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Bosch 940 ESO Installation Manual

For outdoor installations only temperature modulated with electronic ignition suitable for heating potable water and space heating (intended for variable flow applications)
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940 ESO
For Outdoor Installations Only
Temperature Modulated with Electronic Ignition
Suitable for heating potable water and space heating
(Intended for variable flow applications)
940 ESO - Natural Gas
940 ESO - Liquefied Petroleum (LP) Gas
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
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
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
• Installation and service must be performed by a
qualified installer, service agency or the gas supplier.



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  Summary of Contents for Bosch 940 ESO

  • Page 1 (Intended for variable flow applications) 6720644956-00.1V 940 ESO - Natural Gas 940 ESO - Liquefied Petroleum (LP) Gas Warning: If the information in this manual is not What to do if you smell gas followed exactly, a fire or explosion may result •...
  • Page 2: Table Of Contents

    Electrical diagram Heater placement and clearances Sensor resistance charts Installation instructions Gas piping & connections Water connections GWH 940 ESO Functional scheme Water quality Domestic hot water recirculation Interior components diagram Space heating applications and parts list Measuring gas pressure 15.1 Interior components...
  • Page 3: Warning

    Warning Warning Warning: The maximum inlet gas pressure must not exceed the value For your safety specified by the manufacturer and the minimum value listed is for the purpose Do not store or use gasoline or other flammable, of input adjustment. combustible or corrosive vapors and liquids in the vicinity of this or any other appliance.
  • Page 4 Warning 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. 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,...
  • Page 5: Appliance Details

    • Recess box (7736500043) • Minimum recommended water pressure: 30 PSI • Pressure relief valve (FWL-2). (2.07 bar). BOSCH is constantly improving its • Minimum well pressure 40 psi, see page 20. products, therefore specifications are • Connections: subject to change without prior notice.
  • Page 6: Unpacking The Heater

    • Energy Guide label (in the front cover). adjustment. Please complete and return the enclosed product registration card. The 940 ESO is not approved or designed for: • Manufactured (mobile) homes, boats or any mobile installation. (Modular homes are acceptable for installation).
  • Page 7: General Rules To Follow For Safe Operation

    Appliance details To remove front cover General rules to follow for safe operation B Loosen the two Phillips head screws located on bottom rear of cover (see Fig. 3). B 1. 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.
  • Page 8: Dimensions And Minimum Installation Clearances

    Appliance details Dimensions and Minimum installation clearances 6 ½" " 5 ¼" " 11 ¼" " 5 ¼" r e s e t 6720644956-01.1V Fig. 6 Dimensions On/Off button Reset button Program key Power ON or stand-by LED LCD display Up button Down button 6 720 644 956...
  • Page 9: Installation Requirements

    Installation requirements Installation requirements Specialized tools The following specialized tools may be required for installation: • Manometer • Multi-meter • Combustion Gas Analyzer. Introduction Please follow these instructions. Failure to follow instructions may result in: B Damage or injury. B Improper operation. B Loss of warranty.
  • Page 10: Installation Using Outdoor Kit (Btok)

    Installation using Outdoor Kit (BTOK) Installation using Outdoor Kit (BTOK) Warnings Danger: the water in this appliance is cold and always remains cold except for Danger: The top of the outdoor kit will the times when the burner is on. In the get very hot during operation.
  • Page 11 Installation using Outdoor Kit (BTOK) 6720644956-03.1V Fig. 8 Before mounting the outdoor kit in the appliance: B 3. Attach the gasket provided with the kit as shown in Fig. 9. 6720645551-11.1V Fig. 10 B Attach the outdoor vent cap to the appliance by fas- tening the two provided screws and washers, see Fig.
  • Page 12: Selecting Heater Location

    Installation using Outdoor Kit (BTOK) Selecting heater location Best practice note: The clearances in Fig. 12 and table 1 are the minimum Before proceeding, read the water heater installation allowed by the standard. manual. If the information in that manual is not followed When possible consider maximizing the exactly, a fire, explosion or poisoning by carbon monox- clearances A, B, C, D and E to allow for...
  • Page 13: Mounting Instructions

    Installation using Outdoor Kit (BTOK) Mounting instructions B The water heater is approved for installation directly on an outside wall. Secure the wall mounting bracket provided with the water heater to a wall surface. See Fig. 13. 3½’ B The installation method of the mounting bracket will Vinyl siding depend on the type of mounting surface.
  • Page 14: Heater Placement And Clearances

    Do not install the recess box in another configuration. Heater placement and clearances Damages resulting from an improper instal- lation will not be covered by Bosch limited Warning: The water heater with recess warranty. box accessory is intended for an out- door installation only.
  • Page 15 Installation using the Recess Box (7 736 500 043) 6720644960-03.1V Fig. 17 Recess box plumbing/electrical openings Hot water opening Pressure relief valve opening Electrical opening Cold water opening Gas opening Condensing opening B Secure the wall mounting bracket provided with the heater to the wall surface.
  • Page 16 Installation using the Recess Box (7 736 500 043) 6720644956-08.1V Fig. 21 Close the recess box cover with Padlock Warning: Appliance must be installed vertically. 6 720 644 956...
  • Page 17: Installation Instructions

    Installation instructions Installation instructions 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 con- nected.
  • Page 18 Installation instructions 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. 24, 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.
  • Page 19 0.3” in Water Column (0.75mbar).(Based on a 0.60 Specific Gravity Gas) Btu numbers given in thousands. Follow boxed numbers for piping just one 940 ESO (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.
  • Page 20: Water Connections

    For water analysis data call your local water department, or if on a well, have well water analyzed periodically. If Fig. 25 water quality exceeds one or more of the values specified below, Bosch recommends consulting a local water treatment professional for water softening/ conditioning options. Description Max.
  • Page 21: Domestic Hot Water Recirculation

    Timed or thermostatically controlled operation of the pump is commonly done. Contact Bosch Thermotechnology if further information is needed. 6 720 644 956...
  • Page 22: Space Heating Applications

    GPM). Warning: The use of a flow switch may Bosch tankless water heaters are allowed to be used in be used to ensure DHW priority and to combination DHW and space heating applications prevent “cold-blow” situations when the (open-loop setup).
  • Page 23 Installation instructions 6720644887-02.1V Fig. 30 Space heating diagram Hot water outlet Cold water inlet Pressure relief valve Gas supply Shut off gas valve Thermal expansion tank (as required) Atmospheric vacuum breaker Cold inlet Check valve Pump Thermostatic mixing valve Thermometer (optional) DHW outlet Water to water heat exchanger Backflow preventer...
  • Page 24: Measuring Gas Pressure

    Installation instructions Measuring gas pressure B Record lowest operating gas pressure reading in table 4. Confirm gas pressure upon installation. Gas pressures lower than 3.5" W.C. for Natural Gas or 8" W.C. for LPG will result in insufficient degree rise to Connecting manometer the hot water being used, reduced hot water volume, B Shut off gas supply at installer supplied shutoff valve...
  • Page 25: Electrical Connections

    Electrical connections Electrical connections Electrical power supply Position of the fuses in control unit To check fuses, proceed as follows: safety reasons, Warning: B Remove the front cover, see Fig. 4, page 7. disconnect the power supply cord to the heater before any service or testing B Remove the three screws on front of the control unit.
  • Page 26: Operation Instructions

    Operation instructions Operation instructions Fig. 36 On/Off button Reset button Program Key LCD display Up button Down button LED - Power On indicator or Stand-by Description of LCD display Fig. 40 Lock indicator (only with remote control) Warning: Do not use any cleaning or corrosive agent to clean the window.
  • Page 27: Your Water Heater

    Operation instructions For your safety read before Temperature selection operating your water heater To select output water temperature: B Press buttons in order to reach desired Warning: If you do not follow these temperature. instructions exactly, a fire or explosion may result causing property damage, personal injury or loss of life.
  • Page 28: Operation

    Operation instructions Solar mode control unit (Fig. 72, component 16) is required when programming the remote control with this heater. The water heater will not ignite if inlet water temperature exceeds the set temperature on the appliance. In this NOTE: up to 6 remote controls can be condition, the solar mode indicator will show on the programmed for one single water heater, LCD display.
  • Page 29: Fan Speed

    Operation instructions Fan speed 8.8.1 Fan speed adjustment IMPORTANT! Installation adjustment: After installing the water heater, the fan speed values for Use the equivalent vent length value to determine the minimum power (P2) and maximum power (P1) may appropriate fan speed value found in the Table 5. Refer need adjustment due to variations in altitude.
  • Page 30 Operation instructions Attention residents of the Commonwealth of signage installed in accordance with the provisions of Massachusetts: 248 CMR 5.08(2)(a)1 through 4. In the Commonwealth of Massachusetts the following (b) EXEMPTIONS: The following equipment is exempt regulation went into effect on 12/30/2005: from 248 CMR 5.08(2)(a)1 through 4: (a) For all side wall horizontally vented gas fueled 1.
  • Page 31: Program Button

    Maintenance and service Program button Caution: Program button can be used on the appliance and in the B Check and clean the complete water remote control. heating system once a year. B Carry out a maintenance overhaul if Programming “Program” function necessary.
  • Page 32: Winterizing For Seasonal Use

    Maintenance and service Descaling A7 and E9 and boiling sounds (knocking and banging) in the heat exchanger. • In areas where the water supply has a high mineral content (see Table 2, page 20), the heat exchanger Descaling using a pump should be periodically flushed with a descaling 1.
  • Page 33: Adjusting Co2

    Maintenance and service 16.Reconnect electrical supply to unit, open water B To access measuring port, remove two screws on shutoff valves, and return the unit to service. either side of the louvered grill. B Pull louvered grill free from vent cap. B Insert CO analyzer probe into the measuring port.
  • Page 34 Maintenance and service B Press the ‘ ’ button until P2 appears. Unit will 3. Verify both P1 and P2 CO readings are within the ramp down to low fire and the flow should decrease. ranges specified in table 7. Repeat steps 1 and 2 as necesssary until CO values are within the specified B Record the CO...
  • Page 35: Program Values

    “P” - button Cascading type This menu is only available when cascade mode is select CC. Contact Bosch Water Heating for details. Master/Slave mode Table 8 Program values, factory default settings and ranges. * Incorrect setting causes errors.
  • Page 36: Control Board Diagnostics

    Maintenance and service Control board diagnostics Most recent error/failure 1. Turn on/off switch on water heater to off (O) position. 2nd most recent error B Press and hold the program ' ' button while 3rd most recent error pushing the on/off button to the on (I) position. The display will cycle through a startup procedure 4th most recent error including the software version.
  • Page 37: Troubleshooting

    Troubleshooting Troubleshooting crossover is present and must be corrected. Consult a Warning: If you are unable to perform professional plumber for help in correcting a crossover. the tasks listed below, or need Failing single lever faucets and mixing valves are additional assistance please contact common causes of plumbing crossovers.
  • Page 38: Low Water Flow/Pressure

    Troubleshooting mix cold water with the hot water leaving the heater. The hot water lines. In such cases, when mixing in the higher end result is a cooler water temperature than desired. pressure cold water at the tap, the lower pressure hot To check for a plumbing crossover, shut off the cold water can be overpowered.
  • Page 39: Problem Solving

    Problem solving Problem solving 11.1 Error code diagnostics To remove error code from the display, press the reset button. Display Cause Solution Fault in the flue gas limiter. 1. Check continuity of the flue gas limiter (see Fig. , page Temperature above 230°F...
  • Page 40 4. Check supply voltage. It must be 120VAC and properly grounded. 5. Possible defective control unit call Bosch Water Heating for further instructions. Primary fan rotation too low on 1. Disconnect power supply cord and check wire connection on operation.
  • Page 41 The appliance will close the burner 3. Check vent openings. A blockage may cause this failure. and lock. 4. Call Bosch Water Heating for further instruction. Overheat sensor (ECO) open 1. Disconnect power supply cord and check wire connections on...
  • Page 42 The voltage should measure 24VDC between the left pair of wires and 24VDC between the right pair of wires when the unit is operating. If voltage is not proper, contact Bosch Water Heating for further instruction. 3. Gas valve may be defective, contact Bosch Water Heating for further instrucation.
  • Page 43: Electrical Diagram

    Electrical diagram Electrical diagram T=104°C T=220°F T=110°C T=230°F Casc. input Casc. output Back flow 6720608158-92.1AL Fig. 60 Electrical scheme Intlet water temperature sensor Outlet water temperature sensor Backflow temperature sensor Cascading output connection Cascading input connection Ionization sensor Water flow sensor Flue gas limiter Heat exchanger overheat sensor (ECO) Gas valve...
  • Page 44: Sensor Resistance Charts

    Sensor resistance charts Sensor resistance charts Outlet NTC characteristics 2 2 2 2 17 10 5 2 12 10 0 2 0 7 2 0 2 19 7 19 2 18 7 18 2 16 7 16 2 14 7 14 2 13 7 13 2...
  • Page 45 Sensor resistance charts Back Flow characteristics 3 0 2 2 9 7 2 9 2 14 5 2 8 7 2 8 2 14 0 2 7 7 2 7 2 13 5 2 6 7 2 6 2 13 0 2 5 7 12 5 2 5 2...
  • Page 46: Gwh 940 Eso Functional Scheme

    GWH 940 ESO Functional scheme GWH 940 ESO Functional scheme IDLE Water flow > 0.5 gpm water tap See error code table (> 1.9 l/min) open? (see WF calc.) Fan speed = correct Ionization = off Appliance Temp. limiter = closed ready to start? Temp.
  • Page 47: Interior Components Diagram And Parts List

    Interior components diagram and parts list Interior components diagram and parts list 15.1 Interior components Fig. 65 Components Flue gas collector Ignition electrodes Heat exchanger Observation window Flame sensor Backflow temperature sensor Primary fan (Mixer) Secondary air fan Outlet temperature sensor Gas valve LCD display Water valve with engine and temperature sensor...
  • Page 48 Interior components diagram and parts list Fig. 66 Appliance overview 6 720 644 956...
  • Page 49: Components Diagram

    Interior components diagram and parts list 15.2 Components diagram 15.2.1 Group 1 6720644956-07.1V Fig. 67 Components Diagram Item Description Reference Item Description Reference Combustion cover clip 8 701 201 032 Front cover 8 705 431 408 Grommet set 8 710 203 039 Cover shield 8 705 506 907 Mounting bracket...
  • Page 50 Interior components diagram and parts list 15.2.2 Group 2 6720902974.AA JF Fig. 68 Components Diagram Item Description Reference Item Description Reference Site window 8 701 000 401 Heat exchanger 8 705 406 422 Ignition group 8 701 302 249 Heat exchanger top gasket 8 704 701 052 Heat exchanger O-ring 8 700 205 147...
  • Page 51 Interior components diagram and parts list 15.2.3 Group 3 6720902975.AA JF Fig. 69 Components Diagram Item Description Reference Item Description Reference Gas / Air Mixer 8 705 700 170 Main burner 8 708 120 699 Air duct O-ring 8 700 205 149 Burner gasket 8 704 701 087 Venturi...
  • Page 52 Interior components diagram and parts list 15.2.4 Group 4 6720608158-73.1AL Fig. 70 Components Diagram Item Description Reference Item Description Reference Gas filter 8 700 507 002 Gas valve 8 707 021 019 Gasket 8 704 701 085 Pressure tapping 8 703 404 219 Gas / Fan connector 8 705 202 140 Washer...
  • Page 53 Interior components diagram and parts list 15.2.5 Group 5 6720902977.AA JF Fig. 71 Components Diagram Item Description Reference Item Description Reference Inlet fitting 8 703 305 348 Water valve with engine 8 708 505 024 O-ring 8 700 205 157 O-ring 8 700 205 147 Watervalve clip...
  • Page 54 Interior components diagram and parts list 15.2.6 Group 6 6720644956-09.1V Fig. 72 Components Diagram Item Description Reference Item Description Reference Electrode cables 8 704 401 346 Control unit 8 707 207 368 Flue gas limiter 8 700 400 032 Fuse T2.5A 1 904 521 342 Kit intelligent cascading (optional) 7 709 003 962...
  • Page 55: Protecting The Environment

    Protecting the en vironment Protecting the environment Packing The packing box may be fully recycled as confirmed by the recycling symbol Components Many parts in the heater can be fully recycled in the end of the product life. Contact your city authorities for information about the disposal of recyclable products.
  • Page 56: Limited Warranty

    Bosch Thermotechnology Corp. shall be in lieu of any • 4. to failure of the heat exchanger resulting from the and all other warranties, express or implied, including...
  • Page 57 Limited Warranty 6 720 644 956...
  • Page 58 Limited Warranty 6 720 644 956...
  • Page 59 Limited Warranty 6 720 644 956...
  • Page 60 Installation manual should be left with the owner after the installation is tested and completed Replacement Parts available from: BOSCH THERMOTECHNOLOGY CORP. Bosch Termotecnologia SA 50 Wentworth Avenue Estrada de Cacia Londonderry, NH 03053 Tel. 866-330-2730 3800 - 533 Cacia - PORTUGAL © 2010 Bosch Thermotechnology Corp., Londonderry, NH...