area of one square inch per 1000 Btu/hr (22 cm2/kW) of the total input of all appliances in the enclosure, but not less than 100 square inches (645 cm2).

If the confined space is within a building of tight construction, air for combustion and ventilation must be obtained from outdoors. When directly communicating with the outdoors or communicating through vertical ducts, two permanent openings, located in the above manner, shall be provided. Each opening shall have a free area of not less than one square inch per 4000 Btu/hr (5.5 cm2/kW) of total input of all appliances in the enclosure. If horizontal ducts are used, each opening shall have a free area of not less than one square inch per 2000 Btu/ hr (11cm2/kW) of the total input of all appliances in the enclosure.

A. ALL AIR FROM INSIDE BUILDINGS: (See Figure 5 and 6)

The confined space shall be provided with two permanent openings communicating directly with an additional room(s) of sufficient volume so that the combined volume of all spaces meets the criteria for an unconfined space. The total input of all gas utilization equipment installed in the combined space shall be considered in making this determination. Each opening shall have a minimum free area of one square inch per 1,000 Btu per hour (22 cm2/kW) of the total input rating of all gas utilization

equipment in the confined space, but not less than 100 square inches (645 cm2). One opening shall commence within 12 inches (30 cm) of the top and one commencing within 12 inches (30 cm) of the bottom of the enclosures.

FIGURE6.

B. ALL AIR FROM OUTDOORS: (See Figures 7, 8 and 9)

The confined space shall be provided with two permanent openings, one commencing within 12 inches (30 cm) of the top and one commencing within 12 inches (30 cm) from the bottom of the enclosure. The openings shall communicate directly, or by ducts, with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors.

1.When directly communicating with the outdoors, each opening shall have a minimum free area of 1 square inch per 4,000 Btu per hour (5.5 cm2/kW) of total input rating of all equipment in the enclosure, see Figure 7.

FIGURE7.

2.When communicating with the outdoors through vertical ducts, each opening shall have a minimum free area of 1 square inch per 4,000 Btu per hour (5.5 cm2/kW) of total input rating of all equipment in the enclosure, see Figure 8.

3.When communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 square inch per 2,000 Btu per hour (11 cm2/kW)) of total input rating of all equipment in the enclosure, see Figure 9.

FIGURE8.

4.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 short side dimension of rectangular air ducts shall not be less than 3 inches (7.6 cm), see Figure 9.

FIGURE9.

5.Alternatively a single permanent opening may be used when communicating directly with the outdoors, or with spaces that freely communicate with the outdoors. The opening shall have a minimum free area of 1 square inch per 3,000 BTU per hour (8.3 cm2/kW) of total input rating of all equipment in enclosure. See Figure 9A.

FIGURE9A.

6.Louvers and Grilles: In calculating free area, consideration shall be given to the blocking effect of louvers, grilles or screens protecting openings. Screens used shall not be smaller than 1/4 inch (6.4 mm) mesh. If the free area through a design of louver or grille is known, it should be used in calculating the size opening required to provide the free area specified. If the design and free area is not known, it may be assumed that wood louvers will be 20-25 percent free area and metal louvers and grilles will have 60-75 percent free area. Louvers and grilles shall be fixed in the open position or interlocked with the equipment so that they are opened automatically during equipment operation.

7.Special Conditions Created by Mechanical Exhausting or Fireplaces: operation of exhaust fans, ventilation systems, clothes dryers or fireplaces may create conditions requiring special attention to avoid unsatisfactory operation of installed gas utilization equipment.

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A.O. Smith ARGSS02708 instruction manual ALL AIR from Inside Buildings See, ALL AIR from Outdoors See Figures 7, 8
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ARGSS02708 specifications

The A.O. Smith ARGSS02708 is a standout product in the realm of water heating solutions, designed with a focus on efficiency, durability, and user convenience. This particular model exemplifies the cutting-edge technology that A.O. Smith is known for, making it a preferred choice for both residential and commercial applications.

One of the main features of the ARGSS02708 is its high efficiency. The unit employs advanced insulation techniques, which minimize heat loss and ensure that energy is utilized effectively. With an Energy Factor that meets or exceeds industry standards, this water heater can significantly reduce energy bills, making it an environmentally friendly choice that doesn't compromise on performance.

Another notable characteristic of the A.O. Smith ARGSS02708 is its robust construction. Built with high-quality materials, this water heater is designed to withstand the wear and tear of daily use. The units are manufactured with a coating that helps resist corrosion, which not only prolongs the lifespan of the heater but also ensures that it operates safely and reliably over time.

The ARGSS02708 also incorporates smart technology that enhances user experience. It features an intelligent electronic control panel that allows for easy monitoring and adjusting of temperature settings, ensuring optimal comfort. This user-friendly interface provides real-time feedback, making it straightforward for users to manage their hot water needs efficiently.

Moreover, the model supports faster recovery rates compared to traditional water heaters. With its powerful heating elements, the ARGSS02708 can provide a steady supply of hot water at consistent temperatures, catering to households or businesses with high hot water demands.

Safety is another critical aspect that A.O. Smith prioritizes in the design of the ARGSS02708. The unit is equipped with multiple safety features, including thermal cut-off switches and pressure relief valves, which ensure safe operation under varying conditions.

In summary, the A.O. Smith ARGSS02708 emerges as an excellent option for those seeking a reliable, efficient, and user-friendly water heating solution. Its combination of advanced technology, durable construction, high efficiency, and safety features make it a commendable investment for anyone looking to enhance their water heating experience.
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