5
enclosure and another one near the bottom (
see
Figures 6 and 7
). Each opening shall communicate
directly or by means of ducts with the outdoors or to
such spaces (such as a crawl space) that freely com-
municate with the outdoors and shall be sized in
accordance with the instructions in the section
Air
Duct Sizing.
Air Duct Sizing
The air duct requirements should be met by one of the
following methods:
(a) vertical duct(s) with a free-flow area of not less
than one (1) square inch per 4,000 BTU/h (5.5
cm
2
/kWh) of the total input rating of all oil-fired
appliances in the enclosure;
(b) horizontal duct(s), as shown in
Figure 7
, with an
equivalent length of less than 50 ft (15 m), having
a free-flow area of not less than one (1) square
inch per 2,000 BTU/h (11 cm2/kWh) of the total
input of all oil-fired appliances in the enclosure; and
(c) air openings that communicate directly with the
outdoors, as shown in
Figure 6
, having a free-flow
area of not less than one (1) square inch per 4,000
BTU/h (5.5 cm2/kWh) of the total input rating of all
oil-fired appliances in the enclosure.
Note:
Duct runs that are primarily horizontal and that
have an equivalent length greater than 50 ft (15 m)
should be sized larger as required to provide
the same airflow as would be provided by the
requirements of Item (b).
Figure 4
Figure 6
Figure 7
Figure 5
INSTALLATION INSTRUCTIONS
