User Guide

RH180 Manual 15
When communicang indirectly with the outdoors
through vercal ducts, each opening shall have a
minimum free area of 1 in
2
/4000 Btu/hr (550 mm
2
/
kW) of total input rang of all appliances in the
conned space. Combuson air to the appliance can
be provided from a well venlated ac or crawl
space.
Combuson Air Requirements
through two permanent openings, one commencing within 12 in. (300mm) of the top and one commencing
within 12” (300mm) of the boom, of the conned space. The openings shall communicate to the outside by
one of two ways:
When communicang directly with the outdoors
through horizontal ducts, each opening shall have a
minimum free area of 1 in
2
/2000 Btu/hr (1100 mm
2
/
kW) of total input rang of all appliances in the
conned space.
Note: If ducts are used, the cross seconal area of
the duct must be greater than or equal to the
required free area of the openings to which they are
connected.
Using Indoor Air For Combuson
When using air from other room(s) in the building, the total volume of the room(s) must be of adequate volume
(Greater than 50 cubic feet per 1000 Btu/hr). Each Combuson air opening must have at least one square inch
of free area for each 1000 Btuh, but not less than 100 square inches each.
Directly through horizontal ducts Indirectly through vercal ducts