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P/N 42-9470 11/07 Copyright 2007 Mestek, Inc.
Cast iron condensing boiler
Cast iron condensing boiler
— Installation and operation manual
Figure 3
Air opening options for combustion air
drawn from boiler room
Installation site preparation
(continued)
Combustion air requirements
Air ducted to boiler air intake
If air is ducted from outside to the boiler air intake, follow instructions in the
200i
Vent/Air manual to size and install the air piping.
If the boiler is located in a small room (clearances less than the recommended
SERVICE/OPERA
TION clearances given in Figure 2, page 7):
No other appliances in the room — Provide two ventilation openings
through one of the enclosure walls. Each opening must be sized for a free
area of at least 1 square inch per 1,000 BTUH input of the
200i
boilers in
the room. One opening must be within 12 inches of the ceiling, the other
within 12 inches of the fl oor.
Other appliances in the same room — Th e room must have combustion
air openings sized for the other appliances. Increase the free area of the air
openings by one square inch per 1,000 BTUH of the
200i
boilers located
in the room.
Air from boiler room
When the boiler draws combustion air from the boiler room:
If the room volume is at least 50 cubic feet per BTUH of the combined
input of all appliances in the room, no special openings are needed
UNLESS the building is of tight construction (see defi nition). If the building is
of
tight construction
, provide openings to the
building
in accordance
with all applicable codes.
If the boiler is in a space smaller than 50 cubic feet volume per BTUH input,
provide air openings using one of the methods in Figure 3.
Defi nitions
Free area
— Louvers or grilles reduce the area of an opening. Free area is the
area remaining with the louver or grille in place. If the free area of a louver is
unknown, use the following:
Metal louver — Multiply required free area of the opening times 1.7 to
determine actual area of the required opening.
Wood louver — Multiply required free area of the opening times 5 to de-
termine actual area of the required opening.
Tight construction
— When a building is extensively sealed to prevent air
infi ltration, it cannot provide enough air for combustion unless openings are
provided to the outside. Th e National Fuel Gas Code defi nes such buildings as
having all of the following:
Walls and ceilings exposed to the outside atmosphere have a continuous
water vapor retarder with a rating of 1 perm or less with openings gasketed.
Weather-stripping has been added on openable windows and doors.
Caulking or sealants are applied to areas such as joints around windows
and door frames, between sole plates and fl oors, between wall-ceiling
joints, between wall panels, at penetrations for plumbing, electrical, and
gas lines, and in other openings.
Conversion factors
In
2
/1,000 BTUH
to
cm
2
/kw
— Multiply
In
2
/1,000 BTUH
times
22
In
2
/2,000 BTUH
to
cm
2
/kw
— Multiply
In
2
/2,000 BTUH
times
11
In
2
/3,000 BTUH
to
cm
2
/kw
— Multiply
In
2
/3,000 BTUH
times
7.4
In
2
/4,000 BTUH
to
cm
2
/kw
— Multiply
In
2
/4,000 BTUH
times
5.5
•
•
•
•
•
•
•
•
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Upper openings (
U
) must be within 12 inches of the ceiling. Lower
openings (
L
) must be within 12 inches of the fl oor.
Option 1 —
air openings through interior wall
When air is supplied to the boiler room through openings in an interior
wall (air supply from inside the building), size each opening to provide
minimum free area of:
1 in
2
per 1,000 BTUH
of all
200i
boilers in the room.
Option 2 —
air openings through outside wall
When air is supplied to the boiler room through openings in an outside
wall (air supply from outside the building), size each opening to provide
minimum free area of:
1 in
2
per 4,000 BTUH
of all
200i
boilers in the room.
Option 3 —
horizontal ducts to outside wall
When air is supplied to the boiler room through horizontal ducts to an
outside wall (air supply from outside the building), size each opening
to provide minimum free area of:
1 in
2
per 3,000 BTUH
of all
200i
boilers in the room.
Option 4 —
openings to attic/crawl space
Air openings can be connected to a ventilated att ic or crawl space. Th e
upper opening must be to the att ic. Th e lower opening can be a vertical
duct from the att ic or an opening in the fl oor from the crawl space. Size
each opening to provide minimum free area of:
1 in
2
per 3,000 BTUH
of all
200i
boilers in the room.
Option 5 —
single opening (not shown)
A single opening directly connected to the outdoors through a wall or
a vertical or horizontal duct can be used if the installation provides the
clearances of Figure 2, and the top of the opening is within 12 inches of
the ceiling. Size the opening to provide minimum free area of:
1 in
2
per 3,000 BTUH
of all
200i
boilers in the room.
If other appliances are located in the same room
as the boiler, increase the size of air openings
to provide the free area required for the other
appliances in addition to the air required for the
200i
boiler(s).
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