Install Instructions

D. COMBUSTION AND VENTILATION AIR
1. The PUREFIRE
®
boiler is designed for operation with
combustion air piped directly to the boiler from
outside the building (sealed combustion). Combustion
air may be supplied from within the building only if
adequate combustion air and ventilation air is
provided in accordance with the National Fuel Gas
Code or applicable sections of the local building code.
Subsections 3 through 10 as follows are based on the
National Fuel Gas Code requirements.
2. If the combustion air is piped directly to the boiler
from outside the building, no additional combustion
or ventilation air is required. Otherwise, follow the
National Fuel Gas Code recommendations
summarized in subsections 3 through 10.
3. Required Combustion Air Volume: The total required
volume of indoor air is to be the sum of the required
volumes for all appliances located within the space.
Rooms communicating directly with the space in
which the appliances are installed and through
combustion air openings sized as indicated in
Subsection 3 are considered part of the required
volume. The required volume of indoor air is to be
determined by one of two methods.
a. Standard Method
: The minimum required volume
of indoor air (room volume) shall be 50 cubic feet
per 1000 BTU/Hr (4.8 m3/kW). This method is to
be used if the air infiltration rate is unknown or if
the rate of air infiltration is known to be greater
than 0.6 air changes per hour. As an option, this
method may be used if the air infiltration rate is
known to be between 0.6 and 0.4 air changes per
hour. If the air infiltration rate is known to be
below 0.4 then the Known Air Infiltration Rate
Method must be used. If the building in which this
appliance is to be installed is unusually tight, PB
Heat recommends that the air infiltration rate be
determined.
b. Known Air Infiltration Rate Method
:
where:
I
fan
= Input of the fan assisted appliances
in Btu/hr
ACH = air change per hour (percent of the
volume of the space exchanged per
hour, expressed as a decimal)
Note: These calculations are not to be used for
infiltration rates greater than 0.60 ACH.
4. Indoor Air Opening Size and Location: Openings
connecting indoor spaces shall be sized and located as
follows:
a. Combining Spaces on the Same Floor
: Provide two
permanent openings communicating with additional
spaces that have a minimum free area of 1 in
2
per
1000 Btu/hr (22 cm
2
per 1000 W) of the total input
rating of all gas fired equipment but not less than
100 in
2
(645 cm
2
). One opening is to begin within
12 inches (305 mm) from the top of the space and the
other is to begin within 12 inches (305 mm) from the
floor. The minimum dimension of either of these
openings shall be 3 inches (76 mm). See Figure 1.3
for an illustration of this arrangement.
b. Combining Spaces on Different Floors
: Provide
one or more permanent openings communicating
with additional spaces that have a total minimum
free area of 2 in
2
per 1000 Btu/hr (44 cm
2
per
1000 W) of total input rating of all equipment. See
Figure 1.4 for an illustration of this arrangement.
4
15 ft
3
I
fan
ACH 1000
Btu
/
hr
Required Volume
fan
=
⎛
⎜
⎝
⎛
⎜
⎝
Figure 1.3: Air Openings – All Air from Indoors
on the Same Floor
Figure 1.4: Air Openings – All Air from Indoors
on Different Floors
PREINSTALLATION