Bosch 125FX LP, 125FX NG User Manual

INSTALLATION AND OPERATING INSTRUCTIONS FOR AUTOMATIC
INSTANTANEOUS TYPE WATER HEATER FOR USE WITH NATURAL AND
LIQUEFIED PETROLEUM GAS

MODEL 125FX LP and 125FX NG

(Flow Modulated with Electronic Ignition and Power Venting – a Type III Category Appliance)

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 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.

WHA T 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.

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

6 720 606 519 (02.01) AL

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.

FEA TURING: Automatic V ariable Power Modulating Gas
V alve, Electronic Ignition and Power Venting

T ABLE OF CONTENTS

Specifications .................................................... Page 2

Rules for safe operation .................................... Page 4

Locating the Heater ............................................ Page 4

Combustion Air Requirements ............................ Page 5

Mounting the Heater........................................... Page 5

Venting the Heater ............................................. Page 6

Gas Connections ............................................... Page 9

Water Connections .......................................... Page 10

Electrical Connections ......................................Page 1 1

Safety before turning on the heater................... Page 12

Lighting and Operating instructions .................. Page 12

Setting water temperature ................................ Page 12

Maintenance & Service..................................... Page 13

Trouble Shooting .............................................. Page 14

Diagram of AquaS tar......................................... Page 17

Components and Parts List.............................. Page 18

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. Y our 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.

AquaStar 125FX LP and 125FX NG Specifications

AQ125FXNG AQ125FXLPG

130 000 Btu/hr 125 000 Btu/hr

Gas input

max.

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” (Category III Gas Appliance)
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.

- Easy one person installation.

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

BOSCH is constantly improving our products, therefore
specifications are subject to change without prior
notice.

UNP ACKING THE AQUASTAR HEATER

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 Aquastar regulator) max.14” W.C.*

Required LP GAS pressure at inlet
tap while Aquastar is operating: 10.5” W.C.

LP GAS Burner Manifold pressure while
Aquastar is operating at maximum input: 9.9” W.C.

Natural Gas Supply Pressure
(before Aquastar regulator) min.: 7” W.C.

max.: 14”W.C.*

Required Natural Gas Pressure at
inlet tap while Aquastar is operating: 5.7”W.C.

Natural Gas Burner Manifold pressure while
Aquastar is operating at maximum input: 5.38” W.C.

* Inlet gas pressure before Aquastar regulator must not
exceed this value. Pressure may need to be adjusted for
high altitudes, see page 10.

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, a warranty statement
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 125FX water heaters. There is a set of installation instructions in the FXHOOD box.

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D084_089

FRONT VIEW SIDE VIEW

MINIMUM INST ALLATION CLEARANCES FROM COMBUSTIBLE AND NON
COMBUSTIBLE MATERIALS FOR ALCOVE OR CLOSET INSTALLATIONS

MODEL 125FX

TOP (A) 12 "
FRONT (B) 4 "
BACK 0 " *
SIDES 4 "
FLOOR (C) 12 " **
VENT DIAMETER 4 "

* 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.
** Some local codes require 18” in garage installations

AQUASTAR MODEL 125FX

3

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/NFP A 54.
In Canada: The Installation should conform with CGA
B149.(1,2) INST ALLATION 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. Venting must comply with all
requirements for Category III gas appliances. 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 ANSINFP A 70 and/or the CSA 22.1 Electrical Code.

The heater may still operate even when improperly vented.
It will, however, be less ef ficient 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 Aquastar 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. Y our 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 elbow connections
at the rear of heater. Additionally, remove the drain plug
under the water valve. See Fig 0.”

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.

4

Fig. 0 - 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.

COMBUSTION AIR REQUIREMENTS

CLEARANCES

The AquaStar 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 can rob the
make-up air in the AquaStar’s vent pipe, leaving the cold
infiltrating air capable of freezing the cold water in the
AquaStar heat exchanger. To prevent this the FXHOOD
horizontal vent terminator, which is supplied sep arately with
the water heater, needs to be installed on the end of the
horizontal vent run (see page 7). The FXHOOD is a CSA
approved vent terminator for the Aquastar 125FX 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 AquaS tar 125FX 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.

The Aquast ar 125FX 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)**

* On a combustible wall surface the unit should be mounted
away from the wall to provide adequate clearance of the
vent pipe. See mounting instructions below.
** Some local codes require 18” in garage installations.

Clearance from vent pipe is dependent upon the clearance
rating of the venting material used. Single wall flue pipe
should be used and it is approved for 3” clearance for this
appliance. NOTE: See mounting instructions below to prop-
erly maintain a 3” clearance from the vent pipe to a com­bustible surface.

Note: this clearance can be reduced if combustible material
are protected as per table VI of the National Fuel Gas Code.

MOUNTING INST ALLATION

The Aquastar 125FX 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 125FX should be spaced away from
any combustible wall surface by a minimum of 1 ½” to
provide the needed 3” clearance between the vent pipe and
the wall surface. Review the FXHOOD horizontal vent
terminator instruction sheet (provided with the FXHOOD)
prior to heater 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. T o 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.

5

WALL STUDS

13 ¼”

SUPPORT BOARD

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

Minimum vent size diameter must be 4”. The appliance

must be located as close as practicable to a vent terminal.

Maximum vent length is 15 feet (4.6m) with two 90­degree elbows. This unit may be directly connected to

an approved vent termination with a 90-degree elbow. The
vent pipe connections must be secured to each other with
a minimum of 4 sheet metal screws per connection, and
all seams must be sealed with an approved high temperature
silicone sealant and aluminum duct tape. The vent system
must be gas tight. See Fig 4 for suggested venting
installation diagrams.

For best results, the horizontal vent system should be as
short and straight as possible. Vent pipe must be single
wall stainless steel (AL29-4C) or galvanized vent pipe of 26
minimum gauge. The maximum allowable horizontal

length of vent pipe is 15 feet. 2 elbows are allowable
within this maximum vent length. For each additional
elbow deduct 5 feet from maximum vent length. Any
vertical portion of the vent pipe that is part of the
horizontal vent system must be considered part of the
allowable 15 foot maximum. When the horizontal vent

run exceeds 5 feet the following criteria must be observed:

- Support the vent run at 4-foot intervals with overhead
hangers.

- Horizontal sections of vent connectors must rise ¼”
for every foot of horizontal length. Any vent section
greater than 45 degrees from vertical is considered
horizontal.

VENTING

WARNING: Do not reduce the vent pipe size.

This appliance must be vented horizontally to the outside
with sealed 4” single wall vent pipe following all local
ordinances and specifications for installing a power vented
Category III appliance. The 4” single wall vent pipe can be
either stainless steel (AL29-4C) or galvanized vent of at
least 26 gauge. Stainless steel is preferred. All connections
must be properly sealed. The vent system must be installed
by a qualified installer in accordance with all applicable
local gas codes. The venting system must be designed
and constructed so as to develop a positive flow adequate
to remove flue gases to the outdoors.

CAUTION: Aquast ar 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.
Controlled Energy Corporation will not be responsible for
improperly installed appliances.

Plan the vent system so that code and manufacturer’s
clearances are maintained.
The minimum clearance from the top of the heater is 12
inches. Single wall vent pipe when mounted to the 125FX
requires a 3-inch clearance from combustibles. In all cases,
follow local codes:

- In Canada, CAN/CGA-B149 Installation Code for detailed
requirements.

- In USA, ANSI Z223.1 – latest edition, National Fuel Gas
Code for detailed.

Note: Single wall vent pipe cannot be used in any
concealed locations and should not be used in any unheated
space without an insulated chase. Unsealed 5” or 6” size
double wall B-Vent may be used as a chase for straight
lengths (no elbows) of the 4” single wall vent pipe. All
connections of the 4” single wall vent inside the 5” or 6”
B-Vent must be properly sealed. A 1” clearance is required
from the B-Vent pipe to combustibles.

Freeze Warning:

As mentioned on Page 5, negative air pressure in cold
climates will cause a reverse airflow in the vent system
that can freeze and damage the Aquast ar 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 7). The FXHOOD is a CSA
approved vent terminator for the Aquastar 125FX and has a
built in back draft flapper .

Spill Switch Safety:

The 125FX is equipped with a Spill Switch; it’ s mounted on
the left side of the draft diverter (Flue gas safety device - #9
on page 19). Before leaving the installation site verify proper
Spill Switch 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.

6