Mark MEGAFLEX User manual

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Technical manual
MARK MEGAFLEX 0660440

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INSTRUCTIONS FOR USER
If you have questions concerning the use of your boiler or heating system, please ask your installer. It is in
your own interest and that of the installer that you are aware of how to operate your boiler and heating
system safely and efciently.
The appliance is not to be used by children or persons with reduced physical, sensory or mental
capabilities, or lack of experience and knowledge.
Children, even if being supervised, must not play with the appliance
In the case of failure or malfunction of the appliance, do not attempt to repair it yourself.
Please contact your installer. Repairs must only be carried out by qualied technicians. Failure to
comply with these requirements can compromise the safety of the appliance.
Operation
Water, coming from the radiators or from the DHW unit is heated in the aluminium heat exchanger.The
CH or DHW pump guarantees circulation of water.The air needed for combustion is sucked in by a rpm
controlled fan. At low boiler temperatures the ue gases can be cooled sufciently for condensation of
the water.This water is drained to the sewer via a built in syphon.This drainage must never be blocked.A
burner controller with built in micro processor provides the electrical control of the boiler.
Topping up
The built in manometer indicates if the waterpressure is sufcient. As soon as the water pressure drops
below 1 bar topping up is necessary. If topping up becomes a regular ocurrance, your installation should
be checked by an installer.
Disconnect from the main. Connect the lling hose to the cold water tap and to the ll and drain valve
of the boiler. Before tightning the coupling in the installation slowly ll the hose with water allowing any
air present to escape. Open the ll and drain valve and slowly ll the installation until a pressure between
1.5 and 2.0 bar is reached. When nished connect again to the main.
Bleeding
To remove any air present in the heating system and boiler, bleeding is necessary. Disconnect from the
main. Open all the radiator valves. Bleed the air from all the radiators starting with the ones at the
lowest point in the system.After bleeding, check the water pressure and top-up if required (if water
pressure has dropped below 1 bar). Connect to the main again.
Starting the boiler
Please ask your installer how to start the boiler. Depending on how your heating system is controlled,
this could be via an external timeclock, thermostat, switch or otherwise. Once the boiler volt-free enable
contacts are closed, the boiler will commence its starting sequence.
Boiler ow temperature
The burner controller can adjust the ow temperature between 20 ° and 85 °C. The temperature setting
can be changed using the control panel.
The installation manual provides the instructions for setting the ow temperature.
DHW (Hot Water) temperature ( if applicable)
From the factory, the DHW temperature is set to a value of 60 °C. This set value can be changed to any
value between 35 and 65 °C using the buttons on the control panel. If the DHW device has a thermostat
the DHW temperature can be adjusted by setting this thermostat.

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Switching off the boiler
During summer time the room thermostat can be set to a lower value to turn off the boiler. During
winter or during a longer period of absence this temperature never should be set to a lower value than
15 °C. Don’t switch off the power. During a period of frost all the radiators should be partly or totally
opened to avoid danger of freezing.
The integrated pump control will activate the pump every 24 hours for a short period even if no
demand is present.This prevents the pump jamming.
Only when work on the boiler is being carried out may the main electricity supply and gas supply be
turned off (your installer can show where these are located).
Errors
If an error occurs rst check the following
• Is the room thermostat properly set?
• Is the boiler connected to the main? Power supply present?
• Is the gas valve opened?
• Are the radiator valves open?
• Is the water pressure in the installation higher than 1 bar?
• Is the installation bled thoroughly?
An error is indicated by a code on the display. It is very important for the sake of a correct diagnosis to
mention this code when calling your installer. Reset the burner controller by pressing the ok button on
the control panel. If the error occurs frequently contact your installer.
Maintenance
A yearly inspection of the boiler must be done by your installer.The lifespan and the reliability of the
installation are improved by doing so.The casing of the boiler may be cleaned with a soft cloth (no
abrasives). Never use solvents like thinner!
Caution
The air supply (for air needed for combustion) and the ue parts are essential parts for safe and efcient
operation of the boiler. Changes on these systems by non qualied persons are not allowed e.g. the
settings of the gas valve.The gas/air ratio is set to a lambda value of approximately 1.26.This corresponds
with a CO2 level of 9,3 % (full load).
For further information see installation manual.

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1 Description boiler 6
2 Technical data 9
2.1 Component Matrix 10
3Dimensions 11
4Operation 13
4.1 General 13
4.2 Central Heating (CH) 13
4.2.1 On-off room thermostat 13
4.2.2 Optional 0-10V 13
4.2.3 Outside Temperature Control OTC (optional) 14
4.2.4 Optional digital communication 14
4.2.5 Slow start 15
4.2.6 Protection against insufcient ow through boiler 15
4.3 Domestic Hot Water (DHW) 16
4.3.1 External storage tank (choice by manufacturer between opt. 1 and opt. 2) 16
4.3.2 External storage tank with NTC sensor 16
4.3.3 DHW priority/General behaviour with external storage tank 17
4.4 Cascade 17
5Boiler control 18
5.1 Control Panel 18
5.2 Push buttons on control panel 18
5.3 User menu 19
5.3.1 Parameter/value setting 19
5.3.2 Parameters accessible by user 19
5.4 Installer (technician) menu 23
5.4.1 Parameters accessible by installer (technician) 23
5.5 Manual Chimney sweep mode 30
5.6 Disabling CH request 30
5.7 Service code 30
5.8 Tacho fan speed 30
5.9 Errors 30
5.10 ECO working mode 30
5.11 Holiday mode 30
5.12 Schedules for CH and DHW 30
5.13 Cascade and Modbus 30
5.14 Parameter settings 30
6 Installation 34
6.1 Installing the boiler 34
6.2 Frost protection 34
6.3 Water connection 35
6.3.1 Pump 35
6.3.2 Minimum ow 35
6.3.3 Water-treatment 35
6.3.3 Water connection general 35
6.4 Gas connection 37

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6.5 Air-supply and ue-gas connection 37
6.5.1 B23 37
6.5.2 C33 37
6.5.3 C63 38
6.5.4 Pressure drop calculations 39
6.5.5 Installing ue-exhaust and air inlet 41
6.6 Electrical connection 43
6.6.1 Wiring diagram 45
6.6.2 NTC resistance table 47
6.7 Pneumatic connections 48
6.8 PC-connection 48
7 Commissioning 48
7.1 Gas category 48
7.2 Adjustment % CO2(O2%) and check input 50
8 Errors 51
8.1 General 53
8.2 DHW errors 53
8.3 CH-errors 53
8.4 Errors (hard and soft lockouts) 53
9 Annual service 55
9.1 Service-maintenance table 57

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1 DESCRIPTION BOILER
1 Manometer
2 Display LCD
3 Power switch
4 Fuse
5 Burnerhood
6 Sight glass
7 Flow NTC
8 Ignition electrode
9 Ionisation ame detector
10 Inspection cover

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11 Gas pipe
12 Gas valve
13 Air supply
14 Fan
15 Overheat limiter
16 Flow
17 Flue gas NTC
18 Exhaust
19 Return
20 Maxsys
21 Terminal strip
22 Syphon pressure switch
23 Air pressure switch

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24 Sump inspection cover
25 Syphon
26 Fill and drain valve
27 Water pressure switch
28 Return NTC
29 Automatic air vent
30 Venturi

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2 TECHNICAL DATA
Technical data Megaex series
Type 850-11 range rated 1020-13 range rated
Central heating
Nominal input max load (Hi) 850 680 1020 850 kW
Power range percentage %
Manual technician menu advanced setting CH 100 75 100 80
Nominal input min load (Hi) 170 170 204 204 kW
Nominal ouput max load 80-60 °C 828,8 663 994,5 828,8 kW
Nominal output min load 80-60°C 165,4 165,4 198,5 198,5 kW
Efciency max load 80-60 °C (Hi) 97,5 97,5 97,5 97,5 %
Efciency min load 80-60 °C (Hi) 97,3 97,3 97,3 97,3 %
Efciency max load 50-30 °C (Hi) 103,1 103,1 103,1 103,1 %
Efciency 30 % load 30 °C (return) (Hi) 108,3 108,3 108,3 108,3 %
Flue gas
Temperature ue gas max load 80-60 °C 65-70 65-70 65-70 65-70 °C
Temperature ue gas min load 80-60 °C 60-65 60-65 60-65 60-65 °C
Mass ow ue gases at max load 1221 977 1465 1221 m3/h
Mass ow ue gases at min load 245 245 294 294 m3/h
Maximum ue resistance 500 310 500 480 Pa
Emission CO 96 96 ppm
Emission NOx class 6 6 6 6
Types B23,C33,C63 yes yes yes yes
Gas
Gas ow max load G25 104,5 83,6 125,4 104,5 m3/h
Gas ow min load G25 21 21 25,1 25,1 m3/h
Gas ow max load G25.3 99,9 79,9 119,8 99,9 m3/h
Gas ow min load G25.3 20 20 24 24 m3/h
Gas ow max load G20 90 72 108 90 m3/h
Gas ow min load G20 18 18 21,6 21,6 m3/h
CO2content max load G25/G20/G25.3 9,3 9,3 9,3 9,3 %
CO2content min load G25/G20/G25.3 9,1 9,1 9,1 9,1 %
O2content max load G25 3,90 +0,10-0,30 3,90 +0,10-0,30 %
O2content min load G25 4,30 +0,35-0,20 4,30 +0,35-0,20 %
O2content max load G25.3 3,95 +0,10-0,35 3,95 +0,10-0,35 %
O2content min load G25.3 4,35 +0,35-0,25 4,35 +0,35-0,25 %
O2content max load G20 4,25 +0,10-0,35 4,25 +0,10-0,35 %
O2content min load G20 4,60 +0,40-0,20 4,60 +0,40-0,20 %
Water
Maximum ow temperature 90 90 90 90 °C
Content heat exchanger 100 118 ltr
Minimum/maximum operating pressure 0,8/6 0,8/6 bar
Hydraulic resistance 200 225 mbar
(DT 20 nominal ow at full load 80-60 °C)
Maximum DT max load/min load 25/35 25/35 25/35 25/35 °C
Maximum water ow DT 10 K 71,3 57 85,6 71,3 m3/h

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Weight
Mass heat exchanger* 348,4 412,6 kg
Total mass Megaex boiler kg
Sizes of casing
Width 877 877 877 877 mm
Depth without manifold ange 2096 2096 mm
Height excluding feet 1551 1551 1551 1551 mm
Electrical
Electrical voltage/frequency 400V~3N/50 400V~3N/50 V/Hz
Standby power consumption* 15 15 15 15 W
Min load power consumption* W
Max load power consumption* W
Maximum allowable power consumption 6900 6900 W
Fuse 400V~3N/10 400V~3N/10 V/A
* as coming from factory without extra devices connected
2.1 COMPONENT MATRIX
Overview of main components used in MegaFlex series
Part 850-11 1020-13
Boiler control Honeywell Maxsys S4966V2052 S4966V2052
Display (user interface) DSP 49G2193 DSP 49G2193
2 Line EMC Filter 250V EPCOS B84112G
Fan MVL 230VAC G3G250MW5001 G3G250250MW5001
Gas-valve Dungs 230VAC MBC-700-SE-S02 MBC-1200-SE-S02
Venturi type DT DT850 DT1020
Texi Burner round 140 mm Worgas 1011 1200
Silencer ue-gas round 250 mm L=500mm yes yes
NTC-12k, L=50 mm x D5 , ¼” BSP 3 3
NTC 12 k OTC optional optional
Water low pressure device 1,4/0,8 bar yes yes
Pressure difference switch 40 Pa in and 25 Pa out yes yes
Syphon pressure difference switch 15 mbar out yes yes
Gas pressure switch : in 11,7-14,3 and out 8,6-11,4 mbar yes yes

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3 DIMENSIONS

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The appliance is not to be used by children or persons with reduced physical, sensory or mental
capabilities, or lack of experience and knowledge.
Children, even if being supervised, must not play with the appliance.
In the case of failure or malfunction of the appliance, do not attempt to repair it
yourself. Please contact your installer. Repairs must only be carried out by qualied technicians.
Failure to comply with these requirements can compromise the safety of the appliance.

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4 OPERATION
4.1 General
The Megaex is a oor standing boiler, equipped with a cast aluminium heat-exchanger. During heat
demand the controller activates the pump.The controller checks the air pressure switch (zero check)
and increases the fan speed to perform an airow-check. Once the air pressure switch closes, the fan
speed increases to ignition speed and a 5 second pre-purge is performed.The water pressure sensor, gas
pressure switch and siphon pressure switch are checked.When all pressure switches are closed and the
water pressure is ok, the ignition is started.
The air needed for combustion is taken in from the outside (if room sealed) or the boiler house (type
B ue installation) by the fan. The air is transported through a gas/air mixing device creating a negative
pressure.This negative pressure is an indication of the amount of air being transported.The negative
pressure is supplied to the gas valve by an internal tube.The gas valve automatically adjusts the amount
of gas that will be injected into the venturi and that will be mixed with the air-ow. This mixture is
supplied to the burner.
Ignition and ame-control of the mixture is done by two electrodes mounted on the burnerhood.
Temperature control and safeguarding is done using two NTC’s. The boiler monitors the sensors
continuously in order to control operation and ensure safe operation.
4.2 Central Heating (CH)
4.2.1 On-off room thermostat
As standard the boiler is programmed for using an on-off room thermostat.The room thermostat has to
be connected to the pin nrs. 1 + 2 on the terminal strip. Open Therm will be recognized if connected on
1 + 2. The desired ow temperature is adjustable, but as standard is set to 85 °C.
At CH heat request from the room thermostat (and no DHW heat request present) the CH-pump
is activated after 10 seconds. The controller will adjust the burner-input in such a way that a ow-
temperature of 85 °C towards the CH-circuit is achieved.
Warning : do not supply any voltage to these terminals as you may damage the controller
4.2.2 Optional 0-10V
The boiler may be controlled using a 0-10V DC signal. Connect the negative (0V DC) to No. 3, and the
positive (0-10V DC) to No.4 on terminal strip C2.
A loop of wire must be placed between the pin nrs. 1 and 2 of terminal strip C2.
In the technician menu, enable 0-10V in the advanced CH settings menu by setting, CH request to either
0-10V DC % or 0-10V DC SP.
4.2.2.1 0-10V DC % power control
A value between 2 and 10V DC generates a CH power demand proportional to this value between 0
and 100% (0% = minimum load, 100% = nominal load). The heat demand is removed when the control
signal falls below 1 volt.
The setpoint of maximum ow temperature is set to 90°C.
In the user/technician menu, under diagnostics, boiler information the actual voltage input and target
power are displayed.
4.2.2.2 0-10V DC Setpoint
A value between 2 and 10V DC generates a CH setpoint demand proportional to this value between
CH minimum ow temperature and maximum CH ow temperature. The heat demand is removed when
the control signal falls below 1 volt.
The minimum and maximum CH ow temperature can be set in the technician menu, advanced CH
settings, CH temperatures.

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In the user/technician menu, under diagnostics, boiler information the actual voltage input and boiler
setpoint are displayed.
Caution : Ensure that the 0-10V DC signal is free from electrical interference!
4.2.3 Outside Temperature Control OTC (optional)
The boiler may use an outdoor sensor to provide weather compensation (OTC).
To activate weather compensation connect an oudoor sensor to numbers 5 and 6 on the terminal strip
C2. Pin numbers 1 and 2 have to be bridged by a wire.Alternatively those pin numbers (1 and 2) can
be used for connecting room thermostat on/off. In the technician menu, under advanced CH settings,
CH request, OTC only must be selected.The outdoor sensor is then automatically detected by the
controller. The parameters corresponding with A-E in the gure below can be set in the technician menu
(advanced CH settings).
A OTC offset: minimum CH setpoint value
B OTC setpoint maximum: maximum CH setpoint value
C OTC weather cold: external temperature value at which the maximum CH value will be used.
D OTC weather warm: external temperature value at which the minimum CH value will be used
E OTC warm weather shutdown: external temperature value at which the CH demand will end
In the user menu an eco setpoint reduction (night reduction) can be set.
Day, week and weekend options are also available (on, eco, off)
The outdoor sensor is available as an optional accessory.
The sensor should be installed on the north-side of the building at a height of approximately 2 meters.
Note: The resistance of the outdoor NTC should be 12 kOhm at 25 °C.
Also see table of resistance for NTC’s at 6.6.2
4.2.4 Optional digital communication
The boiler supports digital communication with room thermostats using Open-Therm communication
protocols (automatically recognised if connected to pins 1 + 2 on terminal strip C2, also see 4.2.1.)

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4.2.5 Slow start
The boiler uses the “slow start” procedure to prevent the boiler from supplying excessive power in low
load situations.
After “zero check” APS and closure APS with pre purge ignition starts. Following, a stabilization period,
the boiler modulates down to low capacity and maintains this capacity for 1 minute. Subsequently the
boiler power increases at a target rate of 4°C/min until maximum capacity or set temperature has been
reached. Once heat demand has nished the burner will turn off following a set post purge period.
The graph below illustrates this;
4.2.6 Protection against insufcient ow through boiler
When the requirements of 6.3.2 are fullled the boiler will protect itself against insufcient ow. This is
done by checking the difference in temperature between ow and return (so called ΔT).
In a low ow scenario the ΔT will rise rapidly. The ΔT safe-guarding principle is as follows ;
At ΔT > 22 the boiler starts modulating
At ΔT between 22 and 27 the boiler continues modulating
At ΔT > 27 boiler the fan speed will reduce until ΔT < 25

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4.3 Domestic Hot Water (DHW)
4.3.1 External storage tank (choice to be made by manufacturer between option 1 and option 2)
4.3.1.1 Option 1. External storage tank with thermostat (hydraulic 3-way valve)
As standard the DHW conguration is factory pre-set for an external storage tank + tank thermostat.
For hydraulic connection of an external storage tank to the boiler one should either
use :
• the default conguration with 2 pumps: 230 VAC DHW pump (terminal strip C1:6,7,8) and CH pump
(terminal strip C1: 9,10,11) or
• a hydraulic 3-way valve (terminal strip C1: 6,7,8)
The 2 wires of the tank thermostat must be connected to numbers 7 and 8 on terminal strip C2.
In the case of using a hydraulic 3-way valve adjust setting in technician menu, system settings, boiler
parameters, number of pumps to: pump and 3-way valve.
4.3.1.2 Option 2. External storage tank with thermostat (electric 3-way valve)*
As standard the DHW conguration is factory pre-set for an external storage tank + tank thermostat.
For hydraulic connection of an external storage tank to the boiler via an electric 3 way valve one should
either use :
• the default conguration 2 pumps: 230 VAC DHW pump (terminal strip C1: 6,7,8) and CH pump
(terminal strip C1: 9,10,11)
• an electric 3-way valve with a maximum travel time of 255 sec. (terminal strip C1: 6,7,8,9). At the end
of the travel time in either direction DHW or CH the 230VAC on the 3-way valve will be switched
off.
The 2 wires of the tank thermostat must be connected to numbers 7 and 8 on terminal strip C2.
In the case of using an electric 3-way valve adjust the setting in the technician menu, system settings,
boiler parameters, number of pumps to: pump and 3-way valve.
The 3-way valve travel time can be changed in the technician menu, system setting, boiler parameters,
3-way valve travel time.
*The 3-way valve can either be a hydraulic valve or an electric valve.This is an OEM factory setting and
CAN NOT be changed from the (technician) menu.The default setting is a hydraulic 3-way valve
In case an electric 3-way valve should be the default one, please ask your OEM supplier for
the correcty settings
4.3.2 External storage tank with NTC sensor
In case the storage tank is equipped with an NTC sensor, adjust the setting in technician menu, advanced
DHW settings, DHW request to sensor.
Note: The resistance of the NTC sensor must have a value of 12 kOhm at 25 °C.
The 2 wires of the tank NTC sensor must be connected to numbers 7 and 8 on terminal strip C2.

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The set point temperature of the storage tank is adjustable (default set at 60°C,the ow temperature is
DHW setpoint + 20K). Warning : if a CH heat demand exists immediately after nishing the heat request
for DHW, it is possible for high temperatures to ow into the CH system regardless of CH set point
(hot shot).
4.3.3 DHW priority/General behaviour with external storage tank
Disabling hot water operation: press Summer-Winter button R2-C4 (not active in main screen). See
later in manual for further explanation.
Enabling hot water operation: press Summer-Winter button R2-C4 (active in main screen). See later
in manual for further explanation.
In the default boiler conguration, (2 pumps-DHW and CH pump), a DHW request has priority over
CH request
In the technician menu, advanced DHW settings, DHW priority, the DHW priority over CH can either
be disabled or a maximum DHW priority time may be set.
In the case where the DHW priority is disabled and both demands are active at the same, both pumps
(CH and DHW) will be activated. During this time the ow temperature is set to either 80 °C (tank
thermostat) or DHW setpoint + 20K (NTC sensor).
Notice: At outputs ≥ 40 kW double separation between exchanging media is required.
4.4 Cascade
For cascade application see appendix “cascade”

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5 BOILER CONTROL
5.1 Control Panel
The control panel has 12 buttons and a display as shown in the gure below.
5.2 Push buttons on control panel
Description of push button use
R1-C1, R2-C1 and R3-C1 (back) buttons follow, if pressed, the associated icon in the display (left)
R1-C2 and R3-C2 (up-down) buttons, scroll, if pressed, through the different menus
R2-C2 button conrms, if pressed, the highlighted selection, or conrms what is requiered by LCD
R1-C3 button (escape) returns, if pressed, to main screen
R1-C4 (on-off) button puts boiler in off mode, main logo and date/time stay displayed
R2-C3 (menu) button enables, if pressed, access to both user and installer menu
R2-C4 (summer-winter) button enables-disables, if pressed, CH and DHW in main screens
R3-C3 (holiday) button enables, if pressed, holiday function in main screens
R3-C4 (eco) enables, if pressed, eco function in main screens

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5.3 User menu
By pressing the “menu-button” the display will show the text as given in the gure below.
By pressing the button marked “3” in the gure above the user menu is accessed. Pressing the button
marked “5” returns back to the main screen. By pressing the button marked “4” the installer menu is
accessed.
In the user menu the following options will be shown :
1. HEATING
2. DOMESTIC HOT WATER
3. HOLIDAY
4. MAINTENANCE
5. SETTINGS
6. CHIMNEY-SWEEPER
7. DIAGNOSTICS
By pressing up and down (R1-C2 and R3-C2) one of the six options as shown above will highlight the
desired parameter. By pressing the OK button (R2-C2) the chosen option will be selected.
Once an option has been slected it is possible to change the parameters corresponding with the chosen
option
5.3.1 Parameter/value setting
Pressing the up and down (R1-C2 and R3-C2) buttons will highlight the desired parameter. Pressing the
OK button (R2-C2) will allow the chosen parameter to be modied. This is shown below.
The actual value can be changed by pressing the R1-C1 and R2-C1 buttons.The changed value can
be conrmed by pressing the OK (R2-C2) button. Pressing the back (R3-C1) button leaves the actual
displayed parameter. If there are more parameters shown in the parameter value area (4) the desired
parameter can be selected by pressing the up and down ((R1-C2 and R3-C2) buttons.
5.3.2 Parameters accessible by user
An overview of the parameters accessible by the user is given on the next pages

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User menu Submenu 1 Submenu 2 Submenu 3 Submenu 4 Notes 1. HEATING Heating user settings
1. CH temperature/OTC set Set the CH temperatures and OTC curves parameters
1. CH setpoint Adjust setpoint of CH circuit 2. Outside temperature for CH off Set the external temperature at which heat demand is
removed. If set OFF, heat demand will never be removed by controller (only by removing RT or bridge between terminal strip C2:1,2)
2. Eco setpoint reduction Set the temperature that will be subtracted from the actual
setpoint when ECO mode is activated
3. Scheduler set Invoke scheduler menu
1. Enable/disable on board scheduler Based on selection is possible to enable/disable on board
scheduler
Enable Enable on board scheduler Disable Disable on board scheduler
2. Scheduler set Select to set scheduler
1 Monday 2 Tuesday 3 Wednesday 4 Thursday 5 Friday 6 Saturday 7 Sunday 8 Monday-Friday 9 Monday-Sunday 10 Saturday- Sunday
Used to program on board scheduler (On, Off, Eco)
2. DOMESTIC HOT WATER
Domestic hot water user settings
1 DHW set point Set the DHW temperature (in case of a DHW with sensor
this is the actual DHW temperature, in case of DHW with thermostat this is the base boiler ow temperature).
2. ECO set point reduction Set the temperature that will be substracted from the
actual setpoint when ECO mode is activated.
3. Scheduler set Invoke scheduler menu
1. Enable/disable on board scheduler Based on selection possible to enable/disable DHW on
board scheduler
Enable Enable on board scheduler Disable Disable on board scheduler