All gas fired appliances require air for the combustion process. If sufficient combustion air is not available, the furnace or other appliances will operate inefficiently and unsafely. Enough air must be provided to meet the needs of all fuel burning appliances and appliances such as exhaust fans which force air out of the house. When fireplaces, exhaust fans, or clothes dryers are used at the same time as the furnace, much more air is necessary to ensure proper combustion and to prevent a downdraft. Insufficient air causes incomplete combustion which can result in carbon monoxide.

In addition to providing combustion air, fresh outdoor air dilutes contaminants in the indoor air. These contaminants may include bleaches, adhesives, detergents, solvents and other contaminants which can corrode furnace components.

The requirements for providing air for combustion and ventilation depend largely on whether the furnace is installed in an unconfined or a confined space.

Unconfined Space

An unconfined space is an area such as a basement or large equipment room with a volume greater than 50 cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the combined input rating of all appliances installed in that space. This space also includes adjacent rooms which are not separated by a door. Though an area may appear to be unconfined, it might be necessary to bring in outdoor air for combustion if the structure does not provide enough air by infiltration. If the furnace is located in a building of tight construction with weather stripping and caulking around the windows and doors, follow the procedures in the air from outside section.

Confined Space

A confined space is an area with a volume less than 50 cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the combined input rating of all appliances installed in that space. This definition includes furnace closets or small equipment rooms.

When the furnace is installed so that supply ducts carry air circulated by the furnace to areas outside the space containing the furnace, the return air must be handled by ducts which are sealed to the furnace casing and which terminate outside the space containing the furnace. This is especially important when the furnace is mounted on a platform in a confined space such as a closet or small equipment room. Even a small leak around the base of the unit at the platform or at the return air duct connection can cause a potentially dangerous negative pressure condition. Air for combustion and ventilation can be brought into the confined space either from inside the building or from outside.

Equipment in Confined Space - All Air From Inside

NOTE: Each opening shall have a free area of at least one square inch per 1,000 Btu (645 mm² per .29 kW) per hour of the total input rating of all equipment in the enclosure, but not less than 100 square inches (64546 mm²).

Figure 3

Air from Inside

If the confined space that houses the furnace adjoins a space categorized as unconfined, air can be brought in by providing two permanent openings between the two spaces. Each opening must have a minimum free area of 1 square inch (645 mm2) per 1,000 Btu (.29 kW) per hour of total input rating of all gas fired equipment in the confined space. Each opening must be at least 100 square inches (64516 mm2). One opening shall be within 12 inches (305 mm) of the top of the enclosure and one opening within 12 inches (305 mm) of the bottom. See Figure 3.

Air from Outside

If air from outside is brought in for combustion and ventilation, the confined space must have two permanent openings. One opening shall be within 12 inches (305 mm) of the top of the enclosure and one opening within 12 inches (305 mm) of the bottom. These openings must communicate directly or by ducts with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors or indirectly through vertical ducts. Each opening shall have a minimum free area of 1 square inch (645 mm2) per 4,000 Btu (1.17 kW) per hour of total input rating of all equipment in the en-closure. See Figures 4 and 5. When communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 square inch (645 mm2) per 2,000 Btu (.56 kW) per total input rating of all equipment in the enclosure. See Figure 6.

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Allied Air Enterprises 80G1UH2V, A80UH2V installation instructions Unconfined Space, Confined Space, Air from Outside
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80G1UH2V, A80UH2V specifications

Allied Air Enterprises has made a significant mark in the HVAC industry with its innovative and high-performance heating and cooling solutions. Among its impressive lineup, the Allied Air Enterprises 80G1UH2V and A80UH2V models stand out for their efficiency, reliability, and advanced features.

The 80G1UH2V is a two-stage gas furnace that operates on natural gas or propane. With an efficiency rating of up to 80%, it provides excellent heating performance while contributing to cost savings on utility bills. Its durable cabinet design ensures long-lasting performance and protection from harsh weather conditions, making it ideal for a variety of home environments.

One of the key features of the 80G1UH2V is its two-stage heating capability. This technology allows the furnace to operate at a lower capacity to maintain consistent temperatures during milder weather, reducing energy consumption and noise. When the temperature drops significantly, the furnace automatically shifts to high capacity, delivering the required heat promptly. This flexibility not only creates a more comfortable living space but also enhances energy efficiency.

The A80UH2V model shares similar traits with the 80G1UH2V but offers some additional features. It includes a variable-speed blower motor that optimizes airflow throughout the home. This innovation not only increases comfort levels but also facilitates quieter operation. The A80UH2V's advanced control system provides precise temperature management and can be integrated easily with smart home systems for enhanced automation.

Both models are designed to operate quietly, with noise levels minimized through improved insulation and sound-dampening technologies. This makes them suitable for residential applications, where comfort and peace are a priority. Additionally, they come equipped with a self-diagnostic control board that makes troubleshooting and maintenance simpler and more efficient.

Durability is another critical characteristic of both the 80G1UH2V and A80UH2V. They feature a robust heat exchanger made from high-quality materials, enhancing longevity and reliability. With these models, homeowners can expect reliable performance for years with minimal upkeep.

In summary, the Allied Air Enterprises 80G1UH2V and A80UH2V models deliver exceptional heating solutions through advanced technology, efficiency, and reliability. Their innovative features cater to the modern homeowner's need for comfort, control, and energy savings, making them excellent choices for residential heating needs.
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