Rinnai RH180 Operation And Installation Manual page 14

Combus on Air Requirements
Confined Space:
(Small Room, Closet, Alcove, U lity Room, Etc.)
A confined space is defined 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 confined
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
Metal: 10 in x 12 in x 0.75 = 90 in
Loca on
To maintain proper circula on of combus on air two
permanent openings (one upper, one lower) must be
posi oned in confined spaces. The upper shall be
within 12 inches of the confined space and the lower
opening shall be within 12 inches of the bo om of the
confined space. Openings must be posi oned as to
never be obstructed.
Using Outdoor Air For Combus on
Outdoor air can be provided to a confined space
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).
14
2
2
RH180 Manual
Figure 1