Strebel S-CB+400 User manual

STREBEL
S-CB+Boiler Range
Models +400 & +550
Floor Standing High Efficiency Condensing Boiler
Installation, Operating & Maintenance Manual
Please read and understand before commencing installation and leave the manual with the customer for future reference.
2017-09-01 v1

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TABLE OF CONTENTS
INTRODUCTION…………………………………………………………………………………………….….....6
1SAFETY GUIDELINES...............................................................................................................................6
2TECHNICAL DATA S-CB+400 AND S-CB+550.........................................................................................7
2.1 INTRODUCTION ......................................................................................................................................7
2.2 TECHNICAL SPECIFICATIONS DATASHEET.................................................................................................8
2.3 ERP SPECIFICATION DATASHEET..........................................................................................................10
2.4 SAFETY MEASURES FOR PREVENTING INTERNAL FLUE GAS RECIRCULATION.............................................11
2.5 BENEFITS OF THE S-CB+400 &550 BOILER .........................................................................................11
2.6 DESCRIPTION OF THE MOST IMPORTANT BOILER PARTS..........................................................................12
3TECHNICAL DIMENSIONS OF THE S-CB+400 / S-CB+550...................................................................13
4ACCESSORIES AND UNPACKING OF THE BOILER ...........................................................................14
4.1 ACCESSORIES .....................................................................................................................................14
4.2 UNPACKING.........................................................................................................................................14
5INSTALLATION OF THE S-CB+ 400 & 550.............................................................................................15
5.1 GENERAL NOTES .................................................................................................................................15
5.2 BOILER ROOM......................................................................................................................................15
5.2.1 General ...................................................................................................................................................................15
5.2.2 Boiler room..............................................................................................................................................................15
5.2.3 Ventilation ...............................................................................................................................................................16
5.3 REMOVING THE TOP,FRONT AND SIDE PANELS ......................................................................................16
5.4 MOUNTING THE BOILER.............................................................................................................................17
6CONNECTIONS WATER SIDE................................................................................................................17
6.1 BOILER CONNECTIONS .........................................................................................................................17
6.2 CONDENSATE DRAIN CONNECTION........................................................................................................18
6.3 FLOW AND RETURN CONNECTIONS........................................................................................................18
6.4 THE EXPANSION VESSEL.......................................................................................................................18
6.5 PRESSURE RELIEF VALVE.....................................................................................................................19
6.6BYPASS...............................................................................................................................................19
6.7 PUMP FUNCTIONALITY..........................................................................................................................19
6.8 FROST PROTECTION.............................................................................................................................19
6.9 INSTALLING A STRAINER AND/OR DIRT SEPARATOR.................................................................................20
6.10 WATER QUALITY ..................................................................................................................................20
6.11 PLASTIC PIPING IN THE HEATING SYSTEM...............................................................................................21
6.12 AUTOMATIC AIR VENT...........................................................................................................................21
6.13 AUTOMATIC WATER FILLING SYSTEMS ...................................................................................................21
6.14 WATER PRESSURE...............................................................................................................................21
6.15 CHEMICAL WATER TREATMENT .............................................................................................................22
6.16 UNDER FLOOR HEATING .......................................................................................................................22
6.17 FLUSH THE SYSTEM WITH FRESH WATER ...............................................................................................22
6.18 INSTALLATION EXAMPLES .....................................................................................................................22
6.18.1 Installation containing one S-cb+400 / 550 CH boiler.............................................................................................22
6.18.2 Installation containing two S-cb+400/550 CH boilers using NON-RETURN valves ...............................................23
7HYDRAULIC GRAPHS.............................................................................................................................24
8FLUE GAS AND AIR SUPPLY SYSTEM.................................................................................................25
8.1 GENERAL ............................................................................................................................................25
8.2 FLUE GAS SYSTEM...............................................................................................................................25
8.3 BOILER CATEGORIES -TYPES OF FLUE GAS SYSTEMS.............................................................................26
8.4 C63 CERTIFIED....................................................................................................................................27
8.5 FLUE TERMINAL...................................................................................................................................28
8.5.1 Vertical Flue Terminal Positioning...........................................................................................................................28
8.5.2 Common Flue / Ducts .............................................................................................................................................28
8.6AIR SUPPLY.........................................................................................................................................28
8.6.1 Air quality ................................................................................................................................................................28
8.6.2 Air supply through humid areas ..............................................................................................................................28
8.7 PIPE HEIGHTS AND MUTUAL DISTANCES ON A FLAT ROOF........................................................................29

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8.8 S-CB+400 &550 AIR INLET /FLUE GAS OUTLET CALCULATION EXAMPLES...............................................30
8.8.1 Flue gas and air supply resistance table - concentric parts ....................................................................................30
8.8.2 Twin pipe flue gas and air supply resistance table:.................................................................................................31
8.8.3 Example A: Twin pipe system.................................................................................................................................32
8.8.4 Example B: Single pipe system for flue gas outlet only ..........................................................................................33
8.8.5 Example C: Twin pipe system with wall mounted air duct. .....................................................................................34
8.8.6 Example D1: Twin pipe system with concentric roof terminal. ...............................................................................35
8.8.7 Example D2: Twin pipe system with concentric roof terminal. ...............................................................................36
8.9 SEPARATE AIR SUPPLY AND FLUE TERMINAL FOR A PITCHED ROOF..........................................................37
8.10 SEPARATE AIR SUPPLY AND FLUE TERMINAL FOR A FLAT ROOF ...............................................................37
9ELECTRICAL INSTALLATION................................................................................................................38
9.1 GENERAL ............................................................................................................................................38
9.2 CONNECTIONS.....................................................................................................................................39
9.3 CASCADED CONNECTION INCLUDING SHIELDING.....................................................................................39
9.4 CONNECTING THE POWER SUPPLY AND BOILER PUMP P1, 230V/1~ OR 400V/3~ ....................................40
9.5 FUSES.................................................................................................................................................41
9.6 LIST FOR CONNECTIONS.......................................................................................................................41
9.7 SENSORS............................................................................................................................................43
9.8 ELECTRICAL CIRCUIT DIAGRAM TOP BURNER (PCB A, LEFT) ..................................................................44
9.9 ELECTRICAL CIRCUIT DIAGRAM BOTTOM BURNER (PCB B, RIGHT)..........................................................46
10 USER INTERFACE...................................................................................................................................48
10.1 CONTROL PANEL /DISPLAY UNIT ...........................................................................................................48
10.2 MENU STRUCTURE..............................................................................................................................49
10.3 DISPLAY DURING OPERATION................................................................................................................51
10.4 MONITOR SCREENS..............................................................................................................................52
10.5 SERVICE FUNCTION..............................................................................................................................54
10.6 SCHORNSTEINFEGER FUNCTION ...........................................................................................................55
10.7 PROGRAMMING IN STANDBY MODE........................................................................................................56
10.8 SETTING THE TIME &DATE....................................................................................................................56
10.9 SET POINTS.........................................................................................................................................57
10.10 SETTING THE TIMER PROGRAMS ...........................................................................................................58
10.11 SETTING THE OUTDOOR SPECIFICATIONS ..............................................................................................61
10.11.1 Parameters for setting the outdoor graph ...............................................................................................................61
10.11.2 Outdoor graph - main settings.................................................................................................................................62
10.11.3 Outdoor graph - additional settings .........................................................................................................................63
10.11.4 Display ....................................................................................................................................................................64
10.12 CHECKING THE OPERATING HISTORY.....................................................................................................65
10.13 CHECKING THE FAULT HISTORY.............................................................................................................66
10.14 SETTING THE MAINTENANCE SPECIFICATIONS........................................................................................67
10.15 SETTING THE USER LOCK .....................................................................................................................70
10.16 SETTING THE PARAMETERS AT THE CONTROL PANEL..............................................................................71
10.17 FAULT CODES DISPLAY.........................................................................................................................78
10.17.1 Lock-out codes........................................................................................................................................................78
10.17.2Blocking codes........................................................................................................................................................80
10.17.3 Important message .................................................................................................................................................81
11 CONTROLLING OPTIONS AND SETTINGS ..........................................................................................82
11.1 GENERAL ............................................................................................................................................82
11.1.1 Extra boiler control ..................................................................................................................................................82
11.1.2 Max cooling time .....................................................................................................................................................82
11.1.3 temperature display on/off.......................................................................................................................................82
11.1.4 Water pressure........................................................................................................................................................82
11.1.5 Gas type selection...................................................................................................................................................82
11.1.6 Soft start option .......................................................................................................................................................83
11.1.7 Pump mode (EC technology) ..................................................................................................................................83

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11.2 HEATING .............................................................................................................................................84
11.2.1 Controlling behaviour settings.................................................................................................................................84
11.2.2 Room thermostat on/off...........................................................................................................................................84
11.2.3 Room thermostat OPENTHERM.............................................................................................................................85
11.2.4 Outside temperature related flow control ................................................................................................................85
11.2.5 0-10 VDC remote flow temperature set point..........................................................................................................85
11.2.6 0-10 VDC remote burner input control ....................................................................................................................86
11.2.7 timer contact function ..............................................................................................................................................86
11.3 INDIRECT HOT WATER /CALORIFIER.......................................................................................................87
11.3.1 pump and 3-way valve control ................................................................................................................................87
11.3.2 tank thermostat .......................................................................................................................................................87
11.3.3 tank sensor..............................................................................................................................................................87
11.3.4 Low/high flow temperature to tank coil....................................................................................................................88
11.3.5 Heating and hot water switching time .....................................................................................................................89
11.3.6 Heating and hot water switching time at a sudden temperature drop .....................................................................89
11.3.7 anti-Legionnaires’ disease (pasteurisation) function ...............................................................................................90
11.4 CASCADE CONTROL.............................................................................................................................91
11.4.1 Parameter settings for cascaded boilers.................................................................................................................91
11.4.2 Monitor screens.......................................................................................................................................................93
11.4.3 Output control and burner sequence.......................................................................................................................93
12 COMMISSIONING THE BOILER .............................................................................................................94
12.1 FIRST:FLUSHING THE BOILER WITH WATER............................................................................................94
12.2 SECOND:FILLING &VENTING THE BOILER AND THE SYSTEM....................................................................94
12.3 THIRD:CHECK THE WATER FLOW ..........................................................................................................94
13 STARTING THE BOILER.........................................................................................................................96
13.1 GENERAL ............................................................................................................................................96
13.2 FIRING FOR THE FIRST TIME..................................................................................................................97
14 ADJUSTING AND SETTING THE BURNERS.........................................................................................98
14.1 INTRODUCTION ....................................................................................................................................98
14.1.1 Adjustment tables....................................................................................................................................................98
14.1.2 Adjustment values...................................................................................................................................................98
14.1.3 Gas valve setting screws: drawing........................................................................................................................100
14.1.4 How to remove and mount the flue plug: ..............................................................................................................101
14.1.5 Adjustment actions: general scheme ....................................................................................................................102
14.1.6 Note: CO2measuring position...............................................................................................................................103
14.2 ADJUSTING IN CASE OF A NEW BOILER,OR AFTER MAINTENANCE (CASE A)............................................103
14.2.1 General remark .....................................................................................................................................................103
14.2.2 Checking and adjusting the bottom burner ...........................................................................................................104
14.2.3 Checking both burners ..........................................................................................................................................104
14.3 ADJUSTING AFTER GAS VALVE REPLACEMENT OR IN CASE OF GAS CONVERSION (CASE B)......................105
14.3.1 General remarks ...................................................................................................................................................105
14.3.2 Case B adjustments ..............................................................................................................................................105
14.3.3 Setting parameter P4BD gas type (display D8) ....................................................................................................106
15 PUTTING THE BOILER OUT OF OPERATION ....................................................................................107
16 FAULT CODES, BLOCKING CODES ...................................................................................................108
16.1 FAULT CODES....................................................................................................................................108
16.2 BLOCKING CODES..............................................................................................................................115
16.3 MAINTENANCE ATTENTION MESSAGE...................................................................................................119
17 MAINTENANCE......................................................................................................................................120
17.1 GENERAL ..........................................................................................................................................120
17.2 INSPECTION &MAINTENANCE..............................................................................................................120
18 USER INSTRUCTIONS..........................................................................................................................123
19 EXAMPLES OF INSTALLATIONS ........................................................................................................124

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INTRODUCTION
This manual is written for:
▪The installer.
▪System design engineer.
▪The service engineer.
▪The user.
The following symbol is used in this manual:
Warning: Important information concerning the safety of persons and/or the appliance.
Strebel Ltd is not accountable for any damage caused by incorrect following the mounting instructions. For service
and repair purposes use only original Strebel spare parts.
All documentation produced by the manufacturer is subject to copyright law.
1 SAFETY GUIDELINES
Read all these instructions before commencing installation.
Keep this user manual near the boiler for quick reference.
The appliance should be installed by a skilled installer according to all applicable standards and regulations. Failure
to comply with these regulations could deem the warranty invalid.
Without written approval of the manufacturer the internals of the boiler may not be changed. When these changes
are executed without approval, the boiler certification is invalid.
Commissioning, maintenance and repair must be done by a skilled installer/engineer, according to all applicable
standards and regulations.
What to do if you smell gas:
▪Do NOT use any electrical equipment.
▪Do NOT press any switches.
▪Close the gas supply.
▪Ventilate the room (open the windows and/or outside boiler room doors).
▪Warn the installer immediately.
The manufacturer / supplier is not liable for any damage caused by inaccurately following of these mounting
instructions. Only original parts may be used when carrying out any repair or service works.
This appliance is not intended for use by persons (including children) with reduced physical, sensory or
mental capabilities, or lack of experience and knowledge, unless they have been given supervision or in-
struction concerning use of the appliance by a person responsible for their safety. Children should be su-
pervised to ensure that they do not play with the appliance.

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2 TECHNICAL DATA S-CB+400 AND S-CB+550
2.1 Introduction
The S-CB+ 400 & 550 heating boilers are central heating boilers with a maximum high efficiency. Such performance
can also be reached by using a special heat exchanger made of stainless steel. The heat exchanger helps to cool
down the flue gases below their condensation point; through this condensing of the flue gases extra heat is released.
This has an immediate positive effect on the efficiency, exceeding the 100%.
The S-CB+boiler is standard set for Natural gas G20
Gases used must comply with the European standard EN 437.
Fuel used should have sulphur rates within the European standard, a maximum annual peak over a short period of
time of 150 mg/m3and an annual average of 30 mg/m3.
Boiler control includes:
▪Boiler pump control.
▪Cascade control for up to six boilers.
▪Remote signals from each burner:
-Lock-out indication.
-Heat demand indication.
-Burner burning indication.
▪Weather compensation control.
▪Calorifier control.
Connections for:
▪0-10 VDC remote flow temperature (set point) control.
▪0-10 VDC remote burner input control.
▪Outside temperature sensor.
▪External calorifier pump or diverter valve.
Flue gas
Because the flue gases can have a low temperature, the boiler needs to have a high efficiency approved stainless
steel flue gas system. Also, plastics of the right temperature class are allowed. For details, see applicable section.
Aluminium flue gas systems are never allowed to be connected to S-CB+boilers.
Cascade control
When using the integrated cascade control, a maximum of six boilers (meaning twelve burners) can be controlled in
a cascade configuration. When using dedicated control, this number can be increased at will.
0-10 VDC connection available
The boiler flow temperature or burner input can be controlled by an external 0-10 VDC signal. If several boilers are
in cascade, using the integrated cascade control, the signal should be directed to the master boiler only. When using
alternative control systems, all boilers in cascade systems may be controlled using these 0-10 VDC signals. A signal
of 1,48 Volt will switch on the boiler(s), less than 1,4 Volt will switch off the boiler(s).
Time program
For both central heating and hot water function of the boiler, time programs with three programmable periods per day
are available. These time programs can be set and activated directly at the boiler control panel.

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2.2 Technical specifications datasheet
GENERAL
Product Identification Number
CE 0063 BS3806
Dimensions (h x w x d)
cm
161,7 x 73,6 x 122,5
Classification
II2H3P
Gas Appliance Type
B23, B23P; C13, C33, C43, C53, C63, C83
Type boiler
S-CB+400
S-CB+550
CH boiler water content
litres
30
43
Weight (empty)
kg
400
450
Connections flow/return
inches
R 2 ½"
Gas connection
inches
R 2"
Flue gas / air supply connection 1
mm
180-180
HEATING Values min-max:
Nominal input (Net)
kW
50,0 –400
68,0 –550
Nominal input (gross) (G20, G25.3)
kW
55,4 –444
75,5 –611
Nominal input (gross) (G31)
kW
54,3 –435
73,9 –598
Nominal input (gross) (G30/G31)
kW
54,2 –434
73,7 –596
Nom. output 80/60°C
kW
48,3 –386
66,1 –535
Nom. output 50/30°C
kW
52,2 –418
71,2 –576
Nom. output 37/30°C
kW
54,1 –433
73,7 –597
Efficiency 40/30°C DIN4702-8
%
Up to 109,5
GAS CONSUMPTION 2Gases according to EN437 Values min-max:
Natural gas G25.3
m³st/h
6,0 –48,1
8,2 –66,2
Natural gas G20
m³st/h
5,3 –42,3
7,2 –58,2
Propane gas G31 1
m³st/h
2,1 –16,4
2,8 –22,5
Butane/Propane (B/P) G30/G31 1
m³st/h
1,6 –12,4
2,1 –17,1
Gas supply pressure nominal 3
G25.3
mbar
25
G20
mbar
20
G312
mbar
30/37
G30/G312
mbar
50
NOTES
1All boilers are supplied as twin pipe model.
2Using propane, butane and B/P, maximum fan speed needs to be reduced (parameter P4BD)
3Below a table is given in which the min. and max. gas supply pressures are listed according to
EN437:
p nominal [mbar]
p min [mbar]
p max [mbar]
G25.3
25
20
30
G20
20
17
25
G31
30
25
35
37
25
45
G30/G31
50
43
57

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Type boiler
S-CB+400
S-CB+550
EMISSION [EN437]
Nominal value at min. max. load
CO2flue gas G25.3, G20 min-max
%
9,0- 9,0
CO2flue gas G31, G30, B/P min-max
%
10,0-10,5
NOxclass [EN483/ EN15420]
-
6
Flue gas temperature at atmospheric tempera-
ture of 20°C
°C
90
Mass flow flue gas [min-max]
Qfluegas condensing
g/s
24,1 - 207,8
33,1 - 285,7
Available pressure for the flue system 4
Pa
200
Available pressure for the flue system with speci-
fied Concentric Roof Terminal4
Pa
250
INSTALLATION
Hydraulic resistance of the
boiler
T = 20 K
mWK
4,0
4,1
T = 25 K
mWK
2,6
2,8
Water pressure boiler min-max.
bar
1,0 –4,0 5
Maximum flow temperature
°C
85
ELECTRICAL
Power supply / frequency
V / Hz
230 (400 6) / 50
Maximum power consumption (exclusive pump)
W
960
Max. current P1 pump relay (I nom)
A
9
Protection class
IPX0B
NOTES
4 Maximum combined resistance of flue gas
and air supply piping at high fire.
5With the standard built-in pressure sensor
replaced by a pressure switch, pressure
may go up to 6.0 bar. Parameter P4AD
needs to be changed.
6230 Vac is necessary for the boiler to func-
tion. If a 400 Vac boiler pump is applied, 400
Vac must be connected to the appliance so
the power supply for the pump can be deliv-
ered by the system. (An optional safety
switch for the pump motor must be added ex-
ternally).

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2.3 ERP specification datasheet.
Technical parameters according the European ERP (Energy Related Products) legislation:
Type Boiler:
S-CB+400
S-CB+550
Condensing boiler:
Yes
Yes
Low temperature boiler:
Yes
Yes
B11 boiler:
No
No
Cogeneration space heater:
No
No
Combination heater:
No
No
Unit:
Value
Value
Rated heat output
kW
386
535
P-rated (P4) at 60-80⁰C
kW
386
535
Heat output (p1) 30% at 30-37⁰C
kW
129,9
179,1
Seasonal space heating energy efficiency (ɳs).
%
92,54%
92,89%
energy efficiency (ɳ4) at 60-80⁰C
%
86,90%
87,60%
energy efficiency (ɳ1) at 30-37⁰C
%
97,50%
97,70%
Auxiliary electricity consumption
At full load (elmax).
kW
0,752
0,829
At part load (elmin)
kW
0,12
0,12
In standby mode (Psb)
kW
0,015
0,016
Other
Standby heat loss (Pstby)
kW
0,227
0,366
Ignition burner power consumption
kW
0,000
0,000
Emissions (Nox) of nitrogen oxides (EN15502-
1:2012+A1:2015 )
mg/kWh
44
41
Sound power level, indoors (EN 15036-1:2006)
dB
74
78

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2.4 Safety measures for preventing internal flue gas recirculation
The heat exchanger of the S-CB+400 & 550 boiler contains two burners. The air supply channels of both burners
are internally connected to each other, so the installer only needs to connect one air supply duct to the boiler. The
controller allows the situation in which only one burner is burning, while the other one is off. When in this situation
the flue gas canal resistance is (too) high, flue gases may go into the burner room of the burner that’s off, instead of
into the flue gas canal. These flue gases will flow into that burner room, pass its fan, and eventually enter the air
supply to the other fan and back to the burning burner, influencing combustion of that burner negatively.
The phenomenon is called recirculation.
Three safety features have been installed in the boiler to prevent this recirculation from happening.
1. Non-return valve. Behind both fans a non-return valve is installed. Both burners communicate with each other
checking the non-return valve to be closed on the burner that is off so the other burner can burn. The non-return
valve is equipped with a proximity switch which is signalling on the burner controller whether the valve is closed
or opened. The communication between these burner controllers is checked every 20 seconds and when this fails
the other burner(s) will be switched off. In normal operation of the boiler the fan of the burner that is not burning
will be switched off because recirculation is prevented by the non-return valve and checked by the burner control-
ler.
2. Fan counter pressure. If the electronic safety features are functioning well, a non-return valve fitted behind the
fan will prevent recirculation (see 1). The position of this non-return valve is monitored continuously by the
electronics. If the non-return valve is not closed the electronics will activate the fan to run at a speed relative to
that of the fan of the other burner so enough pressure is created to prevent recirculation.
-So, if the non-return valve is not functioning its function is taken over by the fan. In this case the unit will still be
able to burn for 100% of its total capacity when both burners are used.
-When the fan is not functional (of the burner that is not burning), this fan is not able to run and build up any
pressure to prevent recirculation. The burner controller that controls that burner/fan then checks if the non-return
valve is closed. If closed the burner controller communicates to the other burner controller(s) that it is able to
burn. The unit has then only 50% of its total capacity because only one burner is available.
-If both non-return valve and fan fail the complete unit will go into a lock out, if cascaded the other units will be
blocked because this unit is in a lock out.
3. Flue gas monitoring. The tendency to re-circulate also depends of the flue gas resistance. Within normal oper-
ational specifications the boiler will not re-circulate. If the flue gas resistance (by blocking the canal) rises too high,
apressure switch will put the whole boiler into lockout.
2.5 Benefits of the S-CB+ 400 & 550 Boiler
The special features of this boiler range are:
a. The weight is low:
Maximum 450 kg (empty) and filled with water 493 kg.
b. Small dimensions: due to the width of 750 mm, the boiler can access premises using a standard door to
bring it to the place, where it will be installed. It is easy to put the boiler on its exact position, by using the two
wheels at the back.
c. The small diameter of the air supply and flue gas discharge tube.
d. The boiler consists of one heat exchanger with two burners that are controlled by the internal cascade man-
agement system.
e. Extremely low noise production.
f. Very small water content.
g. Reliable through use of twin burner and smart electronics.

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2.6 Description of the most important boiler parts
1. Fan
The fan is a compact unit: the motor and fan housing are an integral part and can be replaced as a complete unit.
The fan varies in speed due to the boiler control, which ensures that the modulation of the boiler is attained.
2. Gas train
The boiler has two equal gas control valves (one for each burner).
Both gas control valves have two main gas valves internally that are opened simultaneously. When there is a heat
demand, modulation takes place under the influence of the fan speed variation. The correct amount of gas is sucked
in, by creating an under pressure through the fan, from the gas control valve.
3. Mixer
There is a mixer on the suction side of the fan(s) in which the gas and air are mixed together until a uniform gas/air
quantity is obtained. This is pushed into the burner.
4. Boiler pump (not in drawing on this page)
The separately supplied boiler pump must be connected to the return of the boiler. The head of this pump must be
sufficient to overcome the boiler resistance and the external system resistance for a connection to a low loss header.
5. Burner control
The boiler has two equal burner controls: one for each burner unit. One of the burner controls has a built-in cascade
manager for the overall control of the boiler.
6. Electrical connections
All electrical components can be connected at the rear/top of the boiler. A relay has been installed to give power to
the boiler pump.

13
7. Non-return valve
A non-return valve fitted behind the fan will prevent recirculation of flue gases from one burner to the other burner
(when this burner is not operating).
8. Heat exchanger
The heat exchanger consists of spirals of stainless steel smooth tube. Through the openings between the spirals the
flue gases are pushed, establishing an optimal heat transfer.
The ends of these spirals are welded with stainless steel nozzles that start at the return connection of the boiler and
end in the supply connection of the boiler.
9. Burner
Both parts of the heat exchanger contain their own burner that consists of a perforated cylinder from stainless steel
with an extra porous layer for protection against high temperatures. This porous layer is a weaving layer; the wires
are made of an alloy with high temperature resistance.
3 TECHNICAL DIMENSIONS OF THE S-CB+400 / S-CB+550
Connection
Function
Diameter (inch/mm)
A
water flow (outlet)
R 2½ "
B
water return (inlet)
R 2½ "
C
cable input
Ø 22,5 mm
D
combustion air inlet
Ø 180 mm
E
flue terminal
Ø 180 mm *
F
gas connection
R 2 ”
G
condensate discharge hose
Ø 25 mm outer diameter

14
4 ACCESSORIES AND UNPACKING OF THE BOILER
4.1 Accessories
Depending on the selected controlling of the central heating system and the type of boiler, the following items can be
ordered and delivered with the boiler:
Item
Part no.
Outside (air) temperature sensor: 12 kOhm@25°C (to be mounted to the boiler connections)
E04.016.585
External flow temperature sensor for behind the low velocity header: 10 kOhm@25°C (to be
mounted to the boiler connections only needed on cascades)
E04.016.304
Calorifier temperature sensor: 10kOhm@25°C (to be mounted to the boiler connections)
E400277
Room Controller “OpenTherm” RC (modulating) with clock function
S04.016.355
Room Controller “OpenTherm” RC (modulating) with remote room sensor
S04.016.358
Interface cable and software for programming the boiler
E400278
4.2 Unpacking
The S-CB+ 400 & 550 boiler comes with the following documents and accessories:
•One “Installation manual” for the installer.
•Three spare nuts for the installation of the burner plate, one Torx key T40, one Allen key no.3 and one gas
conversion sticker (all in a bag attached to the front of the gas valve).
•Bottom part of the siphon.
After delivery, immediately check if the boiler is complete and without any defects. Report any damage immediately
to the supplier.

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5 INSTALLATION OF THE S-CB+ 400 & 550
5.1 General notes
The boiler is mounted on a pallet with a wooden “support”frame around it. The boiler is wrapped in shrink warp
before the wooden support frame is mounted. After the frame is placed the whole pallet, boiler and frame package is
shrink wrapped again.
Only remove this packaging when the boiler has been positioned at the place where it will be installed. After removing
the wrapping and the frame, the boiler can be taken off the pallet using a forklift or another suitable lifting device. The
boiler is fixed to the pallet with screws. Make sure these are removed before attempting to lift the boiler from the
pallet. Also make sure that the wheels at the back are not damaged during lifting (for example by the forks of the fork
lift).
Positioning
The boiler will now be positioned on the four adjustment bolts.
Ensure the boiler levels in both directions are horizontal by using these four bolts.
Side legs
The boiler has four legs at the bottom that can be turned. The following is possible with these legs:
1. If the legs will not be used, they can be turned and positioned underneath the boiler.
2. If the boiler will be anchored to the floor, these legs can be turned to the front or side and attachment can take
place by using the holes in these legs
3. When the boilers are placed cascaded, the legs need to be turned sideways in a position that the following
boiler can be placed and mounted. This to make sure, that all boilers are placed at the same height and with
the correct distance between the boilers. Advice is to choose this distance at least 0,5 m, in view of service
purposes.
5.2 Boiler room
5.2.1 GENERAL
The boiler must be positioned and installed by a certified installer in accordance with all applicable standards and
regulations. Commissioning of the boilers must be done by a skilled service/commissioning engineer, who has been
trained and selected by the installer and/or the manufacturer.
5.2.2 BOILER ROOM
For the installation of the boiler(s) the following demands regarding the boiler room should be considered:
1. The radiation losses of the unit are low.
2. The boiler has a built-in fan that will generate noise, depending on the heat demand. The sound emissions are
quite low from the boiler, but be aware that some noise is produced.
3. You need a power supply of at least 230V-50 Hz with an earth connection and may need a supplyof 400V-50Hz
depending on the pump. We advise to install a separate “safe working switch on which all poles are switched”
externally so one can work on the boiler while having all the wiring free of supply voltage.
4. The air supply of the boiler can be connected independent from the boiler room.
Other considerations related to the boiler location.
•The ventilation of the boiler room must meet all applicable standards and regulations, regardless of the se-
lected supply of fresh air to the boiler location.
•The flue gas tube must be connected to an outside wall or roof duct. The air supply can may come from
outside or from the plant room itself.
•The installation area must be dry and frost-free.
•There must be sufficient lighting available in the boiler room to work safely on the boiler.
•When a boiler is positioned at the highest point of the installation, the supply and return pipes must first
protrude 0.5m above the top of the boiler, before these pipes go to the installation side. In other words, the
water level must always be 0,5 metre above the top of the boiler and an automatic air vent must be installed
in the supply or return pipe. A low-water level protection should also be installed at the installation side.
•Mind the positioning of electrical components in relation to the temperature sensitivity.
•Make sure there is an open connection with the sewer to drain the condensate. This connection should be
lower than the condensate drain level of the boiler.

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•Ensure that the correct space is provided when positioning the boiler for maintenance and replacement of
parts. The recommended minimum clearance is:
- Side clearance: 500 mm (advised 1000 mm)
- Front clearance: 800 mm
- Rear clearance: 500 mm
•Make sure that the floor on which the boiler is placed can hold the weight of the boiler.
The following facilities are needed in the technical room:
•One wall socket (electricity) with earth connection near the boiler
According to the valid standards and regulations a fire switch needs to be installed outside the boiler room; in case
of emergencies the electrical power to the boiler(s) can be shut off.
5.2.3 VENTILATION
Either when the boiler is connected independently or when it takes the combustion air out of the technical room, the
ventilation of the technical room needs to meet all applicable standards and regulations.
5.3 Removing the top, front and side panels
The top panel can be removed by loosening the screw on the middle of the control panel, if the top panel is removed
the side and front panels can also be easilyremoved by lifting them up and moving them away from the boiler. These
panels can only be removed if the top panel has been removed first!

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5.4 Mounting the boiler
Before mounting the boiler, the installer needs to design and calculate the following parts:
•Flue gas pipe connection.
•Air supply connection.
•Flow and return connection.
•Condensate and pressure relief valve drainage.
•Power supply.
•A proper design to control the boiler (room thermostat, 0-10V etc.)
All lines/piping must be mounted free of tension. The weight of all the installation components should be
supported separately from the boiler so there will be no standing force on the connections.
Don't use excessive force on the connections while mounting the boiler.
6 CONNECTIONS WATER SIDE
6.1 Boiler connections
Rear view
AAir supply
BFlue gas outlet
CCH water flow (outlet)
DCH water return (inlet)
EGas
FCondensate discharge
GCable entry
G
A
B
C
D
F
E

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6.2 Condensate drain connection
The condensate drain is placed at the centre and at the
bottom of the boiler and has a ¾ inch hose discharge.
Connect this flexible hose to the sewer system.
Use only plastic parts with the condensate drain. Metal
lines are not allowed.
Blockage of this drain might damage the boiler. The drain
connection is correct when the condensate can be seen
flowing away, e.g. using a funnel. Any damage that might
occur, when the drain is not installed correctly, is not
covered by the warranty of the boiler.
There should be an open connection of the condensate
hose into the sewage system. A possible under pressure
in the sewage system must never give the opportunity to
suck on the boiler’s condensate drain hose.
When mounting the bottom part of the siphon, before commissioning the boiler and/or after maintenance,
the siphon must ALWAYS be completely filled with water.
This is a safety measure: the water in the siphon keeps the flue gases from entering the plant room
by leaving the heat exchanger via the condensate drain.
6.3 Flow and return connections
We advise to install two service valves in the flow
and return pipes to the boiler, so the boiler can be
isolated from the heating system, when mainte-
nance or service needs to be carried out.
Mount the boiler pump ALWAYS in the return of
the boiler.
Do not use chlorine based fluxes for soldering any
pipes of the water system.
6.4 The expansion vessel
The capacity of the expansion vessel must be se-
lected and installed to match the capacity of the
central heating system and the static pressure. It
is suggested you fit the expansion vessel in the
return of the central heating system. It can be
combined with a drain valve for service and
maintenance.
Turn LEFT to open
Turn RIGHT to close
Fill with
water
to the
edge
S-CB+ 400 &
550
TOP VIEW
SUPPLIED
WITH
BOILER
SUPPLIED
WITH
BOILER
SAFETY
PRESSURE
RELIEF
VALVE
BOILER
SERVICE
VALVE
EXTERNAL
BOILER
PUMP (P1)
EXPANSION
VESSEL
ISOLATION
VALVE
EXPANSION
VESSEL
BOILER
SERVICE
VALVE
BOILER
DRAIN
VALVE

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6.5 Pressure relief valve
The S-CB+ 400 & 550 boiler has no internal pressure relief valve. This should be fitted in the flow line of the system
near the boiler. When having multiple boilers, each boiler must have its own pressure relief valve. We advise to install
service valves, so the boiler can be isolated from the heating system, when maintenance or service needs to be
carried out. Make sure the pressure relief valve is mounted between the boiler and the service valves. The pressure
relief valve must always be installed in such a way that it cannot be isolated from the boiler by a valve.
The specifications and size of the relief valve should be determined by the installer and must comply with all appli-
cable standards and regulations.
6.6 Bypass
The boiler has no internal bypass. If many thermostatic valves are being used, the system should have a bypass to
allow adequate flow in case all the thermostatic valves are closed.
The boiler flow will also be influenced when a pipe of the heating system is frozen/blocked. Make sure all heating
pipes are free from the risk of frost. If there is the risk of freezing of the heating system, all the pipe sections must be
insulated and/or protected with the help of a tracing.
Installing the boiler flow circuit in series with the heating system is possible, but not preferable. We advise
to install a low loss header behind the boiler, so flow restrictions on the installation side can never influence
the boiler flow. Using a low loss header prevents both before mentioned boiler threats (frost and too many
thermostatic valves) and guarantees free boiler flow.
6.7 Pump functionality
The pump capacity must be determined for each project. The boiler pump (P1) can be controlled directly by connect-
ing it to the internal relay.
The boiler pump must be controlled by the boiler controller. If, for any reason, an external pump control is
applied without written approval of Strebel, the complete warranty on the boiler and all supplied parts will
become invalid.
A safety switch for the pump motor must be installed externally (when needed) and is not included
in the boiler supplies.
We supply a 230 VAC signal for controlling the external relays that will switch the system pump (P3) or the calorifier
pump (P2). Do not use these connections as a supply, always use an external relay for controlling these
pumps.
6.8 Frost protection
The boiler has a built-in frost protection, that is automatically activating the central heating pump when the boiler
return (water) temperature drops below the 5°C (programmable). When the boiler return temperature drops below
the 3°C (programmable), the burner is also ignited. The pump and/or burner will shut down as soon as the return
temperature has reached the 10°C (programmable). The mentioned temperatures are related to the temperatures
measured by the RETURN sensor of the boiler. This frost protection function will not fire up the boiler in case of a
“general blocking” of the burner demand.
NOTICE: This “Frost Protection” function is only useable for the boiler and not for the whole central heating system.
Because it concerns a programmable setting, a boiler damaged by frost is not covered under warranty.

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6.9 Installing a strainer and/or dirt separator
Always install a strainer (water filter) and/or
a dirt separator on the system side after a
low loss header / Strebel boiler guard / plate
heat exchanger on the return pipe pipework
–not on the boiler side (primary)! This will
ensure that the water going to the boiler is
free of any flow restrictions. When using a
water filter always check a week after instal-
lation to determine the strainer cleaning in-
terval. Advice is to mount valves before and
after the strainer, including an air bleed
valve, so the strainer can be isolated from
the heating circuit for service operations.
Clean water is very important, blocked
and/or polluted heat exchangers,
including failures and/or damages caused by
this blockage are not covered by the war-
ranty.
Clean water is important, blocked and/or
polluted heat exchangers, including fail-
ures and/or damages caused by this
blockage are not covered by the war-
ranty.
6.10 Water quality
The pH value of the water must be within the following limits: 7,5 < pH < 9,5. This pH value is reached with the steady
conditions. These steady conditions will occur, when after filling the heating system (pH around 7) with fresh water,
the water will lose its air because of the air bleeding operation and heating up (dead water conditions).
Water hardness must be within the following limits:
3,5° Clark (50 ppm CaCO3) < total hardness < 10,5° Clark (150 ppm CaCO3)
When the water might contain aluminium particles, this should be of a maximum of 0,2 mg/litres. If there is the risk
of contamination of the water by any kind of debris/chemicals in the period after installing, a plate heat exchanger
should be used to separate the boiler circuit from the heating circuit (see drawing next section).
It is advised to prevent the possible air intake and water leakage of the central heating system. Fresh oxygenated
water might damage the heat exchanger of the boiler and should therefore be prevented. Usual spots where air is
most likely to seep in are: suction gaskets, pumps, air valve working as a venting pipe, O-rings / gaskets in stuffing
box, under floor heating pipes.
SYSTEM WITH DIRT SEPARATOR
SYSTEM WITH STRAINER
SYSTEM WITH STRAINER AND DIRT SEPARATOR
DIRT SEPARATOR
DIRT SE-
PARATOR
WATER RETURN
FROM SYSTEM
WATER
RETURN
FROM
SYSTEM
WATER
RETURN
FROM
SYSTEM
WATER FLOW TO LLH /
BOILER GUARD / PHE
)
WATER FLOW TO LLH
/ BOILER GUARD / PHE
WATER FLOW
TO LLH /
BOILER
GUARD / PHE
DIRT
BLEED
VALVE
DIRT
BLEED
VALVE
AIR
BLEED
VALVE
AIR
BLEED
VALVE
VALVE
VALVE
VALVE
VALVE
STRAINER
(WATER FILTER)
STRAINER
(WATER FILTER)