Masonry Magazine January 1984 Page. 29
Crown
The crown of the fountain-style heater should be at least 12 in. (300 mm) thick, including the refractory slab forming the top of the smoke chamber. The crown should terminate at least 12 in. (300 mm) below the ceiling of the room. This may require that the baffle chambers be extended below the floor line of the room.
Chimney
The chimney for the fountain-style heater is similar to those used for residential appliances. The chimney should be constructed of fireclay flue liners and 8 in. (200 mm) of brick masonry surrounding the liner in such a way as to maintain a nominal 1-in. (25 mm) space between the flue liner and the brick chimney walls. Additional information on chimney design and construction is provided in Technical Notes 19B Revised.
The chimney height required for draft is usually higher than that necessary for a conventional fireplace, but following building code requirements for fire safety will usually result in a sufficiently high chimney. The major model building codes require that chimneys must terminate at least 3 ft (1 m) above the roof at the highest point of exit and at least 2 ft (600 mm) above any portion of the building or adjacent structures within 10 ft (3 m) of the chimney. If draft is determined to be inadequate by a smoke test, the chimney height should be increased to provide adequate draft.
CONTEMPORARY-STYLE HEATERS
# General
The brick masonry heater formed by modifying a conventional fireplace, as shown in Figs. 4 through 7, is one of the easiest brick masonry heaters to construct and also retains most of the esthetic value of a conventional fireplace. This style of heater has the baffle system, through which combustion gases are circulated, incorporated solely in the smoke chamber assembly. Variations in the smoke chamber and the firebox are the only major differences from a conventional fireplace. The front and side sections of the contemporary-style heater are shown in Figs. 4 and 5, respectively. The heater under construction is shown in Fig. 6, and Fig. 7 shows a completed contemporary-style heater.
Base Assembly
The requirements for the base assembly are essentially the same as for the other brick masonry heaters and conventional fireplaces. The foundation system requirements discussed for fountain-style heaters are also applicable to the modified conventional fireplace.
The hearth support is similar to that of a conventional fireplace, as discussed in Technical Notes 19 Revised and 19A Revised. The hearth support is usually constructed of a reinforced concrete slab, as previously discussed. For this style heater, it is necessary to have only a 20-in. (500 mm) extended hearth at the front face of the heater. The thickness of the side and rear walls at the floor line usually provides adequate fire protection. However, because the higher portions of this heater are much hotter, a minimum 12-in. (300 mm) clearance should be maintained between the back and sides of the heater and any combustible materials.
If an ash pit is desired, it may be constructed the same as for a conventional fireplace. External combustion and draft air systems used with conventional fireplaces may also be incorporated into this style heater. Additional information is provided in Technical Notes 19 Revised and 19A Revised.
Firebox Assembly
The firebox is constructed as a rectangular box that is usually about 20 in. (500 mm) deep and 30 in. (750 mm) wide. The opening of the firebox is usually about 27 in. (675 mm) high. Immediately behind the top of the firebox opening, which is constructed of face or building brick on a steel lintel, is the top of the firebox. The top of the firebox is formed as a brick masonry arch, extending from the inside face of the heater and terminating about 6 in. (150 mm) to 8 in. (200 mm) from the rear wall of the firebox. At the crown of the arch, above the opening, the first horizontal baffle is constructed. This baffle extends about 8 in. (200 mm) to 12 in. (300 mm) on either side of the firebox, and is constructed of refractory units.
Smoke Chamber Assembly
The conventional smoke chamber is replaced by a baffle system as shown in Figs. 4 and 5. The baffle