Rinnai Demand Duo R-Series Installation And Operation Manual page 22

(Small Room, Closet, Alcove, Utility Room, Etc.)
A confined space is defined in the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, and/or CSA
B149.1 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 rating of all
appliances installed in that space." A confined
space must have two combustion air openings.
Size the combustion air openings based on the
BTU input for all gas utilization equipment in the
space and the method by which combustion air is
supplied.
When sizing the permanent opening as illustrated
in Figure 12, consideration must be taken for the
design of the louvers or grills to maintain the
required free area required for all gas utilizing
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:
Free Area = Height x Length x % free area
Wood: 18 in x 24 in x 0.25 = 108 in
Metal: 18 in x 24 in x 0.75 = 324 in
To maintain proper circulation of combustion air
two permanent openings (one upper, one lower)
must be positioned in confined spaces. The upper
shall be within 12 in. (300 mm) of the top of the
confined space and the lower opening shall be
within 12 in. (300 mm) of the bottom of the
confined space. Openings must be positioned as
to never be obstructed.
Combustion air provided to the appliance
should not be taken from any area of the
structure that may produce a negative
pressure (i.e. exhaust fans, powered
ventilation fans).
22
Figure 11
Note: 8 ft. ceiling
Figure 12
2
2
Figure 13
18 in.
(450 mm)
Demand Duo™ R-Series (REC) Installation and Operation Manual
12 in.
(300 mm)
12 in.
(300 mm)
24 in. (600 mm)