Bosch GWH 425 EF User Manual
TABLE OF CONTENTS
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.
FEATURING: Electronic Ignition and Power Venting
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.
Specifications............................................................... Page 3
Rules for safe operation............................................. Page 5
Locating the Heater .................................................... Page 5
Combustion Air Requirements .................................. Page 6
Mounting the Heater ................................................... Page 7
Venting the Heater ...................................................... Page 8
Gas Connections ...................................................... Page 11
Water Connections ................................................... Page 13
Electrical Connections ............................................. Page 14
Safety before turning on the heater ...................... Page 15
Lighting and Operating instructions ...................... Page 15
Setting water temperature ....................................... Page 15
Maintenance & Service ............................................ Page 16
Trouble Shooting......................................................... Page 17
Diagram of AquaStar ................................................ Page 20
Components and Parts List..................................... Page 21
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
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 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 the first two burners to ignite. The flame sensor
confirms correct activation and all burners 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.
425 EF LP and 425 EF NG Specifications
425EF NG 425 EF LP
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 NPT
H x W x D 29 3/4” x 18 1/4” x 8 3/4"
Vent 4”
Gas Connection 1/2” NPT thread
Min. Water Pressure 18 Psi
Max. Water Pressure 150 Psi
FEATURES
- Electronic Pilot Ignition
- On/Off switch to activate system
- Power Venting with safety shutoff
- 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.
- 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.
Shipping Weight 50.6 LB
Net Weight 44 LB
2.0 GPM at 90° rise
4.0 GPM at 45° rise
Min. Water Flow 1/2 gal/min
120V/60Hz 1.2 Amps
LP GAS Supply Pressure min. 11” W.C.
(before 425 EF regulator) max.14” W.C.*
Required LP GAS pressure at inlet
tap while 425 EF is operating: 10.5” W.C.
LP GAS Burner Manifold pressure while
425 EF is operating at maximum input: 9.9” W.C.
Natural Gas Supply Pressure min.: 7” W.C.
(before 425 EF regulator) max.: 14”W.C.*
- Easy one person installation.
Required Natural Gas Pressure at
- Adjustable water flow restrictor to ensure that water flow
inlet tap while 425 EF is operating: 5.7”W.C.
demand will not exceed the heating capacity of the heater.
Natural Gas Burner Manifold pressure while
425 EF is operating at maximum input: 5.38” W.C.
* Inlet gas pressure before 425 EF regulator must not
exceed this value. Pressure may need to be adjusted for
high altitudes, see page 11.
UNPACKING THE 425 EF 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. The FXHOOD horizontal vent terminator is supplied separately from the 425EF
water heaters. There is a set of installation instructions in the FXHOOD box.
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FRONT VIEW SIDE VIEW
MINIMUM INSTALLATION CLEARANCES FROM COMBUSTIBLE AND NON
COMBUSTIBLE MATERIALS FOR ALCOVE OR CLOSET INSTALLATIONS
* On a combustible wall surface the unit should be mounted away
from the wall to provide adequate clearance of the vent pipe.
See page 5 for instructions.
MODEL 425 EF
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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 install your heater so that the venting complies
with all requirements. See section on Venting the Heater,
pages 6 and 7.
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
during any pressure testing of the gas supply piping system
at test pressures in excess of 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 that might burn. Do not install heater over carpeting.
7. Correct gas pressure is critical for the optimum
operation of this heater (see specifications on page 2 and
chart on page 9). Gas piping must be sized to provide the
required pressure at the maximum output of the heater.
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.
9. Do not use this appliance if any part has been under
water. Immediately call a qualified service technician to
inspect the appliance and to replace any part of the control
system and any gas control that has been under water.
10. When installed, the appliance must be electrically
grounded in accordance with local codes or, in the absence
of local codes, in accordance with the National Electrical
Code ANSINFPA 70 and/or the CSA 22.1 Electrical Code.
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.
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).
Follow the guidelines below:
1. National building codes require that you do not install
this appliance in bathrooms, bedrooms, unvented closet
or any occupied rooms normally kept closed.
2. 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 EF is venting
properly when all these other appliances are running. See
page 6 to test venting performance.
Do not obstruct the flow of combustion air to the
appliance. This appliance is power vented and uses room
air. Note: Electrical power is required to operate the power
exhaust. Proper air supply to the appliance is essential.
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.
3. Your hot water lines should be kept short to save energy.
It is always best to have hot water lines insulated.
WARNING: 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.
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
installation.
Fig. 1 - Water heater drain plug
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.
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COMBUSTION AIR REQUIREMENTS
The 425 EF 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 in through the
unit’s vent pipe is capable of freezing these components.
This Installation Manual specifies the vent length
requirements 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 through the 425 EF vent pipe, leaving the
cold infiltrating air capable of freezing the cold water in the
425 EF heat exchanger. To prevent this the FX HOOD
horizontal vent terminator, which is supplied separately with
the water heater, needs to be installed on the end of the
horizontal vent run (see page 9). The FXHOOD is a CSA
approved vent terminator for the 425 EF and has a built in
back draft flapper.
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 6500 cubic feet for the 425 EF alone.
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.
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, assume it is 20 % to 25%
of the total opening for wood louvers and 60 % to 75% for
metal louvers. Refer to the National Fuel Gas Code for
complete information. In buildings of tight construction all
air should be taken from outside.
This product is not approved for manufactured homes
(mobile home), recreational vehicles (RV) or boats.
Reference ANSI Z21.10.3.
This product is neither designed or approved for outside
installations.
CLEARANCES
The 425 EF 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 (305 mm)
B. Front 4 inches (102 mm)
C. Back 0 inches*
D. Sides 4 inch (102mm)
E. Bottom 12 inches (305 mm)
Air Vents
(10 ¾ X 10 ¾ in. each)
425 EF
* On a combustible wall surface the unit should be mounted
away from the wall to provide adequate clearance of the
vent pipe. Clearance from the vent pipe is dependent upon
the clearance rating of the venting material used. See
VENTING section.
425 EF
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Air Vents
(5 ½ X 5 ½ in. each)
MO UN TI NG I N STA LL ATI ON
The 425 EF 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.
NOTE: Additionally the 425 EF should be spaced away
from any combustible wall surface to provide the
necessary clearance that the venting material specifies
must be maintained between the vent pipe and a
combustible surface. See VENTING section. Also, review
the FXHOOD horizontal vent terminator instruction sheet
(provided with the FXHOOD) prior to installation.
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.
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.
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 PA RTICLE TRAY
Fig. 3 - Incandescent Particle Tray Illustration
13 ¼ ”
SUPPORT BOARD
Fig. 2 - Mounting the Heater
WALL STUDS
1” X 4”
SPACE BOARD
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VENTING
pip
WARNING: Do not reduce the vent pipe size and
do not common vent with any other vented appliance or
stove.
This appliance must be vented horizontally to the outside
with a sealed 4” single wall vent pipe. The appliance’s flue
gasses are under positive pressure and must travel through
a single wall 4” pipe that is sealed gas tight. The 4” single
wall vent pipe can be either stainless steel (AL29-4C) or
galvanized steel with at least 26 gauge. CEC recommends
the use of stainless steel vent pipe (which is equipped with
sealing gaskets) for ease of installation and durability. When
using galvanized vent pipe a minimum of 4 sheet metal
screws per connection must be installed and all seams must
be sealed with an approved high temperature silicone
sealant. The vent system must be gas tight. See Fig. 4 for
suggested venting installation diagrams.
The 425EF shall not be vented in combination with any
other appliance. This appliance may only be vented
horizontally with a dedicated sealed single wall vent. The
425EF shall not be vented into masonry chimneys or existing
vertical vents of any material.
CAUTION: 425EF vent system must be installed by a qualified
agency in accordance with these instructions. If improperly
installed a hazardous condition such as explosion or Carbon
Monoxide poisoning could result. Controlled Energy
Corporation will not be responsible for improperly installed
appliances.
Establish vent clearances that comply with vent
manufacturer’s specifications. In all cases follow local codes.
See table below.
The vent diameter must be 4”. The appliance should be
located as close to the point of termination as possible (see
Fig. 5 for locating the terminator). The vent system should
be as straight and short as possible. The vent pipe must be
4” single wall stainless steel (AL29-4C) or galvanized steel
pipe of 26 minimum gauge. Maximum vent length is 15
feet (4.6 m) with two 90-degree elbows. Subtract 5 feet
from the total vent length for each additional 90-degree
elbow used. No more than four 90-degree elbows may be
used. Any short vertical portion of vent pipe used in the
vent system shall be considered part of the allowable 15
feet (4.6 m) maximum run. Support the vent run at 4 foot
intervals with overhead hangers. Horizontal sections of vent
must rise ¼” for every foot of horizontal length. Any vent
section greater than 45 degrees is considered and elbow.
Note: Single wall pipe should not be used in concealed,
unoccupied or unheated locations. Listed thimbles or collars
are necessary to pass through wall partitions. If the vent
system passes through combustible areas where the vent
clearance requirements cannot be maintained, it is
permissible to chase straight sections of sealed 4 inch single
wall vent through 5 inch (or greater) Type-B vent. The
distance to combustibles using this chase technique is 1
inch. Note: Type-B vent should never be used as the actual
vent system for the 425EF, as it is not gas tight.
Freeze Warning:
As mentioned on Page 6, negative air pressure in cold
climates will cause a reverse airflow in the vent system that
can freeze and damage the 425 EF heat exchanger when
not in use. To prevent this the FXHOOD horizontal vent
terminator, which was supplied separately with the water
heater, needs to be installed on the end of the horizontal
vent run (see page 9). The FXHOOD is a CSA approved
vent terminator for the 425 EF and has a built in back draft
flapper.
Flue Gas Sensor:
The 425 EF is equipped with a Flue Gas Sensor; it’s mounted
on the left side of the draft diverter (Flue Gas Sensor - #33
on page 21). Before leaving the installation site verify proper
Flue Gas Sensor operation by temporarily blocking
termination outlet. Once blocked then operate the heater,
the unit should shut down within 1-3 minutes when the flue
gases are blocked. You must reset the electrical power to
the heater after this safety test has been conducted,
otherwise the unit will not operate.
The flue gas exhaust temperature on the 425 EF is 356°F (180°C)
Venting Material
Options
Single wall stainless
steel (AL29-4C)
sealed vent
Single wall galvanized
vent pipe (min. 26
gauge and sealed
with high temperature
silicone)
*Stainless steel (AL29-4C) vent pipe manufacturer's are Z-Flex, Protech and Heat Fab. The manufacturer's specified clearances
are identified on the venting material. NOTE: clearance distances are variable depending if the vent pipe is installed in an
enclosed or unenclosed space, the exhaust flue gas temperature and the orientation of the vent pipe.
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Exhaust vent
e
diameter
4 inch
4 inch
Exhaust vent maximum
distance
15 feet (4.6 m) with two
elbows. Less 5 feet for
each additional elbow.
15 feet (4.6 m) with two
elbows. Less 5 feet for
each additional elbow.
Clearances
from venting
material
Vent pipe within an
unenclosed space
*See manufacturer's
specifications
6 inches NOT PERMISSIBLE
Vent pipe within an
enclosed space
*See manufacturer's
specifications
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