User Guide

C. AIR FOR COMBUSTION &
VENTILATION
1. Adequate combustion air and ventilation air must
be provided for this appliance in accordance with
the section of the National Fuel Gas Code entitled,
“Air for Combustion and Ventilation” or applicable
provisions of the local building code. Subsections 2
through 8 as follows are based on the National Fuel
Gas Code requirements.
2. 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 m
3
/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
the air infiltration rate of a structure is known,
the minimum required volume of indoor air
for appliances other than fan assisted and for
the Series MI-e™ Boiler shall be determined as
follows:
where:
I
other
= Input of appliances other than fan
assisted in Btu/hr
ACH = air change per hour (percent of the
volume of the space exchanged per
hour, expressed as a decimal)
For fan assisted appliances, calculate the required
volume of air using the following equation:
I
fan
= Input of the fan assisted appliances in
Btu/hr
Note: These calculations are not to be used for
infiltration rates greater than 0.60 ACH.
3. 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
1.1 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 1.2 for an illustration
of this arrangement.
PREINSTALLATION
Figure 1.1: Air Openings – All Air from Indoors
on the Same Floor
Figure 1.2: Air Openings – All Air from Indoors
on Different Floors
3
21 ft
3
I
other
ACH 1000
Btu
/
hr
Required Volume
other
=
(
)
15 ft
3
I
fan
ACH 1000
Btu
/
hr
Required Volume
fan
=
( )