Bosch T2400S 8 ND 23 Operating and installation instructions

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LOW NOX INSTANTANEOUS
GAS WATER HEATER
ROOM SEALED FAN ASSISTED / PRESSURIZED
GAS WATER HEATER
FOR INDOOR INSTALLATION
TRAINING AND SERVICE INFORMATION FOR AFTER SALES
This document is restricted to exclusive use by the official service partners. Each
country should adapt the manual and its contents to the available range.

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Contents
1. INTRODUCTION ..............................................................................................3
2. APPLIANCE DESCRIPTION ............................................................................3
2.1 APPLIANCE DESIGNATION...................................................................................................... 3
2.2 AVAILABLE ACCESSORIES ..................................................................................................... 3
3. INSTALLATION ................................................................................................5
3.1 APPLIANCE FIXATION ON THE WALL ........................................................................................ 5
3.2 WATER CONNECTIONS........................................................................................................... 6
3.3 GAS CONNECTION ................................................................................................................. 6
3.4 APPLIANCE PERFORMANCE.................................................................................................... 7
4. COMPONENTS OVERVIEW............................................................................8
4.1 CONTROL PANEL................................................................................................................... 9
4.2 HEAT CELL WITH BURNER PIPES ........................................................................................... 12
4.3 GAS MANIFOLD ................................................................................................................... 13
4.4 FAN ................................................................................................................................... 14
4.5 GAS VALVE ........................................................................................................................ 14
4.6 HEAT EXCHANGER.............................................................................................................. 16
4.7 WATER INLET ASSY ............................................................................................................ 17
4.8 WATER TEMPERATURE SENSORS ......................................................................................... 18
4.9 BOX TEMPERATURE SENSOR ............................................................................................... 18
4.10 WATER FLOW SENSOR..................................................................................................... 19
4.11 IGNITION ELECTRODE ....................................................................................................... 20
4.12 IONIZATION ELECTRODE.................................................................................................... 21
5. WORKING PRINCIPLE / ELECTRIC MEASUREMENTS ............................ 22
6. SERVICE ....................................................................................................... 31
7. MAINTENANCE............................................................................................. 40
8. TROUBLE SHOOTING.................................................................................. 43

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1. Introduction
This manual is a complement to the instruction/operation manual delivered with the
appliance, with the main important technical details that are relevant for the official service
partners and trainers in the country. In any case one of the documents replaces the use of
the other, so always ensure after sales service have updated manuals supplied with the
product, spare part list to be used as complement of this specific service manual.
2. Appliance description
This appliance is a LOW NOx gas water heater (ErP directive demands < 56 mg/kWh),
which will replace the actual room sealed forced exhaust range of appliances offering a
wider range of modulation and installation advantages with both indoor and outdoor
models available.
2.1Appliance Designation
The designation allows the identification of the main characteristics of the units, especially when
report is needed through call centre or after sales technicians.
Example of variants:
T2400S 8/11 ND 23/31
T5600S 12/15/18 D 23/31
T5700S 12/15/18 D 23/31
W 8/10 AME 23/31
WD 8/11 AME 23/31
WTD 12/15/18-3 AME 23/31
WTD 12/15/18-4 AME 23/31
Bosch:
T–Instantaneous gas water heater
T 2400 –Fixed power with electronic ignition and power steps
T 5600 –Thermostatic control (variable power through electronic control)
T 5700 –Thermostatic control (variable power through electronic control with water valve)
T … S–Room sealed operation (indoor unit)
T … S 8 / 10 / 11 / 12 / 15 / 18 –Output (flow rate at 25ºC rise)
T … S XX D–Display
T …S XX D 23/31 –Gas type (23 = natural gas / 31 = liquefied petroleum gas)
Junkers / Vulcano:
W–GWI with Fixed power with electronic ignition and power steps
WT -3 –GWI Thermostatic control (variable power through electronic control)
WT -4 –GWI Thermostatic control (variable power through electronic control with water valve)
W/WT D–Display
W/WT D 8 / 10 / 11 / 12 / 15 / 18 –Output (flow rate at 25ºC rise)
W/WT D… AM –Room sealed operation (indoor unit)
W/WT D… AM E –Electric connection
W/WT D… AM E 23/31 –Gas type (23 = natural gas / 31 = liquefied petroleum gas)
2.2Available accessories

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Hydraulic & Gas Connections (supplied together with set of documents) with installation manual
for each destination market are the original accessories and must be used by installer (see
manual to check scope of delivery.
Remote control
Possible wired connection to both indoor (optional accessory) and outdoor versions
(included in packaging). This is done with a direct connection to the appliance with no
need to configure in the unit the existence of the wired remote control.
The kit includes 10 m of cable, which needs to be connected to the remote by opening the
back cover (rotation) and then removing 3 screws to release the circuit board and make
the connection in the available connection.
Pict. 1 –Wired remote scope of delivery
Pict. 2 –Remote Control View and connection
Anti-Freeze
Allows the protection of the appliance against water freezing inside of its pipes until -20ºC
and to be used in cases where ambient temperature can be lower than 5ºC. It is optional
for indoor models but included from factory in outdoor models.
This kit includes 6 heating elements and 1 sensor (in blue at picture) to install in the heat
exchanger and the activation is according conditions in table 1.

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Pict. 3 –Anti-Freeze Kit in appliance
Activation
Deactivation
T sensor ≤ 4ºC
T sensor ≥ 15ºC
Table 1 –Anti-freeze activation conditions
3. Installation
The installation manual of each product must be checked and used by the installer in order
to optimize and leave the appliance in correct operation conditions.
3.1Appliance fixation on the wall
Requisite
Confirmation
Appliance is levelled and in the vertical position?
Delivered accessories are used accordingly?
Appliance is supported exclusively by the wall fixation and
not by hydraulic and/or gas connections?
Table 2 –Check List for Fixation
Installer must ensure correct wall fixation and water / gas pipe positions using supplied
accessories as the wall hung bracket.
Pict. 4 –Wall Fixation Preparation

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3.2Water connections
Requisite
Observations
Confirmation
Water pipes were cleaned
before connected to the
appliance?
Leakage test was done
successfully?
Inlet water filter was checked
and is cleaned, ensuring the
necessary water flow?
Accessories for water
connections are adequate?
Water pressure and flow are
according to the appliance
specifications?
- Nominal pressure: 1- 4 bar
- Minimum pressure: 0,15 bar
- Maximum pressure: 12 bar
Table 3 –Check list hydraulic connections
3.3Gas connection
Requisite
Confirmation
The appliance is suitable for the available gas type?
Pressure reducer and gas pipe are adequate for the required
pressure and gas flow?
Accessories for gas connection are adequate and according to
the country specification/standards?
Table 4 –Check list for gas connections
3.4Flue Exhaustion
The correspondent appliance manual have indicated the maximum flue length according model
and flue type orientation, nevertheless there is with this new line a new approach where for flue
lengths > 4 m it will be required to have configured in HMI a parameter to indicate to
Flue Exhaustion > 4 m (Note: only for MPP2 (with water valve))
▶Access menu AA.
▶Scroll until find F9.
▶Press ok
▶Scroll and select the flue length
▶Press ok
Length selected
Model
Flue Length
Parameter
12
0 –4 m
00
4 –8 m
01
8 –12 m
02
15
0 –8 m
00
17
0 –4 m
00
5 –9 m
01
Table 5 –Flue Configurations

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Pict. 5 –Wall distance in mm required in horizontal termination
Pict. 6 –Example of wall terminations in 80/110 and 60/100 type
3.5Appliance performance
Measure water flow and temperature increase to check temperature and instantaneous
water flow, assuring correct operation of the appliance.
Pict. 7 –Use of water flow meter and thermometer

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4. Components Overview
[1] Fan
[2] Temperature Limiter
[3] Heat Exchanger
[4] Burner
[5] Gas manifold
[6] Gas valve
[7] Outlet NTC
[8] Hot water
[9] Electrical supply cable
[10] Pressure switch
[11] Transformer
[12] Control Unit
[13] Ignition / Ionization Electrode
[14] Display
[15] Power switch
[16] Flow sensor
[17] Flow rate control
[18] Cold water
[19] Gas inlet
Pict.8 –Internal layout of T2400 / WD versions

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[1] Temperature limiter
[2] Thermo-fuse
[3] Burner
[4] Gas manifold
[5] Gas valve
[6] Fan
[7] Gas pipe
[8] Outlet Temperature sensor
[9] Hot water
[10] Flue collector
[11] Heat Exchanger
[12] HMI
[13] Control Unit
[14] Inlet Temperature sensor
[15] Flow sensor
[16] Cold water
[17] Flow rate control
[18] Gas inlet
[19] Electrical supply cable
Pict.9 –Internal layout of T5600 / WTD version
4.1Control panel
The control panel allows the user, installer or technician, to perform all different operations
needed. User manual explain how to access and use the HMI (human machine interface).

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Pict.10 –Control Panel HMI Overview WD-T2400 / T5600-T5700
On / Off button
The main switch is assembled on the PCB and disconnects the
unit so no voltage at components is present although anti-freeze
kit keeps active due to temperatures checks even in Off mode.
Menu Button
-Used to Enter in service mode to access service parameters
which can be used by the user, installer, technician
Program Button
-Used to Scroll back in the service mode menu when navigating
menus
OK Button
-Save value or adjust set values
-Save a temperature setting (user)
Selection button
Used to scroll inside menu ensuring navigation on parameters
inside the diagnostic mode
Table 6 –Control Panel Buttons
Symbol
Description
Observation
Temperature Unit:
ºC –default value
ºF –alternative value
Selection can be done by
changing default value on
service mode (P6) inside SA
(settings) parameter

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Power bar indicator:
Indication of the current
operation power
Indicative Value (in %)
Note: each segment of the bar
represents 10% of power from 0
to maximum power in kW
Flame indication:
Indication of flame in the
burner
Symbol displayed when
ionization is detected - flame
presence
Warning symbol:
Error / warning symbol is turned
ON every time there is an error or
a warning
Connectivity
Connectivity symbol is ON when
a mobile device is connected to
the water heater wifi module
Tap symbol:
Indication of not enough power
to reach set point.
Note: In case symbol is displayed,
decrease (-) or increase (+) flow
accordingly
Excessive water flow symbol is ON
when the setpoint ±3ºC cannot be
reached at maximum
power because there is too much
water going through the water
heater, or at minimum power
because there is not enough water
going through the water heater
Solar application:
Indication that the automatic
solar function is activated,
meaning that the appliance is
receiving pre-heated inlet
water, with no need for burner
to start
The symbol is displayed and
burner is shutdown when T in
is under following conditions:
T in ≥T set –1K
The symbol is deactivated and
burner restarted when:
T out < 60ºC
Fan operation:
Indication that the fan is in
operation
Fan rotation detection symbol is
ON when rotation of the fan
speed is detected
Table 7 –Display Symbols

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4.2Heat cell with burner pipes
The heat cell includes the copper heat exchanger and the burner with flame visualization
window, ignition electrode and ionization electrode and the gas manifold for the burner.
Pict.11 –Burner and gas valve view (example from LPP / MPP)
Primary air plate
In the burner there is a primary air plate assembled between the gas manifold with
injectors and the burner itself in order to ensure the correct mixture of air and gas
according to the specific appliance model.
The plate has indexation pins that ensure the correct assembly on the heat cell and must
be always replaced together with the injectors in gas conversion.
Pict. 12 –Primary air plate (in this example for LPP)

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4.3Gas manifold
The gas manifold is a gas distribution pipe with 2 types of injectors as in this burner there
are two distinct primary flames with different air/fuel ratios and during whole burning
process flue temperature is kept low reducing the emission of NOX assured by lean
combustion and the mandatory flame stability ensured by rich flame
Pict. 13 –Gas manifold injectors example for LPP
This manifold is part of the gas conversion kit and injectors are not to be replaced individually,
so the kit will always supply the complete manifold. The stamp indicates the size of injectors
used for reference.
The Burner design allows to have on the same burner surface:
-One primary rich flame (oxygen enriched combustion for stabilization) which
corresponds to the injectors with smaller diameter in top of manifold
-One primary lean flame (lack of oxygen for low NOx emissions) which corresponds to
the injectors with bigger diameter in the bottom of manifold.
Pict.14 –Burner design
The manifold cover allows the gas supply to the burner over 2 different segments, in order
to assure a wide modulation, range according to the capacity of the appliance,
nevertheless in the LPP models, the segmentation is manually selected and the power is
fixed and in the MPP models, the segmentation is automatically selected according power
demand.

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4.4 Fan
The control unit monitories the primary air flow to the burner by varying the fan motor
power supply voltage (DC), ensuring a correct variable speed during the operation
according to the output needed in MPP range while in LPP the fan have a fixed speed due
to the unit be fix power version.
The fan motor provides an additional control signal to enable/disable operation and the
speed of the fan is measured by the feedback signal provided by the fan’s motor. The
signal consists on a square wave with a frequency proportional to the speed of the fan.
Pict. 15 –DC Fan (WTD-3&4 / T5600&T5700)
In order to simplify the after sales stock of parts, the modes share same type of fan according:
Low Power Fan:
MPP1 12/15 shares same fan of MPP2 12
High Power Fan:
MPP1 17 shares same fan of MPP2 15/17
The Fan in the LPP range is AC powered and have fix speed. The safety element that controls
the fan start up / stop and blockage is a pressure switch.
Pict. 16 –AC Fan (W/WD/T2400)
4.5 Gas Valve
Over the control unit it is possible to control the gas flow to the burner by the modulating
gas valve (MV1). This valve controls the thermal load in order to ensure the correct hot
water set temperature, under water flow or temperature variations.

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The gas valve is composed by other solenoids identified as safety valves (SV + SV1 +
SV2) releasing the modulated gas to and from the solenoid gas valve.
The safety valve (SV) is the first main safety element that releases gas to the burner and
the safety valves 1 (SV1) and 2 (SV2) are the second safety level elements, that release
gas to the first and second burner segments, respectively, acting as safety and
segmentation valves.
Pict. 17 –Gas Valve in LPP version
The burner is composed by 2 segments which are fed according to the solenoid valves
activation (SV2 and/or SV3) which can be switched over according to the different thermal
load, in order to obtain a stable combustion. These valves ensure the most suitable
condition under the control of microcomputer, based on the values detected by the water
flow sensor and hot water thermal sensors.
Pict.18 –Gas valve / burner scheme for MPP
SV1
SV3
SV2
MV1
SV1
SV
SV2
MV1
Burner
segment 1
Burner
segment 2

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The LPP unit as a fixed power version, allows through the power selector to switch manually
between power level 1 (right side of burner ON = SV1) to power level 2 (left side of burner ON =
SV2) to power level 3 (both sides ON = SV1 + SV2).
Pict.19 –Schematic view of 3 power levels in LPP
4.6 Heat Exchanger
The copper heat exchanger has a special configuration to ensures sealed combustion and
optimized heat transfer from the flame heat to the water that flows through the copper
pipes.
Pict.20 –Heat exchanger
For its protection and ensuring maximum life time, there is over-heating protection ensured by a
bimetallic thermostat in direct contact with the copper and one thermal fuse around the heat
exchanger.

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Pict.21 –Temperature limiter (activation at 85ºC)
The thermal fuse is located around the heat exchanger and for protection is insulated,
nevertheless is composed by 4 specific fuses that melt at 192 ºC in the event of an overheating.
Pict.22 –Thermal Fuse with / without insulation
Pict.23 –Thermal Fuse detail
4.7Water Inlet Assy
The inlet water valve contains the water connection of ¾” that integrates also the filter and
the flow restrictor according country characteristics.
Flow rate valve / Filter
The inlet water valve contains the filter and is acessible removing screw nº1 and pulling out the
valve with know nº2.

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Pict.24 –Inlet flow restrictor with filter
4.8Water temperature sensors
The outlet and inlet water temperature is measured by a 8.5 kΩ NTC (outlet) and 50 kΩ
NTC (inlet). Both NTC measures temperature and are connected to different cable colors
and connectors in the control unit.
Pict.25 –Cold / Hot Temperature sensor
4.9Box Temperature sensor
The Box air temperature is measured by a 10 kΩ NTC (See table with characteristic
values) and is assembled inside the room sealed box, in order to monitor the temperature
inside of the cabinet.
Pict.26 –Box air temperature sensor

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4.10 Water Flow Sensor
Water flow is measured by a turbine flow sensor that is fed by a DC signal of 5 V, and
gives a proportional feedback to the measured water flow.
-Flow rate to operate the appliance: 2.8 l/min
-Flow rate to shut off the appliance: 2.4 l/min
Water flow characteristic curve formula：f = 6.9 x Q
Note:
f is output frequency (Hz)
Q is water flow rate (L/min)
Flow (L/min)
Frequency (Hz）
15
103.5
14
96.6
13
89.7
12
82.8
11
75.9
10
69
9
62.1
8
55.2
7
48.3
6
41.4
5
34.5
4
27.6
3
20.7
2
13.8
Table 8 –Water flow sensor values
Pict.27 –Water Flow Sensor
In case Q > 2.8l/min following Pout verification occurs:
- If Pout > Minimum Power, the appliance will run with the calculated minimum water
flow, in order to reach the set point with a temperature stability of + / - 1ºC;

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4.11 Ignition electrode
Spark generation is started immediately before opening the gas valve, and stopped when
ionization is sensed.
Pict.28 –Ignition electrode (left MPP 12 l / right MPP 15/17 l)
In order to prevent harder ignition processes and be sure of conditions of gas supply and
burner stability, following situation is verified during the so called safety time period.
In each of the attempts, the system monitors the ionisation signal; this signal drives the
start of normal operation, however and, in case the ionization signal is not detected during
the ignition sequence, the failure indication EA will be displayed. In this case a non-volatile
lock-out is activated, and only a manual reset can lead the system back to normal
operation. If the ionisation signal is interrupted during normal operation, this ignition
sequence is re-started.
Fan Ignition spark
1st Ignition Sequence
Safety Time = 31 sec
1st Attempt
(5 sec)
Purge Period
(3 sec)
2nd Attempt
(5 sec)
Purge Period
(3 sec)
3rd Attempt
(5 sec)
Pos Purge
(10 sec)
+
+
+