Bosch Worcester Greenstar 24 User manual

UK/IE
USER INSTRUCTIONS
WALL HUNG RSF GAS FIRED CONDENSING COMBINATION BOILER
GREENSTAR 24/28/30
6720801019-00.1Wo
FOR SEALED CENTRAL HEATING SYSTEMS AND MAINS FED
DOMESTIC HOT WATER
6 720 811 923 (2014/07) UK

2
Preface
6 720 811 923 (2014/07)
PREFACE
PLEASE READ THESE INSTRUCTIONS CAREFULLY
These instructions are applicable to the Worcester, Bosch Group boiler model stated
on the front cover only.
These instructions apply in the UK/IE only and must be followed except for any
statutory obligation.
After installation please leave this User instruction Manual, Installation,
Commissioning and Servicing Instructions and completed Benchmark Checklist with
the user.
DEDICATED TO HEATING COMFORT
Thank you for purchasing a Greenstar gas-fired condensing combination boiler
manufactured by Worcester, Bosch Group. The company prides itself on
manufacturing boilers to the strictest quality control standards throughout every
stage of production.
Worcester, Bosch grouphas led the field in innovative boiler design and performance
for over 50 years. This heritage means all our products are of exceptional quality and
proven reliability.
The Greenstar range in particular is extremely energy efficient, offering you
economical running costs and value for money. It sits in SEDBUK Band A, and is
therefore amongst the top energy rated boilers available.
There is also the reassurance of ourno-nonsense 2 years parts and labour guarantee
- backed up by Worcester Total Cover, an optional complete maintenance scheme to
keep your boiler operating at peak condition and efficiency.

3
Contents
6 720 811 923 (2014/07)
CONTENTS
1 Symbols and safety precautions . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Explanation of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Safety precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Opening the control panel cover . . . . . . . . . . . . . . . . . . . . . . . . 8
4 Overview of controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 Switching the appliance on/off . . . . . . . . . . . . . . . . . . . 10
5.2 Switching on the central heating . . . . . . . . . . . . . . . . . . 11
5.3 System controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.4 Setting hot water temperature . . . . . . . . . . . . . . . . . . . 13
5.5 Frost protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.6 Button lock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.7 Boiler reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.8 Display codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.9 Extreme cold weather . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4
Contents
6 720 811 923 (2014/07)
6 System Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1 Sealed heating systems . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.2 External filling loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7 Fault or Breakdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8 Environment / disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9 Tips on energy saving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
10 Your guarantee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
11 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
12 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
13 Quick reference guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

5
Symbols and safety precautions
6 720 811 923 (2014/07)
1SYMBOLSANDSAFETY PRECAUTIONS
1.1 EXPLANATION OF SYMBOLS
WARNING SYMBOLS
Signal words indicate the seriousness of the hazard in terms of the consequences of
not following the safety instructions.
•NOTICE indicates possible damage to property or equipment, but where there is
no risk of injury.
•CAUTION indicates possible injury.
•WARNING indicates possible severe injury.
•DANGER indicates possible risk to life.
IMPORTANT INFORMATION
ADDITIONAL SYMBOLS
Safety instructions in this document are framed and identified by
a warning triangle which is printed on a grey background.
Notes contain important information in cases where there is no
risk of personal injury or material losses and are identified by the
symbol shown on the left. They are bordered by horizontal lines
above and below the text.
Symbol Meaning
▶ a step in an action sequence
a reference to a related part in the document or to other related
documents
• a list entry
– a list entry (second level)

6
Symbols and safety precautions
6 720 811 923 (2014/07)
1.2 SAFETY PRECAUTIONS
IF YOU SMELL GAS!
A gas leak could potentially cause an explosion.
If you smell gas, observe the following rules.
▶ Prevent flames or sparks:
– Do not smoke, use a lighter or strike matches.
– Do not operate any electrical switches or unplug any equipment.
– Do not use the telephone or ring doorbells.
▶ Turn off the gas at the meter.
▶ Open windows and doors.
▶ Leave the building and warn your neighbours.
▶ Prevent anyone from entering the building.
▶ Well away from the building: call the National Gas Emergency Service on 0800
111 999.
BOILER OPERATION:
This boiler must only be operated by a responsible adult who has been instructed in,
understands and is aware of the boiler's operating conditions and effects.
COMBUSTIBLE AND CORROSIVE MATERIALS:
Chemically aggressive substances can corrode the boiler and invalidate any
guarantee.
• Do not store or use any combustible materials (paper, thinners, paints,
propellants, cleaning agents etc.) inside or within the vicinity of the appliance.
FITTINGS AND MODIFICATIONS:
Only a competent engineer can remove the boiler case and carry out any work, in
accordance with the Gas Safety (Installation and Use) Regulations.
•Donotremovetheboilercase.
Any misuse or unauthorised modifications to the boiler, flue or associated
accessories and heating system will invalidate the guarantee.
• Do not modify the boiler or flue system in any way.
Worcester, Bosch Group accepts no liability arising from any such actions. This does
not affect your statutory rights.

7
General information
6 720 811 923 (2014/07)
2 GENERAL INFORMATION
SERVICING
• The boiler must be serviced regularly by a competent, qualified person, such as
a Worcester service engineer or other Gas Safe registered engineer.
• Always use original spares, to help maintain the efficiency, safety and reliability
of the boiler and have the Service Record completed in the Benchmark Checklist.
The completed Benchmark Checklist will be required in the event of any guarantee
work and may be required by the local Building Control Inspector.
BENCHMARK STANDARD
The Benchmark initiative is a code of practice to
encourage the correct installation, commissioning and
servicing of domestic central heating boilers and
system equipment.
A “checklist” is dispatched with every boiler. This is a vital document that needs to be
completed by the installer at the time of installation. It confirms that the boiler has
been installed and commissioned according to the manufacturer's instructions.
The log book provides space for the recording of regular servicing of the boiler/
heating system and this can become a valuable document when, for example, you
wish to sell the property. The log book will show a potential purchaser that the
heating system has received regular professional maintenance and servicing during
its lifetime.
The Benchmark initiative aims to:
• Raise standards among professional installers
• Build and maintain high safety standards in the industry
• Improve customer satisfaction levels
• Make a contribution to the nation's commitment to climate change
Ensure that the service engineer completes the Service Record in
the Benchmark Checklist after each service. The Benchmark
Checklist and service interval record can be found at the rear of
the Installation, Commissioning and Servicing Instructions.

8
Opening the control panel cover
6 720 811 923 (2014/07)
3 OPENING THE CONTROL PANEL COVER
Fig. 1
▶ To unlatch the flap, push and release at the point indicated.
▶ To close and secure the flap, swing up and push in once to latch.
6 720 612 660-01.2R

9
Overview of controls
6 720 811 923 (2014/07)
4OVERVIEWOFCONTROLS
Fig. 2 Basic boiler controls
[1] Service engineer symbol = boiler is set to maximum or minimum output for
service
[2] Service button for heating engineers
[3] Indicator for burner operation
[4] Boiler ON/OFF - does not electrically isolate the boiler
[5] Button lock
[6] Eco button
[7] Reset button
[8] Display
[9] Hot Water temperature control
[10] Pressure gauge
[11] Position for optional programmer
[12] Central Heating temperature control
[13] Indicator for burner operation (ON)/faults (flashing)
6720801019-01.2Wo
1 2 4 5 6 7 8 103
11 12 13
9

10
Operation
6 720 811 923 (2014/07)
5OPERATION
5.1 SWITCHING THE APPLIANCE ON/OFF
SWITCHING ON FOR THE FIRST TIME
▶ Switch appliance on at the main switch.
The display indicates the current heating water flow temperature.
The indicator for burner operation/faults is permanently on, as long as the burner
is operational.
Fig. 3
• Please do not turn your boiler OFF. If you switch your boiler off your frost
protection mode will be deactivated.
• Switching the boiler OFF does not electrically isolate the appliance. Your installer
must isolate the mains electricity before starting work and observe all relevant
safety precautions.
• In the event of an electrical power interruption when the boiler re-starts it will
enter a start-up mode for approximately 15 minutes duration.
The trap filling function ensures that the condensate trap is filled after the appliance
is first installed or if it has not been used for a long period. For that reason, the
appliance is held at minimum heat output for 15 minutes.
When the flow temperature alternates with the symbol on
the display, the trap filling function is active.
max
1
2
34
5
6
6 720 613 896-05.1O

11
Operation
6 720 811 923 (2014/07)
5.2 SWITCHING ON THE CENTRAL HEATING
The maximum flow temperature can be set to between 35°C and approx. 90°C.
▶ Turn CH flow temperature control to adjust the max. CH flow temperature
according to the central heating system:
– Underfloor heating: e.g. position 3(approx. 50°C)
– Low-temperature heating system: position 6
(approx. 75°C)
– Heating system for flow temperatures up to 88°C:
max position
Fig. 4
When the burner is alight, the green indicator lights up.
With underfloor heating systems, take care to observe the
maximum permissible CH flow temperatures.
Position CH flow temperature Position CH flow temperature
1 Approx. 35 °C 4Approx.60°C
2Approx.43°C 5Approx.67°C
3Approx.50°C 6 Approx. 75 °C
max Approx. 90 °C
Table 1
eco
reset
6 720 615 065-12.1O
max
1
2
34
5
6
max
1
2
34
e
6
min

12
Operation
6 720 811 923 (2014/07)
5.3 SYSTEM CONTROLS
These Operating Instructions apply only to the boiler.
Depending on the room thermostat and optional programmer used, some functions
may be controlled differently.
Fig. 5
Therefore, please read the operating instructions for the heating
controller used.
Follow the operating instructions for the heating controller used.
Those instructions will tell you
▶ how to set the operating mode and the heating curve for
weather-dependent controllers,
▶ how to adjust the room temperature,
▶ how to heat economically and save energy.
912
h
15
18
21
24
h
3
6
6 720 612 660-07.2O

13
Operation
6 720 811 923 (2014/07)
5.4 SETTING HOT WATER TEMPERATURE
▶ Set the hot water temperature on the hot water temperature control .
The set hot water temperature is shown flashing on the display for 30 seconds.
Fig. 6
Hot water temp. control Hot water temperature
min to 1 Approx. 40 °C
e Approx. 50 °C
6 to max Approx. 60 °C
Table 2
6 720 614 156-10.1O
max
1
2
34
5
6
reset
eco
max
1
2
34
e
6

14
Operation
6 720 811 923 (2014/07)
ECO BUTTON
Pressing and holding the Eco button until it lights up switches between Comfort
mode and Economy mode.
COMFORT MODE, ECO BUTTON IS NOT LIT (DEFAULT SETTING)
The appliance is held constantly at the set temperature. This means that hot water
is available almost instantaneously at the tap.
Consequently the appliance will switch on at intervals, even if no hot water is being
drawn.
ECONOMY MODE, ECO BUTTON LIT
• The water is not heated up until a hot water tap is turned on.
•Signalling demand.
Briefly turning a hot water tap on and then off signals demand so that the water
is then heated up to the set temperature.
Signalling demand enables maximum gas and water economy.

15
Operation
6 720 811 923 (2014/07)
5.5 FROST PROTECTION
Frost Protection is active as long as there is power to the boiler.
If the temperature within the boiler falls below 8°C the pump will run to circulate
water and prevent the system freezing.If the temperature within the boiler falls
below 5°C the boiler will fire periodically, bringing the boiler temperature up to 12°C
to avoid the possibility of the system freezing.
This process will be repeated until such time that the boiler temperature does not
drop below 5°C.
Fig. 7
eco
reset
max
1
2
3
5
6
max
1
2
34
e
6
min

16
Operation
6 720 811 923 (2014/07)
5.6 BUTTON LOCK
The button lock affects the CH flow temperature control, the hot water temperature
control and all buttons except the main switch and the service engineer mode button.
To switch on the button lock:
▶ Press and hold the button until the display shows .
Fig. 8
To switch off the button lock:
▶ Press and hold the button until the display shows only the CH flow temperature.
max
1
2
34
5
6
max
1
2
34
e
6
eco
reset
min

17
Operation
6 720 811 923 (2014/07)
5.7 BOILER RESET
In the unlikely event of a fault occurring while the appliance is in operation:
The reset button will flash once per second and the mains indicator (blue light) also
flashes. The display will show a fault code.
To reset the boiler, press the reset button until is displayed. The reset button
will no longer be illuminated and the blue light will stop flashing.
If the reset was successful the boiler will return to normal operation, depending on
programmer and room thermostat settings.
If the reset was not successful then the blue light will continue to flash and a fault
code will be displayed again.
Info symbol: If the fault remains and cannot be cleared by pressed the reset button,
or if the fault persists please contact Worcester, Bosch Group for assistance on
0330 123 3366.
In the event of a fault, the reset button will flash once per second and the blue mains
indicator light will flash.

18
Operation
6 720 811 923 (2014/07)
5.8 DISPLAY CODES
Display code Description
Inspection due
Button lock active
Trap filling function active
Air purge function active
Excessively rapid increase in CH flow temperature (temp.
gradient monitoring).
Heating mode is disabled for two minutes.
Not applicable in the UK.
Not applicable in the UK

19
Operation
6 720 811 923 (2014/07)
5.9 EXTREME COLD WEATHER
In some instances where the condensate pipe work is run externally or in an
unheated area, such as a garage, the condensate pipe work can be at risk of freezing,
even if well insulated.
A frozen/blocked condensate pipe will cause the boiler to shut down.
If the condensate pipe has frozen:
▶ Locate the blockage.
It is likely that the pipe is frozen at the most exposed point outside the building or
where there is an obstruction to flow.
This could be the open end of the pipe, at a bend or elbow, or where there is a sag
in the pipe in which condensate can collect.
The location of the blockage should be identified as closely as possible before
taking further action.
▶ Thaw the frozen pipe.
The pipe can be thawed by applying a hot water bottle, a microwaveable heating
pack (the sort used for muscular aches and pains) or a cloth soaked in hot water
to the exterior of the pipe, close to the point of blockage.
Hot water, but not boiling, can also be poured onto the pipe from a watering can
or similar container.
▶ Once the pipe has been thawed the boiler must be reset, press the reset button
for five seconds and wait two to three minutes for the boiler to restart.
WARNING: Falling hazard!
Failure to follow this guidance may result in personal injury.
▶ Only attempt to thaw a condense pipe that is at ground level, and
that is easily accessible.
▶ Never attempt to thaw a condense pipe that is at height.
CAUTION: Pipe damage
▶DO NOT use boiling water to thaw the condensate pipe!

20
System Pressure
6 720 811 923 (2014/07)
▶ If the boiler does not restart, contact Worcester, Bosch Group Appointments
team on: 0330 123 3366.
▶ Contact your installer in order to find a permanent solution to the problem.
6 SYSTEM PRESSURE
6.1 SEALED HEATING SYSTEMS
This boiler is fitted to a sealed heating system which is pre-pressurised.
Your installer will advise you of the minimum and maximum pressure indicated on the
pressure gauge.
▶ Check regularly that the pressure is maintained.
Fig. 9 Optimum pressure when the boiler is cold (area A)
▶ Contact your installer or maintenance engineer if a permanent significant
decrease or increase in pressure is indicated on the pressure gauge.
The filling method will be an external filling loop, fitted valves and flexible hose.
NOTICE: To comply with the Water Authority regulations you must
disconnect the external filling loop after re-pressurisation.
6720643356-11.1Wo
2
3
1
04
bar
1
A
Min
1 bar
1.5 bar
Max