DK System EKOSter 420 User manual

Boiler
temperature
controller
Service Manual
INS-017-001 130x184,5
EKOSter 420

Safety instructions and notes on installation
Boiler temperature controller EKOSter 420
2
qThe controller is designed to work with central heating boilers for solid fuels.
qThe controller must be installed by an authorized person.
qThe controller must be connected to a socket with a protective contact.
qIt is required that the boiler had its own safeguards against excessive
temperature rise of the boiler caused e.g. boiler controller or related equ-
ipment malfunction.
qThe controller should be placed in a location that prevents its heating to a
temperature higher than 40°C.
qThe controller must not be exposed to water and conditions causing con-
densation (e.g. sudden changes in ambient temperature).
qThe device should be installed and operated as described in the assembly
description and rules for electrical equipment.
qA blown fuse due to bad wiring or a short circuit in the electrical system does
not constitute grounds for a warranty repair.
qBefore starting the controller, you should check the electrical connections.
qThe controller is protected with two 2,5 A fuses.
qConnection of the power cord and fuse replacement should be made with the
controller powered off (the controller power plug must be disconnected from
the mains). Connection of the receiving devices and replacement of fuses
with the mains plug of the controller plugged in creates an electric shock
hazard.
qThe connection cables of the controller can be replaced only by the manu-
facturer or their authorized service establishment.
qYou must not use a damaged controller.
qAny damage caused by lightning, improper power surges in the power grid or
random events are not eligible for warranty repair (please refer to the
warranty terms and conditions).
Notice: Fuses should be replaced only with the controller powered
off and the plug disconnected from the mains.
!

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Spis treści
1. Description of a controller.................................................................................................
2. Description of the controller components.......................................................................
3. Description of connections Controller.............................................................................
4. Pump and blower connection diagram............................................................................
5. Controller installation........................................................................................................
5.1 Connection of the controller to the electrical system......................................................
6. Diagram for the connection of controller to the hydraulic system................................
7. Maintenance menu - structure..........................................................................................
8. Hot water - menu................................................................................................................
9. Switching the controller on and starting operation........................................................
10. Setting the boiler operating parameters and lighting up................................................
11. Feeding fuel to the boiler...................................................................................................
12. Setting the operating parameters of the domestic hot water heater.............................
13. Summer work mode...........................................................................................................
14. Maintenance menu - Work Parameters............................................................................
14.1 Work Parameters - Hysteresis of blower operation........................................................
14.2 Work Parameters - Blower type......................................................................................
14.3 Work Parameters - Modulation of blower operation.......................................................
14.4 Work Parameters - Adjusting the maximum power of the blower...................................
14.5 Work Parameters - Adjusting the minimum power of the blower....................................
14.6 Work Parameters - Adjustment of the CH pump operating threshold.............................
14.7 Work Parameters - Blower START / STOP.....................................................................
14.8 Work Parameters - Burn out time adjustment................................................................
14.9 Work Parameters - Blowing - operating time..................................................................
14.10 Work Parameters - Blowing - break time......................................................................
14.11 Work Parameters - Blower pause - fuel feeding...........................................................
14.12 Work Parameters - Room thermostat...........................................................................
15. Maintenance menu - HOT WATER.....................................................................................
15.1 Hot water - ON / OFF domestic hot water priority...........................................................
15.2 Hot water - The temperature difference between the boiler and heater.........................
15.3 Hot water - Hysteresis of the DHW pump......................................................................
15.4 Hot water - Constant operation of the DHW pump in the summer mode.......................
16. Maintenance menu - Alarm................................................................................................
16.1 Alarm - pump temperature..............................................................................................
16.2 Alarm - boiler temperature.............................................................................................
16.3 Alarm - sound................................................................................................................
17. Maintenance menu - Language.........................................................................................
18. Maintenance menu - Manual operation............................................................................
18.1 Manual operation - blowing power.................................................................................
18.2 Manual operation - testing outputs................................................................................
19. Maintenance menu - Factory settings..............................................................................
20. The COMFORT SYSTEM function.....................................................................................
21. The protection against freezing function.........................................................................
22. Protection of the boiler against overheating...................................................................
23. Remote control - optional..................................................................................................
24. Alarms - description...........................................................................................................
24.1 Alarms - Over temperature on the boiler or drop below 0°.............................................
24.2 Alarms - Damaged boiler temperature sensor...............................................................
24.3 Alarms - Damaged DHW temperature sensor................................................................
24.4 Alarms - Thermal fuse...................................................................................................
25. Technical data.....................................................................................................................
26. Information on waste electrical and electronic equipment............................................
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Boiler temperature controller EKOSter 420

4
Boiler temperature controller EKOSter 420
1. Description of a controller
Central heating boiler temperature controller with domestic hot water heater
service EKOSter 420 is designed for boiler blow-in control, switching on the
circulation pump in heating installations and domestic hot water heater charging
pump (DHW).
The controller has the following features:
q maintaining the preset temperature of a boiler by controlling the air blow-in
q modulated and adjustable power of the fan
q function of supporting the combustion process by the so-called blow-bys
q adjustable damping time and automatic control turn off after extinguishing of
the boiler
q stopping the fan operation when adding fuel to a boiler / damping
q control of the central heating circulation pump
q option of enabling or disabling the DHW priority
qcontrol of the domestic hot water heater charging pump depending on the
required temperature
qprotection system - a TERMIK thermal fuse as an additional, mechanical
protection of the boiler against uncontrolled temperature increase
q option to work in the SUMMER mode
q COMFORT SYSTEM function, which protects the pump against scaling
qfunction of protecting the system against freezing and overheating of the
boiler
q damage indication of the temperature sensor
q adjustable display brightness - increased during settings modif cation
qability to connect the remote control panel CONTROL with audible alarm
function
qpossibility of connecting a room thermostat
q large, readable, alphanumeric LCD display with 2x16 characters
NUMBER OF PUMPS
CONTROLLING
OUTPUTS
2
CENTRAL
HEATING PUMP DHW PUMP FAN
FAN
MODULATION
DHW
PRIORITY
PRIORYTET
THERMAL
FUSE
ROOM
THERMOSTAT
CONTROL
PANEL
COMFORT
SYSTEM

!!
5
Boiler temperature controller EKOSter 420
2. Description of the controller components
Fig.1 Description of the controller components
1.
2.
3. / START / STOP
4.
5.
6.
Display
Signal LEDs
The back button
Adjust setting UP button ( )
MENU button
Adjust setting DOWN button ( )
3. Description of connections Controller
Fig. 2 Description of connections Controller
Opis diod sygnalizacyjnych
CH pump
DHW pump
fan
error
6
5
4
3
21
!
bezpiecznik termiczny
PE L N
M
1~
M
1~
PE L N PE L N PE L N
M
1~
wenty-
lator
pompa
c.o.
pompa
c.w.u.
zasilanie
~ 230 V
bezpiecznik 2,5 A
control
termostat pokojowy
czujnik c.w.u.
czujnik kotła c.o.
bezpiecznik 2,5 A
PE L N PE L N PE L N PE L N
POMPA CWU
CONTROL POMPA CO DMUCHAWA ZASILANIE
TERM.
POK.
CZUJ
CWU
CZUJ
KOTŁA
TER
MIK
Fig. 3 View connections regulator

6
Boiler temperature controller EKOSter 420
5. Controller installation
1. The controller is designed to be mounted on the boiler.
2. Using the provided template for positioning of the controller.
3. Install a screw in the boiler housing in the place indicated on the template.
4. Decide on the method of routing the cable from the controller (rear, bottom)
and remove the corresponding caps from the housing.
5. Slide the controller onto the fixed screw, use the other two screws to fasten
it to the boiler housing.
6. Install the optional cables at the appropriate connectors and put them
through the holes in the housing.
7. Protect the installed cables against pulling out, fixing then to the housing in
special sockets using the provided brackets and screws.
8. Install the controller door.
5.1 Connection of the controller to the electrical system
1. Connect the fan, pump and feeder with the appropriate power cables (see
- Figure 3).
2. Install all necessary sensors (and reed relay for the piston feeder) acc. to
Fig.4 and Fig.6.
3. Put the plug of the controller power supply cable in a ~ 230 V socket.
4. Switch the controller on, using the power switch.
Note: If after the controller is switched on, the display is not lit
up, check whether there is voltage in the mains socket, then
check the fuses and replace if damaged with new ones 2 x 5 A. If,
after the replacement of fuses the display remains dark, please
contact the maintenance provider.
Always replace fuses with the unit switched off and the plug
removed from the socket.
!
4. Pump and blower connection diagram
Fig. 4 Connection diagram of the
blower cable
M
N
L
PE
blower
blue wire N
Fig. 5 Connection diagram of
the pump cable
brown wire L
yellow-green wire PE
Mpump

Boiler temperature controller EKOSter 420
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6. Diagram for the connection of controller to the hydraulic
system
5.1 Connection of the controller to the electrical system (cont.)
Note: Each time you connect or disconnect the sensor hot water
or remote control requires a reset controller EKOSTER 420, by
switching on and off switch.
None made the reset will cause the malfunction of the controller.
!
1. Fan 6. DHW heater sensor
2. Central heating boiler temperature sensor 7. CONTROL panel
3. EKOSter 420 controller 8. Room thermostat
4. Central heating pump 9. TERMIK thermal fuse
5. DHW pump
Fig. 6 Example of the heating installation diagram with a EKOSter 420
controller without the cutting off and protecting devices. It does not replace a
professional project at the assembly spot.
9
Ekoster 420

Boiler temperature controller EKOSter 420
8
7. Maintenance menu - structure
Maintenance menu Press and hold approx. 5 seconds.
8. Hot water - menu
The menu of hot water is only available when you connect the dhw sensor
Main menu press
Hot water
Temperat: 40°÷70°
Hot water
Turn on: yes/no
Work
parameters
Factory
settings
Manual
operation Alarms Hot
water
Hysteresis: 00÷09
Blow. Type: 01/02
Modulation of
blower oper.: yes/no
Blower
Max.pow. 30%÷100%
Blower
Min. power: 30%÷70%
C.H. pump 02°÷50°
dt: 10°÷30°
Delay<m> 00÷45
Blowing
Oper.time<sek>00÷90
Blowing
Break t.<min> 01÷60
Loading
time: 0.30÷9.30
Room therm. no/yes
Fact. Sett.
+ Acknowl.
Manual operation
Blow.Pow: 30%÷100%
CO Wentyl
CWU Alarm
Language
polski/english
Alarm
Pumpe T.: 80°÷90°
Alarm
Temperat: 80°÷90°
Alarm
Sound: yes/no
Hot water
Prioruty: tak/nie
Hot water
+T.H. 02°÷20°
Hot water
Hysteresis:02°÷09°
Hot water
pump sum.: yes/no
Langua
ge

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Boiler temperature controller EKOSter 420
DK SYSTEM
Ekoster 420
ver 5.13
STOP Temp:42°
:36°
Temp:42°
Switch the controller on with the power
switch - the display will show the follo-
wing information: Controller name and
program number.
Then the display will start showing the
currently measured temperature of the
boiler and the heater (if the heater
sensor is installed and support for the
DHW pump is enabled); at the same
time the current condition of operation of
connected equipment will be signalled.
STOP Temp:42°
The display will show indicating that
the lighting up process is in progress.
During operation, the controller displays
the current measured temperature of
the boiler.
In order to light up the furnace, you need to:
1. Fill the boiler cavity with fuel and set fire to it.
2. Close the door of the furnace chamber tight.
3. Start the blower by pressing the button .
After pressing the button ▲ or ▼once
the screen of the required boiler temper-
ature will be displayed. Set the required
value, using the same buttons: ▲ to
increase the setting or ▼ to reduce the
setting.
10. Setting the boiler operating parameters and lighting up
9. Switching the controller on and starting operation
Nast:50°
Temp:56°
Change range from 40 °C to 90°C
Factory setting (typical): 50 °C

Heat Water
Temperat: 50°C
Heat Water
Turn on:no
10
Boiler temperature controller EKOSter 420
Note: The symbol that the display shows: or indicates
the current temperature change trend in the boiler: indicates
the trend to reach the set temperature; indicates reduction of
the temperature in the boiler to the value specified by the "HI"
parameter.
When you feed fuel to the boiler, stop the blower. Do this by pressing the button
the display will show the symbol with a countdown to restarting. The time
required for fuel feeding is set in the WORK PARAMETERS maintenance menu -
see the Blower pause - fuel feeding. .
Pressing the button during the
countdown will exit the fuel feeding
mode and return of the controller to
automatic mode.
1:30 Temp:56°
If you press the button again will
take you to a screen where it is possible
to enable or disable the domestic hot
water pump functionality. The setting is
made using the buttons: or .
.
During operation of the controller press
the button the display will show the
screen for setting the required tempe-
rature of the heater. Set the required
temperature using the buttons: to
increase the set point value, or to
reduce it.
Note: The prerequisite for entry into the set operating
parameters of the hot water heater is to connect the sensor hot
water heater.
12. Setting the operating parameters of the domestic hot
water heater
11. Feeding fuel to the boiler
10. Setting the boiler operating parameters and lighting up
!
!
Change range: 40 °C ÷ 70°C
Factory setting (typical): 50 °C
Change range: yes / no
Factory setting: no

Boiler temperature controller EKOSter 420
11
The controller can operate in the
SUMMER mode, which means that out-
side of the heating season the heating
pump is not used and all the heat gener-
ated by the boiler is used for the domes-
tic hot water. In order to enable this
mode change the temperature setting
by pressing the button until the
display shows the “SUMMER” symbol.
Sett:SUMM
Sett:SUMM
:36°
The maintenance menu is used to set the specific equipment parameters, such
as those regarding the central heating pump and the blower. To enter the
maintenance menu, press and hold for a few seconds the button .
A parameter that specifies the number
of degrees Celsius by which the boiler
temperature must fall below the set
point for the blower to switch on
The display will show the WORK.
PARAM. symbol. Each pressing of the
button will enter the parameter's
setup screen; changing the parameter is
performed by using the or .
14. Maintenance menu - Work Parameters
13. Summer work mode
< Work Param.>
14.1 Work Parameters - Hysteresis of blower operation
Hysteres. : 02°
Change range: 0 °C ÷ 9°C
Factory setting: 2 °C

Boiler temperature controller EKOSter 420
12
Blow.Type : 01
14.3 Work Parameters - Modulation of blower operation
Blower
Modulation : yes
14.2 Work Parameters - Blower type
The parameter for setting of one of two
characteristics of adjustable blower
power, depending on the type mounted
on the boiler.
This parameter causes the modulation
of the blower motor operation to go on or
off. When modulation is enabled ("yes"
symbol), the fan will reduce its speed
when the boiler is about to reach the set
temperature and will increase its speed
when the temperature of the boiler
drops, disabled modulation is indicated
by the "no" symbol.
Note: Modulation of the blower is performed only in the
hysteresis range i.e. in a temperature range between the boiler
setting and that resulting from the hysteresis parameter - below
the hysteresis, the blower operates at maximum power.
14.4 Work Parameters - Adjusting the maximum power of the blower
This parameter allows you to set the
maximum operating power of the blower Blower
Max.Power: 100%
Note: Blower type 1 - applies to RV05, RV14.
Blower type 2 - applies to RV12 and others with power of 80
W, based on EBM/EMC If the type of installed blower is not
known, it is recommended to choose setting 1.
!
!
Change range: 01 / 02
Factory setting: 1
Change range: yes/no
Factory setting: no
Change range: 30% ÷ 100%
Factory setting: 100%

Boiler temperature controller EKOSter 420
13
14.6 Work Parameters - Adjustment of the CH pump operating threshold
C.H. Pump :20°
14.5 Work Parameters - Adjusting the minimum power of the blower
This parameter allows you to set the
minimum operating power of the blower.
The parameter that specifies the
operating range of the heating circuit
pump - the pump will operate at
temperatures higher than the tempera-
ture set on the boiler minus the CH
PUMP parameter.
Note: Some types of blowers cannot be switched on at the
lowest power setting parameter. In such a situation, it is
recommended to increase the minimum power.
14.7 Work Parameters - Blower START / STOP
A parameter that specifies how many
degrees Celsius below the temperature
set on the boiler the blower starts up in
automatic mode (during lighting up) or
will enters burning the residual fuel
(burning out).
dt :15°
Note: As a result of user settings, there may be a situation where
the central heating pump should theoretically turn on, for
example, at the temperature of 24 °C (boiler's temperature
setting 60 °C CH PUMP 36°C). However the pump will not turn
on, because the controller allows it to start only at the
temperature of > 35 °C
!
!
Change range: 30% ÷ 70%
Factory setting: 30%
Change range: 2 °C ÷ 50°C
Factory setting: 20 °C
Change range: 10 °C ÷ 30°C
Factory setting: 15 °C
Blower
Min.Power: 30%

Boiler temperature controller EKOSter 420
14
14.8 Work Parameters - Burn out time adjustment
Delay <m>:30
14.7 Work Parameters - Blower START / STOP (cont.)
14.9 Work Parameters - Blowing - operating time
Pulses
Runn<sec>:15
Example: 2. During burning out of the boiler,
- the temperat. set on the boiler: 50 °C when the temperature drops to the
- “dt”: 10 °C level of 40 °C (50°C 10°C), the contro-
1. When lighting up the boiler, the ller will start counting the time set
blower switches to automatic mode (allowing the remaining fuel to burn
when the temperature reaches 40 °C out) - see item Burn out time adjust-
(50 °C - 10 °C), then furnace will ment - after which the blower will finally
continue to light up, and after reaching turn off.
a temperature of 50 °C, the fan turns
off.
This parameter allows you to set the
blower operating time during burning
out, i.e. temperature drop at the boiler by
the "dt" parameter.
This parameter defines the duration of
blower operation (in seconds) when the
BLOWING functionality is active.
BLOWING or the function of regular supply of air to the furnace has the purpose
of:
- maintaining the burning in a situation when the temperature set point on the
boiler has been reached
- burning out gases in the combustion chamber and expelling them through the
stack to the outside.
Change range: 0 min ÷ 45 min
Factory setting: 30 min
Change range: 0 s ÷ 90 s
Factory setting: 15 s

Boiler temperature controller EKOSter 420
15
14.11 Work Parameters - Blower pause - fuel feeding
Loading
Time: 3:00
14.10 Work Parameters - Blowing - break time
14.12 Work Parameters - Room thermostat
Room regu.
:no
A parameter that specifies the duration
of the blower pause needed to feed fuel
to the boiler.
This parameter specifies the break time
in blower operation (in minutes)
between each blowing sequence.
Pulses
Pause<min>:15
Note: The blowing functionality is activated when the boiler
reaches the temperature set point.
Blowing will not operate, when
1. boiler temperature is higher than 85 °C
2. boiler temperature is lower than specified by the "HI"
parameter.
Setting the operation time to “0” will disable the BLOWING
functionality
You can connect a room thermostat that
controls the activation of the central
heating pump, depending on the room
temperature. In order to operate the
pump the boiler must also reach its
corresponding minimum temperature.
!
Change range: 1 min ÷ 60 min
Factory setting: 15 min
Change range: 0:30 min ÷ 9:30 min
Factory setting: 3:00 min
Change range: yes / no
Factory setting: no

Boiler temperature controller EKOSter 420
16
15. Maintenance menu - HOT WATER
15.1 Hot water - ON / OFF domestic hot water priority
Heat Water
HW Priori :no
15.2 Hot water - The temperature difference between the boiler and
heater
Heat Water
+T.H.Wat.: 10°
The controller can operate in the domestic hot-water priority mode or without it.
Priority means that when the water temperature in the heater drops below the set
point, then the boiler stops working for the central heating system and begins to
heat up warm water. If the "boiler + heater" system is matched correctly, a break
in heating does not cause deterioration of thermal comfort.
<Heat Water>
The maintenance menu is used to set the specific equipment parameters, such
as those regarding the domestic hot water pump.
Entry into the HOT WATER maintena-
nce menu is done by pressing and
holding the button ; The display will
show the WORK. PARAM. and then you
must press the button.
The "yes" setting enables the hot water
priority function, and "no" disables it.
The parameter that specifies the
minimum measured temperature
difference between the boiler and the
domestic hot water heater that must
occur for the heating of domestic hot
water to be cost effective and the
domestic hot water pump to be turned
on. If this difference is less than the set
point, the DHW pump will not switch on
(regardless of whether priority of hot
water is turned on or not.
Change range: yes / no
Factory setting: no
Change range: 2 °C ÷ 20°C
Factory setting: 10 °C

Boiler temperature controller EKOSter 420
17
15.3 Hot water - Hysteresis of the DHW pump
Heat Water
pump(summ):yes
< Alarm >
Heat Water
Hysteresis:05°
A parameter that specifies the number
of degrees Celsius by which the
temperature must fall on the domestic
hot water heater below the set point for
the domestic hot water pump to turn on.
15.4 Hot water - Constant operation of the DHW pump in the summer
mode
The effect of this parameter is that when
the controller is in SUMMER mode, the
domestic hot water heater pump is
working despite reaching the desired
temperature for domestic hot water. It is
done to protect the boiler from rapid
temperature increases
Note: The prerequisite for the pump to start is maintaining
minimum temperature difference between the temperature
measured on the reservoir and that measured on the boiler.
16. Maintenance menu - Alarm
The menu has settings for triggering the alarm for excessive temperature on the
boiler. In an alarm situation the red ERROR LED will blink and an audible signal is
generated.
To access the alarm menu, press and
hold the button ; the screen will
show WORK. PARAM. Then use the
or button to select ALARM and
confirm .
!
Change range: 2 °C ÷ 9°C
Factory setting: 5 °C
Change range: yes / no
Factory setting: yes

This parameter allows you to set the
temperature above which both pumps
will start in emergency mode (hot water
pump starts, provided that the controller
will operate in the domestic hot water
mode).
Boiler temperature controller EKOSter 420
18
16.1 Alarm - pump temperature
Alarm
Temperat: 93°
Alarm
Sound :yes
Alarm
Pump Temp: 90°
16.2 Alarm - boiler temperature
This parameter allows you to set the
temperature above which an alarm is
triggered.
16.3 Alarm - sound
This parameter allows you to enable or
disable the alarm sounds
17. Maintenance menu - Language
Language
polski
< Language >
The maintenance menu is used to set
the language for displaying of messa-
ges. To enter the LANGUAGE maint-
enance menu, press and hold for a few
seconds the button ;The display will
show the WORK PARAM. then use the
or button to select the option
Language and confirm .
Change range: 80 °C ÷ 99°C
Factory setting: 90 °C
Change range: 80 °C ÷ 99°C
Factory setting: 93 °C
Change range: yes / no
Factory setting: yes
Change range: polski / english
Factory setting: polski

This function is used testing the cor-
rectness of the connected equipment.
Enter the menu MANUAL OPER. after
pressing and holding the button .
The display will show the WORK.
PARAM. then use the or button
to select the option MANUAL OPER.
and confirm
.
.
Boiler temperature controller EKOSter 420
19
18. Maintenance menu - Manual operation
Manually
Blowe: 80%
< Manually >
18.1 Manual operation - blowing power
18.2 Manual operation - testing outputs
This parameter allows you to set the
power at which the blower is to operate
in manual mode (testing). Change
range: from minimum to maximum
blower power (parameters set in the
maintenance menu - see item Minimum
blower power adjustment and Maximum
blower power adjustment).
Pressing again takes you to the
next setting.
Select the tested output with the button
, and enable/disable it by pressing
the or button. The currently
tested output is indicated by a blinking
symbol on the screen, and enabling it,
by the corresponding LED.
A window allowing testing the correctness of operation of individual outputs
(blower, CH pump, DHW pump) and of the alarm.
CH Blower
HW Alarm

This function is used to remove the
parameters set by the user and return to
the factory settings. To access the
FACTORY SETTINGS maintenance
menu press and hold the button ;
The display will show the WORK
PARAM. then use the or button
select the option FACTORY SETTINGS
and confirm .
Confirmation of parameters change to
factory settings is done with the
button.
.
Boiler temperature controller EKOSter 420
20
19. Maintenance menu - Factory settings
Fact.Sett.
+ Acknowl.
< Fact.Sett. >
20. The COMFORT SYSTEM function
21. The protection against freezing function
22. Protection of the boiler against overheating
The COMFORT SYSTEM built-in in the controller prevents pump blockage by
deposition of scale between the rotor and stator of the pump. The controller
automatically switches the pump on for 30 seconds every 24 hours from its last
run. Pump operation in this mode is indicated by the blinking LED CH PUMP The
function takes effect after 24 hours from turning the controller on.
Note: For the COMFORT SYSTEM function to be active after
the end of the heating season, leave the controller plugged in.
The controller reduces the risk of overheating the boiler through the continuous
operation of the pumps in the event of the boiler temperature sensor failure or if
the alarm temperature for both pumps is exceeded - see Alarm - pump
temperature
The controller protects the heating system from freezing, both pumps running all
the time when the temperature of water falls to 4 °C or lower (DHW pump will
start, provided that the controller runs in the DHW mode).
!