Venting The Heater; Gas Connections - Bosch 38B LP Installation And Operating Instructions Manual

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).
5 ½"
Fig. 1 - Mounting the Heater
VENTING
Vent pipe connection. WARNING: Do not reduce
the vent pipe size.
This appliance must be vented to the outside following all
local ordinances and specifications for installing a gas
appliance vent or chimney. The venting system must be
designed and constructed so as to develop a positive flow
adequate to remove flue gasses to the outdoors. Minimum
vent size must be 4". Minimum height must be 6 feet,
provided there are no elbows. Termination of vent
must be 2 feet above any obstruction within a 10 foot
radius. Consult your gas utility or National Fuel Gas
Code if vent will have elbows or share venting with
another appliance. The vent connector should have
as much vertical rise as possible (minimum 12") before
any horizontal run. The appliance must be located as
close as practicable to a chimney or vent. The vent pipe
sections must be secured to each other with sheet metal
screws. Keep in mind the minimum clearance from the
top of your heater. Remember also that single wall vent
pipe connectors require a 6 inch clearance from
combustibles. National Fuel Gas Code specifies double
wall — Type "B" — vent pipe be used in cold climates and
for gas vents running through attics. We consider double
wall vent pipe preferable in all circumstances. Any vent
section greater than 45 degrees from vertical is considered
horizontal. Horizontal sections of vent connectors must
slope upwards at least 1/4 inch for every foot of its
horizontal length. Keep the horizontal section short and
avoid too many elbows.
6
To check the draft:
Close all doors and windows to the outside.
Turn on all appliances that force air out of the building.
These include all exhaust/ventilation fans, furnaces, clothes
dryers, wood burning stoves, etc.
Open all doors between the AquaStar and these other
appliances.
Run the unit for at least 10 minutes. Then hold an ordinary
mirror at the side above the front shell. Any flue gases
backdrafting will cause the mirror to fog. This is a serious
health hazard and must be corrected. Poor venting can
result in soot building up inside the heater, overheating of
the heater and freezing of the heat exchanger in a freezing
environment.
The mirror will remain clear with a properly functioning draft.
WALL STUDS
Note: The burners of an instantaneous "on demand" water
SUPPORT BOARD
heater such as the AquaStar are only on at the time that
hot water is actually being used, the vent pipe is therefore
cold except for the short durations when hot water is being
used, it is therefore very important that the venting and air
supply be adequate to provide a good positive draft as soon
1" X 4"
as the burners turn on.
SPACE BOARD
The AquaStar 38B instantaneous water heaters have built-
in draft diverters and are designed for indoor installation
only. The draft diverter outlet must be connected to a clear,
unobstructed vent of the 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.
GAS CONNECTIONS and Gas Regulator
Before connecting the gas supply, check the rating plate
on the right side of the front cover to be sure that the heater
is rated for the same gas to which it will be connected.
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
INSTALLATION CODES and /or local installation codes.
NOTE: The Aquastar 38 B is supplied with a gas
pressure regulator that must be installed on the heater
before attaching the gas supply line. See figure 2.
Place the gas regulator between the gas supply
connection (which comes with a manual shutoff valve)
and the gas fitting wich is connected to the heater's
gas inlet. There is a pressure tap on this gas fitting.
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.
WARNING