Bosch WR430-7K User Manual

Instantaneous gas water heater

POWER VENTED - ELECTRONIC IGNITION

Model
WR430-7K

• installation

• operation

• maintenance

The Bosch instantaneous water heater is a high efficiency,
space saving answer to your water heating needs. All Bosch
instantaneous water heaters heat water only as required;
no energy is lost maintaining a large volume of water at
elevated temperatures as in tank-type storage water heaters.
Suitable for heating potable water only. Not approved for
space heating purposes.

READ INSTRUCTIONS CAREFULLY BEFORE INSTALLING

NOTICE TO INSTALLER: Please leave this

manual with the owner or affix adjacent to
appliance.

ASTRAVAN DISTRIBUTORS, LTD.

6 720 606 599 CA (03.11) AL

123 Charles Street
North Vancouver, B.C. V7H 1S1

Phone Canada: [phone]
Phone USA: [phone]
Web Site: www astravan.com

WARNING: If the information in this
manual is not followed exactly, a fire or
explosion may result causing property
damge, personal injury or death.

- Do not store or use gasoline or other
flammable vapors and liquids in the vicinity of
this or any other applicance

- 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.

Note: In case of problems please contact your salesman or installer

BOSCH WR430-7K

NAT. GAS PROPANE

Principle of Operation:

When a hot water faucet is opened, the flow of water through
the heater causes the gas valve to open. At the same time
a microswitch is activated which sends a spark to the pilot.
The flame sensor confirms that the pilot has been lighted
and allows burners to ignite. The pilot goes out. The power
exhaust system runs as long as the burners are on. 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, followed immediately by the exhaust
system. Your hot water faucet is an ignition key to turn on
the water heater, giving you control over your hot water energy
use. Every time you turn off your hot water faucet, the energy
consumption for hot water returns to zero.

FEATURES

- Power Venting with safety shutoff

- Electronic Pilot Ignition

- On/Off switch to activate system

- High Quality Materials for Long Working Life.

- Copper heating coils for endless supply of hot water.

Gas Input

max. 130 000 Btu/hr 125 000 Btu/hr
min. 28 000 Btu/hr 28 000 Btu/hr

Water Connection 1/2” Thread fitting

H x W x D 29 3/4” x 18 1/4” x 8 3/4”

Vent 4” (Category III Gas Appliance)

Max. lineal vent pipe length 15" (4.5m)

Gas Connection 1/2” NPT thread

Minimum recommended house supply pressure 40 Psi

Warm position minimum water pressure 18 psi (no fittings)

Hot position minimum water pressure13 psi (no fittings)

Max. Water Pressure 150 Psi

Shipping Weight 55 Lbs

Net Weight 44 LB

2.5 GPM at 90° rise (32°C) (9.5 l)

- Burner output proportional to hot water flow demand for
maximum energy efficiency.

- Safety flame sensor at pilot burner.

- Automatic over heating protection shut-off sensor.

- Stainless steel burners with stabilized blue flame.

- Built-in corrosion resistant power venter.

- Compact space saver: mounts on a wall with two hooks.

- Easily removable one-piece cover.

- Easy one person installation.

- Adjustable water flow restrictor ensure that water flow
demand will not exceed the heating capacity of the heater.

UNPACKING THE BOSCH WR430-7K HEATER

5.0 GPM at 45° rise (16°C) (19.5 l)

Min. Water Flow 1/2 gal/min

120V/60Hz 1.2 Amps

LP GAS Supply Pressure inlet. min. 11”W.C.*

LP GAS regulator outlet pressure 9.9”W.C.*

Natural Gas Pressure inlet min.: 7”W.C.*

Natural Gas Regulator Pressure 5.38 W.C.**

* Inlet gas pressure must not exceed this value

** For purposes of input adjustment

ELECTRICAL 3 ft. ( 0.9 m) power cable supplied c/w CSA
3 prong plug.

This heater is packed securely. The box includes two water connection fittings, a control knob, a gas pressure regulator, a
pressure relief valve, an incandescent particle tray, two hooks for hanging the heater, this manual. Do not lose this manual

as there is a charge for replacement.

2 6 720 606 599

DIMENSIONS

EXTERIOR

TERMINATION

Figure 1

Maximum Hydrostatic water pressure - 1.03 MPa (150 p.s.i.)
Maximum recommended working pressure - 0.69 MPa (100 p.s.i.)
Minimum working pressure - 0.09 MPa (13 p.s.i.) no piping attached
Reccomended pressure for showers and domestic, 0.27 MPa (40 p.s.i.)

Model Type of Gas Altitude Input

natural gas 130 000 Btu/hr (38 kW) 1.20 diam. 18

WR430-7.K..

• The high altitude ratings listed are Canadian Gas Association high altitude ratings and are valid only in Canada. In the U.S., the
National Fuel Gas Code, ANSI Z223.1-1988, recommends for high altitude installations above 2,000 feet, that the input rate be
reduced 4% for each 1,000 feet above sea level. - See page 15.

propane/LP 125 000 Btu/hr (36.6 kW) 0.79 diam. 18

natural gas 117 000 Btu/hr (34.3 kW) 1.20 diam. 18

propane/LP 112 000 Btu/hr (32.8 kW) 0.79 diam. 18

standard

(0 - 2 000 ft)

high *

(2 000 - 4 500 ft)

Main Burner Orifices

Size, mm Qt.

36 720 606 599

FORWARD

The design of the WR430-7K complies with CAN 1-4.3
and ANSI Z21.10 (latest edition) as an instantaneous gas
water heater. In addition, the WR430-7K also complies with
CAN 1-2.17 for use at high altitudes, 2,000 - 4,500 ft. above
sea level.

Installation, operation and maintenance instructions are
provided in this manual. Installation and operation
instructions should be thoroughly reviewed before
proceeding with installation of the BOSCH instantaneous
gas water heater.

The BOSCH instantaneous gas water heater is designed
to operate on natural or propane gas: however, make sure
that gas on which heater is to operate is the same as
specified on the heater’s model/rating plate.

In addition to these instructions, the water heater shall be
installed in accordance with CAN/CGA-B149 Installation
Code (in Canada) or Z223.1-latest edition, National Fuel
Gas Code (in U.S.A.) and/or local installation codes. These
shall be carefully followed in all cases.

INSTALLATION INSTRUCTIONS

The Bosch WR430-7K is a high efficiency fin tube heater and should not be installed and operated during construction or
building renovations if location is exposed to above normal dust levels. This can cause dust build up in the finned heat
exchanger and result in damage to heater and be a hazard to health.

Note: Proper plumbing, venting, gas connections and an

adequate supply of combustion air are required for
safe and reliable operation. Ability equivalent to that
of a licensed tradesman in the field involved is
required for installation and/or service of these water
heaters.

AIR REQUIREMENTS

For safe operation, sufficient air for combustion, ventilation
and dilution of flue gases must be available. An insufficient
supply of air will result in a yellow luminous burner flame,
causing carboning or sooting of the heat exchanger.

LOCATION

Before installing the BOSCH instantaneous gas water
heater, consideration must be given to proper location. The
location should be as close to outside vent termination as
practicable, in an area with an adequate air supply and as
centralized with the piping system as possible. The heater
should not be located in an area where it will be subject to
freezing. The heater should be located in an area where
leakage of the heater or its connections will not result in
damage to the area adjacent to the heater or to lower floors
of the structure. See venting page 6.

Note: When such locations cannot be avoided, it is

recommended that a suitable drain pan, adequately
drained, be installed under the water heater. The pan
must not restrict combustion air flow.

ELECTRICAL

A grounded switched plug receptable must be provided
immediately below the left hand corner of heater to accept
and provide power to supplied 3 ft. (0.9m) appliance cable
and plug.

In order to prevent corrosion, make sure that the combustion
air is kept free of aggressive substances. Substances that
especially contribute to corrosion are halogenated
hydrocarbons (e.g., chlorine and fluorine) which are
contaned in solvents, paint, adhesives, propellant gases,
various household cleaners, etc. Take precautionary
measures as necessary.

In unconfined spaces, in buildings of normal construction,
infiltration normally is adequate to provide air for combustion,
ventilation and dilution of flue gases. However, a confined
space must be provided with two permanent openings to
provide combustion and ventilation air to the appliance. Each
opening shall have a free area of one square inch per 1,000
Btu/Hr* of total input rating of all the appliances in the
enclosure. One opening shall be within 12 inches of the
top and one within 12 inches of the bottom of the enclosure.

* Special Note
When the WR430-7K is installed in a confined space of
minimum size the openings described above must be
increased in to a size of 1-1/2 square inches per 1,000
BTU/Hr. In other words, when installed in a minimum sized
confined space the two openings that are to be made in
the enclosure within 12 inches of the top and 12 inches of
the bottom must each have a minimum free area of, (1 ­1½” - 2" x (130) = 195 square inches.

4 6 720 606 599

For either a confined or unconfined space in a building of
tight construction with inadequate infiltration, air must be
drawn from the outdoors or from spaces that freely
communicate with the outdoors. Two permanent openings
located as indicated are to be provided as follows:

1. When communicating with outdoors directly or by

means of vertical ducts, each opening shall have a
free area of not less than one square inch per 4,000
BTU/Hr. of total input of all appliances in the space.

2. When communicating with outdoors by means of

horizontal ducts, each opening shall have a free area
of not less than one square inch per 2,000 BTU/Hr. of
total input of all appliances in the space.

For detailed requirements see:

• in Canada, CAN/CGA-B149 Installation Codes

• in U.S.A., ANSIZ223.1-latest edition, National Fuel Gas

Code.

MOUNTING

The WR430-7K is design certified for mounting to a wall.
The heater must not be installed on a carpeted wall. The
heater must be mounted to the wall using appropriate
anchoring materials.

Note: If wall is a stud wall sheathed with plasterboard it is

recommended that support board(s), either 1 x 4's
or 1/2” (minimum) plywood first be attached across
a pair of studs and then the heaters should be
attached to the support boards. See Figure 2.

Figure 2

WALL STUDS

WARNING!

1. Flammable materials, gasoline, pressurized containers,

or any other items or articles that are potentially fire
hazards must never 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.

2. Do not obstruct the flow of combustion and ventilation

air to the appliance.

CLEARANCE

The WR430-7K is design certified for installation on a
combustible wall and for installation in an alcove or closet
with minimum clearances to combustible construction of 0
mm from back, 102 mm (4 inches) from sides, 305 mm (12
inches) from top and bottom, and 102 mm (4 inches) from
front. A minimum of 305 mm (12 inches) shall be allowed
for maintenance of serviceable parts. Clearance from vent
is dependent upon the clearance rating of the venting
material used; see venting page 6.

Warning!

SUPPORT BOARD

1” X 4”

SPACE BOARD

Fig. 2 - Mounting the Heater

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
plasterboard, can cause failure of mounting.

Check Flue Gas Safety Device good functioning, please
proceed as explained in "Flue gas safety device" page 16.

THIS APPLIANCE MUST BE INSTALLED IN ACCORDANCE WITH THE NATIONAL FUEL GAS CODE ANSI Z223.1­latest edition in U.S.A. or CAN/CGA-B149 INSTALLATION CODES IN CANADA. LOCAL CODES AND/OR THE
REQUIREMENTS OF THE AUTHORITY HAVING JURISDICTION MUST BE FOLLOWED.

56 720 606 599

Bosch POWER VENTING SYSTEM

INTRODUCTION

Bosch power venting models are designed to overcome difficult venting problems which cannot be performed

with atmospheric venting: to meet your hot water demand load very efficiently, with an environmentally friendly
appliance which conserves energy and significantly reduces combustion emissions to atmosphere.

GENERAL INFORMATION

This Power Vent System must be installed by a *qualified installer in accordance with all applicable local gas
and electrical codes and in the absence of:

• With the current CAN1/CGA B149 installation code for gas burning appliances and the Canadian Electrical
code C22.1-M90 part 1 (for Canada).

• With the National Fuel Code and the ANSI Z223.1-LATEST and National Electrical Code ANSI/NFPA No
70-LATEST electrical code (for USA).

The Bosch warranty will be voided by, and Bosch disclaims any responsibility for the following actions:

• Use of any unapproved venting component part not manufactured or approved by Bosch in combination
with the Bosch WR430-7K unit.

• The Bosch WR430-7K must not be modified in any way when installing the Power Vent System. All
systems must be installed as per Bosch Installation Guide.

• Installation other than instructed in this manual.

CAUTION:
Bosch Power Vent System must be installed by a qualified agency in accordance with these instructions.
If improperly installed a hazardous condition such as an explosion or Carbon Monoxide poisoning
could result. Bosch will not be responsible for any and all improperly installed appliances.

*QUALIFIED INSTALLING AGENCY: Any individual, firm, corporation or company which either in person or

through a representative is engaged in and is responsible for the installation and operation of gas appliances and
draft control devices, who is experienced in such work, familiar with all precautions required, and has complied
with all the requirements of the authority having jurisdiction.

GENERAL VENTING INFORMATION

SIZING & DISTANCES:

Plan the vent system so that code clearances and manufacturer’s distances are maintained from combustible
materials, plumbing and wiring.

This unit may be directly connected to approved vent termination with a 90° elbow or located with a maximum
lineal length of 15 ft. (4.6m) including two 90° elbows from termination. All vent pipe and fittings must only be
4” (10.2cm) in diameter.

6 6 720 606 599

Bosch POWER VENTING SYSTEM

GENERAL VENTING INFORMATION - continued

APPROVED VENTING MATERIALS:

Single wall:

As gauge listed in the current CAN1/CGA B149 installation code for gas burning appliances (for Canada),

National Fuel Code ANSI Z223.1-LATEST (for USA).

Note: Cannot be used in concealed locations.

B-Vent materials:

Straight lengths only (no elbow) may be used under following conditions
(i) Unsealed 5” B-vent may be used as a chase for sealed 4” single wall through concealed or unheated
areas.

Clearances to combustible materials for walls and partitions:

• 1” (25mm) for B-Vent.

• 3” (76mm) for single wall and uninsulated PVS-1 vent piping.
A wall thimble must be installed for internal wall applications.

All runs through unheated space or exposed to outside temperatures must be insulated to prevent condensation.

All portions of the vent system under positive pressure during operation (on the outlet side of the WR430-7K)
shall be sealed with high temperature silicone and high temperature aluminum duct tape and installed so as to
prevent leakage of flue or vent gases into building.

GENERAL CODE REQUIREMENTS

Before commencing an installation always consult with local gas and electrical codes and authorities, in the
absence must be installed:

• With the current CAN1/CGA B149 installation code for gas burning appliances and the Canadian Electrical
code C22.1-M90 part 1 (for Canada).

• With the National Fuel Code and the ANSI Z223.1-LATEST and National Electrical Code ANSI/NFPA No 70­LATEST electrical code (for USA).

76 720 606 599

Bosch POWER VENTING SYSTEM

VENT TERMINAL INSTALLATION:

Before installing Bosch WR430-7K determine the location of vent system termination which may be immediately
connected with a 90° elbow or with a maximum lineal length of 15 feet including two 90° elbows. (See Fig. 1)

90° el

12 ft straight
(5.7m)

90° el

90° el

3 ft straight
(0.3m)

15 ft straight
(4.6m)

90° el

MAXIMUM LENGTH OF ALL PIPE LENGTHS
MUST NOT EXCEED 15 FT (4.6M)

Note: In cold climate areas negative air pressure such as unbalanced heating and ventilating systems can
cause reverse air flows in gas vent and chimney systems. Under extreme cold conditions this can cause
freezing and damage Bosch heat exchanger during prolonged period of times when they are not in use,
such as night time hours. Vent termination with back draft flapper is supplied in order to minimize outside
air infiltration and risk of freezing equipment.

The approved terminal shall be so arranged for flue gases to be directed in a manner which will not jeopardize
people, overheat combustible structures or enter into buildings, and that proper clearances are maintained (See
Fig. 2 )

a) The vent terminal of this Power Vent System shall not be less than 7 feet (213cm) above grade when

located in areas accessible to public walkways.

b) A vent terminal shall terminate at least 3 feet (91cm) above and a minimum of 10 feet (305cm) horizontally

from any (mechanical) air inlet.

c) The vent terminal shall not be within 6 feet (183cm) radius from a gas meter or regulator, and horizontally

it must be a minimum of 3 feet (91cm) from the centre line of such regulator.

d) The vent terminal shall be a minimum of 6 feet (182cm) from any combustion air inlet.

e) The vent terminal shall terminate from an

opening window, at least 4 feet (122cm) below or below the
opening and 12 inches (30cm) horizontally. From a door 1 foot (30cm) above and 9 inches (23cm)
horizontally.

f) The vent terminal shall not be less than 3 feet (91cm) from an adjacent building.

g) The vent terminal shall not be less than 2 feet (61cm) above grade.

8 6 720 606 599

Bosch POWER VENTING SYSTEM

Figure 2

36”

36”

7

2

”

72”

REGULATOR VENT

ELECTRICAL WIRING:

1. The electrical contact ratings are as follows:

______ 1/10 HP at 120 VAC
______ 3 Amps (full load) at 120 VA

2. Provide switched plug receptacle to accommodate Bosch grounded plug.

3. Make certain the power source is adequate for the fan motor requirements.

VENT INSTALLATION

1. Choose approved terminal location

2. Cut vent terminal opening through outside wall - Refer to installation instructions supplied with termination.

3. Install vent terminal by fastening from outside with 4 screws and caulking around flange edge. Check that
optional flapper moves freely if applicable.

4. Install 4” venting materials and secure all joints with a minimum of four screws for each joint. Please note that
wherever possible use continual lengths of pipe to reduce the number of joints.

5. Seal all positive vent pipe and elbow joints between Bosch unit and vent terminal with high temperature
silicone and/or hi temperature aluminum tape following manufacturer’s instructions (i.e. always push silicone
ahead of nozzle)

96 720 606 599

Bosch POWER VENTING SYSTEM

VENT INSTALLATION (continued)

6. Support venting duct with plumber’s strap (supplied by installer). Solid piping need only be supported every
four feet. All horizontal pipe joints must be secured with a minimum of four screws per joint. (See Figure 3)

7. All runs through unheated spaces must be wrapped and insulated with a minimum of 1” insulation.

Figure 3

Vent support hangers (plumber's
strapping) should be 4 ft. apart on
horizontal runs.

Use 4 screws
per joint

RIGID PIPE

positive pressure

All joints must be sealed with high temperature silicone
and high temperature aluminum vent pipe tape

All clamped joints on the positive
side of the power venter are to
be sealed with high temperature
silicone.

OPERATION AND CHECKING THE DRAFT

A. Place Bosch appliance into operation. Follow lighting pilot and operating instructions on Bosch

cover.

1. Draw water continuously to activate appliance which will turn on gas burner.

2. CHECKING THE DRAFT. Operate the appliance with cover in place for a minimum of five minutes and
check for proper venting, and assure that the combustion products are venting properly, by passing a
lighted match flame or smoke taper over the top edge of the Bosch cover and towards draft hood. If the
vent is drawing properly, the smoke or match flame will be drawn over the top edge of the Bosch cover
and into the draft hood or opening. (see drawing below Checking The Draft)

CHECKING THE DRAFT

NOTE: If smoke is not drawn in then the combustion products are

escaping from the relief opening into the room. Under these
conditions, the equipment shall not be operated until proper

adjustments or repairs are made to provide adequate draft.

3. Check draft spill safety switch by obstructing outside vent terminal and by drawing water. Spill switch

should trip and shut off gas supply to Bosch unit. Remove outside obstruction.

4. If spill switch trips allow 5 minutes to reset.

10 6 720 606 599

Bosch POWER VENTING SYSTEM

B. The Air-Flow Adjustment on the Power Venter is factory set for optimum air flow. Operating at its setting will

assure that combustion gases are safely removed to the outside.

MAINTENANCE

Points of inspection are:

1. Motor - Motor must rotate freely.

2. Fan Wheel - Wheel must be clean of dust or any other coating which inhibits rotation or air flow. Remove
all foreign material from vent system before operation.

3. Spill Switch - Verify proper spill switch operation by observing Operation Sequence and by temporarily
blocking termination outlet.

4. Check Draft - Check for flue gas spillage following steps in the Operation And Checking Draft on page 9.

5. Vent Termination - Inspect to ensure installation and clearances have not been altered or obstructed and
that the back draft flapper (when used) movement is free and operational. Note that terminal hood is
removable for easy flapper maintenance or replacement.

Hinge

Vent termination hood

Flapper

116 720 606 599

DRIP TRAY

WATER CONNECTIONS

If the water heater is being mounted above a floor of
combustible construction the drip tray (shipped loose in the
carton with the water heater) must be attached to the bottom
of the front cover of the water heater at the time of
installation. The drip tray should be attached to the front
cover, using screws provided, as shown in Figure 3.

Failure to use drip tray when installing unit above a floor of
combustible construction will cause an unsafe condition and
possible fire and will be in violation of A.G.A. and C.G.A.
certification of the unit.

SCREWS

INCANDESCENT PARTICLE TRAY

Figure 3

The BOSCH instantaneous water heaters are provided with
two S-bend water connectors/adaptors that must be
connected to inlet and outlet connections on water valve
assembly, see Figure 4, below.

Water valve and S-bends, top view

Figure 4

The purpose of the S-bend water connectors/adaptors is to
provide threaded water connections that meet standards
used in North America, ANSI Standard Taper Pipe Thread
(1/2” NPT). The cold water supply should be connected to
S-bend attached to inlet of water valve and the hot water
connection should be made to S-bend attached to the outlet
of water valve.

If plastic piping is to be used, a 1.5 meter (approx. 5 feet)
length of metal piping must first be attached to both the
cold water inlet and hot water outlet of the water heater.

Note: A shut-off valve should be placed in the cold water

supply line to the heater to facilitate servicing the
heater.

12 6 720 606 599

RELIEF VALVE

The listed pressure relief valve supplied must be installed
near the hot water outlet at time of installation of the heater.
No valve is to be placed between the relief valve and the
heater. A drain line must be connected to the relief valve to
direct discharge to a safe location. Do not install reducing
coupling or any other restriction in the discharge line. The
discharge line must be installed so as to allow complete
drainage of both the valve and the line. See figure 5.

Figure 5

Check to make sure that the gas listed on the rating plate is
same as gas listed on the pressure regulator. See
PRESSURE REGULATION section of this manual for
information regarding gas pressure settings.

Note: Before attaching the gas supply line, be sure that all

gas pipe is clean on the inside. To trap any dirt or
foreign material in the gas supply line, a drip leg must
be incorporated in the piping. The drip leg must be
readily accessible and not subject to freezing
conditions. Install in accordance with the
recommendations of serving gas supplier.

Joint compounds (pipe dope) shall be applied sparingly and
only to the male threads of pipe joints. Do not apply
compound to the first two threads. The joint compound must
be resistant to the action of liquified petroleum gases.

Before placing water heater in operation, check for gas
leakage. Soap and water solution, or other material
acceptable for this purpose shall be used in locating gas
leaks. Matches, candles, lighters, or other ignition sources
shall not be used for this purpose.

GAS CONNECTIONS

Before connecting the gas supply to the heater, check
heater’s model/rating plate to make sure that the gas on
which heater is to operate is the same as specified on the
model/rating plate.

The WR430-7.K.. instantaneous water heaters are supplied
with a gas pressure regulator that must be installed on the
heater before attaching the gas supply line. See figure 6.
Failure to install the gas pressure regulator as shown in
figure 6 will be a violation of A.G.A. and C.G.A. certification
of the unit.

BOSCH water heaters are shipped from the factory with
the gas pressure regulators preset for the gas shown on the
rating plate to the correct pressure:

• in Canada, for high altitude operation;

• in U.S.A., for standard altitude operation unless
specifically marked as a high altitude unit.

GAS INLET PIPE

PRESSURE TAP T

WARNING

The heater and its individual shutoff valves must be
disconnected from the gas supply piping system during any
pressure testing of that system at test pressures in excess
of 3.45 kPa (1/2 psig).

The water heater, including the pressure regulator provided
with it, must not be operated at gas supply pressures in
excess of 3.45 kPa (1/2 psig). If overpressure has occurred
such as through improper testing of the gas lines or
emergency malfunction of the supply system, the gas valve
and regulator must be checked for safe operation. Make
sure that the outside vent valves are protected against
blockage. These are part of the gas supply system, not the
water heater. Vent blockage may occur during ice storms.

Figure 7 Gas Burner test point D for measuring burner
manifold pressure at full flow and input:
Standard Altitude: 4.58”W.C. Nat Gas, 9.11”W.C. Propane.
High Altitude: 3.73”W.C. Nat Gas, 7.27”W.C. Propane.

APPLIANCE PRESSURE
REGULATOR

Figure 6 GAS MANIFOLD PRESSURE TEST POINT

T For measuring correct regulator operating pressure.

Figure 7

136 720 606 599

OPERATING INSTRUCTIONS

WARNING!

If the water heater has been damaged or exposed to fire or
sooting, or if any part has been underwater, do not use. If
unit has been operated during construction or alterations
and exposed to above normal dust levels the heat exchanger
should be examined and cleaned regularly. Operation with
dust obstructed fins could be a health hazard. 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 and to clean the heat
exchanger assembly and water valve.

FILLING

Before proceeding with operation of the water heater make
sure that the system is filled with water:

• Make sure drain is closed. See figure 8, below.

• Open a nearby hot water faucet to permit the water to
fill the heater and piping.

• Close the hot water faucet after the water flows freely
and all air has escaped from the system.

The water heater is now ready to be lit.

WA TER VAL VE

TO HEAT EXCHANGER

LIGHTING AND OPERATING INSTRUCTIONS

1. STOP! Read the safety information above on this lable.

2. The gas valve must be shut off by putting the ON/OFF
switch to position “ ” Wait five (5) minutes to clear out

any gas. If you smell gas, STOP! Follow “B” in the safety
information above. If you do not smell gas, go to the
next step.

3. This water heater is equipped with a safety pilot burner
and an automatic ignition control system.

4. Set the ON/OFF switch (flip down cover plate on frontal
panel strip) marked / to the " " position. In this
position, the water heater is ready to use. (See Fig. 9).

5. Turn the hot water faucet on the minimum flow rate
required to activate the heater. The automatic ignition
system first ignites the safety pilot burner which then
ignites the main burner in about 4 seconds.

6. The pilot flame will extiguish 10-30 seconds after the
burners come on. The burners will remain on until the
hot water tap is turned off.

7. Vent fan turns on and off with burner.

NOTE: On a first time initial installation, existence of air in
the gas supply line and in the water line may cause some
ignition delay. In that case, repeatedly open and close the
hot water tap in order to restart the ignition process until all
the air has been purged.

TO TURN OFF GAS TO APPLIANCE

FROM HEAT
EXCHANGER

DRAIN PLUG

Figure 8

SERVICE HINT

The screen (strainer) in the water valve, located in the inlet
of the water valve, may require occasional cleaning due to
foreign material in the water supply. This will restrict the
flow of water and may affect heater operation and prolong
filling time. To inspect the strainer, close the cold water supply
valve ahead of the heater, disconnect the S-bend from the
inlet of the water valve and remove strainer from inlet. Clean
if required, replace strainer in inlet to the water valve,
reconnect S-bend and turn on water supply.

Light the water heater in accordance with the instructions
on the Lighting and Operating Plate on the water heater.
For your convenience, the instructions are repeated here:

Turn off the manual lever on the gas supply line to the heater
and set the ON/OFF switch to the OFF ( ) position.

To operate the heater, set the ON/OFF switch to position
“ ”. The switch is located behind the flip down cover
plate on the front panel strip.
To shut down the gas to the heater, set the ON/OFF
switch to position “ ”.

Figure 9

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PRESSURE REGULATION

The pressure regulator supplied with the water heater is
adjusted to operate on the gas specified on the rating plate
and:

• in Canada, is factory preset to deliver gas at the high
altitude setting listed on the rating plate and as shown
below.

• in the U.S.A., is factory preset to deliver gas at the
standard altitude setting listed on the rating plate and as
shown below.

The pressure setting of the gas pressure regulator should
be checked at installation to assure that the setting is correct
for the gas being used and the altitude at which the
appliance is installed. See rating plate on the unit, Table 1,
below, for proper setting.

In Canada, for a heater being installed at standard altitude
(0-2,000 ft above sea level) the manifold pressure should
be reset at installation to the value shown on the rating
plate, or Table 1, below, for standard altitude.

REGULATOR
SUPPLY TEST
PRESSURE TAP T

Your appliance dealer and/or your local gas supplier should
be consulted in regard to any high altitude installation. If
field adjustment is required it should be performed by a
qualified serviceman experienced in such work.

TEMPERATURE REGULATION

The BOSCH WR430-7K is equipped with a modulating
gas valve which adjusts the flow of gas to the main burner
in proportion to the water flow rate. Within its heating
capacity the WR430-7K attempts to maintain the set
temperature rise across the heater. This temperature rise
can be set in range of 25°C - to - 50°C (45°F - to - 90°F),
by means of the water flow selector. See Figure 11. When
the water flow selector is turned to the right hand stop the
water heater is set for 50°C (90°F) temperature rise; when
the water flow selector is set to the left hand stop it is set
for 25°C (45°F) temperature rise.

Temperature Adjustment Knob

Decreases temperature

and increases flow

Increases temperature

and decreases flow

ADJUSTABLE
PRESSURE REGULATOR

Figure 10

The gas pressures specified below refer to flow pressure
taken at the pressure tap in the gas inlet pipe just above the
pressure regulator, (see figure 10) while the heater is
operating at full input.
Gas pressures read at burner test point D (see fig. 7) page

13.

Table 1.
Appliance Regulator Pressure Setting

Model Type of Gas

natural 1.41 5.38 standard

WR430-7K

*Note: The high altitude ratings listed are Canadian Gas Association

propane 2.61 9.9 (0-2,000 ft.)

natural 1.14 4.4 high*

propane 2.09 7.9 (2,000-4,500 ft.)

high altitude ratings for the appliances and are only valid in
Canada. In the U.S.A. the National Fuel Gas Code, ANSI 1­1988, recommends for high altitude installations, above 2,000
feet, that the input rate be reduced 4% for each 1,000 feet
above sea level.

Pressure tap

kPa Inches, W.C.

Altitude

Figure 11 - Principles of Operation

With the water flow selector turned to its right hand stop
position (50°C rise setting) and with an inlet water
temperature of 10°C (50°F) the outlet water temperature
will be maintained at approximately 60°C (140°F) in the
water flow rate range of approximately 2 litres/min. (0.5 U.S.
gals./min.) to 9.5 litres/min. (2.5 U.S. gals./min.).

The minimum flow rate for operation, the “Threshold Flow
Rate” referred to in the lighting instructions is 2 litres/min
(0.5 U.S. gals./min.). If the water flow rate is below this level
the main burner will not fire. If the flow rate exceeds 9.5
litres/min (2.5 U.S. gals./min.) the temperature rise aross
the heater will decrease in proportion to the rate above this
temperature.

HIGH TEMPERATURE LIMIT SWITCH

The BOSCH series instantaneous gas water heaters are
equipped with a high temperature limit switch with a set
point of approximately 90°C (195°F). If the water temperature
at the sensing points exceeds the set point the switch will
open, interrupting the safety circuit and stopping gas flow
to the pilot and main burner.

Outage as the result of high limit operation indicates that
the heater is not functioning properly. The heater should be
checked by a qualified serviceman and the reason for the
malfunction is corrected.

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