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.

6 720 644 956
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

6 720 644 956
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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4
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.
6720608643-16.1AL

6 720 644 956
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.