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Bosch 520-HN -L Manual

Bosch 520-HN -L Manual

Table of Contents


INDOOR MODEL Flow Modulated with Hydro-generated Ignition
520 HN
520-HN-N / 520-HN -L
Suitable for heating potable water only - Not approved for space heating purposes
(Intended for variable flow applications with steady cold water inlet temperatures)
Warning: If the information in this manual is not followed exactly, a fire
or explosion may result causing property damage, personal injury or
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
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.


Table of Contents

Summary of Contents for Bosch 520-HN -L

  • Page 1 INDOOR MODEL Flow Modulated with Hydro-generated Ignition 520 HN 520-HN-N / 520-HN -L Suitable for heating potable water only - Not approved for space heating purposes (Intended for variable flow applications with steady cold water inlet temperatures)
  • Page 2: Table Of Contents

    4.9 Recirculation application ....21 10 LIFETIME LIMITED WARRANTY FOR BOSCH TANKLESS WATER HEATERS ......34 5 Operation instructions .
  • Page 3: Key To Symbols And Safety Instructions

    Key to symbols and safety instructions | 3 Key to symbols and safety instructions Key to symbols Installation and servicing ▶ Risk of fire when soldering and brazing! Warnings Take appropriate protective measures when soldering and brazing around combustible and flammable material. Warnings in this document are identified by ▶...
  • Page 4 ▶ immediately correct all faults to prevent system damage. temperature and pressure! Installation of a T&P safety ▶ use only bosch spare parts! damage caused by the use of valve is required. parts not supplied by bosch may void the warranty.
  • Page 5 Key to symbols and safety instructions | 5 Flooding DANGER: Electric shock! ▶ After a flood, do not use the appliance if any part has been Shock hazard: line voltage is present. submerged. Damage to appliances that have been submerged can be quite severe and pose numerous safety ▶...
  • Page 6: Warning

    6 | Warning WARNING: Fire danger! WARNING: Personal Injury from toxic chemicals. ▶ Keep appliance area clear and free from combustible materials, gasoline and ▶ Toxic chemicals, such as those used for other flammable vapors and liquids. boiler treatment, shall not be introduced into the potable water used for space heating.
  • Page 7: Appliance Details

    (PA) Capacity Temperatures rises: 520 HN: 4.36 GPM Table 2 Accessories (Bosch part #) • Freeze prevention kit (7709003775) • Pressure relief valve (FWL-2) 1) The freeze prevention kit is designed to provide protection for the water heater down to approximately 5°F for short Water protection term conditions only.
  • Page 8: Unpacking The 520 Hn Heater

    8 | Appliance details - 45F rise @ 4.1 gpm - 50F rise @ 3.7 gpm - 55F rise @ 3.4 gpm - 65F rise @ 2.8 gpm - 77F rise @ 2.4 gpm - 90F rise @ 2.0 gpm Connections: Bottom of heater Dimensions...
  • Page 9 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. BOSCH is constantly improving its products, therefore specifications are subject to change without prior notice.
  • Page 10: Dimensions And Installation Clearances

    10 | Appliance details Dimensions and installation clearances 8,66" (220) 4,92"(125) 1,97" (50) 3,82" (97) 6720608036-01.2Av Fig. 3 Dimensions in Inches and (mm) [4] Heat exchanger [34] LED indicator for burner status [5] Burner [35] On/Off switch [10] Flow control knob [36] Front cover [11] Water valve [37] Mounting holes...
  • Page 11: Installation Instructions

    Mounting Heater Please contact Bosch Water Heating with any questions. The 520 HN is approved for installation on a combustible wall Proper location for installing your heater provided the floor covering below the heater is noncombustible.
  • Page 12 12 | Installation instructions pair of studs and then the heater should be attached to the WARNING: before starting installation: support boards, see Fig. 7. ▶ check that there are no loose parts ▶ Install the two included L shaped hooks to wall studs or inside the appliance support board 13 ¼”...
  • Page 13: Combustion Air Requirements

    Installation instructions | 13 combustion air per the National Fuel Gas Code. Consult a HVAC specialist if your air infiltration rate is questionable. Appliances located in confined spaces: The confined space must be provided with two permanent openings, one commencing within 12 inches of the top and one commencing within 12 inches of the bottom of the enclosure.
  • Page 14: 1Horizontal Venting

    14 | Installation instructions Vent termination: WARNING: The gas vent constructed of double wall Type B gas vent must ▶ Do not combination vent with a power terminate above the roof surface with a listed vent cap at a vented appliance. height that's in accordance with Fig.
  • Page 15 Installation instructions | 15 recommended. The masonry chimney may have to be tile or metal lined before the insertion of the gas vent pipe; check local codes for clarification. The lining material must be listed for use 5” X 6” ADAPTOR only with naturally drafting, draft hood equipped gas USED AT HIGH appliances.
  • Page 16: Gas Piping & Connections

    16 | Installation instructions Gas piping & connections Before connecting the gas supply, check the rating plate on the GAS VENT TERMINATIONS FOR LISTED VENT CAPS right side of the heater to be sure that the heater is rated for the Roof pitch H (minimum) feet meters...
  • Page 17 Installation instructions | 17 GAS CONNECTIONS ▶ Install a manual gas shut off valve, on the gas supply line. ▶ Install a union when connecting gas supply. ▶ Attach the appliance regulator to the inlet gas pipe. ▶ The minimum diameter required for any appliance connector used is ¾”...
  • Page 18 18 | Installation instructions GAS LINE SIZING The gas supply piping should be sized according to the applicable code for a maximum draw of 117,000 BTUH. Measure the length of gas supply line and use the tables in Fig. 14 or the gas line manufacturer’s sizing tables to determine the pipe diameter necessary to accommodate the BTU demand of the unit.
  • Page 19 Installation instructions | 19 FOR LP GAS Maximum Capatity 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). Lenght of Flexible Corrugated Stainless Steel Tubing (CSST), Feet Tube size inches EHD*...
  • Page 20: Measuring Gas Pressure

    20 | Installation instructions Measuring gas pressure Water connections When facing the heater, the ½ ” cold water inlet is on the bottom Connecting manometer right and the hot water outlet is on the bottom left. ▶ Shut off gas. ▶...
  • Page 21: Recirculation Application

    A timed or thermostatically controlled operation of the pump is commonly done. The 520 HN must be plumbed in line before the mini-tank water heater. Contact Bosch Water Heating if further instruction is needed. Operation instructions For your safety read before operating your...
  • Page 22: To Turn Off Appliance

    22 | Operation instructions ▶ The gas valve must be shut off by putting the ON/OFF switch to position OFF Wait five (5) minutes to clear out any gas. If you smell gas, STOP! Follow “B” in chapter 4.1. If you do not smell gas, go to the next step. Fig.
  • Page 23: Power Adjustment Knob

    Operation instructions | 23 6720608036-09. 1 Av Fig. 21 Fig. 20 ▶ Turning the power adjustment knob counter-clockwise supplies more gas to the burners and raises the water ▶ Turning the flow control knob clockwise restricts water temperature. flow. This provides higher temperature because the water is moving slower, spending more time over the burner flames.
  • Page 24: Maintenance And Service

    Lubricating the water valve air (20-40psi) through the outlet water Service bulletins are available on our website at connection to remove the residual water Shut off the installer supplied cold water shut-off in the horizontal pipes and water valve.
  • Page 25: Pilot

    Maintenance and service | 25 valve can result in decreased performance or water leaks in the 6.6.1 Descaling heat exchanger heater. 1. Shut off the water supply to the water heater using (installer supplied) shut-off valve. Pilot 2.Open hot water taps to drain and relieve pressure from the plumbing system.
  • Page 26: Troubleshooting

    (installed on the draft diverter). this unit can be answered by following the troubleshooting Consult powervent manual for more details. steps as outlined below. Visit our web site at – If the button clicks when pushed, the switch was for more detailed troubleshooting bulletins.
  • Page 27: Pilot Lights, But Burners Will Not Come On

    NG is a natural gas unit and LP is for liquid propane (See disconnect wire); Voltage must be at least 1.1VDC. If chapter 2.2). less, contact Bosch Tech Support. – Clean or replace pilot orifice. See Bulletin CT-22. 2. Pilot flame should be blue in color and completely engulfing the flame sensor.
  • Page 28: Main Burners Go Out During Hot Water Use

    See chapter 4.5. If the problem supplied by the heater. Wait 5 minutes and check all taps. Any persists, go to for service bulletin CT- water running, even a trickle, is a sign of a plumbing crossover.
  • Page 29: Water Is Too Hot

    Troubleshooting | 29 (directly after the pressure tank on well systems) may be an using. NG is a natural gas unit and LP is for liquid propane (see effective way to maintain constant water pressure to the water chapter 2.2). heater.
  • Page 30: 7.11 Noise When Heater Is Running

    Once the burners are removed, the fins in the top of the heat exchanger can be accessed from below and brushed or vacuumed clean. Consult service bulletin CT-13 on for removing and cleaning the burners. Protecting the environment...
  • Page 31: Interior Components And Diagram Parts List

    Interior components and diagram parts list | 31 Interior components and diagram parts list Interior components 6720608036-04.3AL Fig. 26 Functional scheme [4] Heat exchanger [21] Flexible cold inlet [5] Burner [22] Flexible hot outlet [9] Ignition unit [26] Power adjustment knob [10] Flow control knob [30] Pilot burner [11] Water valve...
  • Page 32: Components Diagram

    32 | Interior components and diagram parts list Components diagram 6720608036-05.2 JF Fig. 27 Components Diagram 6 720 644 942 (2014/11) 520 HN...
  • Page 33: Parts List

    Interior components and diagram parts list | 33 Parts list Item Description Reference Item Description Reference Heat exchanger washer 8 700 103 658 0 Front cover 8 738 708 498 Threaded bushing 8 700 306 148 0 Shield 8 738 708 499 Connector 8 700 306 187 0 Trade mark badge...
  • Page 34: Lifetime Limited Warranty For Bosch Tankless Water Heaters

    34 | LIFETIME LIMITED WARRANTY FOR BOSCH TANKLESS WATER HEATERS LIFETIME LIMITED WARRANTY FOR BOSCH TANKLESS WATER HEATERS MODELS COVERED performance caused by improper installation, repair or maintenance. This limited warranty is provided by Bosch Thermotechnology Corp. (BTC) and covers models 520 HN and 520 PN 4.
  • Page 35: Installation

    Water heater. If this action is not possible or Operating you don't receive a response, contact Bosch Thermotechnology Corp., 50 Wentworth Avenue, Water Pressure Londonderry, NH 03053. To process your claim, you will need...

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