Combustion Air Requirements; Mounting The Heater - Bosch 125FX LP Installation And Operating Instructions Manual
Bosch model 125fx lp and 125fx ng user manual
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- Installation and operating instructions manual (26 pages) ,
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- Installation and operating instructions manual (24 pages)
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COMBUSTION AIR REQUIREMENTS
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 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.
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 AquaStar 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.
CLEARANCES
The Aquastar 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 com-
bustible surface.
Note: this clearance can be reduced if combustible material
are protected as per table VI of the National Fuel Gas Code.
MOUNTING INSTALLATION
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. 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.
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