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 (2008.01) 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.

6 720 608 782
2
Index
Index
1Warning 3
2 Appliance details 4
2.1 Features 4
2.2 GWH 2400 ES Specifications
(Technical data) 4
2.3 Unpacking the GWH 2400 ES heater 5
2.4 General rules to follow for safe operation 6
2.5 Dimensions and Minimum installation
clearances 7
3 Installation instructions 8
3.1 Tools required for installation 8
3.2 Introduction 8
3.3 Venting 8
3.4 Combustion air requirements 15
3.5 Proper location for installing your heater 16
3.6 Heater placement and clearances 16
3.7 Mounting installation 16
3.8 Gas piping & connections 17
3.9 Water connections 20
3.10 Water quality 20
3.11 Recirculation application 21
3.12 Measuring gas pressure 21
4 Electrical connections 23
4.1 Electrical power supply 23
4.2 Position of the fuses in control unit 23
5 Operation instructions 24
5.1 LCD Display functions 24
5.2 For your safety read before operating
your water heater 25
5.3 Power 25
5.4 Temperature selection 25
5.5 Use of optional remote control accessory
(part no. TSTAT2) 26
5.6 Operation 26
5.7 Reset button 26
5.8 Program button 26
5.9 Locked condition 26
6 Maintenance and service 27
6.1 Annual maintenance 27
6.2 Winterizing for seasonal use 27
6.3 Mineral scale build-up 28
6.4 Adjusting CO2 (carbon dioxide) 28
6.5 Program values 31
6.6 Control board diagnostics 32
6.7 Fan speed adjustment 33
7 Troubleshooting 35
7.1 Introduction 35
7.2 Burner do not ignite when hot water
is turned ON 35
7.3 Water is too hot 35
7.4 Water is not hot enough 35
7.5 Low water flow/pressure 36
7.6 Hot water temperature fluctuates at tap 36
7.7 Noisy burner/heater during operation 36
8 Problem solving 38
8.1 Error code diagnostics 38
9 Electrical diagram 42
10 Sensor resistance charts 43
11 GWH 2400 ES Functional scheme 45
12 Interior components diagram
and parts list 46
12.1 Interior components 46
12.2 Components diagram 48
13 Protecting the environment 54
14 Limited Warranty 55

6 720 608 782
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.
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
operation.
Fig. 1
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.

6 720 608 782
4
Appliance details
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).
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.
iBOSCH is constantly improving its
products, therefore specifications are
subject to change without prior notice.

6 720 608 782
Appliance details
5
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)
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
• Outdoor installation without installation of Outdoor
kit (AQOK)
• Space heating purposes
• Preheated inlet water supply.
iIf appliance is installed at elevations
between 2000ft and 4500ft, a
combustion gas analyzer is required for
proper calibration of appliance. (see page
22).

6 720 608 782
6
Appliance details
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
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 8). 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 16) and 3.4
(page 15).
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.

6 720 608 782
Appliance details
7
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

6 720 608 782
8
Installation instructions
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.
lenght
Max.
length
Material
Exhaust
Vent
3 or 4
inches
3 feet 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

6 720 608 782
Installation instructions
9
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
Fig. 8
Maximum exhaust vent and combustion air inlet
lengths
Fig. 9 Maximum vent and combustion air lenghts
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 8.
Refer to chapter 3.3.2, page 12 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 35. 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
The maximum exhaust
vent and combustion air
inlet lengths with one
elbow are ≥26ft.

6 720 608 782
10
Installation instructions
Recommended exhaust vent terminator position
Fig. 10
* Subject to local codes and anticipated snow level
** Other equipment that operates with a mechanical air inlet may require greater distances, reference manufacturer's instructions
NOTE: terminating exhaust vent under a deck is not permitted
Ref. Description Minimum distance
ADirectly below an opening; operable windows, doors and any non-
mechanical fresh air openings
36 in (twin pipe installation)
48 in (single pipe installation)
B
Below a gutter, sanitary pipework or eaves 24 in
Below a gutter, sanitary pipework or eaves, protected by metal
shielding 12 in
CFrom any internal corner 12 in
D* Above ground or snow pack 12 in
Above a paved sidewalk 7 ft
EFrom an opposing wall or structure facing the termination 24 in
From the relief valve of a Ip gas regulator 60 in
FFrom a terminator facing a terminator 48 in
GVertically between two exhaust vent terminators on the same wall 60 in
HHorizontally between two exhaust vent terminators on the same wall 36 in
I**
Horizontally and vertically from combustion air inlet of a twin pipe
system 36 in
From the gravity combustion air inlet any other equipment 6 ft
JFrom any external corner 12 in
KHorizontally from an opening; operable windows, doors and any non-
mechanical fresh air openings
12 in (twin pipe installation)
48 in (single pipe installation)
LVertically from a wall, roof slope, or obstruction (venting through a flat
or pitched roof)
see ABOVE THE ROOF
requirements on following page
Table 6

6 720 608 782
Installation instructions
11
Venting configuration examples
Fig. 11 Horizontal side wall venting installation
(combustion air piping not shown)
Important:
Note: Pitch horizontal runs down toward the
heater, except horizontal run between last elbow
and termination which must slope 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.
Fig. 12 Vertical venting installation (combustion air
piping not shown)
Fig. 13 Above the roof clearance requirements from
rain cap (combustion air piping not shown)
Fig. 14 Vertical venting installation - Masonry
Chimney (combustion air piping not shown)

6 720 608 782
12
Installation instructions
3.3.2 Condensate drain requirements
A condensate drain must be installed under the
following conditions:
• All vertical terminating vent installations
• Horizontal terminating vent installations where the
total equivalent exhaust vent length is greater than 10
feet. See table 17, page 33.
• Vent installations where any section of the exhaust
vent pipe passes through an unconditioned space.
Note: Do not install condensate drain in areas where it
may freeze.
1. Install condensate drain as close to heater as
possible.
2. Use 3/8" ID high temperature silicone tube to
connect to condensate drain port. Do not use copper
piping for any portion of the condensate drain.
3. Form a condensate trap by means of a 3" loop
partially filled with water.
4. To increase the tube length, connect to end of the
high temperature silicon tubing with vinyl tubing, PVC or
CPVC pipe. Do not reduce the internal diameter at any
point.
5. Dispose of condensate according to local codes.
Fig. 15 Condensate drain installation
Room sealed installation (TWIN PIPE SYSTEM)
Installing this water heater as a room sealed (TWIN
PIPE SYSTEM) is the recommended method. Contact
your dealer for available vent termination kits and vent
materials for this water heater.
The exhaust and combustion air piping must vent
directly to the outside of the structure.
Fig. 16
Combustion air pipe: ≤26 ft (8 m) from collar
Exhaust vent pipe: ≤26 ft (8 m) from collar
Fig. 17
3" Venting Z-flex ProTech Heat Fab
90°
Condensate
Drain Tee
2SVEVWCF03 FST3 &
FSDF3
93PPLSTEE
Horizontal
Condensate
Drain
2SVEDWCF03 FSHDT3 9321
Condensate
Drain Tube
2SVEDTK24 N/A 7000TUBE
Table 7 Approved Condensate Drain Part Numbers
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.

6 720 608 782
Installation instructions
13
Fig. 18
Open combustion installation (SINGLE PIPE
SYSTEM)
Not recommended in cold climate areas, see
chapter 3.4, page 15.
Fig. 19
Connecting a one piece 90 degree elbow pipe to the
combustion air inlet adaptor is required. This will
prevent debris or objects from falling into the appliance.
The exhaust vent system must vent directly to the
outside of the building and an adequate amount of
indoor combustion air must be provided for this
installation. See chapter 3.4.
Note: reduce 2.5 ft for each 90° elbow used after the
first one, reduce 1.25 ft for each 45° elbow.
A maximum of three 90-degree elbows are permitted.
Determining installation adjustment
The GWH 2400 ES comes factory set to accomodate
most common venting arrangements. Determine the
elbows and straight pipe you will require for exhaust and
combustion air. Refer to the the table below to deter-
mine if the factory setting for the fan is adequate. If your
venting system is longer and exceeds the values listed
in Table 8, proceed to Section 6.7, page 33 for fan
speed adjustment.
Note: Maximum of three 90° elbows allowed for exhaust
and three 90° elbows allowed for intake.
Warning: Approved terminators must
be used for inlet and exhaust vent
systems to prevent rain from entering
the appliance, failure to do so may result
in damage to the appliance. This failure
is not covered under the manufacturer’s
warranty.
TWIN PIPE
Exhaust
Intake One 90° elbow
or Less (feet)
Two 90°
elbows
Three90°
elbows
1 x 90°
elbow or
Less
19’ 16.5’ 14’
2 x 90°
elbow 16.5’ 14’ 11.5’
3 x 90°
elbow 14’ 11.5’ 9’
SINGLE PIPE
No intake
piping 19’ 16.5’ 14’
Maximum combined intake and exhaust
vent length without fan speed
adjustment.
Table 8

6 720 608 782
14
Installation instructions
3.3.3 Vent connections
BAttach the flue gas exhaust accessory (8 705 504
151) to the top of the unit (position 1) using the 4
screws and gasket provided. Fully insert stainless
steel vent pipe 1.5” minimum into the accessory and
tighten the clamp (position 2).
Fig. 20
BAttach the combustion air inlet accessory (8 705
504 154) to the top of the unit (position 3) using the
3 screws and gasket provided, and install air intake
pipe over the accessory. NOTE: The appliance has
the option to mount the combustion air inlet acces-
sory on the top right or on the top left side of the
heater. The combustion air inlet that is not used must
be kept sealed.
Fig. 21
BEnsure that exhaust vent pipe is fully inserted in collar
to enable proper connection.
Attention residents of the Commonwealth of
Massachusetts:
In the Commonwealth of Massachusetts the following
regulation went into effect on 12/30/2005:
(a) For all side wall horizontally vented gas fueled
equipment installed in every dwelling, building or
structure used in whole or in part for residential
purposes, including those owned or operated by the
Commonwealth and where the side wall exhaust vent
termination is less than seven (7) feet above finished
grade in the area of the venting, including but not limited
to decks and porches, the following requirements shall
be satisfied:
1. INSTALLATION OF CARBON MONOXIDE
DETECTORS. At the time of installation of the side wall
horizontal vented gas fueled equipment, the installing
plumber or gasfitter shall observe that a hard wired
carbon monoxide detector with an alarm and battery
back-up is installed on the floor level where the gas
equipment is to be installed. In addition, the installing
plumber or gasfitter shall observe that a battery
operated or hard wired carbon monoxide detector with
an alarm is installed on each additional level of the
dwelling, building or structure served by the side wall
horizontal vented gas fueled equipment. It shall be the
responsibility of the property owner to secure the
services of qualified licensed professionals for the
installation of hard wired carbon monoxide detectors.
a. In the event that the side wall horizontally vented gas
fueled equipment is installed in a crawl space or an at
tic, the hard wired carbon monoxide detector with alarm
and battery back-up may be installed on the next
adjacent floor level.
b. In the event that the requirements of this subdivision
can not be met at the time of completion of installation,
the owner shall have a period of thirty (30) days to
comply with the above requirements; provided,
however, that during said thirty (30) day period, a
battery operated carbon monoxide detector with an
alarm shall be installed.
2. APPROVED CARBON MONOXIDE DETECTORS.
Each carbon monoxide detector as required in
accordance with the above provisions shall comply with
NFPA 720 and be ANSI/UL 2034 listed and IAS
certified.
3. SIGNAGE. A metal or plastic identification plate shall
be permanently mounted to the exterior of the building
at a minimum height of eight (8) feet above grade
directly in line with the exhaust vent terminal for the
horizontally vented gas fueled heating appliance or
equipment. The sign shall read, in print size no less than
one half (1/2) inch in size, "GAS VENT DIRECTLY
BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS".
4. INSPECTION. The state or local gas inspector of the
side wall horizontally vented gas fueled equipment shall
not approve the installation unless, upon inspection, the
inspector observes carbon monoxide detectors and
iExhaust venting must be 3" or 4" sealed
single wall stainless steel (AL29-4C) vent
pipe.

6 720 608 782
Installation instructions
15
signage installed in accordance with the provisions of
248 CMR 5.08(2)(a)1 through 4.
(b) EXEMPTIONS: The following equipment is exempt
from 248 CMR 5.08(2)(a)1 through 4:
1. The equipment listed in Chapter 10 entitled
"Equipment Not Required To Be Vented" in the most
current edition of NFPA 54 as adopted by the Board;
and
2. Product approved side wall horizontally vented gas
fueled equipment installed in a room or structure
separate from the dwelling, building or structure used in
whole or in part for residential purposes.
(c) MANUFACTURERS REQUIREMENTS - GAS
EQUIPMENT VENTING SYSTEM REQUIRED. When
the manufacturer of Product Approved side wall
horizontally mounted gas equipment provides a venting
system design or venting system components with the
equipment, the instructions provided by the
manufacturer for the installation of the equipment and
the venting shall include:
1. Detailed instructions for the installation of the venting
system or the venting system components: and
2. A complete parts list for the venting system design or
venting system.
(d)MANUFACTURER REQUIREMENTS - GAS
EQUIPMENT VENTING SYSTEM NOT PROVIDED.
When the manufacturer of a product approved side wall
horizontally vented gas fueled equipment does not
provide the parts for the venting of flue gases, but
identifies "special venting systems," the following
requirements shall be satisfied by the manufacturer:
1. The referenced "special venting system" instructions
shall be included with the appliance or equipment
installation instructions; and
2. The "special venting systems" shall be product
approved by the Board, and the instructions for that
system shall include a parts list and detailed installation
instructions.
(e) A copy of all installation instructions for all products
approved side wall horizontally vented gas fueled
equipment, all venting instructions, all parts lists for
venting instructions, and/or all venting design
instructions shall remain with the appliance or
equipment at the completion of the installation.
3.4 Combustion air requirements
Twin pipe
The GWH 2400 ES is designed as a sealed
combustion appliance. It is recommended that the
combustion air be provided by a dedicated 3” or 4” pipe
from the outside. The combustion air pipe may be PVC
or any other rigid sealed 3” or 4" pipe. The combustion
air piping must pitch down 1/4 inch per foot towards
termination to prevent rain water from entering the
appliance. The combustion air inlet, whether terminating
vertically or horizontally, must be located in such a
manner as to provide a minimum 3 foot clearance
from the exhaust vent terminator. See Fig. 10
Letter I, page 10.
The maximum length of the combustion air inlet
is 26 feet with one elbow. Subtract 2.5 feet for
each additional 90° elbow and 1.25 feet for each
additional 45° elbow. Maximum number of
elbows permitted is 3.
Single pipe
Note: This appliance requires 8750 cubic feet of
available combustion air, or a minimum of 1094
square feet of space with an 8 foot ceiling to
operate. If the large amount of air space, which
equates to about half of most average sized
homes, is not available, the appliance must pull
air from outside (see twin pipe system above).
Although it is permissible to draw combustion air from
inside the structure, it is not the manufacturer’s
recommended installation method. Always install a 3
inch elbow on the top of the combustion air inlet
adaptor to prevent foreign objects from falling into the
unit.
If a single pipe installation is utilized, follow guidelines
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.
Warning: When installed in an
environment where corrosive chemicals
or dirty air are present the twin pipe
system is required.
Warning: Vent terminations must
prevent rain from entering the
combustion air and exhaust vent piping.

6 720 608 782
16
Installation instructions
below for providing adequate combustion air for the
water heater as well as any other appliances that may
consume air in the space. Always follow local codes if
they are more stringent.
This Installation Manual specifies the minimum exhaust
vent length (Fig. 8, page 9) and the amount of
combustion air required for this unit. When all
requirements are followed, the unit will operate properly
and safely. However, there may still be a risk of freezing
due to negative draft if the other combustion appliances
in the building are not supplied with sufficient
combustion air. A wood stove or furnace can pull its
combustion air from the heater's vent pipe, allowing the
cold incoming air to freeze the cold water in the heat
exchanger. Supplying more combustion air for all
combustion appliances is the solution. A HVAC
specialist should be consulted to design solutions for
providing more combustion air. Observe the following
guidelines:
Installations in structures that have been tightly
constructed (air infiltration rate of 0.40 ACH or less)
must be provided with combustion air per the National
Fuel Gas Code. Consult a HVAC specialist if your air
infiltration rate is questionable.
The space must have two permanent openings, one
commencing within 12 inches of the top and one
commencing within 12 inches of the bottom of the
enclosure.
Each opening must have a minimum free area of one
square inch per:
• 1000 Btu/hr if all air is taken from inside the building
• 2000 Btu/hr if all air is taken from the outside by
horizontal ducts
• 4000 Btu/hr if all air is taken from the outside by
direct openings or vertical ducts.
Or the space must be provided with one permanent
opening or duct that is within 12 inches of the ceiling of
the enclosure.
This opening must have a minimum free area of one
square inch per:
• 3000 Btu/hr if all air is taken from the outside by a
direct opening or vertical duct.
Louvers, grills and screens have a blocking effect. If the
effective free area is not known, increase the sizes of
your openings by 300% if your louvers are wood and by
43% if your louvers are metal. Refer to the National Fuel
Gas Code for complete information.
3.5 Proper location for installing your
heater
Carefully select the location of the water heater. For
your safety and for proper heater operation, you must
provide combustion air to the heater and a proper
exhaust vent system.
Follow the guidelines below:
B1. Locate the heater where venting, gas and
plumbing connections are feasible and convenient.
B2. The hot water lines should be kept short and
insulated to save energy. Centrally locating the water
heater is recommended to keep hot water
distribution times even throughout the structure.
3.6 Heater placement and clearances
The GWH 2400 ES is approved for installation on
a combustible wall (see chapter 3.7 Mounting
installation) provided the floor covering below
the heater is noncombustible. For installations in an
alcove or closet, maintain the minimum clearances to
combustible and non-combustible materials listed
below. See also Fig. 7 and Table 1 on page 7.
Clearances from any exhaust vent pipe are dependent
upon the clearance requirements of the stainless steel
vent pipe manufacturer. Single wall stainless steel
(AL29-4C) vent pipe (vent type rated for Category III
appliances) must be used when exhaust venting this
appliance. See chapter 3.3 (page 8) Venting.
3.7 Mounting installation
Warning: The water in this water
heater is cold and always remains cold
except for the times the burner is on. In
the event of power outage in
conjunction with freezing temperatures,
it is recommended that the heater be
drained.
See chapter 6.2, page 27 “Winterizing”
for draining instructions.
Warning: Flammable materials,
gasoline, pressurized containers, or any
other items or articles that are potential
fire hazards must NOT be placed on or
adjacent to the heater. The appliance
area must be kept free of all
combustible materials, gasoline and
other flammable vapors and liquids.
Warning: before starting
installation
BCheck that there are no loose or
damaged parts inside the
appliance
BConfirm the gas type of the heater
matches the gas supply you will be
connecting the heater, see Fig. 2,
page 5.

6 720 608 782
Installation instructions
17
If wall is sheathed with plaster or drywall, it is
recommended that two support boards, either 1”x4” or
1/2" (minimum) plywood first be attached across a pair
of studs, see Fig. 22.
BSecure the wall mounting bracket provided with the
heater to the wall surface. The heater must be kept
level on the wall surface (see Fig. 23).
BHang the appliance on the bracket, see Fig. 24.
Fig. 22 Distance between support boards
Fig. 23 Leveling the mounting bracket on the studs
Fig. 24 Mounting the heater
3.8 Gas piping & connections
Before connecting the gas supply, check the rating
plate on the right side of the heater to be sure that the
heater is rated for the same gas to which it will be
connected.
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 to CSA B149
iFront cover should be removed (see
instructions on page 6) in order to inspect
components visually.
Warning: Do not install this appliance
on a carpeted wall. The heater must be
mounted on a wall using appropriate
anchoring materials.
Studs 16"
(406mm) on
center
Warning: Appliance must be installed
vertically.

6 720 608 782
18
Installation instructions
INSTALLATION CODES and/or local installation
codes.
GAS CONNECTIONS
BInstall a manual gas shut off valve on the gas supply
line within easy reach of the appliance.
BInstall a union when connecting gas supply.
BThe minimum internal diameter required for
any appliance connector is ¾”.
BUndersized flexible appliance connectors not
permitted.
BNational Fuel Gas Code requires that a sediment
trap (drip leg) be installed on gas appliances not so
equipped. The drip leg must be accessible and not
subject to freezing conditions. Install in accordance
with the recommendations of the serving gas sup-
plier, see Fig. 25.
Fig. 25 Gas connection (drip leg)
Once connections are made, check for gas leaks at all
joints. Apply some gas leak detection solution to all gas
fittings. Bubbles are a sign of a leak. A combustible gas
detector may also be used to detect for leaks.
GAS LINE SIZING
The gas supply piping for a single heater should be
sized for a maximum draw of 199,000 BTUH. Measure
the length of gas supply line and use the tables in
Fig. 27, page 19 or the gas line manufacturer’s sizing
tables to determine the pipe diameter necessary to
accommodate the 199,000 BTU demand of the heater.
If there are more gas appliances on the line, size the gas
line according to the total maximum amount of BTU
input rating for all appliances.
Note: Undersizing the gas line may result in diminished
hot water flow rate and temperature. See chapter 3.12,
page 22 for the procedure to confirm gas pressure.
Proper gas pressure must be confirmed at time of
installation.
Fig. 26
Warning: DO NOT connect to an
unregulated or high pressure propane
line or to a high pressure commercial
natural gas line.
Warning: The heater must be isolated
from the gas supply piping system
during any pressure testing of that
system at test pressures equal to or
more than 0.5 psig. If overpressure has
occurred, such as through improper
testing of the gas lines or malfunction of
the supply system, the gas valve must
be checked for safe operation.
Gas supply
Cap
Minimum
3”
Danger: If you have a leak, shut off the
gas. Tighten appropriate fittings to stop
leak. Turn the gas on and check again
with a gas leak detection solution.
Never test for gas leaks using a match
or flame.
Gas piping
Inlet gas particle screen
(included)

6 720 608 782
Installation instructions
19
FOR NATURAL GAS
Maximum Capacity of pipe in Cubic Feet of Gas per Hour for Gas Pressure of 0.5 Psig or less and a Pressure drop
of 0.3” in Water Column (0.75mbar).(Based on a 0.60 Specific Gravity Gas) Btu numbers given in thousands.
Fig. 27
Follow boxed numbers for piping just one GWH 2400 ES (example: ¾” B.I. Natural Gas pipe for 10 ft (3.0m).
will handle 278,000 btu’s (81.5 kWh). For multiple appliances combine the total maximum btu input load and
then refer to applicable chart below.
* EHD = Equivalent Hydraulic Diameter. The greater the
value of EHD, the greater the gas capacity of the tubing.
Maximum Capacity of Semi-Rigid (flexible, non
corrugated) Tubing in Thousands of BTU per Hour of
Undiluted Liquefied Petroleum Gases (at 11 inches
Water Column Inlet Pressure).
(Based on a Pressure Drop of 0.5 Inch Water Column)
* Source National Fuel Gas Code NFPA 54, ANSI
Z223.1 - No Additional Allowance is necessary for an
ordinary number of fittings
FOR LP GAS
Maximum Capacity of Pipe in Thousands of BTU per Hour of Undiluted Petroleum Gases (at 11 inches Water Column Inlet
Pressure) (Based on a Pressure Drop of 0.5 Inch Water Column).
* EHD = Equivalent Hydraulic Diameter. The greater the
value of EHD, the greater the gas capacity of the tubing.
Nominal
Iron Length of Black iron Pipe , Feet
Pipe Internal
Size, Diameter
inches inches 10 20 30 40 50 60 70 80 90 100 125 150 175 200
1/4 0.364 32 22 18 15 14 12 11 11 10 9 8 8 7 6
3/8 0.493 72 49 40 34 30 27 25 23 22 21 18 17 15 14
1/2 0.622 132 92 7363 56504643403834 312826
3/4 0.824 278 190 152 130 115 105 96 90 84 79 72 64 59 55
1 1.049 520 350 285 245 215 195 180 170 160 150 130 120 110 100
1 1/4 1.380 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
1 1/2 1.610 1600 1100 890 760 670 610 560 530 490 460 410 380 350 320
2 2.067 3050 2100 1650 1450 1270 1150 1050 990 930 870 780 710 650 610
Tube
size,
inches EHD*
10 20 30 40 50 60
1/2 18 EHD 82 58 47 41 37 34
3/4 23 EHD 161 116 96 83 75 68
1 30 EHD 330 231 188 162 144 131
1 1/4 37 EHD 639 456 374 325 292 267
Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
Copper
Outside Length of Tubing, Feet
diameter
Inch 10 20 30 40 50 60 70 80 90 100
3/8 39 26 21 19 _ _____
1/2 9262 50 41 37 3531292726
5/8 199 131 107 90 79 72 67 62 59 55
3/4 329 216 181 145 131 121 112 104 95 90
Tube
size
inches EHD*
10 20 30 40 50 60
1/2 18 EHD 129 91 74 64 58 53
3/4 23 EHD 254 183 151 131 118 107
1 30 EHD 521 365 297 256 227 207
Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
Nominal
iron Black Iron Pipe
pipe Length of Pipe, Feet
Inches 10 20 30 40 50 60 80 100 125 150 200
1/2 291 200 160 137 122 110 94 84 74 67 58
3/4 608 418 336 287 255 231 197 175 155 140 120
11145 787 632 541 480 434 372 330 292 265 227

6 720 608 782
20
Installation instructions
3.9 Water connections
BWhen facing the heater, the ¾” cold connection is on
the bottom right and the hot connection is on the
bottom left. Centrally locating the water heater is
recommended to keep hot water distribution times
even throughout the structure.
Fig. 28
BThe use of unions when connecting both water
pipes to the inlet and outlet connections is
required. This will facilitate any necessary
servicing.
BPlastic or PEX type plumbing line materials are not
suitable for connecting directly to the water heater.
BAlthough water piping throughout the building may
be other than copper, we recommend that copper or
suitably rated stainless steel flex line piping be used
for the water connections for 1.5’ on either side of
the water heater (follow local codes if more
stringent).
BNever sweat any piping directly to or beneath
the water connections, as damage can occur to
the internal water valve from heating of the
pipe.
BKeep water inlet and outlet pipes to no less
than ¾" (19.05mm) diameter to allow the full
flow capacity.
BIf the cold and hot connections to the heater are
reversed, the heater will not function. Be certain there
are no loose particles or dirt in the piping. Blow out
or flush the lines before connecting to the water
heater.
BFull port shutoff valves should be installed on both
the cold water supply and hot water outlet lines to
facilitate servicing the heater (see Fig. 29).
BFor installation on a private well system with the use
of a pressure tank, the lowest pressure range setting
recommended is 40-60 psi (2.75 and 4.15 bar).
3.10 Water quality
Water quality can have an impact on appliance
longevity and may not be covered under the
manufacturer's warranty.
For water analysis data call your local water department,
or if on a well, have well water analyzed periodically. If
water quality exceeds one or more of the values
specified below, Bosch recommends installing a water
conditioner or softener.
Warning: This heater is not approved
for preheated water applications.
See chapter 3.11 for approved
recirculating application.
HOT
COLD
Description Max. Levels
pH pH 6.5 - 8.5
TDS (total Dissolved
Solids) mg/l or ppm 500
Total hardness mg/l or ppm 100
(6 grains)
Aluminum mg/l or ppm 2.0
Chlorides mg/l or ppm 250
Copper mg/l or ppm 1.0
Iron mg/l or ppm 0.3
Manganese mg/l or ppm 0.05
Zinc mg/l or ppm 5.0
Table 9