Bosch GWH 2400 ES NG User manual

MODEL GWH 2400 ES NG and GWH 2400 ES LP -
INDOOR MODEL
Temperature Modulated with Electronic Ignition
Suitable for heating potable water only
Not approved for space heating purposes
(Intended for variable flow applications)
GWH 2400 ES NG - Natural Gas
GWH 2400 ES LP - Liquefied Petroleum (LP) Gas
6 720 608 782 US (2008.07) AL
Warning: If the information in this manual is not
followed exactly, a fire or explosion may result
causing property damage, personal injury or death.
Do not store or use gasoline or other flammable
vapor and liquids in the vicinity of this or any other
appliance.
Improper installation, adjustment, alteration,
service or maintenance can cause injury or
property damage. Refer to this manual. For
assistance or additional information consult a
qualified installer, service agency or the gas
supplier.
In the Commonwealth of Massachusetts this
product must be installed by a licensed plumber or
gas fitter.
Upon completion of the installation, these
instructions should be handed to the user of the
appliance for future reference.
What to do if you smell gas
• Close gas valve. Open windows.
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• If you cannot reach your gas supplier, call the fire
department.
• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions
• Installation and service must be performed by a
qualified installer, service agency or the gas supplier.

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2
Index
Index
1Warning 3
2 Appliance details 4
2.1 Features 4
2.2 GWH 2400 ES Specifications
(Technical data) 5
2.3 Unpacking the GWH 2400 ES heater 6
2.4 General rules to follow for safe operation 7
2.5 Dimensions and Minimum
installation clearances 8
3 Installation instructions 9
3.1 Tools required for installation 9
3.2 Introduction 9
3.3 Venting 9
3.4 Combustion air requirements 17
3.5 Proper location for installing your heater 18
3.6 Heater placement and clearances 18
3.7 Mounting installation 18
3.8 Gas piping & connections 19
3.9 Water connections 22
3.10 Water quality 22
3.11 Domestic hot water recirculation 23
3.12 Measuring gas pressure 24
4 Electrical connections 26
4.1 Electrical power supply 26
4.2 Position of the fuses in control unit 26
5 Operation instructions 27
5.1 LCD Display functions 27
5.2 For your safety read before operating
your water heater 28
5.3 Power 28
5.4 Temperature selection 28
5.5 Use of optional remote control accessory
(part no. TSTAT2) 29
5.6 Operation 29
5.7 Reset button 29
5.8 Program button 29
5.9 Locked condition 29
6 Maintenance and service 30
6.1 Annual maintenance 30
6.2 Winterizing for seasonal use 30
6.3 Mineral scale build-up 31
6.4 Adjusting CO2 (carbon dioxide) 31
6.5 Program values 34
6.6 Control board diagnostics 35
6.7 Fan speed adjustment 36
7 Troubleshooting 38
7.1 Introduction 38
7.2 Burner do not ignite when hot water
is turned ON 38
7.3 Water is too hot 38
7.4 Water is not hot enough 38
7.5 Low water flow/pressure 39
7.6 Hot water temperature fluctuates at tap 39
7.7 Noisy burner/heater during operation 39
8 Problem solving 41
8.1 Error code diagnostics 41
9 Electrical diagram 45
10 Sensor resistance charts 46
11 GWH 2400 ES Functional scheme 48
12 Interior components diagram
and parts list 49
12.1 Interior components 49
12.2 Components diagram 51
13 Protecting the environment 57
14 Limited Warranty 58

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Warning
3
1 Warning
For your safety
Do not store or use gasoline or other flammable,
combustible or corrosive vapors and liquids in the
vicinity of this or any other appliance.
Warning: Carefully plan where you
install the heater. Correct combustion
air supply and flue pipe installation are
very important. If a gas appliance is not
installed correctly, fatal accidents can
result, such as carbon monoxide
poisoning or fire.
Warning: Exhaust gas must be vented
to outside using stainless steel vent
material suitable for category III vent
systems and temperatures up to 480°F.
Vent piping must be sealed gas-tight to
prevent possibility of flue gas spillage,
carbon monoxide emissions and risk of
fire, resulting in severe personal injury
or death. Approved vent terminators
must be used when penetrating to the
outside.
Warning: Place the heater in a location
where water leaks will do NO DAMAGE
to adjacent areas or lower floors.
Warning: Field wiring connections and
electrical grounding must comply with
local codes, or in the absence of local
codes, with the latest edition of the
National Electric Code, ANSI/NFPA 70,
or in Canada, all electrical wiring must
comply with the local codes and the
Canadian Electrical Code, CSA C22.1
Part 1.
Warning: Shock hazard: line voltage is
present. Before servicing the water
heater, unplug power supply cord from
outlet. Failure to do so could result in
severe personal injury or death.
Warning: The heater must be
disconnected from the gas supply
piping system during any pressure
testing of that system at test pressures
equal to or more than 0.5 psig.
Warning: The appliance should be
located in an area where leakage of the
tank or connections will not result in
damage to the area adjacent to the
appliance or to lower floors of the
structure. When such locations cannot
be avoided, it is recommended that a
suitable drain pan, adequately drained,
be installed under the appliance. The
pan must not restrict combustion air
flow.
Warning: The maximum inlet gas
pressure must not exceed the value
specified by the manufacturer and that
the minimum value listed is for the
purposes of input adjustment.
Warning: If a water heater is installed in
a closed water supply system, such as
one having a backflow preventer in the
cold water supply line, means shall be
provided to control thermal expansion.
Contact the water supplier or local
plumbing inspector on how to control
this situation.
Warning: Keeping appliance area clear
and free from combustible materials,
gasoline and other flammable vapors
and liquids.
Warning: Not obstructing the flow of
combustion and ventilation air.
Warning: When manually operating the
relief valve, precautions must be taken
prior to operating the relief valve to avoid
contact with hot water coming out of the
relief valve and to prevent water
damage.
Caution: Label all wires prior to
disconnection when servicing controls.
Wiring errors can use improper and
dangerous operation.
Verify proper operation after servicing.

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Appliance details
FCC:
This device complies with Part 15 of the FCC rules.
Operation is subject to the following two conditions: (1)
This device may not cause harmful interference, and (2)
this device must accept any interference received,
including interference that may cause undesired opera-
tion.
Fig. 1
2 Appliance details
2.1 Features
Parts
• Key Pad interface control
• High power pre-mix compact burner with low NOx
emissions
• Modulating Gas Valve with constant gas:air ratio
control
• Modulating water valve for improved comfort and
temperature control.
High quality materials for long working life
• Copper heat exchanger
• High efficiency Ceramat Burner
• Compact space saver: mounts on a wall with a
supplied bracket.
Features
• Real-time diagnostics for troubleshooting/
informational purposes
• LCD Display with backlight
• On/Off and Temperature control switches
• Reset button
• Program button (Selectable temperature default)
• Failure codes for easy diagnostics and repair
• Easily removable one-piece cover
• Built in freeze prevention.
Note: Freeze prevention is not intended to protect
plumbing outside the appliance or to keep the
appliance from freezing for long periods.
Accessories (Bosch part #)
• Optional wireless remote control accessory to
operate with the appliance (TSTAT2)
• Outdoor kit (AQOK)
• Gas conversion kit (8719002176)
• Vertical vent kit (ESVVT)
• Horizontal vent kit (AQ3ES1)).
Warning: If a relief valve discharges
periodically, this may be due to thermal
expansion in a closed water supply
system. Contact the water supplier or
local plumbing inspector on how to
correct this situation. Do not plug the
relief valve.
HOT
BURN
DANGER
Water temperature over 125°F can
cause severe burns instantly or
death from scalds.
Children, disabled and elderly are
at highest risk of being scalded.
See instruction manual before
setting temperature at water
heater.
Feel water before bathing or
showering.
6720608643-16.1AL
1) AQ3 vent kit is compatible with this appliance but
requires the purchase of an additional 12" piece of
straight pipe to meet minimum vent length requirements.
The aluminum flex piping included with this kit is not per-
missible for use with this appliance.
iBOSCH is constantly improving its
products, therefore specifications are
subject to change without prior notice.

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Appliance details
5
2.2 GWH 2400 ES Specifications
(Technical data)
Approved in US/Canada
Capacity
Maximum flow rate: 6.4 GPM (24 l/min) at a 45°F
(25°C) rise.
Maximum output
147,000 Btu/h (43.0 kW)
Maximum input
175,000 Btu/h (51.2 kW)
Efficiency in %
Thermal efficiency > 82%
Min. Input
19,900 Btu/h (5.8 kW)
Temperature Control
Selection range: 100°F (38°C) - 140°F (60°C)
Default temperature: 122°F (50°C)
Stability: +/- 2°F (+/- 1°C)
Gas Requirement
Gas connection (inches) - ¾”
Inlet gas pressure under operation (with a high hot
water flow rate)*
• Propane: 8” - 13” water column
• Natural Gas: 3.5” - 10.5” water column.
* To measure gas pressure, see Measuring Gas
Pressure, chapter 3.12.
Water
• Hot water connection (inches) - ¾”
• Cold water connection (inches) - ¾”
• Water valve material: Polymer (PPS) (Polypropylene
Sulfid)
• Minimum water flow: 0.65 gallon/minute (2,5 l/m).
Note: Activation varies with inlet water temperatures
from 0.65 - 1.6 gallon/minute.
• Minimum recommended water pressure: 30 PSI
(2.07 bar)
• Minimum recommended well pressure: 40 PSI (2.75
bar), see chapter 3.9.
• Connections:
– Bottom of heater
Combustion
•NOx≤55 ppm
•CO≤250 ppm (measured)
•CO
2level set from factory, see chapter 6.4.
Dimensions
• Depth (in): 11¼” (286 mm)
• Width (in): 17 7/8” (452 mm)
• Height (in): 30½” (775 mm)
• Weight: 67 pounds (30,5 kg).
Gas types
Natural Gas.
LP Gas.
Converting the gas type can only be done by a certified
gas technician with a calibrated CO2analyzer.
Call Bosch Water Heating through Bosch
thermotechnology corporation for conversion
instructions.
Voltage
120 V AC (60 Hz) nominal
Amperage
Idle - 40 mA
Operation - ≤2.5 A
Noise
45 - 65 db (A)
Safety devices
• Flame failure device (ionization flame rod sensor)
• Pressure relief valve (supplied with heater)
• Over heat prevention (temperature limiter)
• Inlet temperature sensor
• Outlet temperature sensor
• Backflow temperature sensor.
Water protection
IP X4 (protection against water drops)
iIf appliance is installed at elevations above
2000ft, refer to table 14, page 25 and
table 21, page 37.

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Appliance details
2.3 Unpacking the GWH 2400 ES
heater
Before installing the unit, be certain you have the
correct heater for your type of Gas: Propane or
Natural Gas. Identification labels are found on the
shipping box, and on the rating plate which is located on
the right side panel of the cover.
Fig. 2 Rating plate
ASerial number
BType of gas
The box includes:
• GWH 2400 ES
• Pressure relief valve (150 psi / 200,000 Btu rating)
• Bracket for wall hanging the heater
• Exhaust vent adaptor (with 4 screws and gasket
provided)
• Combustion air inlet adaptor (with 3 screws and gas-
ket provided)
• Installation manual (manual can be downloaded at
www.boschhotwater.com)
• Product registration card
• Energy Guide label.
Please complete and return the enclosed product
registration card.
The GWH 2400 ES is not approved or designed
for:
• Manufactured (mobile) homes, boats or any mobile
installation (modular homes are acceptable for
installation).
• Use above 4500ft A.S.L. altitude for LP gas
appliances.
• Use above 8000 ft A.S.L. altitude for natural gas
appliances (see page 25).
• Outdoor installation without installation of Outdoor
kit (AQOK).
• Space heating purposes.
• Preheated inlet water supply.
To remove front cover
BLoosen the two Philips head screws located on
bottom rear of cover (see Fig. 3).
Fig. 3 Loosen the two screws
BLift front cover panel upward and remove.
Fig. 4 Removing the front cover
To remove combustion cover (service only)
BOpen the four clips and remove the combustion
cover see Fig. 5.
Fig. 5 Remove the combustion cover

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Appliance details
7
2.4 General rules to follow for safe
operation
B1. You must follow these instructions when you install
your heater. In the United States: The installation must
conform with local codes or, in the absence of local
codes, the National Fuel Gas Code ANSI Z223.1/
NFPA 54.
In Canada: The Installation must conform with CGA
B149.(1,2) INSTALLATION CODES and /or local
installation codes.
B2. Carefully plan where you install the heater. Correct
combustion air supply and vent pipe installation are
very important. If not installed correctly, fatal
accidents can occur, such as carbon monoxide
poisoning or fire.
B3. When the unit is installed indoors and ROOM
SEALED (twin pipe) it is permitted to be located in
bathrooms, bedrooms and occupied rooms that are
normally kept closed. See chapter 3.3 (page 9). If the
unit will be installed indoors and use indoor
combustion air, the place where you install the heater
must have enough ventilation. The National Fuel
Gas Code does not allow UNSEALED gas fired
water heater installations in bathrooms,
bedrooms or any occupied rooms normally
kept closed. See chapter 3.5 (page 18) and 3.4
(page 17).
B4. You must vent your heater. See chapter 3.3 on
VENTING.
B5. The appliance and its gas connection must be leak
tested before placing the appliance in operation.
The appliance must be isolated from the gas supply
piping system by closing its individual manual gas
shutoff valve (not supplied with heater) during any
pressure testing at pressures in excess of ½ Psig (3.5
kPa).
B6. Keep water heater area clear and free from
combustibles and flammable liquids. Do not locate
the heater over any material which might burn.
B7. Correct gas pressure is critical for the proper
operation of this heater. Gas piping must be sized to
provide the required pressure at the maximum output
of the heater, while all the other gas appliances are in
operation. Check with your local gas supplier, and
see the section on connecting the gas supply. See
Section 3.8, page 17.
B8. Should overheating occur or the gas supply fail to
shut off, turn off the gas supply at the manual gas shut
off valve, on the gas line. Note: manual gas shutoff
valve is not supplied with the heater but must be field
installed.
B9. Do not use this appliance if any part has been
underwater. Immediately call a qualified service
technician to inspect the appliance and to replace any
part of the control system and any gas control which
has been underwater.
B10. Failure to install heater correctly may lead to
unsafe operation and void the warranty.

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Appliance details
2.5 Dimensions and Minimum installation clearances
Fig. 6 Dimensions
1On/Off button
2Reset button
3Program key
4Power ON or stand-by LED
5LCD display
6Up button
7Down button
Fig. 7 Minimum clearances
Note: For servicing access, a 2ft clearance to front
cover is recommended.
Model GWH 2400 ES
TOP (A) 12”
FRONT (B) 1”
BACK 0”
SIDES 1”
FLOOR (C) 12”
Table 1 Minimum clearances

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Installation instructions
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3 Installation instructions
3.1 Tools required for installation
• Philips head screwdriver
• Flat head screwdriver
• Adjustable wrench
• Level
• Thermometer
• Standard plumbing tools
•Manometer
• Drill
• Pipe wrench
• Adjustable pliers
• Pipe fitting tools
• Hacksaw with metal blades
•Holesaw.
3.2 Introduction
Please follow these instructions. Failure to follow
instructions may result in:
BDamage or injury.
BImproper operation.
BLoss of warranty.
If you are unable to perform the tasks required to install
this heater properly, please contact a locally licensed
plumber or gas technician.
Common installation practice is to determine the
venting/intake system layout and penetration and then
work back to the heater.
3.3 Venting
3.3.1 Vent material and specifications
Establish vent clearances that comply with the vent
manufacturer's specifications. In all cases, follow local
codes. See Table 2.
The appliance should be located as close to the point
of vent termination as possible. The maximum vent
length is 26 feet (8 m) with one 90 degree elbow and
approved terminator. Subtract 2.5 feet from the total
vent length for each additional 90° elbow used (a
maximum of three 90° elbows are permitted in the
total exhaust vent length), or subtract 1.25 feet for every
45° elbow used. Horizontal sections of vent must pitch
Warning: Do not reduce the vent
(exhaust and combustion) pipe sizes
and do not common vent with any other
vented appliance or stove.
Warning: Failure to vent the exhaust
gases to the outside with sealed
stainless steel vent pipe (AL29-4C)
may result in dangerous flue gases
filling the structure in which it is
installed.
Warning: Do not mix vent pipe or
joining methods from different
manufacturers.
Warning: Proper end terminal / rain
cap must be used. Failure to do so may
result in damage to the appliance.
This damage is not covered under
the manufacturer's warranty.
Caution: The vent system must be
installed by a qualified installer in
accordance with these instructions. If
improperly installed, a hazardous
condition such as explosion or carbon
monoxide poisoning could result.
Bosch Water Heating will not be
responsible for improperly installed
appliances.
Warning: In areas where outside
temperatures routinely come close to
freezing, sealed combustion operation
is required. Use a concentric
termination or separate terminations for
combustion and vent, which must be
installed on the same wall or roof
surface, however never facing the
direction of prevailing winds. Failure to
do so may result in heat exchanger
freezing up and bursting. This failure is
not covered under the manufacturer's
warranty.
Diam. Min.
length
Max.
length
Material
Exhaust
Vent
3 or 4
inches
3 feet of
straight
pipe
26 feet with
1 90° elbow
and terminal
Sealed single wall
stainless steel
(AL29-4C)
Intake
Vent
3 or 4
inches
1 90°
elbow
26 feet with
1 90°elbow
and terminal
Sealed PVC or
any other rigid
pipe
Table 2 Venting Specifications

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Installation instructions
upwards towards termination ¼" for every foot of
horizontal length, to prevent the pooling of condensate,
and be supported at 4 foot intervals with overhead
hangers.
Exception: horizontal run between last elbow
and termination must pitch down to termination
1/4" per foot.
Note: For horizontal terminations, venting must
terminate once it penetrates to the outside of the
structure. There must be no sections of vent pipe
exposed to the outdoors.
Note: Listed thimbles or collars are necessary where
venting passes through wall and ceiling partitions. If the
vent system passes through combustible areas where
the vent clearance requirements cannot be maintained,
it is permissible to chase straight sections of sealed 3
inch single wall vent through 4 inch (or greater) Type-B
vent. The distance to combustibles using this chase
technique is 1 inch1). Note: Type-B vent must never
be used as the actual exhaust vent system for the
appliance, as it is not gas tight and illegal for use
with this appliance. This will create a serious
health hazard and void the warranty.
For specific questions concerning vent material, speci-
fications, usage or installation, please contact the vent
manufacturer directly.
Minimum exhaust vent length
( ≤3 feet of straight pipe)
Fig. 8 (Combustion air piping not shown)
Maximum exhaust vent and combustion air inlet
lengths
Fig. 9 Maximum vent and combustion air lengths
Note: reduce 2.5 ft for each 90° elbow used after the
first one, reduce 1.25 ft for each 45° elbow, see table 2,
page 9.
Refer to chapter 3.3.2, page 14 for condensate drain
requirements.
Vent Safety System
The GWH 2400 ES will shut down if inadequate
exhaust venting is detected or a lack of combustion air
is provided to the unit; see troubleshooting section on
page 38. See error code to confirm error, correct the
problem and then reset the heater before operating.
1) in all cases, follow local codes.
3”
VENTING
Z flex Protech Heat Fab
3”
Horizontal
Terminal
2SVSTB03 FSTB3 9390 TEE
3” Vertical
terminator 2SVSRCF03 FSRC3 5300CI
Table 3 Terminator Part Numbers
Fittings or Piping Equivalent
feet m
45 degree elbow 1.25 0.38
90 degree elbow 2.5 0.76
pipe per foot 1 0.30
Table 4 Friction Loss Equivalent in piping and fittings
Company Contact info
Z-flex www.z-flex.com
800-654-5600
ProTech Industries www.protechinfo.com
800-766-3473
Heat-Fab www.heatfab.com
800-772-0739
Table 5 Vent manufacturers
6720608542-05.1AL
≤26ft