AquaStar NG User Manual
INSTALLATION AND OPERATING INSTRUCTIONS FOR AUTOMATIC
INSTANTANEOUS TYPE WATER HEATERS FOR USE WITH NATURAL AND
LIQUEFIED PETROLEUM GAS
MODEL 38B LP and NG
Suitable for heating potable water only
Not approved for space heating purposes
Intended for low flow domestic hot water 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.
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.
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
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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.
TABLE 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 7
Gas Connections .......................................................... Page 9
Water Connections .................................................... Page 10
Safety before lighting the pilot ................................ Page 11
Lighting instructions ................................................... Page 11
Setting water temperature ........................................ Page 12
Maintenance & Service ............................................. Page 12
Trouble Shooting ......................................................... Page 13
Diagram of AquaStar ................................................. Page 16
Components and Parts List ...................................... Page 19
Warranty ....................................................................... Page 21
This well engineered, gas water heater has all the features a water heater should have:
It operates on the principle of heating water instantaneously
“on demand”. When a hot water faucet is opened, cold water
flows through the coils of the heat exchanger in the Aquastar.
This same flow opens the gas valve, and the burners are
ignited by the pilot flame. 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 turn on the water heater,
giving you control over your hot water energy use. Each
time you turn off your hot water faucet, you also shut off
the water heater.
AquaStar 38B LP and 38B NG Specifications
Gas Input max.: 40,000 Btu/hr
min.: 20,000 Btu/hr
Water Connection 1/2” Thread fitting NPT
H x W x D 25 3/8” x 10 5/8” x 9 1/8"
Vent 4”
Gas Connection 1/2” NPT thread
Min. Water Pressure 13 Psi at 1.3 GPM
FEATURES
- High Quality Materials for Long Working Life.
- Copper heating coils for endless supply of hot water.
- Safety thermocouple at pilot burner.
- Automatic overheating protection shut-off sensor.
- Stainless steel burners with stabilized blue flame.
- Built-in corrosion resistant draft inducer.
- 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.
- Easy pilot flame lighting with push button piezo ignition.
Max. Water Pressure 150 Psi
Shipping Weight 20 LB
Net Weight 18 LB
0.5 GPM at 90° rise
1.3 GPM at 45° rise
Min. Water Flow 1/2 gal/min
LP GAS Supply Pressure
(before Aquastar regulator) min.: 11” W.C.
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: 9.0” W.C.
Natural Gas Supply Pressure
(before Aquastar regulator) min.: 7” W.C.
max.: 14” W.C.*
BOSCH is constantly improving our products, therefore
specifications are subject to change without prior notice.
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: 3.3” 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.
UNPACKING THE AQUASTAR HEATER
This heater is packed securely. The box includes two water connection fittings, a gas pressure regulator, a gas supply elbow
with gasket, a gas shut off valve, a pressure relief valve, 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.
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FRONT VIEW
SIDE VIEW
MINIMUM INSTALLATION CLEARANCES FROM COMBUSTIBLE AND
NON COMBUSTIBLE MATERIALS
MODEL 38B
TOP (A) 12 "
FRONT (B) 4 "
BACK 0 "
SIDES 4 "
FLOOR (C) 12 "
VENT DIAMETER 4 "
AQUASTAR MODEL 38B
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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. The 38B is not approved for boat or
RV installations.
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.
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, unvented closet or
any occupied rooms normally kept closed. The 38B is not
approved for boat or RV installations.
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 Aquastar 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.
WARNING: The water in this water heater is cold
and always remains cold exept 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. Additionally,
remove the drain plug under the water valve. See Fig 0.
WATER VALVE
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 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
installation.
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.
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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.
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.
Fig. 0 - Water heater drain plug
WARNING: Flammable materials, gasoline,
TO HEAT
EXCHANGER
DRAIN PLUG
COMBUSTION AIR REQUIREMENT
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 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 can rob the makeup air in the AquaStar’s vent pipe, leaving the cold infiltrating
air capable of freezing the cold water in the AquaStar 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 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. That would be 2000
cubic feet for the Aquastar 38B alone.
The Aquastar 38 B 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 (102mm)
C. Back 0 inches
D. Sides 4 inch (102mm)
E. Bottom 12 inches (306 mm)
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 clearance 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.
MOUNTING INSTALLATION
The Aquastar 38 B 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 5 ½” apart as
shown in Fig. 1.
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 1.
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.
In earthquake-prone zones, BBTNA 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, BBTNA 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.
AQ38B
Air Vents
(10¾ X 10¾ in. each)
Air Vents
(5½ X 5½ in. each)
Before installing the unit, be certain you have the correct
heater for your type of Gas – Propane or Natural Gas
AQ38B
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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 2000 cubic feet for the AquaStar 38B 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.
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
5 ½”
SUPPORT BOARD
Fig. 1 - Mounting the Heater
1” X 4”
SPACE BOARD
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VENTING
Vent pipe connection. WARNING: Do not reduce the vent pipe size.
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 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 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 4 inch diameter gas vent constructed of double wall Type B gas vent is recommended. 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.
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
LOWEST DISCHARGE OPENING
H (minimum) height
from roof to lowest
discharge opening
LISTED GAS VENT
Figure A Figure B
LISTED VENT CAP
X
12
ROOF PITCH
IS X/12
GAS VENT TERMINATIONS FOR LISTED VENT CAPS
Roof pitch H (minimum) feet meters
Flat to 6/12
6/12 to 7/12 1.25 0.38
Over 7/12 to 8/12
Over 8/12 to 9/12 2.0 0.61
Over 9/12 to 10/12
Over 10/12 to 11/12
Over 11/12 to 12/12 4.0 1.22
Over 12/12 to 14/12
Over 14/12 to 16/12 6.0 1.83
Over 16/12 to 18/12
Over 18/12 to 20/12 7.5 2.27
Over 20/12 to 21/12 8.0 2.44
1.0 0.30
1.5 0.46
2.5 0.76
3.25 0.99
5.0 1.52
7.0 2.13
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MASONRY CHIMNEY: Masonry chimneys shall be built and installed in accordance with NFPS 211 or local codes. A
minimum 4” 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. 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.
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.
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 HVAC engineer 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. See NFPA 54 for guidelines. A HVAC engineer will be required to spec a chimney system. The 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 HVAC professional.
MASONRY CHIMNEYS
LISTED VENT CAP
GAS
VENT
VENT CONNECTOR
ESTABLISH A ONE
FOOT RISE BEFORE
ANY ELBOWS
Figure C
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