User Guide

14 RH180 Manual
Combuson air provided to the appliance
should not be taken from any area of the
structure that may produce a negave pres-
sure (i.e. exhaust fans, powered venlaon
fans).
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
volume 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:
Louvers and Grills
When sizing the permanent opening as illustrated in
Figure 1, 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 ¼”.
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
Locaon
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 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.
Using Outdoor Air For Combuson
Outdoor air can be provided to a conned space
Combuson Air Requirements
Figure 1