12” Max.

free area of the opening to which they connect. The minimum dimension of rectangular air ducts cannot be less than three inches.

Permanent openings to the outside or additional rooms within the building

Closet

or other

confined

space

12” Max.

The size of each of the two openings is determined by the method in which the air is to be provided. Refer to Table 4 to calculate the minimum free area for each opening. Figures 15, 16, 17 and 18 are typical examples of each method.

Louvers and Grilles

In calculating free area for ventilation and combustion air supply openings, consideration must be given to the blocking effect

of protection louvers, grilles, and screens. These devices can reduce airflow, which in turn may require larger openings to achieve the required minimum free area. Screens must not be smaller than 1/4” mesh. If the free area through a particular

FIGURE 13.

All Air from the Building

When additional air is to be provided to the confined area from additional room(s) within the building, the total volume of the room(s) must be of sufficient size to properly provide the necessary amount of fresh air to the water heater and other gas utilization equipment in the area. If you are unsure that the structure meets this requirement, contact your local gas utility company or other qualified agency for a safety inspection. Each of the two openings shall have a minimum free area of 1 square inch per 1,000 BTUH of the total input rating of all gas utilization equipment in the confined area, but not less than 100 square inches (Figure 14).

Confined

Space

Permanent

Openings

1 Square inch/1000

BTUH (min. 100 sq. in.)

FIGURE 14.

All Air from Outdoors

Outdoor fresh air can be provided to a confined area either directly or by the use of vertical and horizontal ducts. The fresh air can be taken from the outdoors or from crawl or attic spaces that freely communicate with the outdoors. Attic or crawl spaces cannot be closed and must be properly ventilated to the outside.

Ductwork must be of the same cross-sectional area as the

design of louver or grille is known, it should be used in calculating the specified free area of the opening. If the design and free area are not known, it can be assumed that most wood louvers will allow 20 - 25% of free area while metal louvers and grilles will allow 60 - 75% of free area.

Louvers and grilles must be locked open or interconnected with the equipment so that they are opened automatically during equipment operation.

Keep louvers and grilles clean and free of debris or other obstructions.

TABLE 4

Minimum Free Area of Permanent Openings for Ventilation and Combustion Air Supply - All Air from Outdoors Only.

Based on total BTUH input rating for all utilizing equipment within the confined space.

 

Minimum Free Area

 

Opening Source

Per Opening (sq. in.)

Reference Drawing

*Direct to outdoors

1 sq. in, per 4000 BTUH

Figure 15

Vertical Ducts

1 sq. in, per 4000 BTUH

Figure 16

Horizontal Ducts

1 sq. in, per 2000 BTUH

Figure 17

Single Opening

1 sq. in, per 3000 BTUH

Figure 18

Example: A water heater with an input rating of 50,000 BTUH using horizontal ducts would require each opening to have a minimum free area of 25 square inches.

Minimum free area = 50,000 BTUH x 1 sq. in. / 2000 BTUH = 25 sq. in.

*These openings connect directly with the outdoors through a venti- lated attic, a ventilated crawl space, or through an outside wall.

Consult the local codes of your area for specific ventilation and combustion air requirements.

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Sears 153.33262 manual Louvers and Grilles, All Air from the Building, All Air from Outdoors
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153.33262 specifications

Sears 153.33262 is a well-regarded electronic device in the field of household tools, specifically known as a versatile and reliable multi-function meter. Designed for both novice users and seasoned professionals, this meter is an essential instrument for a wide range of applications, including electrical diagnostics and home repair tasks.

One of the key features of the Sears 153.33262 is its capability to measure both AC and DC voltage, making it suitable for a variety of electrical projects. The device supports voltage measurements up to a specific range, allowing users to conduct thorough checks on outlets, circuits, and battery-powered systems. This versatility makes it an invaluable tool for electricians, technicians, and DIY enthusiasts alike.

In addition to voltage measurement, the Sears 153.33262 also boasts a multimeter functionality that includes current and resistance measurement capabilities. Users can easily measure current in different ranges, which is essential for assessing circuit loads and diagnosing electrical issues. The resistance measurement feature is beneficial for checking the integrity of wiring and components, ensuring that users can troubleshoot and resolve problems efficiently.

The design of the Sears 153.33262 emphasizes user-friendly operation. The meter typically incorporates a large, easy-to-read display that provides clear readings in various lighting conditions. The rotating selector switch allows users to switch between different measurement modes with ease, streamlining the workflow and minimizing the risk of errors.

This device is built with durability in mind, often featuring a rugged casing that can withstand the wear and tear associated with frequent use in various environments. Its portability is enhanced by its lightweight construction, allowing users to carry it easily to different job sites or locations within the home.

Furthermore, the Sears 153.33262 may also include features such as audible alerts for continuity testing, data hold functions, and battery-saving modes, further enhancing its functionality. The availability of probes and leads designed specifically for the meter ensures that users receive accurate measurements consistently.

In summary, the Sears 153.33262 is a multi-function electrical meter that stands out for its combination of versatility, user-friendly features, and robust construction. Whether one is performing simple checks around the house or engaged in complex electrical diagnostics, this meter serves as a reliable companion for all electrical measurement needs.
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