10
109838-01 - 5/20
X-PV
Installation, Operating & Service Manual
Example:
A 105000 BTU/hr input boiler and a
water heater are to be installed in a room
measuring 6 ft - 3 in x 7 ft with an 8 ft ceiling.
The water heater has an input of 30000 BTU/
hr:
Total input in thousands of BTU/hr = (105000
BTU/hr + 30000 BTU/hr) ÷ 1000 = 135
Volume of room = 6.25 ft x 7 ft x 8 ft = 350 ft
3
350÷135 = 2.59. Since 2.59 is less than 50,
there will be an inadequate fresh air sup-
ply in the boiler room unless openings are
installed between the boiler room and at
least one adjacent room. It turns out that the
boiler room in this example is adjacent to a
full basement which is 20ft x 45ft x 8ft high.
If two openings are installed into this base-
ment that each have a free area of 135in
2
,
the combined volume of the boiler room and
basement will be:
350ft
3
+ 6400ft
3
= 6750ft
3
and:
6750÷135 = 50ft
3
per 1000 BTU/hr.
In the absence of one of the conditions
described in (6) above, this arrangement
should provide an adequate fresh air supply
to all the appliances in the boiler room.
6” MAX
6” MAX
Figure 5.1: Indoor Combustion Air Method
B. Using Outdoor Combustion Air (“Direct Venting”)
This method requires the Direct Vent Conversion Kit
shown in Table 2.2. Appendix A describes how to size
and run the intake pipe.
Although combustion air is supplied through the air
intake piping, ventilation air is still required around the
boiler to prevent overheating of boiler components.
If the boiler is installed in a closet, provide two
openings in the closet, each having a net free area of
100 square inches as shown in Figure 5.1. Note that
these openings are independent of the boiler size.
Additional area may be required if other fuel burning
appliances are installed in this closet.
5
Air for Combustion and Ventilation
(continued)
