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Combustion air source from outdoors
1.
Two permanent openings, one within 12 in. (30.5 cm)
of the top and one within 12 in. (30.5 cm) of bottom
of the confined space, must communicate directly or
by means of ducts with the outdoors, crawl spaces, or
attic spaces.
2.
One permanent opening, starting within 12 in. (30.5
cm) of the top of the enclosure is permitted where
the equipment has clearances of at least 1 in. (2.54
cm) from the sides and back and 6 in. (15.2 cm)
from the front of the appliance. The opening must
communicate directly with the outdoors and have a
minimum free area of:
-
1 in
/3,000 Btu/h (700 mm
2
rating of all equipment located in the enclosure
-
Not less than the sum of all vent connectors in the
confined space
3.
The duct must be least the same cross-sectional area
as the free area of the air supply inlet opening to
which it connects.
4.
The blocking effects of louvers, grilles, and screens
must be given consideration in calculating free area. If
the free area of a specific louver or grille is not known,
see Table 6.
Ventilated combustion air
The ventilated attic space or a crawl space from which
the combustion air is taken must comply with the
requirements specified in
Combustion air source
from outdoors
in this manual or in Section 5.3, Air for
Combustion and Ventilation of the National Fuel Gas
Code, ANSI Z223.1 (latest edition). This type of installation
requires two correctly sized pipes. One brings combustion
air from an adequately ventilated attic space or crawl
space and the second pipe extends from the furnace vent
connection (top right of the unit) to the exterior of the
building.
Vent and supply (outside) air safety check
procedure
For Category I furnaces, vent installations are in
accordance with Parts 7 and 11 of the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, and Section 7 and
Appendix B of the CSA B149.1, Natural Gas and Propane
Installation Codes, the local building codes, furnace and
vent manufactures instructions.
Multi-story or common venting systems are permitted
and must be installed in accordance with the National
Fuel Gas Code, ANSI Z223.1/ NFPA 54 and the CSA B149.1,
Natural Gas and Propane Installation Codes, local codes,
and the manufactures instructions.
Vent connectors serving Category I furnaces are not
connected into any portion of mechanical draft systems
operating under positive pressure.
Horizontal portions of the venting system a supported to
prevent sagging using hangers or perforated straps and
must slope upwards not less than 1/4 in./ft (20.8 mm/m)
from the furnace to the vent terminal.
26
Installation Manual: Z8ES Single-Stage Standard ECM Residential Gas Furnaces (Non-condensing Multi-position Standard
and Low NOx)
/kW) of the total input
2
Johnson Controls Ducted Systems
It is recommended that you follow the venting safety
procedure below.
This procedure is designed to detect an inadequate
ventilation system that can cause the appliances in the
area to operate improperly causing unsafe levels of
carbon monoxide or an unsafe condition to occur.
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