Document 85r1okozqv40MmQzOLX8L0pZd

394 CHAPTER 16 1950 Guide overcome the.friction in the flue pipe and chimney, but does not draw-air into the appliance. Chimneys for venting appliances designed for burning gas can therefore be low in height, but must have adequate area. The height is usually established by the building height. Chimney sizes are usually selected on the basis of Btu input of the appliance. One chart10 designed to facilitate selection is shown in Fig. 7. The assumptions made in preparing the chart, as well as its limitations, should be noted carefully. Since Fig. 7 has been prepared for circular flues, relative capacities for rectangular and semi-elliptical flues11 are shown in Fig. 8. When a flue is connected to several appliances, the number of horizontal runs of various sizes which may be substituted for the single run having a diameter equal to that of the flue may be obtained from Table 5. 0 20 4 0 60 60 100 120 140 16.0 180 . 200 PER CENT INCREASE IN CAPACITY OVER CIRCULAR FLUE Fig. 8. Capacity op a Rectangular Flue ob a Semi-Elliptical Flue, with SemiCircular Ends Having Its Minimum Width Equal to the Diameter op a Circular Flue, Compared with the Capacity op the. Circular Flue RECOMMENDATIONS OF THE NATIONAL BOARD ......... OF FIRE UNDERWRITERS . For general data on the construction of chimneys reference should be made to the Building Code, recommended by the National Board of Fire Underwriters, Article X, Section 1001 to 1006,4n which the following are some of the important provisions listed in the 1949 edition: 1. Flue Connections Required. Every heating apparatus or heat producing ap pliance requiring a flue connection shall be connected'with a flue conforining to the provisions of this article. This shall not include electric appliances; gas appliances, except as specifically required in this article; nor oil fired appliances especially de signed for use without flue connection. 2. Use of Nonconforming Flues. Flues not conforming to the requirements of this article for chimneys; metal smokestacks or vents for gas appliances, shall not be used unless listed by Underwriters' Laboratories, Inc., installed in-full compliance with the listing and the manufacturers' instructions, and approved for such use by the building official. . 3. Smoke,Pipe Connections. a. No flue shall have smoke pipe connections in more than one story of a building, unless provision -is made for effectively closing smoke pipe openings with devices. made of rioncombustible materials whenever their use is discontinued temporarily;' and completely closing them with masonry when discontinued permanently. Chimneys and Draft Calculations 395 b. Two or more smoke pipes shall not be joined for a single connection, unless the smoke pipes and flue are of sufficient size to serve ail the appliances thus con nected. c. The smoke pipe of a heating appliance shall not be connected into the flue of an incinerator which has the rubbisn chute identical with the.smoke flue. 4. Construction of Chimneys. a. Chimneys hereafter erected within or attached to a structure shall be con structed in compliance with the provisions of this section. b. Chimneys shall extend at least 3 ft above the highest point where they pass through the roof of the building, and at least 2 ft higher than any ridge within 10 ft of such chimney. c. Chimneys shall be wholly supported on masonry or self-supporting fireproof construction. d. No chimney shall be corbeled from a wall more than 6 in.; nor shall a chimney be corbeled from a wall which is less than 12 in. in thickness; unless it projects equally on each side of the wall; provided that in the second story of 2-story.dwellings cor beling of chimneys on the exterior of the enclosing walls may equal the wail thickness. In every case the corbeling shall not exceed 1 in. projection for each course of brick projected. Table 5. Equivalent Flue Pipe Sizes* Size of Flub Horizontal Runs 3 4 5 6 8 10 12 3 1 2 3 5 9 12 22 4 1 2 3 5 -7 11 5 12347 6 1 235 8 1 23 * Comfort Heating (American Oat Association). e. No change in the size or shape of a chimney, where the chimney passes through' the roof, shall be made within a distance of 6 in. above or below the roof joists or rafters. 5. Chimneys for Heating Appliances, Low Heat Industrial Appliances and Portable Type Incinerators. a. Chimneys for stoves, cooking ranges, warm air, hot water and low pressure steam heating furnaces, fireplaces, and low heat industrial appliances, other than chimneys for incinerators of nonportable type, shall be constructed of solid masonry units or of reinforced concrete. The walls shall be properly bonded or tied with corrosion-resistant metal anchors. In dwellings and buildings of like heating re quirements, the thickness of the chimney shall be not less than4 in. In other build ings the thickness shall be not less than 8 in., except that rubble stone masonry shall be not less than 12 in. thick. b. Every such chimney hereafter erected or altered shall be lined with a flue lin ing conforming to the requirements below. c. Flue linings shall be made of fire clay or other refractory clay which will with stand the action of flue gases and resist, without softening or cracking, the tempera tures to which they will be subjected, but not less than 2000 F. Flue linings may be of cast iron of approved quality, form and construction. _. . . d. Required clay flue linings shall be not less than f in. thick for the smaller flues, ana shall increase in thickness for the larger flues. e. Flue linings shall be installed ahead of the construction of the chimney as it is carried up, carefully bedded one on the other in Type A, Type B, or fire clay mortar with close fitting joints.left smooth on the inside. f. Flue linings shall start from a point not less than 8 in; below the intake, or, in the case of fireplaces, from the throat of the fireplace. They shall extend, as nearly vertically as possible, for the entire height of thechimney, and be extended 4 in. above the top of cap of the chimney. g. Cleanouts for flues or fireplaces shall be equipped with cast-iron doors and frames arranged to remain tightly closed when not in use: h. When two or more flues are contained in the same,chimney, at least every third