CHANGE THE SETPOINT

1. Push the SET key for more than 2 seconds to change the Set point value;

2. The value of the set point will be displayed and the “°C” or “°F”

3. To change the Set value push the o or n arrows within 10s.

4. To memorise the new set point value push the SET key again or wait 10s.

LED starts blinking;

6.3 HOW TO START A MANUAL DEFROST

Push the DEF key for more than 2 seconds and a manual defrost will start.

With “onF = oFF”, pushing the ON/OFF key, the instrument is switched off. The “OFF”
message is displayed. In this configuration, the regulation is disabled.
To switch the instrument on, push again the ON/OFF key.

6.4 HOW TO CHANGE A PARAMETER VALUE

To change the parameter’s value operate as follows:

1. Enter the Programming mode by pressing the Set + n keys for 3s (the “°C” or “°F”

blinking).

2. Select the required parameter. Press the “SET” key to display its value

3. Use “UP” or “DOWN” to change its value.

4. Press “SET” to store the new value and move to the following parameter.

To exit: Press SET + UP or wait 15s without pressing a key.
NOTE: the set value is stored even when the procedure is exited by waiting the time-out to expire.

LED starts

6.5 THE HIDDEN MENU

The hidden menu Includes all the parameters of the instrument.

6.5.1 HOW TO ENTER THE HIDDEN MENU

1. Enter the Programming mode by pressing the Set + n keys for 3s (the “°C” or “°F”

blinking).

2. Released the keys, then push again the Set+n keys for more than 7s. The Pr2 label will be

displayed immediately followed from the HY parameter.
NOW YOU ARE IN THE HIDDEN MENU.

3. Select the required parameter.

4. Press the “SET” key to display its value

5. Use o or n to change its value.

6. Press “SET” to store the new value and move to the following parameter.

To exit: Press SET + o or wait 15s without pressing a key.
NOTE1: if none parameter is present in Pr1, after 3s the “noP” message is displayed. Keep the keys

pushed till the Pr2 message is displayed.
NOTE2: the set value is stored even when the procedure is exited by waiting the time-out to expire.

6.5.2 HOW TO MOVE A PARAMETER FROM THE HIDDEN MENU TO THE
FIRST LEVEL AND VICEVERSA.

Each parameter present in the HIDDEN MENU can be removed or put into “THE FIRST LEVEL”
(user level) by pressing “SET + n”.
In HIDDEN MENU when a parameter is present in First Level the decimal point is on.

LED starts

6.6 HOW TO LOCK THE KEYBOARD

1. Keep pressed for more than 3 s the UP + DOWN keys.

2. The “POF” message will be displayed and the keyboard will be locked. At this point it will be

possible only to see the set point or the MAX o Min temperature stored

3. If a key is pressed more than 3s the “POF” message will be displayed.

6.7 TO UNLOCK THE KEYBOARD

Keep pressed together for more than 3s the o and n keys, till the “Pon” message will be
displayed.

6.8 THE CONTINUOUS CYCLE

When defrost is not in progress, it can be activated by holding the “o” key pressed for about 3

seconds. The compressor operates to maintain the “ccS” set point for the time set through the “CCt”
parameter. The cycle can be terminated before the end of the set time using the same activation key
“o” for 3 seconds.

6.9 THE ON/OFF FUNCTION

WARNING: Loads connected to the normally closed contacts of the relays are always
supplied and under voltage, even if the instrument is in stand by mode.

7. PARAMETERS

REGULATION
Hy Differential: (0,1 ÷ 25,5°C / 1÷255 °F) Intervention differential for set point. Compressor Cut IN

is Set Point + differential (Hy). Compressor Cut OUT is when the temperature reaches the set
point.

LS Minimum set point: (- 50°C÷SET/-58°F÷SET): Sets the minimum value for the set point.
US Maximum set point: (SET÷110°C/ SET÷230°F). Set the maximum value for set point.
Ot Thermostat probe calibration: (-12.0÷12.0°C; -120÷120°F) allows to adjust possible offset of

the thermostat probe.

P2P Evaporator probe presence: n= not present: the defrost stops by time; y= present: the defrost

stops by temperature.

OE Evaporator probe calibration: (-12.0÷12.0°C; -120÷120°F). allows to adjust possible offset of

the evaporator probe.

P3P Third probe presence (P3): n= not present:, the terminal operates as digital input.; y=

present:, the terminal operates as third probe.

O3 Third probe calibration (P3): (-12.0÷12.0°C; -120÷120°F). allows to adjust possible offset of

the third probe.

P4P Fourth probe presence: (n = Not present; y = present).
o4 Fourth probe calibration: (-12.012.0°C) allows to adjust possible offset of the fourth probe.
odS Outputs activation delay at start up: (0÷255min) This function is enabled at the initial start up

of the instrument and inhibits any output activation for the period of time set in the parameter.

AC Anti-short cycle delay: (0÷50 min) minimum interval between the compressor stop and the

following restart.

AC1 2nd compressor delay at start up (0÷255s) Time interval between the switching on of the first

compressor and the second one.

rtr Percentage of the second and first probe for regulation (0÷100; 100 = P1, 0 = P2 ): it

allows to set the regulation according to the percentage of the first and second probe, as for the
following formula (rtr(P1-P2)/100 + P2).

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CCt Compressor ON time during continuous cycle: (0.0÷24.0h; res. 10min) Allows to set the

length of the continuous cycle: compressor stays on without interruption for the CCt time. Can be
used, for instance, when the room is filled with new products.

CCS Set point for continuous cycle: (-50÷150°C) it sets the set point used during the continuous

cycle.

COn Compressor ON time with faulty probe: (0÷255 min) time during which the compressor is

active in case of faulty thermostat probe. With COn=0 compressor is always OFF.

COF Compressor OFF time with faulty probe: (0÷255 min) time during which the compressor is

OFF in case of faulty thermostat probe. With COF=0 compressor is always active.

DISPLAY
CF Temperature measurement unit: °C=Celsius; °F=Fahrenheit. WARNING: When the

measurement unit is changed the SET point and the values of the parameters Hy, LS, US, Ot,
ALU and ALL have to be checked and modified if necessary).

rES Resolution (for °C): (in = 1°C; dE = 0.1 °C) allows decimal point display.
Lod Instrument display: (P1; P2, P3, P4, SET, dtr): it selects which probe is displayed by the

instrument: P1 = Thermostat probe; P2 = Evaporator probe; P3 = Third probe(only for model
with this option enabled); P4 = Fourth probe, SET = set point; dtr = percentage of
visualization.

rEd X- REP display (optional): (P1; P2, P3, P4, SET, dtr): it selects which probe is displayed by

X- REP: P1 = Thermostat probe; P2 = Evaporator probe; P3 = Third probe(only for model with
this option enabled); P4 = Fourth probe, SET = set point; dtr = percentage of visualization.

dLy Display delay: (0 ÷20.0m; risul. 10s) when the temperature increases, the display is updated

of 1 °C/1°F after this time.

dtr Percentage of the second and first probe for visualization when Lod = dtr (0÷100; 100 =

P1, 0 = P2 ): if Lod = dtr it allows to set the visualization according to the percentage of the

first and second probe, as for the following formula (dtr(P1-P2)/100 + P2).

DEFROST
tdF Defrost type: EL = electrical heater; in = hot gas

dFP Probe selection for defrost termination: nP = no probe; P1 =thermostat probe; P2 =

evaporator probe; P3 =configurable probe; P4 = Probe on Hot Key plug.

dtE Defrost termination temperature: (-50÷50 °C/

-58÷122°F) (Enabled only when EdF=Pb) sets the temperature measured by the evaporator
probe, which causes the end of defrost.

IdF Interval between defrost cycles: (0÷120h) Determines the time interval between the

beginning of two defrost cycles.

MdF (Maximum) length for defrost: (0÷255min) When P2P = n, (not evaporator probe: timed

defrost) it sets the defrost duration, when P2P = y (defrost end based on temperature) it sets
the maximum length for defrost.

dSd Start defrost delay: ( 0÷99min) This is useful when different defrost start times are necessary

to avoid overloading the plant.

dFd Temperature displayed during defrost: (rt = real temperature; it = temperature at defrost

start; SEt = set point; dEF = “dEF” label)

dAd MAX display delay after defrost: (0÷255min). Sets the maximum time between the end of

defrost and the restarting of the real room temperature display.

Fdt Drip time: (0120 min) time interval between reaching defrost termination temperature and the

restoring of the control’s normal operation. This time allows the evaporator to eliminate water
drops that might have formed due to defrost.

dPo First defrost after start-up: (y = immediately; n = after the IdF time)
dAF Defrost delay after continuous cycle: (023.5h) time interval between the end of the fast

freezing cycle and the following defrost related to it.

FANS
FnC Fans operating mode: C-n= runs with the compressor, OFF during defrost;

o-n = continuous mode, OFF during defrost;
C-Y = runs with the compressor, ON during defrost;
o-Y = continuous mode, ON during defrost;

Fnd Fans delay after defrost: (0÷255min) Interval between end of defrost and evaporator fans

start.

Fct Temperature differential avoiding short cycles of fans (0÷59°C; Fct=0 function disabled). If

the difference of temperature between the evaporator and the room probes is more than the
value of the Fct parameter, the fans are switched on.

FSt Fans stop temperature: (-50÷50°C/122°F) setting of temperature, detected by evaporator

probe, above which fans are always OFF.

Fon Fan ON time: (0÷15 min) with Fnc = C_n or C_y, (fan activated in parallel with compressor). it

sets the evaporator fan ON cycling time when the compressor is off. With Fon =0 and FoF ≠ 0
the fan are always off, with Fon=0 and FoF =0 the fan are always off.

FoF Fan OFF time: (0÷15 min) with Fnc = C_n or C_y, (fan activated in parallel with compressor). it

sets the evaporator fan off cycling time when the compressor is off. With Fon =0 and FoF ≠ 0
the fan are always off, with Fon=0 and FoF =0 the fan are always off.

FAP Probe selection for fan management: nP = no probe; P1 =thermostat probe; P2 = evaporator

probe; P3 =configurable probe; P4 = Probe on Hot Key plug.

ALARMS
ALC Temperature alarms configuration: (Ab; rE)

Ab= absolute temperature: alarm temperature is given by the ALL or ALU values. rE =

temperature alarms are referred to the set point. Temperature alarm is enabled when the
temperature exceeds the “SET+ALU” or “SET-ALL” values.

ALU MAXIMUM temperature alarm: (SET÷110°C; SET÷230°F) when this temperature is reached

the alarm is enabled, after the “ALd” delay time.

ALL Minimum temperature alarm: (-50.0 ÷ SET°C; -58÷230°F when this temperature is reached

the alarm is enabled, after the “ALd” delay time.

AFH Differential for temperature alarm/ fan recovery: (0,1÷25,5°C; 1÷45°F) Intervention

differential for recovery of temperature alarm. It’s also used for the restart of the fan when the

FSt temperature is reached

ALd Temperature alarm delay: (0÷255 min) time interval between the detection of an alarm

condition and alarm signalling.

dAO Exclusion of temperature alarm at startup: (from 0.0 min to 23.5h) time interval between the

detection of the temperature alarm condition after instrument power on and alarm signalling.

CONDENSER TEMPERATURE ALARM
AP2 Probe selection for temperature alarm of condenser: nP = no probe; P1 =thermostat probe;

P2 = evaporator probe; P3 =configurable probe; P4 = Probe on Hot Key plug.

AL2 Low temperature alarm of condenser: (-55÷150°C) when this temperature is reached the

LA2 alarm is signalled, possibly after the Ad2 delay.