Bosch Greenstar FS User manual

6720810589 (2021/01) CA/US
Operating instructions
Residential Gas Condensing Boiler
Greenstar FS/Combi FS
6720810589-00.2Wo
KBR21/28-/35/42-3A | KWB28/35/42-3A

Contents
Greenstar FS/Combi FS – 6720810589 (2021/01)
2
Contents
1 Explanation of symbols and safety instructions . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Explanation of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Information about the appliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
2.1 Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
2.2 Proper use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
2.3 Overview of boiler types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3 Prepare for operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3.1 Checking the boiler water pressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
3.2 Topping up the heating system water . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
4 Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
4.1 Overview of controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
4.2 Switching the appliance ON/OFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.3 Turning the space heating ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
4.4 Programming the heating control unit. . . . . . . . . . . . . . . . . . . . . . . . . . . .17
4.5 KBR..-3A appliances with DHW tank:
Setting the DHW temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
4.6 KWB..-3A appliances (combi boilers):
Setting the DHW temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
4.7 Setting manual summer mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
4.8 Setting frost protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
4.9 Activating the key pad lock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
4.10 Display codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
5 Thermal disinfection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Contents
6 Energy saving tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
9 Environmental protection and disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.1 Environmental protection and disposal . . . . . . . . . . . . . . . . . . . . . . . . . 31
10 Quick reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Explanation of symbols and safety instructions
Greenstar FS/Combi FS – 6720810589 (2021/01)
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1 Explanation of symbols and safety instructions
1.1 Explanation of symbols
Warnings
In warnings, signal words at the beginning of a warning are used to indicate the type
and seriousness of the ensuing risk if measures for minimizing danger are not taken.
The following keywords are defined and can be used in this document:
DANGER
DANGER indicates that severe or life-threatening personal injury will occur.
WARNING
WARNING indicates that severe to life-threatening personal injury may occur.
CAUTION
CAUTION indicates a hazardous situation which, if not avoided, could result in minor
to moderate injury.
NOTICE
NOTICE is used to address practices not related to personal injury.
Important Information
The info symbol indicates important information where there is no risk to people or
property.

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Explanation of symbols and safety instructions
Additional symbols
Symbol Explanation
▶Sequence of steps
Cross-reference to another part of the document
•Listing/list entry
– Listing/list entry (2nd level)
Table 1
1.2 Safety instructions
HGeneral information
This manual is available in English and French.
▶ Keep this manual for future use.
▶ Observe the safety instructions of this manual
before putting the heating appliance into operation.
Iftheinformationinthismanualisnotfollowed exactly,
a fire or explosion may result causing property
damage, personal injury or loss of life.
▶ Do not store or use gasoline or other flammable
vapors and liquids in the vicinity of this or any other
appliance.

Explanation of symbols and safety instructions
Greenstar FS/Combi FS – 6720810589 (2021/01)
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▶ What to do if you smell gas
– Do not try to light any appliance.
– Do not touch any electrical switch; do not use any
phone in your building.
– Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
– If you cannot reach your gas supplier, call the fire
department.
▶ Installation and service must be performed by a
trained and certified heating contractor, service
agency or the gas supplier.
HIf you smell gas
▶ Turn off the gas shut-off valve.
▶ Open windows and doors.
▶ Do not touch any electrical switch, telephone, and
do not use outlets.
▶ Extinguish all open flames.
▶ Do not smoke!
▶ Do not use lighters!
▶ Warn all occupants of the building, but do not ring
any bell.

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Explanation of symbols and safety instructions
▶ From outside the building, call the gas supply
company and a trained and certified installer or
service company.
HIf you smell flue gas
▶ Switch OFF the appliance (page 15).
▶ Open windows and doors.
▶ Inform a trained and certified heating contractor.
HFor appliances operating on room air:
Danger of flue gas poisoning if supply of
combustion air is insufficient
▶ Safeguard supply of combustion air.
▶ Do not cover or reduce the size of ventilation
openings in doors, windows and walls.
▶ Safeguard sufficient supply of combustion air also
for appliances installed at a later date, e.g. kitchen
exhaust fans, clothes dryers, and air conditioning
units with vent to the outside.
▶ Never operate the appliance if the supply of
combustion air is insufficient.
HDanger of explosion of flammable gases
▶ Only employ a trained and certified contractor to
carry out work on the gas train.

Explanation of symbols and safety instructions
Greenstar FS/Combi FS – 6720810589 (2021/01)
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HRisk of scalding
▶ If running at DHW temperatures above 104 °F
(40
°C) ask a trained and certified heating
contractor to install a tempering valve to prevent
scalding.
▶ When the thermal disinfection function is
enabled, DHW temperatures above 140
°F (60 °C)
can occur.
HRisk of damage due to operator error
Operator errors can result in personal injury and
damage to property.
▶ Ensure that children never operate this appliance
unsupervised or play with it.
▶ Ensure that only people who know to operate this
appliance correctly have access to it.
HInstallation, conversion
Only have the appliance installed or modified by a
trained and certified heating contractor.
Never modify any parts that carry flue gas.
Never close the outlet of safety valves. Water may be
expelled from any safety valve during heat-up.

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Explanation of symbols and safety instructions
HInspection and maintenance
The operator is responsible for safety and
environmental compliance of the heating system.
Sign a maintenance and inspection contract with a
trained and certified contractor, covering an annual
inspection and demand-dependent maintenance.
This guarantees high efficiency and environmentally
sound combustion.
HExplosive and easily combustible materials
Never use or store easily combustible materials
(paper, thinners, paints, etc.) near the appliance.
HCombustion air / room air
To prevent corrosion, keep the supply of
combustion
air / room air free of corrosive substances
(e.g. halogenated hydrocarbons that contain chlorine
or fluorine compounds).
HOverheating of the appliance
Should overheating occur or the gas supply fail to shut
off, do not turn off or disconnect the electrical supply
to the pump. Instead, shut off the gas supply at a
location outside of the appliance.

Information about the appliance
Greenstar FS/Combi FS – 6720810589 (2021/01)
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HIn case of water damage
Do not use this boiler if any part has been under water.
Immediately call a trained and certified service
technician to inspect the boiler and to replace any part
of the control system and any gas control which has
been under water.
2 Information about the appliance
2.1 Certifications
This product has been tested and certified for the US and the
Canadian market and complies with all applicable standards
required for the US and the Canadian market.
2.2 Proper use
The appliance may only be installed in closed loop hot water central heating systems.
Any other purpose is considered improper use. Any resulting damage is excluded
from the manufacturer's warranty.
The commercial and industrial use of the appliance for generating process heat is not
permitted.

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Prepare for operation
2.3 Overview of boiler types
Table describes the meaning of the model number:
KBR21-3 Heat only appliance A 23
KBR28-3 Heat only appliance A 23
KBR35-3 Heat only appliance A 23
KBR42-3 Heat only appliance A 23
KWB28-3 Combi appliance A 23
KWB35-3 Combi appliance A 23
KWB42-3 Combi appliance A 23
Table 2 Appliances types
KFloor standing heating appliance
WDHW heating
BCondensing technology
RConstant temperature control
21..42 Output in kW. 42kW = 143 310BTU/hr
-3 Version
AFan-supported appliance
23 Natural gas (NG)
3 Prepare for operation
▶ If existing, open the heating supply valve and the heating return valve.
▶ if existing, open the cold water valve and the DHW valve.
▶ When using KBR..-3A appliance with DHW tank, open a DHW tap until water run
out.
▶ Open the gas cock
▶ Open the control cover.

Prepare for operation
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3.1 Checking the boiler water pressure
The standard boiler water pressure is 14.5 - 21.75 psi (1 - 1.5 bar).
Should a higher boiler water pressure be required, refer to a trained and certified
heating contractor.
0010026578-001
1
0
2
3
4
bar
psi
15
30 45
Fig. 1 Pressure gauge
3.2 Topping up the heating system water
Topping up the heating system water is different on every system. Therefore, you
should ask a trained and certified heating contractor to show you how it is done.
Maximum pressure of 30 psi (2.07 bar) at maximum heating water temperature
must not be exceeded (safety valve will spill).

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Operation
4 Operation
These operating instructions apply only to the boiler.
Depending on the heating control unit used, some functions may vary.
The following options for controlling the heating system are available:
• Weather compensating control unit installed in the boiler
• Weather compensating control unit mounted on the wall
• Room thermostat
• Weather compensating control with room influence (room thermostat)
• Third party system control unit
Therefore, please read the operating instructions for the heating control unit used.
Page 32 contains a quick reference.

Operation
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4.1 Overview of controls
0010026577-001
1234 5 6789
12 10
11
Fig. 2 Control panel
[1] Emission test button for contractors (see installation instructions)
[2] Service button for contractors (see installation instructions)
[3] Burner operation indicator lamp
[4] ON/OFF switch
[5] Key pad lock
[6] ECO button
[7] Reset button
[8] Display
[9] System water pressure gauge
[10] DHW temperature control
[11] Blank panel for optional programmer
[12] Heating temperature control

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Operation
4.2 Switching the appliance ON/OFF
Startup
▶ Switch the appliance ON using the ON/OFF switch.
The display shows the supply temperature of the hot water in °F necessary,
convert to °C (a Service function O.E: Metric or US costomary units).
max
1
2
34
5
6
6 720 613 896-05.1O
Fig. 3
If the display shows in alternation with the supply temperature, the trap filling
function is active.
Shutdown
▶ Switch the appliance OFF using the ON/OFF switch.
The display goes out.
▶ If the appliance is taken out of service for a longer period: observe frost
protection (section 4.8).

Operation
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4.3 Turning the space heating ON
The maximum supply temperature can be set from 95 °F (35 °C) up to approx. 194 °F
(90 °C). The current supply temperature is shown on the display.
With radiant floor heating, limit the maximum permissible supply temperature.
▶ Adjusting the supply temperature with the heating temperature control (:
– Radiant floor heating: e.g. setting 3(approx. 122 °F (50 °C))
– Panel or cast iron radiator heating: setting 6(approx. 167 °F (75 °C))
– Heating with supply temperatures up to 194 °F (90 °C): setting max
eco
reset
6 720 641 933-53.1O
max
1
2
34
5
6
max
1
2
34
e
6
min
Fig. 4

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Operation
The burner ON indicator lamp lights up if the burner is operating.
Boiler high limit
dial (
Typical supply
temperatures
Sample application
1 approx. 95 °F (35 °C) Frost protection
2 approx. 109 °F (43 °C)
3 approx. 122 °F (50 °C) Radiant floor heating system
4 approx. 140 °F (60 °C)
5 approx. 153 °F (67 °C)
6 approx. 167 °F (75 °C) Radiator heating system
max approx. 194 °F (90 °C) Convector heating
Table 3 Typical supply temperatures
4.4 Programming the heating control unit
Observe the operating instructions for the heating control unit included in the scope
of delivery. There you can read:
▶ How to set the operating mode
▶ How to adjust the room temperature
▶ How to heat economically and save energy

Operation
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4.5 KBR..-3A appliances with DHW tank:
Setting
the DHW temperature
DANGER
Risk of scalding!
▶ in normal operation, it is recommended to limit the DHW temperature to 122 °F
(50 °C) to limit the risk of scalding.
▶ Only set temperature up to 158 °F (70 °C) for thermal disinfection page 26.
▶ Set the DHW temperature on the DHW thermostat *. The set DHW temperature
flashes on the display for 30 seconds.
6 720 641 933-54.1O
max
1
2
34
5
6
reset
eco
max
1
2
34
e
6
if there is reason for concern for contamination from bacteria such as Legionella,
consider setting the DHW thermostat * to at least “e” (131 °F (55 °C)). This setting
ensures an economical and comfortable DHW generation. Consult your local water
department or municipality for further information.
DHW thermostat *Typical DHW temperatures
min approx. 59 °F (15 °C)
e approx. 131 °F (55 °C)
max approx. 158 °F (70 °C)
Table 4

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Greenstar FS/Combi FS – 6720810589 (2021/01)
Operation
Always set the DHW temperature as low as possible. A lower setting on the
thermostat means a higher rate of energy savings. Futhermore, higher DHW
temperatures result in increased limescale deposits and thereby may impair the
function of the appliance (e.g. longer times for heating up or lower output).
Eco button
Pressing and holding the ECO button until it lights up switches from Comfort mode
to Economy mode.
•Comfort mode, ECO button is not lit (default setting)
In comfort mode, the DHW tank has priority. The DHW tank is heated to the set
temperature first. Then the appliance switches to central heating mode.
•Economy mode, ECO button lit
In Economy mode, the appliance alternates between central heating and DHW mode.
4.6 KWB..-3A appliances (combi boilers):
Setting the DHW temperature
▶ Set the DHW temperature on the DHW thermostat *.
The set DHW temperature flashes on the display for 30 seconds.
6 720 641 933-55.1O
max
1
2
34
5
6
reset
eco
max
1
2
34
e
6
Fig. 5

DHW thermostat *Typical DHW temperatures
min approx. 104 °F (40 °C)
e approx. 122 °F (50 °C)
max approx. 140 °F (60 °C)
Operation
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Table 5
ECO button
When the ECO button is unlit, the appliance is in Comfort mode.
Pressing and holding the ECO button until its lights up switches from Comfort mode
to Economy mode.
•Comfort mode (default setting)
The appliance is continually maintained at the set temperature. Consequently,
DHW draws are immediate, however the appliance may run even if no DHW is
being drawn.
•Economy mode, ECO button lights up
– DHW is only generated when DHW is drawn.
–On demand: Quickly open and close a DHW tap to signal the appliance to
heat to the selected temperature. After a short wait DHW will be available.
The DHW on demand signal allows maximum gas and water savings.
4.7 Setting manual summer mode
In summer mode or warm weather shut down (WWSD), the heating zone pump and
consequently central heating are switched off. DHW generation remains active
following the DHW program.