Bosch 940ESO User manual

940 ESO
For Outdoor Installations Only
Temperature Modulated with Electronic Ignition
Suitable for heating potable water and space heating
(Intended for variable flow applications)
6720644956-00.1V
940 ESO - Natural Gas
940 ESO - Liquefied Petroleum (LP) Gas
6 720 644 956 (2012/02) US
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
vapors 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.
• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire
department.
• 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 5
2.1 Features 5
2.2 Specifications (Technical data) 5
2.3 Unpacking the heater 6
2.4 General rules to follow for safe operation 7
2.5 Dimensions and Minimum
installation clearances 8
3 Installation requirements 9
3.1 Specialized tools 9
3.2 Introduction 9
3.3 Proper location for installing your heater 9
4 Installation using Outdoor Kit (BTOK) 10
4.1 Warnings 10
4.2 Installing outdoor vent cap on the appliance 10
4.3 Selecting heater location 13
4.4 Mounting instructions 14
5 Installation using the Recess
Box (7 736 500 043) 15
5.1 Heater placement and clearances 15
6 Installation for manufactured (mobile) homes
17
6.1 Mounting installation for manufactured
(mobile) homes 17
7 Installation instructions 18
7.1 Gas piping & connections 18
7.2 Water connections 21
7.3 Water quality 21
7.4 Domestic hot water recirculation 22
7.5 Space heating applications 23
7.6 Measuring gas pressure 25
8 Electrical connections 26
8.1 Electrical power supply 26
8.2 Position of the fuses in control unit 26
9 Operation instructions 27
9.1 Description of LCD display 27
9.2 For your safety read before operating
your water heater 28
9.3 Power 28
9.4 Temperature selection 28
9.5 Use of optional remote control accessory
(part no. TSTAT2) 29
9.6 Operation 29
9.7 Reset button 29
9.8 Fan speed 30
9.9 Program button 32
9.10 Locked condition 32
10 Maintenance and service 32
10.1 Annual maintenance 32
10.2 Winterizing for seasonal use 33
10.3 Mineral scale build-up 33
10.4 Adjusting CO2 34
10.5 Program values 36
10.6 Control board diagnostics 37
11 Troubleshooting 38
11.1 Introduction 38
11.2 Burner does not ignite when hot water
is turned ON 38
11.3 Water is too hot 38
11.4 Water is not hot enough 38
11.5 Low water flow/pressure 39
11.6 Hot water temperature fluctuates
or goes cold at tap 39
11.7 Noisy burner/heater during operation 39
12 Problem solving 40
12.1 Error code diagnostics 40
13 Electrical diagram 44
14 Sensor resistance charts 45
15 GWH 940 ESO Functional scheme 46
16 Interior components diagram
and parts list 47
16.1 Interior components 47
16.2 Components diagram 49
17 Protecting the environment 55
18 LIFETIME LIMITED WARRANTY
FOR BOSCH TANKLESS
WATER HEATERS 56

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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 installation
location and proper combustion air
supply air supply 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.
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
heater or connections will not result in
damage to the area adjacent to the
appliance. 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 the
minimum value listed is for the purpose
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: Keep appliance area clear
and free from combustible materials,
gasoline and other flammable vapors
and liquids.
Warning: Do not obstruct the flow of
combustion and ventilation air.
Warning: Precautions must be taken
prior to manually 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 result in improper and
dangerous operation.
Verify proper operation after servicing.
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.
Warning: If the water heater is used in
a space heating application, all piping
and components connected to the
water heater must be suitable for use
with potable water.
Warning: Toxic chemicals, such as
those used for boiler treatment, shall not
be introduced into the potable water
used for space heating.

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Warning
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
Warning: A water heater which will be
used to supply potable water shall not
be connected to any heating system or
component(s) previously used with a
nonpotable water heating appliance.
Warning: Installation in mobile homes
shall conform to Title 24 CFR, Part
3280 and/or CAN/CSA Z240 MH Se-
ries, Mobile Homes.
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.
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Appliance details
5
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 prevention1).
Accessories (Bosch part #)
• Optional wireless remote control accessory to
operate with the appliance (TSTAT2)
• Cascading kit (7709003962)
• External water filter (8703305356)
• Gas conversion kit (8719002176)
• Pipe Cover (PTPCES)
• Recess box (7736500043)
• Pressure relief valve (FWL-2).
2.2 Specifications (Technical data)
Approved in US/Canada
Capacity
Maximum flow rate: 7.15 GPM (27 l/min) at a 45°F
(25°C) rise.
Maximum output
160,500 Btu/h (47.0 kW)
Maximum input
199,000 Btu/h (58.3 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 7.6, page 25.
Water
• Hot water connection (inches) - ¾”
• Cold water connection (inches) - ¾”
• Water valve material: Polymer (PPS) (Polypropylene
Sulfid)
• Minimum water flow: 0.5 gallon/minute (1,9 l/m).
Note: Activation varies with inlet water temperatures
from 0.5 - 1.6 gallon/minute (1.9 - 6.1 l/m).
• Minimum recommended water pressure: 30 PSI
(2.07 bar).
• Minimum well pressure 40 psi, see page 21.
• Connections:
– Bottom of heater
Combustion
• Design is NOx compliant with SCAQMD require-
ments - rule 1146,2 approved type 1 appliances.
•CO250 ppm (measured)
•CO
2level set from factory, see chapter 10.4, page
34.
1) The freeze prevention kit is designed to provide
protection for the water heater down to approximately
5°F for short term conditions only. It will not protect the
appliance in areas where the temperature is routinely
expected to be below freezing.
- The freeze prevention kit will not protect plumbing
outside the appliance from freezing. Precautions should
be taken.
i
BOSCH is constantly improving its
products, therefore specifications are
subject to change without prior notice.

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Appliance details
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.
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)
• Over heat prevention (temperature limiter)
• Inlet temperature sensor
• Outlet temperature sensor
• Back flow temperature sensor.
Water protection
IP X4 (protection against water drops)
2.3 Unpacking the heater
In order for proper installation, this water heater
must be installed with the outdoor kit (BTOK)
accessory.
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:
•940ESO
• Bracket for wall hanging the heater
• Installation manual (manual can be downloaded at
www.bosch-climate.us)
• Product registration card
• Energy Guide label (in the front cover).
Please complete and return the enclosed product
registration card.
The 940 ESO is not approved or designed for:
• Recreational vehicle (RV) or boat installations.
•Use above 8000 ft A.S.L. altitude (see page 30).
• Outdoor installation without installation of
Outdoor kit (BTOK) or Recess Box (7 736 500
043).
• Applications where inlet water temperature is
higher than 140ºF (60°C). A 3-way valve or
mixing valve must be installed before the
appliance if inlet water temperature exceeds
this limit.
i
If appliance is installed at elevations above
2000ft, refer to Section 9.8.1 Fan speed
adjustment.

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Appliance details
7
To remove front cover
BLoosen the two Phillips 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 Remove 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. If not
installed correctly, fatal accidents can occur, such as
carbon monoxide poisoning or fire.
B3. The water heater must be installed outdoors using
the outdoor kit and/or recess box accessory.
B4. You must vent your heater so that the exhaust
gases discharge to the outdoors.
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
chapter 7.1.
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
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3
1
6
5
7
4
5¼" 30 ½"
17 "
785¼"
11 ¼"
2 ¾"
6 ½"
2 "
16
5
5¼"
2 "
16
4 "
116
6 "
516
116
516
reset
P
+

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Installation requirements
9
3 Installation requirements
3.1 Specialized tools
The following specialized tools may be required for
installation:
• Manometer
• Multi-meter
• Combustion Gas Analyzer.
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.
3.3 Proper location for installing your
heater
Carefully select the location of the water heater. For
your safety and for proper heater operation, follow the
guidelines below:
B1. Locate the heater where 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.
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 10.2, page 33
“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.

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Installation using Outdoor Kit (BTOK)
4 Installation using Outdoor Kit (BTOK)
4.1 Warnings
Outdoor kit (BTOK) includes:
• Supports (2) with screws
• Sealing gasket
• Control panel shield
• Outdoor vent cap.
4.2 Installing outdoor vent cap on the
appliance
Replace the control panel shield
BLoosen the two Phillips head screws located on
bottom rear of cover (see Fig. 3).
Fig. 7 Loosen the two screws
B1. Attach the supports (A) to the appliance by fasten-
ing with the four provided screws, as shown in Fig. 8.
Danger: The top of the outdoor kit will
get very hot during operation. Keep
away from children. Install heater in a
location where the top of the kit cannot
be reached by small children.
Danger: Flue gas will be released
through the outdoor kit. Flue gas is very
hot and contains carbon monoxide. The
outdoor kit cannot be installed on a
water heater mounted indoors. To
prevent risk of fire and carbon monoxide
poisoning, maintain all clearances
indicated in these instructions.
Danger: Do not place or store any
combustible material within 5 feet of the
appliance. Maintain specified clearance
to combustibles on the wall where the
appliance is installed and any adjacent
walls or overhang. Observe all
clearances required in this manual.
Danger: Surface temperature of the kit
is less than 140°F, except highest top
surface which may reach 300°F.
Warning: Do not mount water heater
directly onto vinyl siding, see Fig. 15.
Danger: the freeze prevention kit on
the appliance is designed to provide
protection from temperatures down to
approximately 5°F for short term
conditions only. It will not protect the
appliance in areas where the
temperature is routinely expected
to be below freezing. The freeze
prevention kit will not protect plumbing
outside the appliance from freezing.
Precautions must be taken:
BAlways drain the water heater if it will be
exposed to long term freezing condi-
tions.
Danger: the water in this appliance is
cold and always remains cold except for
the times when the burner is on. In the
event of power outage in conjunction
with freezing temperatures, it is
recommended that the heater be
drained.
Warning: Damage to the appliance
from freezing is not covered under the
manufacturer's warranty.
Warning: The control panel shield
must always remain closed, except
when making adjustments, to prevent
damage to heater from weather.
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