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Bosch Pro Tankless GWH-425-HNO-N Instructions For Use Manual

Gwh 425 hno outdoor model for exterior use only
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GWH 425 HNO OUTDOOR MODEL
For exterior use only
Electronic Ignition
Suitable for heating potable water only - Not approved for space heating purposes
GWH-425-HNO-N - Natural Gas
GWH-425-HNO-L - 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
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 is approved only for seasonal use.
Installation must be performed by a licensed
plumber or gas fitter.
Upon
completion
instructions should be handed to the user of the
appliance for future reference.
of
the
installation,
these
What to do if you smell gas
• Close gas valve.
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• If you cannot reach your gas supplier, call the fire
department.
• Immediately call your gas supplier from a neighbor's
phone. Follow the gas supplier's instructions.
• Installation and service must be performed by a
qualified installer, service agency or the gas supplier.

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  Summary of Contents for Bosch Pro Tankless GWH-425-HNO-N

  • Page 1 GWH 425 HNO OUTDOOR MODEL For exterior use only Electronic Ignition Suitable for heating potable water only - Not approved for space heating purposes GWH-425-HNO-N - Natural Gas GWH-425-HNO-L - 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

    Index Index Warning Warning Warning: If the information in this Appliance details manual is not followed exactly, a fire or Features explosion may result causing property GWH-425-HNO specifications (Technical data) damage, personal injury or death. Unpacking the GWH-425-HNO heater General rules to follow for safe operation Dimensions and installation clearances Improper installation,...
  • Page 3 Warning What to do if you smell gas • Close gas valve. • 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.
  • Page 4: Appliance Details

    • Easy one person installation Gas types • Electronic Pilot Ignition driven by hydro-generator. Natural Gas. LP Gas BOSCH is constantly improving its products, therefore specifications are Safety devices subject to change without prior notice. • Flame failure device (ionization flame rod sensor) •...
  • Page 5 Appliance details Unpacking the GWH-425-HNO General rules to follow for safe heater operation This heater is packed securely. B 1. You should follow these instructions when you install your heater. In the United States: The Before installing the unit, be certain you have the installation must conform with local codes or, in the correct heater for your type of Gas - Propane or absence of local codes, the National Fuel Gas Code...
  • Page 6: Dimensions And Installation Clearances

    Appliance details Dimensions and installation clearances Fig. 3 Dimensions Model GWH-425-HNO TOP (A) 3 ft. 4 ft. FRONT (B) BACK 0” SIDES 4 ft. BOTTOM (C) 1 ft. Table 1 Minimum clearances Fig. 4 Minimum clearances 8 716 473 148...
  • Page 7: Installation Instructions

    Installation instructions Installation instructions Introduction Danger: Flue gases will be released through the vent cap. Flue gas is very Please follow these instructions. Failure to follow hot and contains carbon monoxide. The instructions may result in: heater cannot be installed indoors. To B Damage or injury.
  • Page 8: Heater Placement And Clearances

    Installation instructions Heater placement and clearances Mounting installation The GWH-425-HNO is design certified for installation Warning: before starting installation: directly on a combustible wall. (see 3.4 Mounting B check that there are no loose parts installation) For installation on vinyl siding see Fig. 7. inside the appliance Keep the area below the heater free of combustible material.
  • Page 9 Installation instructions Fig. 7 B Secure heater to wall using enclosed mounting screws. Use mounting template for proper screw location. B Locate head of screw in the key hole of the top mounting bracket. Vent Safety System The GWH-425-HNO will shut down if the intake or exhaust louvers on the vent cap are blocked for any reason;...
  • Page 10: Gas Piping & Connections

    Installation instructions Gas piping & connections Danger: If you have a leak, shut off the gas. Tighten appropriate fittings to stop Before connecting the gas supply, check the rating leak. Turn the gas on and check again plate on the right side of the heater to be sure that the with a gas leak detection solution.
  • Page 11 Installation instructions 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. Copper tubing is prohibited for use with Natural Gas in the Commonwealth of Massachusetts and not recommended elsewhere.
  • Page 12: Water Connections

    Installation instructions Measuring gas pressure reversed, the heater will not function. Be certain there are no loose particles or dirt in the piping. Blow out or Connecting manometer flush the lines before connecting to the water heater. Full port valves should be installed on both the cold B Shut off gas.
  • Page 13: Electrical Connections

    Installation instructions Electrical connections Warning: Confirm that the water heater is appropriately grounded and that the installation meets all electrical codes. Outdoor electrical outlets have special requirements. Warning: safety reasons, disconnect the power supply to the heater before any service or testing is performed.
  • Page 14: Operation Instructions

    Operation instructions Operation instructions your safety read before some ignition delay. In that case, repeatedly open and close the hot water tap in order to restart the ignition operating your water heater process until all the air has been purged. B 8.
  • Page 15 Operation instructions Knob counter- clockwise position clockwise Degree rise 90°F 45°F Activation rate 0.5 GPM 1.1 GPM Max flow rate 2.0 GPM 3.7 GPM Table 4 Clearances As the temperature adjustment knob is turned counter- clockwise, the output temperature will lower and the activation rate will be raised.
  • Page 16: Electrical Diagram

    Operation instructions Electrical diagram Fig. 12 Electrical scheme Burner electrovalve Gas control valve Pilot electrovalve Flame sensor Pilot electrode Hydro-generator Electronic control box Temperature limiter on/off switch 8 716 473 148...
  • Page 17: Maintenance And Service

    Maintenance and service Maintenance and service Maintenance intervals Pilot The 425 HNO requires periodic maintenance. The Inspecting pilot below time maintenance intervals should kept the unit The pilot should burn with a clean sharp blue flame. The operating for many years. flame should fully envelope the bend of the flame sensor rod.
  • Page 18: Troubleshooting

    Troubleshooting Troubleshooting Introduction B 9. Check to make sure the manual gas shut off valve is in the open position. Have licensed gas technician Many of the questions customers ask regarding or service person check the presence of gas at the operation of this unit can be answered by following the gas pressure measuring tap on the left side of the troubleshooting steps as outlined below.
  • Page 19: Water Is Too Hot

    Troubleshooting B 4. Check the inlet water pressure. For installation on a private well system with the use of a pressure tank, the lowest pressure range setting recommended is 30-50 psi (2.07 - 3.45 bar). Confirm that the pressure tank is not water logged. B 5.
  • Page 20: Interior Components Diagram And Parts List

    Interior components diagram and parts list Interior components diagram and parts list Interior components Fig. 13 Functional scheme Heat exchanger Water valve Pilot assembly Gas control slide Burner manifold gas pressure test nipple Electronic control box Main gas burner Temperature adjustment selector Pilot gas tubing on/off switch 8 716 473 148...
  • Page 21: Components Diagram

    Interior components diagram and parts list Components diagram Fig. 14 Components Diagram 8 716 473 148...
  • Page 22: Parts List

    Interior components diagram and parts list Parts list Item Description Reference Screw 8 716 461 314 Heating body 8 705 406 235 0 Hydrogenerator 8 707 406 069 0 Wire form spring 8 701 201 020 0 O-ring 8 700 205 023 0 Wire form spring 8 704 705 030 0 Cold water pipe...
  • Page 23: Protecting The Environment

    Protecting the environment 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 24: Fifteen Year Limited Warranty

    General of the original water heater or a replaced water heater. Certain service labor allowances are available to PHCC BOSCH PRO water heaters are warranted by the member contractors, dependent on prior authorization Manufacturer (BOSCH) through BBT North America. by BBTNA.
  • Page 25 Installation manual should be left with the owner after the installation is tested and completed Replacement Parts available from: BBT NORTH AMERICA Bosch Group Bosch Water Heating VULCANO Termodomésticos S.A. 340 Mad River Park Estrada de Cacia Waitsfield, VT 05673...

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Pro tankless gwh-425-hno-l