Bosch Optiflow GWH16 3 CT E23 F6 L S2405 User manual

Installation Manual
Gas continuous flow water heaters
Optiflow
6720817545-00.1V
GWH16/20/26 3 CT E23/31 F6 L S2405
6 720 817 545 (2016/02) AU
Read installation manual prior to installation of this appliance!
Read user manual before putting this unit in operation!
Observe the warnings in the manuals!
The installation location must meet the requirements for sufficient ventilation!
Installation by an authorised person only!

6 720 817 545 (2016/02) Optiflow
2 | Index
Index
1 Key to symbols and safety instructions . . . . . . . . . . 3
1.1 Key to symbols . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Safety Information . . . . . . . . . . . . . . . . . . . . . 3
2 Product details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Declaration of Conformity . . . . . . . . . . . . . . 5
2.2 Model overview . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Included items . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4 Rating plate . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.5 Description of appliance . . . . . . . . . . . . . . . . 5
2.6 Optional accessories . . . . . . . . . . . . . . . . . . . 5
2.7 Dimensions and minimum clearances . . . . . 6
2.8 Appliance layout . . . . . . . . . . . . . . . . . . . . . . 7
2.9 Electrical wiring diagram . . . . . . . . . . . . . . . 8
2.10 Specification . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4 Installation (only by authorised technicians) . . . . 10
4.1 Choice of installation site . . . . . . . . . . . . . . 10
4.1.1 Regulations concerning the
installation site . . . . . . . . . . . . . . . . . . . . . . 10
4.2 Minimum clearances . . . . . . . . . . . . . . . . . . 11
4.3 Installing the appliance . . . . . . . . . . . . . . . . 11
4.4 Water connection . . . . . . . . . . . . . . . . . . . . 12
4.4.1 Temperature mixing device (not supplied
with the appliance) . . . . . . . . . . . . . . . . . . . 12
4.5 Gas connection . . . . . . . . . . . . . . . . . . . . . . 12
4.6 Altitude of installation site . . . . . . . . . . . . . 12
4.7 Remote control connection (optional) . . . . 13
4.8 Electrical connection (only by authorised
technicians) . . . . . . . . . . . . . . . . . . . . . . . . 13
4.8.1 Connecting the power cable . . . . . . . . . . . . 13
4.9 Commissioning of the appliance . . . . . . . . 14
4.10 Changing the setpoint limit temperature
(only for 55 °C preset appliances) . . . . . . . 14
4.11 Delivery temperature calibration . . . . . . . . 14
5 Regulating the gas (only for authorised
technicians) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1 Factory settings . . . . . . . . . . . . . . . . . . . . . . 15
5.2 Service function . . . . . . . . . . . . . . . . . . . . . 15
5.3 Adjusting the appliance . . . . . . . . . . . . . . . 15
5.3.1 Access to test pointsads . . . . . . . . . . . . . . . 15
5.3.2 Adjusting the maximum flow
(Parameter P1) . . . . . . . . . . . . . . . . . . . . . .15
5.3.3 Adjusting the minimum flow
(Parameter P2) . . . . . . . . . . . . . . . . . . . . . .16
5.3.4 Adjusting pressure at the burner
(Parameter P0) . . . . . . . . . . . . . . . . . . . . . .16
5.4 Factory default settings . . . . . . . . . . . . . . . 17
6 Maintenance (only by authorised service
technician) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
6.1 Periodic maintenance . . . . . . . . . . . . . . . . . 17
6.2 Replacement of the fuse (electronic
control unit) . . . . . . . . . . . . . . . . . . . . . . . . .18
6.3 Start-up after completion of maintenance 18
7 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8 Environment considerations . . . . . . . . . . . . . . . . . . 21
9 Water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
10 Warranty details . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

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Key to symbols and safety instructions | 3
1 Key to symbols and safety instructions
1.1 Key to symbols
Warnings
The following keywords are defined and used in this document:
•NOTICE indicates a situation that could result in damage to
property or equipment.
•CAUTION indicates a situation that could result in minor to
medium injury.
•WARNING indicates a situation that could result in severe
injury or death.
•DANGER indicates a situation that will result in severe
injury or death.
Important information
Additional symbols
1.2 Safety Information
If you smell gas:
▶ Close the gas supply valve to the appliance.
▶ Isolate gas supply from gas meter or LPG cylinder.
▶ Do not operate any electrical appliances or switches (on/
off).
▶ Extinguish other sources of ignition.
▶ Go to a different location and call the gas supplier or an
authorised technician in order to check the gas supply.
If you notice dark combustion gases or sooting:
▶ Isolate the gas supply to the heater.
▶ Notify an authorised technician.
Installation, assembly, and modifications
Installation, assembly, and modifications to the heater must
only be performed by an authorised technician.
Maintenance
▶ The water heater is required to have a service and safety
inspection every two years.
▶ The installer is responsible for the safety and
environmental compatibility of the installation, according
to local regulations.
▶ The owner/user is responsible for keeping the area around
the water heater free from debris.
▶ Safe access to inspect and service the water heater is the
responsibility of the property owner.
▶ Use only genuine Bosch spare parts.
Explosive and flammable material
▶ Do not store or use flammable material (paper, spray cans,
solvents, paints, etc) near the heater.
Combustion air and surrounding air
▶ The combustion air and surrounding air must be free from
corrosive substances.
▶ Do not spray aerosols or use chemicals around the heater
unless heater is disconnected from the power supply.
Risk of damage due to user error
User error can result in injury and damage to property.
▶ Ensure that children never play with or operate this
appliance.
▶ Ensure that only personnel who can operate this appliance
correctly have access to it.
▶ Refer to the operating and user instructions before
adjusting the water heater.
To be installed and serviced only by an authorised person
The “authorised installing person” is responsible for:
• Correct installation and commissioning of this appliance.
• Ensuring the appliance performs to the specifications
stated on the rating label.
• Demonstrating the operation of the appliance to the
customer before leaving.
• Handing the operating instructions to the customer.
THIS APPLIANCE IS NOT SUITABLE FOR POOL OR SPA POOL
APPLICATIONS.
NOT SUITABLE FOR COMMERCIAL BOOSTING OF A WARM
WATER RECIRCULATION SYSTEM
Warnings in this document are identified by a
warning triangle printed against a grey
background.
Keywords at the start of a warning indicate
the type and seriousness of the ensuing risk
if measures to prevent the risk are not taken.
This symbol indicates important information
where there is no risk to people or property.
Symbol Explanation
▶ Step in an action sequence
Cross-reference to another part of the document
•Listentry
– List entry (second level)
Table 1

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4 | Key to symbols and safety instructions
Regulations
All local by-laws and regulations pertaining to installation and
use of gas appliances must be observed.
This appliance must be installed in accordance with the
manufacturers installation instructions, AS/NZS5601, AS/
NZS3500, and all Local Building & Gas fitting regulations.
This appliance must not be installed indoors or in an enclosed
space. This appliance is approved for outdoor installation only.
Do not install this appliance withany modification or alteration.
Failure to install this appliance in accordance with these
installation instructions will void the warranty and may create
an unsafe situation.
Installation
Important information
▶ Determine the most appropriate location for the appliance.
Install only on an external wall as close as possible to the
most frequently used hot water outlet.
▶ Ensure the mounting structure is capable of supporting the
weight of the appliance once installed. Secure the
appliance to the wall using fixings suitable for the weight of
the appliance and the wall material.
▶ Install gas and water isolation valves as close as possible to
the appliance. Only use a gate valve or full flow ball valve
(fixed mechanism type) for cold water.
▶ Check the cold water supply pressure to ensure it meets
the required supply pressure for the appliance. (see
table 5, page 9).
▶ If inlet water pressure exceeds 800 kPa a pressure limiting
valve (500 kPa) MUST be fitted. The preferable location for
the pressure limiting valve is at the water meter.
▶ Where the pressure limiting valve is less than 3 metres from
the hot water unit, it must be fitted in conjunction with a
cold water expansion valve (700 kPa), between the water
heater and the pressure limiting valve.
▶ Failure to comply with this requirement may void the
warranty.
▶ Refer to AS/NZS5601 for the relevant gas pipe sizing.
▶ After finishing the gas piping system, the pipes must be
thoroughly purged and leak tested. This test must be
performed with the gas isolation valve of the appliance
closed.
▶ Ensure the gas pressure and flow through the regulator are
appropriate for the consumption of the heater (see table 5,
page 9). Refer to AS/NZS5601.1 for the relevant pipe size.
Note: Incorrect pipe sizing or gas supply pressure may cause
the appliance to under perform. Service calls for incorrect pipe
sizing and/or gas pressure, will NOT be covered under
warranty.
Safety of electrical appliances for domestic use and similar
purposes
The following requirements apply in accordance with AS/
NZS60335 in order to prevent hazards from occurring when
using electrical appliances:
DANGER:
This appliance must not be installed indoors
or in an enclosed space in accordance with
AS/NZS5601.
DANGER: Explosion Risk!
▶ Always turn off the gas valve before
carrying out any work on components
which carry gas.
DANGER: Appliance malfunction!
This appliance must be installed with no
obstructions to air entry openings.
▶ Periodic checking of openings to ensure
no blockage or obstruction from plants,
debris or insects must be carried out.
The installation of gas, water, and electrical
supply, and the initial startup are to be
performed by an authorised person.
Not suitable for pool or spa pool applications.
Not suitable for commercial boosting of
warm water recirculation systems.
Installation in marine environments can lead
toprematurecorrosion.Prematurecorrosion
due to the installationenvironment would not
be covered by warranty.
All gas appliances require adequate air intake
to ensure correct combustion. Insects and
dirt ingress may affect combustion causing
sooting. If you notice sooting from the flue
outlet the unit would require servicing. Pest
and dirt ingress is not covered by the
manufacturers warranty.

6 720 817 545 (2016/02)Optiflow
Product details | 5
“This appliance can be used by children of 8 years and older, as
well as by people with reduced physical, sensory or mental
capabilities or lacking in experience and knowledge, if they are
supervised and have been given instruction in the safe use of
the appliance and understand the resulting dangers. Children
must not play with the appliance. Cleaning and user
maintenance must not be performed by children without
supervision.”
“If the power cable is damaged, it must be replaced by the
manufacturer, its customer service department or a similarly
qualified person, so that risks are avoided.”
2 Product details
2.1 Declaration of Conformity
The appliance has been tested and certified to Australian
Standards.
2.2 Model overview
[GWH]Gas continuous flow water heater
[16] Capacity (l/min)
[3] Generation
[CT] Thermostatic
[E] Electronic ignition
[23] Appliance set for natural gas
[31] Appliance set for LPG (universal LPG)
[F6] Outdoor installation
[L] Locked water temperature adjustment
2.3 Included items
• Gas continuous flow water heater
• Appliance documentation
2.4 Rating plate
The rating plate is located on the outside of the appliance, on
the bottom.
The plate specifies the performance of the appliance, approval
data and the serial number.
2.5 Description of appliance
• External wall-mounted appliance
• Appliance for operating with natural gas or LPG
• Electronic ignition
•Waterflowsensor
•Watervalve
• By-pass valve
• Temperaturesensorsformonitoringthe temperatureofthe
incoming, outgoing and mixed water of the appliance.
•Safetydevices:
–Flamesensorrod
–Thermalfuse
– Outgoing water temperature sensor
– Electronic control unit
–Airtemperaturesensor
– Frost-protection device
• Electrical connection: 230/240 V, 50 Hz
2.6 Optional accessories
• Main remote control
• Bathroom remote control
•RecessBox
• Flue diverters
Model GWH16/20/26 3 CT E23 F6 L S2405
Table 2
GWH 16 3CTE23F6 L
GWH 16 3CTE31F6 L
GWH 20 3CTE23F6 L
GWH 20 3CTE31F6 L
GWH 26 3CTE23F6 L
GWH 26 3CTE31F6 L
Table 3

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6 | Product details
2.7 Dimensions and minimum clearances
Fig. 1 Dimensions (in mm)
6720817545-02.1V
>10 >10
120
16065
344
45
55
105
524
170
Connections
Water Gas
Cold Hot Nat. LPG
GWH16/20/26 ¾ “ ¾“ ¾“ ¾“
Table 4

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Product details | 7
2.8 Appliance layout
Fig. 2
[1] Flue terminal
[2] Flame sensor rod
[3] Burner
[4] Air pressure test point
[5] Water flow sensor and Water valve
[6] Fan
[7] Cold water temperature sensor
[8] Hot water outlet
[9] Cold water inlet
[10] By-pass valve
[11] Gas inlet
[12] Electronic control unit
[13] Gas valve
[14] Gas pressure test point
[15] Ignition electrode
[16] Heat exchanger
1
2
3
4
6
5
8
911 1210
15
13
16
7
6720817545-01.1V
14

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8 | Product details
2.9 Electrical wiring diagram
Fig. 3 Electrical diagram
[1] Flame sensor rod
[2] Fan
[3] Ignition electrode
[4] Power supply
[5] Connection for frost-protection device
[6] Connection for remote control (optional)
[7] By-pass valve
[8] Modulation electrovalve (gas)
[9] Segmentation electrovalve 1 (gas)
[10] Segmentation electrovalve 2 (gas)
[11] Safety electrovalve (gas)
[12] Thermal fuse
[13] Water flow sensor
[14] Air temperature sensor
[15] Hot water temperature sensor
[16] Cold water temperature sensor
[17] Water valve
[18] Outlet water temperature sensor
230 V
AC
M1
5
1,2
3,4
5,6
7,8
9,10
11,12
13,14
10
15,16
1,2
3,4
5,6
7,8
9,10
11,12
13,14
M
6720813761-15.1V
132
4
6
7
8
9
11
13
14
15
16
17
18
12

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Product details | 9
2.10 Specification
Technical features Units 16L 20L 26L
Performance
Nominal gas consumption MJ/h 122 149 199
Minimum gas consumption MJ/h 18 18 25
Efficiency at 100% of nominal load % 81.5 82 81
Gas supply data
Minimum gas supply pressure (flowing)
Natural gas (when operating) kPa 1.13 1.13 1.13
Universal LP gas (when operating) kPa 2.75 2.75 2.75
Water supply data
Maximum permissible pressure (static) kPa 1000 1000 1000
Minimum operating pressure kPa 100 100 100
Minimum operation pressure for maximum performance kPa 300 300 300
Minimum water flow l/min 222
Maximum flow, corresponding to a temperature increase of 25 °C l/min 16 20 26
Maximum inlet temperature °C 80 80 80
Electrical circuit
Power supply voltage VAC 230/240 230/240 230/240
Frequency Hz 50 50 50
Maximum power consumption in standby (including frost protection) W 165 165 228
Maximum power consumption during operation W 57 57 70
General data
Weight (unpacked) kg 15 15 18
Height mm 520 520 520
Width mm 340 340 340
Depth mm 170 170 170
Table 5

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10 | Regulations
3Regulations
Any local by-laws and regulations pertaining to installation and
use of gas-fired appliances must be observed.
This appliance must be installed in accordance with the
manufacturers installation instructions, AS/NZS5601 and all
Local Building & Gas fitting regulations
It is recommended that sanitary fixtures used for the purpose
of personal hygiene have a temperature limiting device such as
a tempering valve be fitted as per AS3498.
This appliance must not be installed indoors or in an enclosed
space as per AS/NZS5601.
4 Installation (only by authorised
technicians)
Thermal solar system (thermosiphon)
Fig. 4 Thermal solar system
[1] Pre heated water line
[2] Incoming water
[3] Thermostatic valve
[4] Expansion tank or valve
[5] Pressure relief valve
[6] Hot water line
4.1 Choice of installation site
4.1.1 Regulations concerning the installation site
▶ Install the appliance outdoors. The top of the unit should be
positioned at less than 1800mm from the ground (the
bottom should remain at more than 300mm).
▶ The water heater may not be installed over a heat source.
▶ Comply with the minimum installation clearances indicated
in Fig. 5 and Table 6.
▶ Ensure there is an external weatherproof powerpoint in the
area and it is easily accessible after the installation of the
water heater.
Location of the appliance
The air intake of this appliance is located on the rear of the
DANGER:
This appliance must not be installed indoors.
DANGER: Explosion!
▶ Always shut off the gas valve before
carrying out work on gas pipes.
The appliance installation, electrical
connection, gas connection, and the initial
start-up, are operations to be carried out by
authorised technicians only.
CAUTION:
▶ The temperature of the incoming water
of the appliance must not exceed 80 °C.
▶ If the incoming water temperature
exceeds 80 °C, fit a 3-way or
thermostatic valve adjusted to less than
80 °C (solar transfer valve).
▶ In the case of a thermal solar system,
(see Fig. 4), ensure that the installation
has an expansion vessel or valve.
Installation in marine environments can lead
to premature corrosion. Premature
corrosion due to the installation environment
would not be covered by warranty.
Not suitable for pool or spa pool applications.
WARNING: Scalding!
Only for 55 °C preset appliances - This
appliance can deliver water exceeding
50 °C.
▶ Please refer to AS/NZS 3500.4 local
requirements and installation
instructions for additional temperature
control requirements.
6
2
1
3
6720817545-08.1V
T
5
4

6 720 817 545 (2016/02)Optiflow
Installation (only by authorised technicians) | 11
housing.
▶ Ensure this intake is free from vegetation and other
obstructions.
In order to prevent corrosion, the combustion air must not
contain any corrosive substances.
Substances classed as corrosion-promoting include
halogenated hydrocarbons containing chlorine and fluorine
compounds. They may be found in solvents, paints, adhesives,
aerosol propellants and household cleaners.
If these conditions cannot be guaranteed, a different site must
be chosen for the appliance.
Surface temperature
The maximum surface temperature of the appliance is below
85 °C. No special safety precautions are required with regard
to flammable building materials.
▶ Ensure local building codes and regulations are followed.
4.2 Minimum clearances
• Install the appliance in accordance with the minimum
installation clearances indicated in Fig. 5 and Table 6,
according to AS/NZS5601.
• The appliance must not be installed over a heat source.
• Do not obstruct the openings of appliance.
• The appliance must installed in a position that is easily
accessible to allow service work. It is recommended the
appliance is installed no more than 2m from the ground to
the base of the appliance.
• The areas 30cms above and below the appliance must be
clear of obstacles.
Fig. 5 Minimum flue clearances
4.3 Installing the appliance
▶ Remove the appliance from the packaging.
▶ Check that all the items indicated are included
(section 2.3).
▶ Remove the covers from the gas and water connections.
▶ Check that the gas type available matches that shown on
the sticker on the front of appliance, and on its dataplate.
6720817545-09.2V
N
CJ
B
J
A
C
A
K
G
A
H
N
F
J
A
C
K
BB
B
G
K
H
Flue terminal positions
for water heaters in accordance
with AS/NZ5601
D
DGM
P
K
EE
Item Min.clea-
rance (mm)
A Below eaves, balconies and other
projections
300
B From the ground, above a balcony or other
surface1)
1) unless appliance is certified for closer installation
300
C From a return wall or external corner1) 300
D From a gas meter (GM) 1000
E From an electricity meter or fuse box (P)2)
2) Prohibited area below electricity meter or fuse box extends
to ground level
500
F From a drain pipe or soil pipe 75
G Horizontally from any building structure 1)
or obstruction facing a terminal
500
H From any other flue terminal, cowl, or
combustion air intake1)
300
J Horizontally from an openable window, door, non-
mechanical air inlet, or any other opening into a building
with the exception of sub-floor ventilation:
Appliances up to 150 MJ/h input1) 300
Appliances over 150 MJ/h input up to 200
MJ/h input1)
300
K From a mechanical air inlet, including a spa
blower
1000
N Vertically below an openable window, non-mechanical air
inlet, or any other opening into a building with the
exception of sub-floor ventilation:
Appliances over 50 MJ/h input and up to
150 MJ/h input
1000
Appliances over 150 MJ/h input 1500
Table 6
NOTICE: The appliance may be damaged if
dirt is allowed to enter via the gas or water
connections.
▶ Purge the pipes to eliminate
possible foreign bodies.

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12 | Installation (only by authorised technicians)
Fixing the appliance to the wall
Fire protection for the installation surface is not required with
this appliance. The wall has to be capable of supporting the
weight of the appliance.
▶ Mark the position of the fixing holes.
Fig. 6
▶ Drill holes to match the selected wall fixings (Ø 13 mm
maximum).
▶ Fix the appliance to the wall using appropriate fixings (not
supplied).
4.4 Water connection
▶ Identify the cold and hot water pipe to avoid possible cross
connection.
▶ Install a pressure reducing valve if required. It's preferable
to install this valve close to the water meter.
▶ Complete the cold (fig. 2. [9]) and hot (fig. 2, [8])
water connections.
Only for 50 °C preset appliances - The hot water line must
have a minimum length of 2 meters with a ½ ” pipe.
4.4.1 Temperature mixing device (not supplied with the
appliance)
Only for 55 °C preset appliances - It is recommended that for
sanitary fixtures use primarily for the purpose of personal
hygiene, that a temperature control device be fitted (such as a
tempering valve) as per AS3498.
4.5 Gas connection
The gas connection to the water heater must comply with AS/
NZS5601.
▶ First ensure that the water heater corresponds to the gas
type available.
▶ Fit a gas isolation valve on the gas supply line as close as
possible to the appliance.
▶ After installation of the gas supply line, thorough purging
and tightness test must be carried out.
4.6 Altitude of installation site
To ensure correct operation of the appliance at altitudes above
500m, the altitude setting must be adjusted.
▶ Enter the Service function (section 5.2).
Display will show “P2”.
▶ Press until the display shows “P4”.
▶ Press the button .
Display will show “E”.
CAUTION:
▶ Never support or balance the water
heater on the water and gas
connections.
Packaging materials can be recycled.
Before fixing the appliance to the wall,
ensure that the water and gas connections
can be installed in this area.
The top bracket must be used when fixing the
appliance to the wall. For extra stability the
appliance can also be fixed at the bottom
bracket.
120
6720817545-03.1V
WARNING:
This water heater can heat water to
temperatures which cause scalding.
DANGER:
Non-compliance with applicable legal
standards may cause, material damage,
personal injury, or even death.
Size gas supply as per AS/NZS5601.
Incorrect gas pipe sizing will not be covered
by the warranty.

6 720 817 545 (2016/02)Optiflow
Installation (only by authorised technicians) | 13
▶ Press until the display shows “AS”.
▶ Press the button .
Display will show “1”.
▶ Press the button or to select the altitude of the
installation site according to Table 7.
▶ Press the button for 3 seconds.
The value flashes to confirm the new Altitude Calibration
Value.
4.7 Remote control connection (optional)
Connecting the communication cable to the remote control
▶ Open the remote control.
▶ Remove the larger connector from the communication
cable.
▶ Connect the larger connector to the controller in the
position shown in Fig. 7.
▶ Remove the plastic tag to allow the cable to be feed
through.
▶ Feed the end of the cable without a connector through the
opening in the back cover.
▶ Reconnect the cable to the larger connector.
▶ Refit the front and back covers back together.
▶ Close the remote control.
Fig. 7
[1] Remote control front cover
[2] Remote control back cover
[3] Communication cable
Connecting the communication cable to the appliance
▶ Unscrew the electronic control unit fixing screw.
▶ Remove the grommet and feed the remote control
communication cable through it.
▶ Route the cable to the inside of the appliance and connect
to one of the available connectors at the base of the
appliance.
Fig. 8
4.8 Electrical connection (only by authorised
technicians)
All the regulating, control and safety devices in the appliance
are factory supplied already connected and ready to operate.
4.8.1 Connecting the power cable
Display Altitude
1 < 500 m
2 500 m - 1 000 m
3 1 000 m - 1 500 m
4 1 500 m - 2 000 m
5 2 000 m - 2 500 m
6 > 2500 m
Table 7
2
1
1.
6720806426-03.1V
3
Up to 4 remote controls can be used for one
single appliance.
Appliance fitted with Bluetooth connectivity
will have 3 remote control connections
available.
DANGER: Due to electric shock!
▶ Before carrying out work on electrical
components, disconnect the power
supply (230/240 V AC) by switching off
the appliance and removing the power
plug from the socket.
The electrical connection must be installed
in accordance with AS/NZS3000.
6720817545-07.1V
2.
1.
3.

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14 | Installation (only by authorised technicians)
▶ Connect the power cable to a power socket.
4.9 Commissioning of the appliance
▶ Open the gas and water isolation valves and check the
tightness of all the connections.
If a controller is connected:
▶ Turn the appliance on using the ON/OFF button.
The appliance is now ready to operate.
When a hot water tap is turned on, the movement of water
through the flow sensor (fig. 2, [5]) sends a signal to the
electronic control unit. This signal triggers the following
actions:
• The fan to start working.
• The ignition sequence and the gas valve (fig. 2, [13])
delivers gas to the burner.
• The burner ignites. Initially only one section of the burner is
lit, with remain sections igniting depending on the heat
required.
• The flame sensor rod (fig. 2, [2]) detects the presence of
the flame.
• The temperature of the water is automatically adjusted by
the fan, gas and water valves.
Safety shut-off when the safety time is exceeded
If the appliance does not maintain a flame within the safety
interval stipulated, a safety shut-off is carried out.
The presence of air in the gas supply line (initial start-up of the
appliance or start-up after long periods of inactivity) may cause
a delay or difficulty when igniting.
If the ignition attempt is unsuccessful after a period of time, the
safety devices block the operation of the appliance, and air will
have to be purged from the circuit.
Safety shut-off due to an excessively high water
temperature
The electronic control unit detects the temperature of the
water through the thermistor placed at the hot water outlet. If
the appliance detects an excessive temperature, a safety shut-
off will occur.
Safety shut-off due to incorrect flue conditions
If the appliance detects an incorrect flue condition, a safety
shut-off will occur.
Re-start after a safety shut-off
To put the appliance back into operation after a safety shut-off:
▶ Close all hot water taps.
▶ Reset the appliance by switching it off at the socket and
unplugging the cord.
4.10 Changing the setpoint limit temperature
(only for 55 °C preset appliances)
The maximum temperature is preset to 55 °C. If required it can
be increased to 60 °C or 70 °C.
▶ Enter the Service function (section 5.2).
Display will show "P2".
▶ Press until the display shows "P4".
▶ Press the button .
Display will show "E".
▶ Press until the display shows "SL".
▶ Press the button .
Display will show "55"
▶ Press until the display shows "60" or “70”.
▶ Press the button for 3 seconds.
The value flashes to confirm the new setpoint limit.
4.11 Delivery temperature calibration
If the delivery temperature at the closest hot water outlet to the
appliance does not match the setpoint it can be adjusted as
follows:
▶ Enter the Service function (section 5.2).
Display will show "P2".
▶ Press until the display shows "P4".
▶ Press the button .
Display will show "E".
▶ Press until the display shows "SC".
▶ Press the button .
Display will show "0"
▶ Press or to adjust the delivery temperature as
required.
The setpoint can be adjusted between -2.5 °C and +2.5 °C.
▶ Press the button for 3 seconds.
The value flashes to confirm the adjustment has been
made.
If the power cable is damaged, it must be
replaced with a Bosch supplied spare part.
Display Setpoint calibration
-5 -2.5 °C
-4 -2.0 °C
--
--
00°C
--
--
42.0°C
52.5°C
Table 8

6 720 817 545 (2016/02)Optiflow
Regulating the gas (only for authorised technicians) | 15
Calibration example
5 Regulating the gas (only for authorised
technicians)
5.1 Factory settings
The data plate on the each appliance will show the factory
setting of that appliance.
Natural gas
LPG
5.2 Service function
Accessing the service menu
▶ Press and hold down at the same time , , and
for 3 seconds.
Fig. 9 Service function
The display will show "P2".
The service function is now activated.
5.3 Adjusting the appliance
5.3.1 Access to test pointsads
▶ Remove the front of the appliance.
Fig. 10
[A] Air pressure test point
[B] Gas pressure test point
5.3.2 Adjusting the maximum flow (Parameter P1)
▶ Turn on the appliance using the ON/OFF button.
▶ Loosen the test point screw of the gas pressure test point
[B].
▶ Connect the pressure gauge connection "+" to the gas
pressure test point.
▶ Loosen the test point screw of the air pressure test point
[A].
▶ Connect the negative (-) side of the pressure gauge to the
air pressure test point [A].
▶ Enter the service mode by pressing and holding down the
, , and buttons simultaneously for 3
seconds.
▶ Display will show “P2”.
▶ Press until the display shows "P1".
▶ Press the button .
Display will show "E".
▶ Press until the display shows "L1".
Setpoint Water temp. at tap Setpoint calibration
55 °C 53 °C +2 °C
Table 9
The appliance must not be operated if the
dynamic connection pressure is less than
1.13 kPa or greater than 2.75 kPa.
The appliance must not be operated if the
dynamic connection pressure is less than
2.5 kPa or greater than 4.5 kPa.
DANGER:
▶ The operations described below must only
be carried out by an authorised technician.
6720806426-02.1V
Always start the adjustment by P1 followed
by P2.
AB
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16 | Regulating the gas (only for authorised technicians)
▶ Press the button .
The appliance is now ready for adjustment of the maximum
gas flow.
▶ Open a hot water tap.
▶ Press or until the pressure gauge shows the
value indicated in table 10.
▶ Press for 3 seconds.
The displayed value flashes as a sign of confirmation.
▶Press .
Display will show "L1".
▶ Close the hot water tap.
▶ Press until the display shows "E".
▶ Press the button .
Display will show P1.
The adjustment of the maximum gas flow is completed.
5.3.3 Adjusting the minimum flow (Parameter P2)
▶ Press until the display shows "P2".
▶ Press the button .
Display will show "E".
▶ Press until the display shows "L2".
▶ Press the button .
▶ Open a hot water tap.
The appliance is now ready for adjustment of the minimum
gas flow.
▶ Press or until the pressure gauge shows the
value indicated in table 10.
▶ Press for 3 seconds.
The displayed value flashes as a sign of confirmation.
▶Press .
Display will show "L2".
▶ Close the hot water tap.
▶ Press until the display shows "E".
▶ Press the button .
Display will show "P2".
▶ Simultaneously press the , and for 3
seconds.
Display will show the temperature selected.
▶ Disconnect the pressure gauge from the test points [A] and
[B].
▶ Tighten the shutter screws of the test points [A] and [B].
The adjustment of the minimum gas flow is complete.
5.3.4 Adjusting pressure at the burner (Parameter P0)
▶ Enter the Service menu by pressing and holding down the
, , and buttons simultaneously for 3
seconds.
Display will show "P2".
▶ Press until the display shows "P0".
▶ Press the button .
▶ Open a hot water tap.
With the pressure gauge connected, let the value measured
stabilise.
▶ Press or until the pressure gauge shows the
value indicated in table 10.
If it is not possible to reach the differential
pressure value:
▶ Adjust the pressure in the burner
(section 5.3.4) and repeat the
procedure for adjusting minimum flow.
If it is not possible to reach the differential
pressure value:
▶ Adjust the pressure in the burner
(section 5.3.4) and repeat the
procedure for adjusting minimum flow.
Natural gas H LPG
Øinjector
GWH16 1.7 1.25
GWH20 10 x 2.0
5 x 1.7
10 x 1.5
5 x 1.3
GWH26 2.0 1.55
Dynamic
connection
pressure
(kPa)
GWH16
GWH20
GWH26
1.13 2.75
Burner
pressure
(kPa) - P0
GWH16
GWH20
GWH26
0.12
Differential
pressure of
the burner
MAX (kPa) -
P1
GWH16 0.22 - 0.28 0.25 - 0.32
GWH20 0.21 - 0.26 0.26 - 0.32
GWH26 0.21 - 0.29 0.18 - 0.26
Differential
pressure of
the burner
MIN (kPa) -
P2
GWH16 0.03 - 0.06 0.04 - 0.06
GWH20 0.03 - 0.05 0.05 - 0.07
GWH26 0.02 - 0.05 0.03 - 0.06
Table 10 Pressure of the burner
Burner pressure adjustment is only required
if “L1” and “L2” cannot be achieved
according to table. 10

6 720 817 545 (2016/02)Optiflow
Maintenance (only by authorised service technician) | 17
▶ Press for 3 seconds.
The displayed value flashes as a sign of confirmation.
▶ Press to exit this function.
Display will show P0.
▶ Close the hot water tap.
The adjustment of the burner pressure is complete.
5.4 Factory default settings
▶ Enter the Service menu by pressing and holding down the
, , and buttons simultaneously for 3
seconds.
Display will show "P2".
▶ Press until the display shows "P4".
▶ Press the button .
Display will show “E”.
▶ Press until the display shows "rP".
▶ Press the button .
Display will show "P1"
▶ Press for 3 seconds.
The displayed value flashes as a sign of confirmation.
▶Press .
Display will show "P1"
▶ Press until the display shows "P2".
▶ Press the button for 3 seconds.
The displayed value flashes as a sign of confirmation.
▶Press .
Factory default settings are now restored.
6 Maintenance (only by authorised service
technician)
Bosch recommend that to maintain optimum performance
from this appliance, servicing should be carried out by suitably
licensed persons at intervals not greater than two (2) years.
▶ Your appliance should only be attended to by a licensed
service technician. To locate your nearest service provider,
call:
AU 1300 30 70 37, NZ 0800 54 33 52
▶ Only use Bosch supplied replacement parts.
6.1 Periodic maintenance
Functional check
▶ Check the correct operation of all the safety, regulation and
verification elements.
Heat exchanger
If the heat exchanger is showing signs of sooting:
▶ Removetheheatexchanger.
▶ Clean by applying a jet of water in the lengthwise direction
of the fins.
▶ If the soot is not removed, use a stiff brush to carefully clean
the fins.
▶ Regions with average/high water hardness: descale the
inside of the heat exchanger and the connection pipes by
using a diluted solution of hydrochloric acid or white
vinegar.
▶ When reinstalling the heat exchanger replace the o-rings
and seals.
Burner
▶ Inspect the burner and clean if necessary.
If cleaning is required:
▶ Dismantle the burner.
▶ Use a brush to clean the surface of the burner elements.
▶ Use a jet of air to blow the burner elements clean.
Maintenance must only be performed by an
authorised service technician.
DANGER: Due to electric shock!
▶ Always isolate the electrical power to
the appliance (by turning off the power
point and removing the power plug from
the electrical socket) before carrying
out any work on electrical parts.
NOTICE: Damage to the appliance.
Damage to the heat exchanger.
▶ Do not apply a jet that is too strong or
aimed in a direction other than that
indicated.

6 720 817 545 (2016/02) Optiflow
18 | Maintenance (only by authorised service technician)
Water filter
▶ Close the cold water inlet isolation valve.
▶ Unscrew the water filter on the cold water pipe.
▶ Clean the water filter.
-or-
▶ Replace if required
Fig. 11 Water filter
6.2 Replacement of the fuse (electronic control
unit)
▶ Open the electronic control unit.
▶ Remove the PCB from the electronic control unit.
▶ Replace the fuse located in the corner of the circuit board.
Fig. 12 Fuse replacement
6.3 Start-up after completion of maintenance
▶ Re-tighten all of the connections.
▶ Check the burner pressure.
▶ Check air tightness of the flue circuit with the front cover
fitted.
▶ Check that there are no gas or water leaks.
6720817545-05.1V
1
1.
6720817545-06.1V
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6 720 817 545 (2016/02)Optiflow
Troubleshooting | 19
7Troubleshooting
Fitting, maintenance and repair must only be carried out by authorised technicians. The following table describes the possible
solutions.
Display Description Possible solution
A0 Cold and hot temperature sensor damaged. ▶ Check temperature sensor and associated
connections.
▶ If the problem persists, call an authorised
service technician.
A1 Temperature inside the water heater housing is high
(heat exchanger calcified or sooted).
The appliance automatically regulates its
performance to avoid overheating.
▶ If the problem persists, call an authorised
service technician.
A4 Faulty air temperature sensor. ▶ Call an authorised service technician.
A6 Faulty inlet water temperature sensor. ▶ Check temperature sensor and associated
connections.
▶ If the problem persists, call an authorised
service technician.
A8 Faulty mixed water temperature sensor. ▶ Check temperature sensor and associated
connections.
▶ If the problem persists, call an authorised
service technician.
A7 Faulty hot water outlet temperature sensor. ▶ Check temperature sensor and associated
connections.
▶ If the problem persists, call an authorised
service technician.
A9 Hot water outlet temperature sensor is not fitted
properly.
Low incoming gas pressure.
▶ Check temperature sensor and associated
connections.
▶ If the problem persists, call an authorised
service technician.
C7 Faulty fan. ▶ Check if the fan is properly connected to
ECU.
▶ If the problem persists, call an authorised
service technician.
CA Water flow above maximum specified value. ▶ Check incoming water pressure.
▶ Install a pressure limiting valve if necessary.
CF
C1
Blocked flue gas outlet.
Air flow insufficient for start-up.
▶ Remove dirt or any other impediment in the
flue and air inlet.
▶ Close and open a hot water tap.
▶ If the problem persists, call an authorised
service technician.
Table 11

6 720 817 545 (2016/02) Optiflow
20 | Troubleshooting
E0 Failure of control module. ▶ Unplug the electrical connection for 10
seconds.
▶ Reconnect and restart the appliance.
▶ If the problem persists, call an authorised
service technician.
E1 Hot water temperature sensor detects overheating. ▶ Let the appliance cool and try again.
If the problem persists, call an authorised
service technician.
E4 Air temperature sensor detects overheating (leaking
combustion products inside the combustion
chamber).
▶ Switch off at the power point and remove the
plug from the electrical socket.
Do not try to Restart the appliance.
▶ Call a service agent immediately.
E9 Activated thermal fuse. ▶ Call an authorised service technician.
EA Flame not detected. ▶ Check that the gas to the appliance has not
been turned off.
▶ Unplug the electrical connection for 10
seconds.
▶ Reconnect and restart the appliance.
▶ If the problem persists, call an authorised
service technician.
EC Loss of ionization in less than 5 seconds during 5
times.
▶ Unplug the electrical connection for 10
seconds.
▶ Reconnect and restart the appliance.
▶ If the problem persists, call an authorised
service technician.
EE Modulating solenoid valve disconnected. ▶ Check solenoid connections.
▶ If the problem persists, call an authorised
service technician.
EF Wrong gas connected. ▶ Call an authorised service technician.
F7 A flame is detected although the appliance is
switched off.
▶ Unplug the electrical connection for 10
seconds.
▶ Reconnect and restart the appliance.
▶ If the problem persists, call an authorised
service technician.
F9 Safety solenoid valve disconnected. ▶ Call an authorised service technician.
FA Fault in the gas control valve. ▶ Call an authorised service technician.
FC Buttons stuck in a 'pressed' position for more than 30
seconds.
▶ Release the button.
▶ If the problem persists, call an authorised
service technician.
Display Description Possible solution
Table 11