Demand Duo
™
H
-
Series Installation and Operation Manual
29
WARNING
TO PREVENT POSSIBLE PERSONAL INJURY
OR DEATH DUE TO ASPHYXIATION,
COMMON VENTING WITH OTHER
MANUFACTURER
’
S INDUCED DRAFT
APPLIANCES IS NOT ALLOWED.
Location
To maintain proper circulation of combustion air
two permanent openings (one upper, one lower)
must be positioned in confined spaces. The up-
per shall be within 12 in. (0.30 m) of the top of
the confined space and the lower opening shall
be within 12 in. (0.30 m) of the bottom of the
confined space. Openings must be positioned as
to never be obstructed.
Louvers and Grills
When sizing the permanent opening considera-
tion must be taken for the design of the louvers
or grills to maintain the required free area re-
quired for all gas utilizing equipment in the
space. If the free area of the louver or grill de-
sign 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 in.
Free Area = Height x Length x % Free Area
Wood: 18 in. x 24 in. x 0.25 = 108 in.
2
Metal: 18 in. x 24 in. x 0.75 = 324 in.
2
Non
-
Direct Vent
(Room Air)
2
Combustion Air (Continued)
24 in.
(600 mm)
18 in.
(450 mm)
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).
IMPORTANT
Figure 30
