Bosch AQ4 GWH 425 HN, GWH-425-HN-L, GWH-425-HN-N User Manual 2

Water heaters for use with Natural and L.P.G.
GWH 425 HN
Flow Modulated with Electronic Ignition Suitable for heating potable water only - Not approved for space heating purposes (Intended for variable flow applications with steady cold water inlet temperatures)
GWH-425-HN-N GWH-425-HN-L
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 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.
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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
• 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.
WARNING: 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. Upon completion of the installation, these instructions should be handed to the user of the appliance for future reference. In the Commonwealth of Massachusetts this product must be installed by a licensed plumber or gas fitter.
WARNING
If the information in this manual is not followed exactly, a fire or explosion may result causing property damage, personal injury or death.
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.
TABLE OF CONTENTS
Specifications................................................................ Page 3
Rules for safe operation .............................................. Page 5
Locating the Heater ..................................................... Page 5
Combustion Air Requirements ................................... Page 6
Mounting the Heater .................................................... Page 6
Venting the Heater ....................................................... Page 7
Gas Connections ......................................................... Page 9
Gas Piping.................................................................... Page 10
Water Connections .................................................... Page 11
Safety before turning on the heater .......................Page 11
Operating instructions ...............................................Page 12
Setting water temperature ........................................Page 12
Maintenance & Service ............................................. Page 13
Trouble Shooting ......................................................... Page 13
Electrical Diagram ...................................................... Page 15
Diagram of 425HN..................................................... Page 17
Interior components diagram.................................... Page 18
Parts List ....................................................................... Page 19
Flowchart ..................................................................... Page 20
Warranty ....................................................................... Page 21
WHAT TO DO IF YOU SMELL GAS
- 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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Principle of Operation:
When a hot water faucet is opened, the water flow through the heater causes the gas valve to open. At the same time the hydro-generator activates the electronics which sends a spark to the pilot. The flame sensor confirms the pilot has been lighted and allows the first two burners to come on. The flame sensor confirms correct activation and all burners come on. The pilot goes off. The heat exchanger coils absorb the heat generated by the burners and transfer heat to the water. When the hot water faucet is shut off, the gas valve automatically closes and the burners turn off. Your hot water faucet is an ignition key to activate the water heater, giving you control over your hot water energy use. Every time you turn off your hot water faucet, the energy consumption of your hot water returns to zero.
425 HN LP and 425 HN NG Specifications
Gas Input max.: 117,000 Btu/hr
min.: 28,000 Btu/hr
Water Connection ½” Thread fitting NPT
H x W x D 29 3/4” x 18 1/4” x 8 3/4"
Vent 5”
Gas Connection 1/2” NPT thread
Min. Water Pressure 18 Psi at 4 GPM
FEATURES
- Electronic Pilot Ignition driven by hydro-generator
- High Quality Materials for Long Working Life.
- Copper heating coils for endless supply of hot water.
- Burner output proportional to hot water flow demand for maximum energy efficiency.
- Safety flame sensor at pilot burner.
- Automatic overheating protection shut-off sensor.
- Flue gas safety device.
- Stainless steel burners with stabilized blue flame.
- Built-in corrosion resistant draft diverter.
- Compact space saver: mounts on a wall with two hooks.
- Easily removable one-piece cover.
- Easy one person installation.
- Adjustable water flow restrictor to ensure that water flow demand will not exceed the heating capacity of the heater.
- On/Off Switch to activate system.
- Red LED indicator flashes with low water pressure.
Max. Water Pressure 150 Psi
Shipping Weight 43 LB
Net Weight 40 LB
1.8 GPM at 90° rise
3.7 GPM at 45° rise
Min. Water Flow 1/2 gal/min
LP GAS Supply Pressure (before 425 HN regulator) min. 11” W.C.
max. 14” W.C.*
Required LP GAS Pressure at inlet tap while 425 HN is operating: 10.5” W.C.
LP GAS Burner Manifold pressure while 425 HN is operating at maximum input: 9.0” W.C.
Natural Gas Supply Pressure min.: 7” W.C. (before 425 HN regulator) max.: 14” W.C.*
Required Natural Gas Pressure at inlet tap while 425 HN is operating: 5.7” W.C.
Natural Gas Burner Manifold Pressure while 425 HN is operating at maximum input: 4.2” W.C.
- Green LED indicator main burner operation.
* Inlet gas pressure before 425 HN regulator must not exceed
BOSCH is constantly improving our products, therefore specifications are subject to change without prior notice.
this value. Pressure may need to be adjusted for high altitudes, see page 7.
UNPACKING THE 425 HN HEATER
This heater is packed securely. The box includes one water connection fitting, a control knob with collar, a gas pressure regulator, a pressure relief valve, an incandescent particle tray, two hooks for hanging the heater, this manual and a warranty registration card. Do not lose this manual, as there is a charge for replacement. Please complete and return the enclosed warranty registration card.
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FRONT VIEW SIDE VIEW
MINIMUM INSTALLATION CLEARANCES FROM COMBUSTIBLE AND NON COMBUSTIBLE MATERIALS FOR ALCOVE OR CLOSET INSTALLATIONS
MODEL 425 HN
TOP (A) 12" FRONT (B) 4" BACK 0" SIDES 4" FLOOR (C) 12" VENT DIAMETER 5"
MODEL 425HN
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GENERAL RULES TO FOLLOW FOR SAFE OPERATION
1. You should 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 should conform with CGA B149.(1,2) INSTALLATION CODES and /or local installation codes.
2. Carefully plan where you install the heater. Correct
combustion air supply and flue pipe installation are very important. If not installed correctly, fatal accidents can be caused by lack of air, carbon monoxide poisoning or fire.
3. The place where you install the heater must have enough
ventilation. The National Fire Codes do not allow gas fired water heater installation in bathrooms, bedrooms or any occupied rooms normally kept closed. See the section below on locating the heater.
4. You must vent your heater. See section on VENTING,
Page 6.
5. The appliance must be disconnected from the gas supply
piping system during any pressure testing at pressures in excess of 1/2 Psig (3.5 kPa). The appliance must be isolated from the gas supply piping system by closing its individual manual shutoff valve during any pressure testing of the gas supply piping system at test pressures equal to or more than 1/2 Psig (3.5Kpa). The appliance and its gas connection must be leak tested before placing the appliance in operation.
6. Keep water heater area clear and free from combustibles
and flammable liquids. Do not locate the heater over any material which might burn.
7. Correct gas pressure is critical for the optimum
operation of this heater (see specifications on page 2). 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.
8. 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.
The heater may still operate even when improperly vented. It will, however, be less efficient and could eventually damage the heater. It could even result in human sickness or death due to oxygen deprivation and carbon monoxide poisoning. Follow the guidelines below:
1. Place your heater as close to a vent or chimney as possible.
2. National building codes require that you do not install this appliance in bathrooms, bedrooms or any occupied rooms normally kept closed.
3. Simultaneous operation of other appliances such as exhaust fans, ventilation systems clothes dryers, fireplaces or wood stoves could create a vacuum effect in your home which could cause dangerous combustion by-products to spill back into your home rather than venting to the outside through the flue. Confirm that your 425 HN is venting properly when all these other appliances are running. See section on venting.
Do not obstruct the flow of combustion and ventilation air to the appliance. If installed near a clothes dryer it is
very important that the dryer be properly vented. Failure to properly vent a dryer could result in a gradual accumulation of lint on the water heater fin coils and burners, leading to a dangerous condition of vent blockage and poor unsafe combustion.
4. Your hot water lines should be kept short to save energy. It is always best to have hot water lines insulated.
5. This product is neither designed nor approved for outside installations. This product is not approved for manufactured homes (mobile home), recreational vehicles (RV) or boats. Reference ANSI Z21.10.3.
WARNING: The water in this water heater is cold and
always remains cold except for the times that hot water is being used DO NOT INSTALL IN AN AREA WHERE IT
COULD FREEZE. This heater is neither designed for nor approved for outside installation. Drain the heater entirely if freezing temperatures are anticipated in area where heater is installed by disconnecting both the inlet and outlet water connections from the heater (disconnect the outlet flex line from where it connects to the copper heat exchanger). Additionally remove the drain plug under the water valve. See Fig. 1.
9. 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.
PROPER LOCATION FOR INSTALLING YOUR HEATER
Carefully select the location of your new heater. For your safety and for proper heater operation, you must provide an abundant supply of combustion air and a proper venting.
Fig. 1 - Water heater drain plug
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WARNING: Flammable materials, gasoline,
pressurized containers, or any other items or articles that are potentially 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.
COMBUSTION AIR REQUIREMENTS
The 425 HN water heater holds cold water in its copper heat exchanger and brass water valve when not in use. Because of this, any cold air that comes down through the unit’s vent pipe is capable of freezing these components. This Installation Manual specifies the minimum vertical vent pipe and the amount of combustion air required for this unit. When all requirements are followed, the unit will operate properly and safely. However, there may still be a risk of freezing due to negative draft if all the combustion appliances in the area are not being supplied with a sufficient amount of make-up air. A wood stove or furnace may pull combustible air down through the 425 HN vent system, leaving the cold infiltrating air capable of freezing the cold water in the 425 HN heat exchanger. More make up air is the solution. Follow the instructions on venting and checking adequacy of make up air. A HVAC specialist should be used to design solutions for providing more make-up air if necessary. Observe the following instructions concerning combustion air.
Appliances located in unconfined spaces: a) An unconfined space is one whose volume is greater
than 50 cubic feet per 1000 Btu per hour of the combined rating of all appliances installed in the space. That would be 5850 cubic feet for the 425HN alone.
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. Each opening must have a minimum free area of one square inch per:
- 1000 Btu/hr if all air is taken from inside the building.
- 2000 Btu/hr if all air is taken from the outside by horizontal ducts.
- 4000 Btu/hr if all air is taken from the outside by direct openings or vertical ducts.
Or the confined space must be provided with one permanent opening or duct that is within 12 inches of the ceiling of the enclosure. This opening must have a minimum free area of one square inch per:
- 3000 Btu/hr if all air is taken from the outside by a direct
opening or vertical duct. Louvers, grills and screens have a blocking effect. If the effective free area is not known, increase the sizes of your openings by 75% if your louvers are wood and by 30% if your louvers are metal. Refer to the National Fuel Gas Code for complete information. In buildings of tight construction all air should be taken from outside.
CLEARANCES
The 425 HN is design certified for installation on a combustible wall and for installation in an alcove or closet with the minimum clearances to combustible and non ­combustible construction listed below
A. Top 12 inches (306 mm) B. Front 4 inches (102 mm) C. Back 0 inches D. Sides 4 inches (102mm) E. Bottom 12 inches (306 mm)
b) In unconfined spaces in buildings of conventional frame,
masonry, or metal construction, infiltration is normally adequate to provide air for combustion, ventilation, and dilution of flue gasses.
Air Vents
(10 ¾ X 10 ¾ in. each)
425HN
425HN
Air Vents
(5 ½ X 5 ½ in. each)
Clearance from vent is dependent upon the clearance rating of the venting material used. For example: type B-1 vent is approved for 1 inch clearance.
Note: Typically, the minimum clearence to combustible materials should not be less than 6 for single wall flue pipe. Note that this clearance can be reduced if combustible
materials are protected as per table VI of the National Fuel Gas Code or if Type B gas vent is used.
MO UNTI NG I NSTA LLAT IO N
The 425HN is design certified for mounting on a wall. Secure the two L shaped hooks, which are provided with heater, to a wall surface. Place them 13 ¼” apart as shown in Fig. 2. Do not install this appliance on a carpeted wall or over floor covering which is combustible, such as carpet. The heater must be mounted on a wall using appropriate anchoring materials. If wall is a stud wall sheathed with plasterboard, it
is recommended that support board(s), either 1x4’s or 1/2" (minimum) plywood first be attached across a pair of studs and then the heater should be attached to the support boards. See Fig. 2.
Expansion and contraction of piping due to changing water temperature in the pipes imparts movement to the heater which, if mounted directly to a brittle, friable board, such as
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plasterboard, can cause failure of mounting. In earthquake-prone zones, CEC recommends that installers use a large washer and lag screw through the existing holes used to hang the heater to affix the upper third of the heater to the mounting board. To affix the lower third of the heater, CEC recommends that two new holes be drilled in the heater’s frame, each one 16 inches below the top two holes, and that washers and lag screws be used to secure the lower portion of the heater to a spacing board.
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. Also, each burner orifice is stamped with a number (79 for LPG and 120 for Natural Gas).
WALL STUDS
13 ¼”
SUPPORT BOARD
appliance. The heater should never be common vented with a mechanically vented appliance. Single wall vent pipe is not recommended, if used consult the National Fuel Gas Code.
Horizontally venting to a sidewall vent terminator or a vertically constructed vent stack along an outside wall of a building is not permissible. A Powervent (Model AQ-1), with a proof-of-draft safety interlock device, is required and is available in order to sidewall vent. Contact your dealer. In
the Commonwealth of Massachusetts: Powervented applications must utilize proof-of-draft safety interlock device.
VERTICAL GAS VENT: A 5 inch diameter gas vent constructed
of double wall Type B gas vent is recommended. 6 inch is required in elevations greater than 2000 feet, see Fig. 4. Any gas vent section that is greater than 45 degrees from the vertical is considered horizontal. Horizontal sections must slope upwards at least ¼ inch for every foot of its horizontal length and be properly supported. Keep the horizontal section short and avoid too many elbows. The minimum vertical gas vent height allowed is 6 feet; horizontal vent connectors and elbows are not to be considered in the total gas vent height. All gas vent sections must be secured to each other with sheet metal screws and be properly supported.
1” X 4”
SPACE BOARD
Fig. 2 - Mounting the Heater
The incandescent particle tray (shipped loose in the carton with the water heater) must be attached at the bottom of the water heater front cover at the time of installation. Use the screws provided. See figure 3
SCREWS
INCANDESCENT PARTICLE TRAY
Fig. 3 - Incandescent Particle Tray Illustration
VENTING
Vent pipe connection.
WARNING: Do not reduce the vent pipe size. See Fig. 4 for high altitude installations
The heater must be vented to the outside following all local ordinances and specifications for installing a gas appliance vent or chimney. The heater must be located as close as practicable to a vertically rising chimney or vent that has a listed vent cap at its termination point. The venting system must be designed and constructed so as to develop a posi­tive flow adequate to remove flue gasses to the outdoors.
Consult the National Fuel Gas Code if the vent will have elbows or share venting with another natural draft
The gas vent constructed of double wall Type B gas vent must terminate above the roof surface with a listed vent cap at a height that’s in accordance with Figure A or B and their table, provided they are at least 8 feet (2.4 m) from a vertical wall or similar obstruction. All other gas vents that are not able to terminate within the minimum specified height allowed must terminate not less than 2 feet (0.6 m) above the highest point where it’s passed through the roof and at least 2 feet (0.6 m) higher than any vertical wall or similar obstruction within 10 feet (3.1 m).
Listed vent cap
Figure A Figure B
GAS VENT TERMINATIONS FOR LISTED VENT CAPS
Roof pitch H (minimum) feet meters
Flat to 6/12 1.0 0.30 6/12 to 7/12 1.25 0.38 Over 7/12 to 8/12 1.5 0.46 Over 8/12 to 9/12 2.0 0.61 Over 9/12 to 10/12 2.5 0.76 Over 10/12 to 11/12 3.25 0.99 Over 11/12 to 12/12 4.0 1.22 Over 12/12 to 14/12 5.0 1.52 Over 14/12 to 16/12 Over 16/12 to 18/12 7.0 2.13 Over 18/12 to 20/12 7.5 2.27 Over 20/12 to 21/12 8.0 2.44
Lowest discharge opening
H (minimum) height from roof to lowest discharge opening
Listed gas vent
Establish a one foot
rise before any elbows
6.0 1.83
Listed vent cap
12
Roof Pitch
IS X/12
X
MINI MUM 6 FEET (1.8M)
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MASONRY CHIMNEY: Masonry chimneys shall be built and
installed in accordance with NFPS 211 or local codes. A minimum 5” diameter gas vent pipe (metal double wall Type B), or an approved clay flue liner or a listed chimney lining system must be used when venting into a naturally drafting, internal masonry chimney. 6 inch is required in elevations greater than 2000 feet, see Fig. 4. Local codes may require the use of both gas vent and an approved lining system when venting into a masonry chimney. The Commonwealth of Massachusetts requires the use of a listed liner. Lining systems include approved clay flue lining, a listed chimney lining system or other approved material that will resist corrosion, erosion, softening, or cracking from exhaust flue gases at temperatures up to 1800 degrees F. The lining system must be listed for use with naturally drafting, draft hood equipped gas appliances. Follow local codes and refer to NFGC 54 and NFPA 58.
minimum vertical chimney length should be no less than 5 ft (1.5 m); the termination point should extend at least 3 feet (0.9 m) above where the chimney meets the roofline and at least 2 feet (0.6 m) higher than any vertical wall or similar obstruction within 10 feet (3.1 m). See Figure C.
C) EXTERIOR masonry Chimney
Refer to the National Fuel Gas Code and consult a local venting HVAC contractor.
MASONRY CHIMNEYS
Listed vent cap
When connecting the water heater to a masonry chimney the following connector guidelines must be followed for safe and proper operation: An approved gas vent connector
must be attached to the top of the water heater and rise vertically at least 12” before entering into an approved gas vent connector elbow. Any gas vent section that is greater than 45 degrees from the vertical is considered horizontal. If a horizontal vent connector is to be used to connect the vertical gas vent connector on the top of the water heater to the masonry chimney, that approved horizontal gas vent connector must be kept as short as possible and must be sloped upwards at least ¼” per foot of its length. This connector must be supported throughout its horizontal length. This horizontal gas vent connection may be no greater than 75% of the total vertical gas flue vent within the chimney. Also, an approved thimble or collar must be used when penetrating a masonry chimney.
A) Existing INTERIOR Masonry Chimney
The metal gas vent pipe should be permanently mounted inside the masonry chimney. Double wall Type B gas vent is 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 only with naturally drafting, draft hood equipped gas appliances. Follow manufactures instructions for installation of listed lining material. You may not vent any other fuel burning appliances into any free space remaining in the chimney. The minimum vertical gas vent length within the masonry chimney should be no less than 5 ft (1.5 m); the vent terminator should extend at least 3 feet (0.9 m) above where the chimney meets the roofline and at least 2 feet (0.6 m) higher than any vertical wall or similar obstruction within 10 feet (3.1 m). The top of the gas vent should have an approved vent terminator. See Figure C.
Gas vent
Vent connector
Establish a one foot
rise before any elbows
Figure C
To check the draft:
Close all doors and windows to the outside. Turn on all appliances that force air out of the building. These include all exhaust/ventilation fans, furnaces, clothes dryers, wood burning stoves, etc. Open all doors between the 425 HN and these other appliances. With the control knob set fully clockwise and strong hot water flow rate, run the unit for at least 10 minutes. The 425 HN is equipped with a Flue Gas Sensor; it’s mounted on the right side of the draft diverter (Flue Gas Sensor #34 on page 17). If the main burners shut off during this test it is because the Flue Gas Sensor has detected inadequate venting. This is a serious health hazard and must be corrected. Poor venting can result in soot building up inside the heater, overheating of the heater and freezing of the heat exchanger in a freezing environment, which is all a result of negative air flow. Additional combustion air and/or improved venting will be necessary to correct this.
B) Tile Lined INTERIOR Masonry Chimney
The masonry chimney must have an approved liner, ceramic tile, clay or metal. The masonry chimney must be able to accommodate the spent fuel gasses; consult a venting HVAC contractor for chimney capacity. A common venting like-fuel appliance into this lined masonry chimney is permissible. The chimney’s diameter must be large enough to adequately draft the spent fuel gasses. A venting HVAC contractor will be required to spec a chimney system. The
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WARNING
Note: The burners of an instantaneous “on demand” water
heater such as the 425 HN are only on at the time that hot water is actually being used, the vent pipe is therefore cold except for the short durations when hot water is being used, it is therefore very important that the venting and air supply be adequate to provide a good positive draft as soon as the burners turn on. The 425 HN instantaneous water heaters have built-in draft diverters and are designed for indoor installation only. The
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