Bosch AquaStar 125B LPS Manual

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 ualified
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: Automatic Variable Power Modulating Gas
Valve wit T ermostatic Control
Warning: If you do not follow t ese instructions exactly, a
fire or explosion may result causing property damage,
personal injury or loss of life.
INSTALLATION AND OPERATING INSTRUCTIONS FOR AUTOMATIC
INSTANTANEOUS TYPE WATER HEATERS FOR USE WITH NATURAL AND
LIQUEFIED PETROLEUM GAS
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 li uids 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
ualified installer, service agency or the gas supplier.
Specifications................................................................. Page 2
Rules for safe operation ............................................... Page 4
Locating t e Heater ......................................................Page 4
Combustion Air Requirements .................................... Page 5
Mounting t e Heater ..................................................... Page 6
Venting t e Heater ........................................................ Page 7
Gas Connections ....................................................... Page 10
Water Connections .................................................... Page 11
Safety before lig ting t e pilot ................................ Page 12
Lig ting instructions ................................................... Page 12
Information on water temperature ........................... Page 13
Maintenance & Service ............................................. Page 13
Trouble S ooting ......................................................... Page 14
Diagram of AquaStar .................................................. Page 17
Components and Parts List ...................................... Page 19
Warranty ....................................................................... Page 21
TABLE OF CONTENTS
6 720 606 518 US (04.11) AL
MODEL 125B LPS and 125B NGS (Thermostatically Modulated)
Suitable for heating potable water only
Not approved for space heating purposes
Intended for domestic hot water with preheated inlet water as with solar hot water.

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This well engineered, gas water heater has been specially
designed to operate with incoming pre-heated water:
It operates on t e principle of eating water instantaneously
“on demand”. W en a ot water faucet is opened, cold water
flows t roug t e coils of t e eat exc anger in t e Aquastar.
T is same flow opens t e gas valve, and t e burners are
ignited by t e pilot flame. T e eat exc anger coils absorb
t e eat generated by t e burners and transfer eat to t e
water. W en t e ot water faucet is s ut off, t e gas valve
automatically closes and t e burners turn off. Your ot water
faucet is an ignition key to turn on t e water eater, giving
you control over your ot water energy use. Eac time you
turn off your ot water faucet, you also s ut off t e water
eater. On t e Aquastar “S” model, if t e incoming water is
colder t an t e t ermostat setting of t e eater, t e burners
will ignite to eat t e water in order to boost it and maintain
it at t e temperature setting. If t e incoming water as been
pre- eated, (ie) solar, and t is water temperature is warm
t en t e t e burners will modulate down accordingly, or
s ut down completely if t e temperature is as ot or otter
t an t e eater t ermostat setting. T e Aquastar 125 BS is
t e perfect backup to a solar ot water system.
FEATURES
- Hig Quality Materials for Long Working Life.
- Copper eating coils for endless supply of ot water.
- Burner output proportional to ot water flow demand for
maximum energy efficiency.
- Automatic T ermostatic Control for steady ot water
temperature
- Input BTU’s modulate to zero to prevent over eating of
water from pre- eat source
- Safety t ermocouple at pilot burner.
- Automatic over eating protection s ut-off sensor.
- Stainless steel burners wit stabilized blue flame.
- Built-in corrosion resistant draft inducer.
- Compact space saver: mounts on a wall wit two ooks.
- Easily removable one-piece cover.
- Easy one person installation.
- Adjustable water flow restrictor to ensure t at water flow
demand will not exceed t e eating capacity of t e eater.
- Easy pilot flame lig ting wit pus button piezo ignition.
BOSCH is constantly improving our products, therefore
specifications are subject to change without prior notice.
A uaStar 125B LPS and 125B NGS Specifications
Gas Input max.: 117,000 Btu/ r
min.: 23,400 Btu/ r
Water Connection 1/2” T read fitting NPT
H x W x D 29 3/4” x 18 1/4” x 8 3/4"
Vent 5”
Gas Connection 1/2” NPT t read
Min. Water Pressure 18 Psi at 4 GPM
Max. Water Pressure 150 Psi
S ipping Weig t 44 LB
Net Weig t 42 LB
1.8 GPM at 90° rise
3.7 GPM at 45° rise
Min. Water Flow 1/2 gal/min
LP GAS Supply Pressure
(before Aquastar regulator) min.: 11” W.C.
max.: 14” W.C.*
Required LP GAS Pressure at inlet
tap w ile Aquastar is operating: 10.5” W.C.
LP GAS Burner Manifold pressure w ile 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.*
Required Natural Gas Pressure at inlet tap
w ile Aquastar is operating: 5.7” W.C.
Natural Gas Burner Manifold pressure w ile Aquastar is
operating at maximum input: 4.2” W.C.
* Inlet gas pressure before Aquastar regulator must not
exceed t is value. Pressure may need to be adjusted for
ig altitudes, see page 11.
UNPACKING THE AQUASTAR HEATER
T is eater is packed securely. T e box includes two water
connection fittings, a gas pressure regulator, a pressure relief
valve, an incandescent particle tray, two ooks for anging
t e eater, t is 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 t e
enclosed warranty registration card.

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D861_059
MINIMUM INSTALLATION CLEARANCES FROM COMBUSTIBLE AND NON
COMBUSTIBLE MATERIALS FOR ALCOVE OR CLOSET INSTALLATIONS
FRONT VIEW SIDE VIEW
AQUASTAR MODEL 125BS
MODEL 125BS
TOP (A) 12 "
FRONT (B) 4 "
BACK 0 "
SIDES 4 "
FLOOR (C) 12 "
VENT DIAMETER 5 "

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PROPER LOCATION FOR INSTALLING YOUR
HEATER
Carefully select t e location of your new eater. For your
safety and for proper eater operation, you must provide an
abundant supply of combustion air and a proper venting
installation.
T e eater may still operate even w en improperly vented.
It will, owever, be less efficient and could eventually damage
t e eater. It could even result in uman sickness or deat
due to oxygen deprivation and carbon monoxide poisoning.
Follow t e guidelines below:
1. Place your eater as close to a vent or c imney as
possible.
2. National building codes require t at you do not install
t is appliance in bat rooms, bedrooms, unvented closet or
any occupied rooms normally kept closed.
3. Simultaneous operation of ot er appliances suc as
ex aust fans, ventilation systems, clot es dryers, fireplaces
or wood stoves could create a vacuum effect in your ome
w ic could cause dangerous combustion by-products to
spill back into your ome rat er t an venting to t e outside
t roug t e flue. Confirm t at your Aquastar is venting
properly w en all t ese ot er appliances are running. See
section on venting.
Do not obstruct the flow of combustion and ventilation
air to the appliance. If installed near a clot es dryer it is
very important t at t e dryer be properly vented. Failure to
properly vent a dryer could result in a gradual accumulation
of lint on t e water eater fin coils and burners, leading to a
dangerous condition of vent blockage and poor unsafe
combustion.
4. Your ot water lines s ould be kept s ort to save energy.
It is always best to ave ot water lines insulated.
WARNING: T e water in t is water eater is cold
and always remains cold except for t e times t at ot water
is being used. DO NOT INSTALL IN AN AREA WHERE IT
COULD FREEZE.
This heater is neither designed for not approved for
outside installation. Drain t e eater entirely if freezing
temperatures are anticipated in t e area w ere eater is
installed by disconnecting bot t e inlet and outletelbow
connections at t e rear of eater. Additionally remove t e
drain plug under t e water valve. See Fig 0.
GENERAL RULES TO FOLLOW
FOR SAFE OPERATION
1. You s ould follow t ese instructions w en you install your
eater. In t e United States: T e installation must conform
wit local codes or, in t e absence of local codes, t e
National Fuel Gas Code ANSI Z223.1/NFPA 54.
In Canada: T e Installation s ould conform wit CGA
B149.(1,2) INSTALLATION CODES and/or local installation
codes.
2. Carefully plan w ere you install t e eater. 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. T e place w ere you install t e eater must ave enoug
ventilation. T e National Fire Codes do not allow gas fired
water eater installation in bat rooms, bedrooms or any
occupied rooms normally kept closed. See t e section below
on locating t e eater.
4. You must vent your eater. See section on VENTING,
Page 6.
5. T e appliance must be disconnected from t e gas supply
piping system during any pressure testing at pressures in
excess of 1/2 Psig (3.5 kPa).
T e appliance must be isolated from t e gas supply piping
system by closing its individual manual s utoff valve during
any pressure testing of t e gas supply piping system at test
pressures equal to or more t an 1/2 Psig (3.5Kpa). T e
appliance and its gas connection must be leak tested before
placing t e appliance in operation.
6. Keep water eater area clear and free from combustibles
and flammable liquids. Do not locate t e eater over any
material w ic mig t burn.
7. Correct gas pressure is critical for t e optimum
operation of t is eater (see specifications on page 2). Gas
piping must be sized to provide t e required pressure at t e
maximum output of t e eater, w ile all t e ot er gas
appliances are in operation. C eck wit your local gas
supplier, and see t e section on connecting t e gas supply.
8. S ould over eating occur or t e gas supply fail to s ut
off, turn off t e gas supply at t e manual gas s ut off valve
on t e gas line.
9. Do not use t is appliance if any part as been underwater.
Immediately call a qualified service tec nician to inspect
t e appliance and to replace any part of t e control system
and any gas control w ic as been underwater.
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

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WARNING: Flammable materials, gasoline,
pressurized containers, or any other items or articles
that are potentially fire hazards must NOT be placed on
or adjacent to the heater. The appliance area must be
kept free of all combustible materials, gasoline and other
flammable vapors and li uids.
COMBUSTION AIR REQUIREMENTS
T e AquaStar water eater olds cold water in its copper
eat exc anger and brass water valve w en not in use.
Because of t is, any cold air t at comes in t roug t e
unit’s vent pipe is capable of freezing t ese components.
T is Installation Manual specifies t e minimum vertical vent
pipe and t e amount of combustion air required for t is unit.
W en all requirements are followed, t e unit will operate
properly and safely. However, t ere may still be a risk of
freezing due to negative draft if all t e combustion appliances
in t e area are not being supplied wit a sufficient amount
of make-up air. A wood stove or furnace can rob t e make-
up air in t e AquaStar’s vent pipe, leaving t e cold infiltrating
air capable of freezing t e cold water in t e AquaStar eat
exc anger. More make up air is t e solution. Follow t e
instructions on venting and c ecking adequacy of make up
air. A HVAC specialist s ould be used to design solutions
for providing more make-up air if necessary.
Observe t e following instructions concerning combustion
air.
Appliances located in unconfined spaces:
a) An unconfined space is one w ose volume is greater
t an 50 cubic feet per 1000 Btu per our of t e combined
rating of all appliances installed in t e space. T at would
be 5850 cubic feet for t e AquaStar 125B “S” 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:
T e confined space must be provided wit two permanent
openings, one commencing wit in 12 inc es of t e top and
one commencing wit in 12 inc es of t e bottom of t e
enclosure. Eac opening must ave a minimum free area of
one square inc per:
- 1000 Btu/ r if all air is taken from inside t e building.
- 2000 Btu/ r if all air is taken from t e outside by orizontal
ducts.
- 4000 Btu/ r if all air is taken from t e outside by direct
openings or vertical ducts.
Or t e confined space must be provided wit one permanent
opening or duct t at is wit in 12 inc es of t e ceiling of t e
enclosure. T is opening must ave a minimum free area of
one square inc per:
- 3000 Btu/ r if all air is taken from t e outside by a direct
opening or vertical duct.
Louvers, grills and screens ave a blocking effect. If t e
effective free area is not known, increase t e sizes of your
openings by 75% if your louvers are wood and by 30% if
your louvers are metal. Refer to t e National Fuel Gas Code
for complete information. In buildings of tig t construction
all air s ould be taken from outside.
CLEARANCES
T e Aquastar 125 B “S” is design certified for installation
on a combustible wall and for installation in an alcove or
closet wit t e minimum clearances to combustible and non
-combustible construction listed below
A. Top 12 inc es (306 mm)
B. Front 4 inc es (102 mm)
C. Back 0 inc es
D. Sides 4 inc es (102mm)
E. Bottom 12 inc es (306 mm)
Clearance from vent is dependent upon t e clearance rating
of t e venting material used. For example, type B-a vent is
approved for 1 inc clearance.
Note: Typically, t e minimum clearance to combustible
materials s ould not be less t an 6” for single wall flue
pipe. Note t at t is clearance can be reduced if combustible
materials are protected as per table VI of t e National Fuel
Gas Code or if Type B gas vent is used.
125BS Air Vents
(5 ½ X 5 ½ in. each)
Air Vents
(10 ¾ X 10 ¾ in. each) 125BS

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Fig. 1 - Mounting the Heater
Fig. 2 - Incandescent Particle Tray Illustration
T e incandescent particle tray (s ipped loose in t e carton
wit t e water eater) must be attac ed at t e bottom of
t e water eater front cover at t e time of installation. Use
t e screws provided. See figure 2
SUPPORT BOARD
WALL STUDS
1” X 4”
SPACE BOARD
13 ¼”
SCREWS
INCANDESCENT PARTICLE TRAY
MOUNTI NG IN STALLATION
T e Aquastar 125 B “S” is design certified for mounting on
a wall.
Secure t e two L s aped ooks provided wit t e eater to
a wall surface. Place t em 13 ¼ inc es apart as s own in
Fig 1. Do not install t is appliance on a carpeted wall or
over floor covering w ic is combustible, suc as carpet.
T e eater must be mounted on a wall using appropriate
anc oring materials. If wall is a stud wall s eat ed wit
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 c anging water
temperature in t e pipes imparts movement to t e eater
w ic , if mounted directly to a brittle, friable board, suc as
plasterboard, can cause failure of mounting.
In eart quake-prone zones, CEC recommends t at installers
use a large was er and lag screw t roug t e existing oles
used to ang t e eater to affix t e upper t ird of t e eater
to t e mounting board. To affix t e lower t ird of t e eater,
CEC recommends t at two new oles be drilled in t e
eater’s frame, eac one 16 inc es below t e top two oles,
and t at was ers and lag screws be used to secure t e
lower portion of t e eater to a spacing board.
Before installing the unit, be certain you have the correct
heater for your type of Gas – Propane or Natural Gas.
Identification labels are found on the shipping box, and on
the rating plate which is located on the right side panel of
t e cover. Also, eac burner orifice is stamped wit a number
(79 for LPG and 120 for Natural Gas).

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VENTING
Vent pipe connection. WARNING: Do not reduce the vent pipe size. See Fig. 3 for high altitude installations
T e eater must be vented to t e outside following all local ordinances and specifications for installing a gas appliance
vent or c imney. T e eater must be located as close as practicable to a vertically rising c imney or vent t at as a listed
vent cap at its termination point. T e venting system must be designed and constructed so as to develop a positive flow
adequate to remove flue gasses to t e 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 (Model AQ-1), wit a proof-of-draft safety interlock device, is required and is available in
order to sidewall vent. Contact your dealer. In the Commonwealth of Massachusetts: Powervented applications must
utilize proof-of-draft safety interlock device.
VERTICAL GAS VENT: A 5 inc diameter gas vent constructed of double wall Type B gas vent is recommended. 6 inc is
required in elevations greater t an 2000 feet, see Fig. 3. Any gas vent section t at is greater t an 45 degrees from t e
vertical is considered orizontal. Horizontal sections must slope upwards at least ¼ inc for every foot of its orizontal
lengt and be properly supported. Keep t e orizontal section s ort and avoid too many elbows. T e minimum vertical gas
vent eig t allowed is 6 feet; orizontal vent connectors and elbows are not to be considered in t e total gas vent eig t.
All gas vent sections must be secured to eac ot er wit s eet metal screws and be properly supported.
T e gas vent constructed of double wall Type B gas vent must terminate above t e roof surface wit a listed vent cap at
a eig t t at’s in accordance wit Figure A or B and t eir table, provided t ey are at least 8 feet (2.4 m) from a vertical wall
or similar obstruction. All ot er gas vents t at are not able to terminate wit in t e minimum specified eig t allowed must
terminate not less t an 2 feet (0.6 m) above t e ig est point w ere it’s passed t roug t e roof and at least 2 feet (0.6
m) ig er t an any vertical wall or similar obstruction wit in 10 feet (3.1 m).
LISTED VENT CAP
LISTED VENT CAP
LISTED GAS VENT
LOWEST DISCHARGE OPENING
H (minimum) eig t
from roof to lowest
disc arge opening
Figure A Figure B
ROOF PITCH
IS X/12
12
X
Roof pitch H (minimum) feet meters
Flat to 6/12 1.0 0.30
6/12 to 7/12 1.25 0.38
Over 7/12 to 8/12 1.5 0.46
Over 8/12 to 9/12 2.0 0.61
Over 9/12 to 10/12 2.5 0.76
Over 10/12 to 11/12 3.25 0.99
Over 11/12 to 12/12 4.0 1.22
Over 12/12 to 14/12 5.0 1.52
Over 14/12 to 16/12 6.0 1.83
Over 16/12 to 18/12 7.0 2.13
Over 18/12 to 20/12 7.5 2.27
Over 20/12 to 21/12 8.0 2.44
GAS VENT TERMINATIONS FOR LISTED VENT CAPS

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MASONRY CHIMNEY: Masonry c imneys s all be built and installed in accordance wit NFPS 211 or local codes. A
minimum 5” diameter gas vent pipe (metal double wall Type B), or an approved clay flue liner or a listed c imney lining
system must be used w en venting into a naturally drafting, internal masonry c imney. 6 inc is required in elevations
greater t an 2000 feet, see Fig. 3. Local codes may require t e use of bot gas vent and an approved lining system w en
venting into a masonry c imney. T e Commonwealt of Massac usetts requires t e use of a listed liner. Lining systems
include approved clay flue lining, a listed c imney lining system or ot er approved material t at will resist corrosion,
erosion, softening, or cracking from ex aust flue gases at temperatures up to 1800 degrees F. T e lining system must be
listed for use wit naturally drafting, draft ood 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 attac ed to t e top of t e water eater and rise
vertically at least 12” before entering into an approved gas vent connector elbow. Any gas vent section t at is greater t an
45 degrees from t e vertical is considered orizontal. If a orizontal vent connector is to be used to connect t e vertical
gas vent connector on t e top of t e water eater to t e masonry c imney, t at approved orizontal gas vent connector
must be kept as s ort as possible and must be sloped upwards at least ¼” per foot of its lengt . T is connector must be
supported t roug out its orizontal lengt . T is orizontal gas vent connection may be no greater t an 75% of t e total
vertical gas flue vent wit in t e c imney. Also, an approved t imble or collar must be used w en penetrating a masonry
c imney.
A) Existing INTERIOR Masonry Chimney
T e metal gas vent pipe s ould be permanently mounted inside t e masonry c imney. Double wall Type B gas vent is
recommended. T e masonry c imney may ave to be tile or metal lined before t e insertion of t e gas vent pipe; c eck
local codes for clarification. T e lining material must be listed for use only wit naturally drafting, draft ood equipped gas
appliances. Follow manufactures instructions for installation of listed lining material. You may not vent any ot er fuel
burning appliances into any free space remaining in t e c imney. T e minimum vertical gas vent lengt wit in t e masonry
c imney s ould be no less t an 5 ft (1.5 m); t e vent terminator s ould extend at least 3 feet (0.9 m) above w ere t e
c imney meets t e roofline and at least 2 feet (0.6 m) ig er t an any vertical wall or similar obstruction wit in 10 feet (3.1
m). T e top of t e gas vent s ould ave an approved vent terminator. See Figure C.
B) Tile Lined INTERIOR Masonry Chimney
T e masonry c imney must ave an approved liner, ceramic tile, clay or metal. T e masonry c imney must be able to
accommodate t e spent fuel gasses; consult a HVAC engineer for c imney capacity. A common venting like-fuel appliance
into t is lined masonry c imney is permissible. T e c imney’s diameter must be large enoug to adequately draft t e spent
fuel gasses. See NFPA 54 for guidelines. A HVAC engineer will be required to spec a c imney system. T e minimum
vertical c imney lengt s ould be no less t an 5 ft (1.5 m); t e termination point s ould extend at least 3 feet (0.9 m)
above w ere t e c imney meets t e roofline and at least 2 feet (0.6 m) ig er t an any vertical wall or similar obstruction
wit in 10 feet (3.1 m). See Figure C.
C) EXTERIOR masonry Chimney
Refer to t e National Fuel Gas Code and consult a local HVAC professional.
MASONRY CHIMNEYS
GAS
VENT
LISTED VENT CAP
VENT CONNECTOR
ESTABLISH A ONE
FOOT RISE BEFORE
ANY ELBOWS
Figure C

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Fig. 3 – Vent Adaptor for High Altitude Installations
5” X 6” ADAPTOR
USED ON HIGH ALTITUDE
To check the draft:
Close all doors and windows to t e outside.
Turn on all appliances t at force air out of t e building.
T ese include all ex aust/ventilation fans, furnaces, clot es
dryers, wood burning stoves, etc.
Open all doors between t e AquaStar and t ese ot er
appliances.
Run t e unit for at least 10 minutes. T en old an ordinary
mirror at t e side above t e front s ell. Any flue gases
backdrafting will cause t e mirror to fog. T is is a serious
ealt azard and must be corrected. Poor venting can result
in soot building up inside t e eater, over eating of t e eater
and freezing of t e eat exc anger in a freezing environment.
T e mirror will remain clear wit a properly functioning draft.
WARNING
Note: T e burners of an instantaneous “on demand” water
eater suc as t e AquaStar are only on at t e time t at
ot water is actually being used, t e vent pipe is t erefore
cold except for t e s ort durations w en ot water is being
used, it is t erefore very important t at t e venting and air
supply be adequate to provide a good positive draft as soon
as t e burners turn on. See venting guide on back page.
T e AquaStar 125B”S” instantaneous water eaters ave
built-in draft diverters and are designed for indoor installation
only. T e draft diverter outlet must be connected to an
unobstructed vent of t e same size, or larger.
In Canada, CAN/CGA-B149 Installation Code for detailed
requirements
In U.S.A., ANSI Z223.1 - NFPA 54, National Fuel Gas
Code for detailed requirements.
T e vent connection for t e Aquastar 125BS is 5 inc es.
However, for installations at ig altitude (over 2000 feet
above sea level) a six inc vent is required. A 5” by 6” vent
adaptor must be affixed to t e flue collar of t e Aquastar
wit at least two screws. See Fig. 3.
WARNING: Failure TO INCREASE THE VENT
SIZE TO SIX INCHES AND/or assure t at t e manifold
pressure is set to proper value listed for applications at ig
altitudes will cause unsafe venting, asp yxiation, and will
void CSA Certification.

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GAS CONNECTIONS and Gas Regulator
NOTE: The A uastar 125 B”S” is supplied with a gas pressure regulator that must be installed on the heater before
attaching the gas supply line. See figure 5. Failure to install the gas regulator as shown in figure 5 will be a violation
of CSA certification of the unit. The regulator supplied with the heater is preset for the gas shown on the rating
plate to the correct pressure. It is an appliance level regulator designed for (low inlet) pressure (less than 1/2 Psig
or 15” W.C.) DO NOT connect to an unregulated or high pressure propane line or to a high pressure commercial
natural gas line.
FOR NATURAL GAS
Maximum Capacity of pipe in Cubic Feet of Gas per Hour
for Gas Pressure of 0.5 Psig or less and a Pressure drop of
0.3 in Water Column.
(Based on a 0.60 Specific Gravity Gas) Btu numbers given
in t ousands.
Follow boxed numbers for piping just one Aquastar 125BS
(example: 3/4” B.I. Natural Gas pipe for 30 ft. will andle
152,000 btu’s). For multiple appliances combine t e total
btu input load and t en refer to applicable c art below.
FOR LP GAS
Maximum Capacity of Pipe in T ousands of
BTU per Hour of Undiluted Petroleum Gases
(at 11 inc es Water Column Inlet Pressure)
(Based on a Pressure Drop of 0.5 Inc Wa-
ter Column).
Maximum Capacity of Semi-Rigid
Tubing in T ousands of BTU per Hour of
Undiluted Liquified Petroleum Gases (at 11
inc es Water Column Inlet Pressure)
(Based on a Pressure Drop of 0.5 Inc Water
Column)
* Source National Fuel Gas Code NFPA 54, ANSI Z223.1 - No
Additional Allowance is necessary for an ordinary number of fittings
GAS LINE SIZING
Nominal
Iron Length of Black Iron Pipe, Feet
Pipe Internal
Size, Diameter
inches inches 10 20 30 40 50 60 70 80 90 100 125 150 175 200
1/4 0.364 32 22 18 15 14 12 11 11 10 9 8 8 7 6
3/8 0.493 72 49 40 34 30 27 25 23 22 21 18 17 15 14
1/2 0.622 132 92 73 63 56 50 46 43 40 38 34 31 28 26
3/4 0.824 278 190 152 130 115 105 96 90 84 79 72 64 59 55
1 1.049 520 350 285 245 215 195 180 170 160 150 130 120 110 100
1 1/4 1.380 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
1 1/2 1.610 1600 1100 890 760 670 610 560 530 490 460 410 380 350 320
2 2.067 3050 2100 1650 1450 1270 1150 1050 990 930 870 780 710 650 610
2 1/2 2.469 4800 3300 2700 2300 2000 1850 1700 1600 1500 1400 1250 1130 1050 980
3 3.068 8500 5900 4700 4100 3600 3250 3000 2800 2600 2500 2200 2000 1850 1700
4 4.026 17,500 12,000 9,700 8,300 7,400 6,80 6,200 5,800 5,400 5,100 4,500 4,100 3,800 3500
Nominal
Iron Pipe Black Iron Pipe
Size, Length of Pipe, Feet
Inches 10 20 30 40 50 60 70 80 90 100 125 150
1/2 275 189 152 129 114 103 96 89 83 78 69 63
3/4 567 693 315 267 237 217 196 185 173 162 146 132
1 107 732 590 504 448 409 378 346 322 307 275 252
1 1/4 220 149 121 103 913 834 771 724 677 630 567 511
1 1/2 330 229 185 155 141 127 118 108 102 976 866 787
2 622 433 346 299 264 239 220 204 192 1811 1606 1496
Copper
Outside Length of Tubing, Feet
Diameter,
Inch 10 20 30 40 50 60 70 80 90 100
3/8 39 26 21 19 _ _____
1/2 9262 5041 37 3531292726
5/8 199 131 107 90 79 72 67 62 59 55
3/4 329 216 181 145 131 121 112 104 95 90
7/8 501 346 277 233 198 187 164 155 146 138
Fig. 4