Owner's Manual

8 C199 Manual

An unconned space is dened in Naonal Fuel Gas
Code, ANSI Z223.1/NFPA 54 as “a space whose vol-
ume is not less than 50 cubic feet per 1000 Btu/hr
(4.8 m3 per kW per hour) of the aggregate input
rang of all appliances installed in that space. Rooms
communicang directly with the space in which the
appliances are installed, through openings not fur-
nished with doors, are considered a part of the un-
conned space.” If the “unconned space” containing
the appliance(s) is in a building with ght construc-
on, addional outside air may be required for proper
operaon. Outside air openings should be sized the
same as for a conned space.

Small Room, Closet, Alcove, Ulity Room, Etc.)
A conned space is dened in the Naonal Fuel Gas
Code, ANSI Z223.1/NFPA 54 as "a space whose vol-
ume is less than 50 cubic feet per 1000 Btu/hr (4.8 m3
per kW per hour) of the aggregate input rang of all
appliances installed in that space." A conned space
must have two combuson air openings. Size the
combuson air openings based on the BTU input for
all gas ulizaon equipment in the space and the
method by which combuson air is supplied:

When sizing the permanent opening consideraon
must be taken for the design of the louvers or grills to
maintain the required free area required for all gas
ulizing equipment in the space. If the free area of
the louver or grill design is not available, assume
wood louvers will have 25% free area and metal
louvers or grills will have 75% free area. Under no
circumstance should the louver, grill or screen have
openings smaller than 1/4”.
Example:
Wood: 10 in x 12 in x 0.25 = 30 in
2
Metal: 10 in x 12 in x 0.75 = 90 in
2
Common Vent & Commercial Hybrid System Applicaons Only

To maintain proper circulaon of combuson air two
permanent openings (one upper, one lower) must be
posioned in conned spaces. The upper shall be
within 12 inches of the top of the conned space and
the lower opening shall be within 12 inches of the
boom of the conned space. Openings must be
posioned as to never be obstructed.

Outdoor air can be provided to a conned space
through two permanent openings, one commencing
within 12 in. (300mm) of the top and one commenc-
ing within 12” (300mm) of the boom, of the con-
ned space. The openings shall communicate to the
outside by one of two ways:
Exhaust
Vent terminaon per ANSI Z223.1/NFPA 54.
For clearances not specied in ANSI Z223.1/
NFPA 54, clearances are in accordance with
local installaon codes and the require-
ments of the gas supplier.
(Be sure to also maintain 12” above grade or
ancipated snow level)