FRESH AIR FOR COMBUSTION, VENTILATION AND HEAT DISTRIBUTION - CONT’D.
STEP 4. Compare the total Btu the area can support (from Step 2) to the total Btu in the area the heater will be installed (from Step 3). If the total from Step 2 is larger this is considered an unconfined space, if Btu total from Step 3 is larger this is considered a confined space and provisions must be made for additional combustion and ventilation air. EXAMPLE: Btu area can support is 56,250, total Btu in area is 106,000 – this would be a confined space.
NOTE: A third construction class is one with unusually tight construction, defined as, construction where: (A) Walls and ceilings exposed to the outside atmosphere have a continuous water vapor retarder with a rating of 1 per
“WARNING: If the area in which the heater may be operated is smaller than that defined as an unconfined space, or if the building is of unusually tight construction, provide adequate combustion and ventilation air by one of the methods described in the National Fuel Gas Code, ANSI Z223.1, Section 5.3 or applicable local codes.” Examples would be to provide two permanent openings either to an adjoining room, or to the outside. See the National Fuel Gas Code for details. See Figure 9 & Figure 10 below.
Chimney or gas vent
Opening
Furnace Water
Heater
Opening
Equipment located in confined spaces; all air from inside the building. See 5.3.3(a).
Chimney or gas vent
Ventilation louvers (each end of attic)
| Outlet Air |
Furnace Water | Inlet Air |
Heater |
Alternate air inlet
Ventilation louvers for unheated crawl space
Equipment located in confined spaces; all air from outdoors - inlet air from ventilated crawl space and outlet air to ventilated attic. See 5.3.3(b).
FIGURE 9 | FIGURE 10 |
INSTALLATION
Installation and service must be performed by a qualified installer, service agency or the gas supplier.
LOCATION
1)For most efficient performance, locate heater as centrally as possible in the area to be heated.
2)Do not install heater in a closet, alcove or small hallway where the heater could be isolated from the space to be heated and adequate combustion air by closing a door.
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