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SERIES 4 — GAS-FIRED WATER BOILER —
1e
Prepare boiler location — air openings
FREE AREA
given in this manual are free area (equals the
area, length times width of opening, after deduc-
tion for louver obstruction).
Use the free area information provided by the louver manufacturer.
When this information is not available, assume:
•
Wood louvers — assume free area is 20% of total; so the
actual area of each opening with wood louvers would be 5
times the required free area.
•
Metal louvers — assume free area is 60% of actual area; so,
for wood louvers, the actual area of each opening must be
1.67 times the required free area.
Single air opening option
A single combustion air opening can be used in lieu of the two-
opening options on page 10, provided:
Clearances from boiler to walls
•
The boiler must have clearances of at least those shown in Fig-
ure 1a, page 7.
Opening must be directly to outside
•
The opening must connect directly to the outdoors or to a space
that communicates directly to the outdoors (not to an interior
space).
•
The air can be provided through a direct opening or through a
horizontal or vertical duct.
Opening placement
•
The top of the air opening must be within 12 inches of the ceiling.
Opening size
•
The free area of the opening must be at least equal to the sum
of the areas of all equipment vent connectors in the space, and
. . .
•
The free area of the opening must be at least 1 square inch per
3,000 Btu/hr input rating of all equipment located in the space.
Exception for large spaces
No combustion air openings are needed when the boiler (and other
appliances) are installed in a space with a volume
of all installed appliances, provided:
feet per 1,000 Btuh
•
the building must not have unusually tight construc-
tion
(see definition, this page).
•
all clearances around the boiler must be no less than shown in
Figure 1a, page 7.
To determine if the space is large enough to qualify:
•
Add the total input of all appliances in MBH (1,000's of Btuh).
•
Multiply this number times 50 to determine minimum room vol-
ume.
•
Example: For a total input of 100 MBH (100,000 Btuh), minimum
volume is 50 x 100 = 5,000 cubic feet. At a ceiling height of 8
feet, the space must have at least 5,000 ÷ 8 = 625 square feet
(25 feet x 25 feet, for instance).
Part Number 550-142-302/0124
Boiler Manual
of openings — the minimum areas
at least 50 cubic
Unusually tight construction
Unusually tight construction means (per ANSI
Z223.1/NFPA 54) buildings in which:
a. Walls and ceilings exposed to the outside atmo-
sphere have a continuous water vapor retarder
with a rating of 1 perm or less with openings
gasketed, and . . .
b. Weather-stripping has been added on openable
windows and doors, and . . .
c. Caulking or sealants are applied to areas such
as joints around windows and door frames,
between sole plates and floors, between wall-
ceiling joints, between wall panels, at penetra-
tions for plumbing, electrical, and gas lines, and
in other openings.
For such construction cases, if appliances use
inside air for combustion,
into the building from outside
these openings per the appropriate case in
on page 10.
3, 4 or 5
Exhaust fans and air mov-
ers
The appliance space must never be under a
negative pressure, even if the appliance(s) are
installed as direct vent. Always provide air open-
ings sized not only to the dimensions required
for the firing rate of all appliances, but also to
handle the air movement rate of the exhaust
fans or air movers using air from the building or
space.
Motorized air dampers
If the air openings are fitted with motorized damp-
ers, electrically interlock the damper to:
•
Prevent the boiler from firing if the damper is
not fully open.
•
Shut the boiler down should the damper close
during boiler operation.
To accomplish this interlock, wire an
(proving the damper open) in series with
contact
the thermostat input to the boiler. The boiler will
not start if this contact is open, and will shut down
should it open during operation.
provide air openings
. Size and locate
Figure
isolated
11
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