14
Figure 7. The water heater shall have clearances of at least 1 inch
(25mm)fromthesides andbackand6inches (150mm)fromthe
front of the appliance. The opening shall directly communicate with
the outdoors or shall communicate through a vertical or horizontal duct
to the outdoors or spaces that freely communicate with the outdoors
and shall have a minimum free area of the following:
1. 1squareinchper3000Btu/hr(700mm2perkW)ofthetotalinput
rating of all appliances located in the enclosure, and
2. Not less than the sum of the areas of all vent connectors in space.
outdoor aIr throuGh two horIZontal ductsfIGure 8.
Confined space shall be provided with two permanent horizontal
ducts,onecommencing within 12 inches (300 mm) of top and one
commencingwithin12inches(300mm)ofbottomofenclosure.Horizontal
ducts shall communicate directly with outdoors. See Figure 8.
Each duct opening shall have a minimum free area of 1 square inch
per2,000Btu/hr(1100mm2perkW)oftheaggregateinputratingofall
appliances installed in the enclosure.
When ducts are used, they shall be of the same cross sectional area
as the free area of the openings to which they connect. The minimum
dimension of rectangular air ducts shall be not less than 3 inches.
outdoor aIr throuGh two vertIcal ductsThe illustrations shown in this section of the manual are a reference for
theopeningsthatprovidefreshairintoconnedspacesonly.
Do not refer to these illustrations for the purpose of vent installation.
See Installation of Vent System on pages 20-21 for complete venting
installation instructions.
fIGure 9.
Theconnedspace shallbeprovidedwith twopermanentvertic al
ducts,onecommenc ingwithin12inches (300mm)ofthetop and
onecommencing within12inches (300mm)of thebottom ofthe
enclosure. The vertical ducts shall c ommunicate directly with the
outdoors. See Figure 9.
Each duct opening shall have a minimum free area of 1 square i nch
per4,000Btu/hr(550mm2pe rkW)oftheaggregateinputratingof
all appliances installed in the enclosure.
When ducts are used, they shall be of the same cros s sectional
area as the free area of the openings to which they co nnect. The
minimum dimension of rectangular air ducts sha ll be not less than
3 inches.
aIr froM other Indoor spacesfIGure 9a.
Theconnedspaceshallbeprovidedwithtwopermanentopenings,
onecommencing wit hin 12in ches (300 mm) of the top and one
commencingwithi n 12inc hes (300 mm) of the bottom of t he
enclosure. See Figure 9A.
Eachopeningshallcommunicatedirectlywithanadditionalroom(s)
ofsufcientvolumesothatthecombinedvolumeofallspacesmeets
thecriteriaforanUnconnedSpace.
Each opening shall have a minimum free area of 1 square inch p er
1,000Btu/hr(1100mm2perkW)oftheaggregateinputrating ofall
appliances installed in the enclosure. Eac h opening shall not be less
than100squareinches(645cm2).