Masonry Magazine January 1984 Page. 21
19E
Technical Notes
on Brick Construction
Brick Institute of America 1750 Old Meadow Road, McLean, Virginia 22102
1983
BRICK MASONRY FIREPLACES-PART II
FOUNTAIN AND CONTEMPORARY STYLE HEATERS
Abstract: Brick masonry heaters may be used instead of conventional fireplaces to provide efficient supplemental heating for residential buildings. The design, detailing and construction of brick masonry fireplaces with baffle systems through which combustion gases are circulated are discussed. Information regarding building code compliance, operation and accessories is presented, along with the basic heating principles.
Key Words: brick, buildings (codes), design, energy, fireplaces, heating, masonry, mortar.
INTRODUCTION
The basic concepts of a fireplace designed with a baffle system replacing the conventional smoke chamber are discussed in Technical Notes 19D. Such fireplaces are often referred to as Russian-style fireplaces. These fireplaces, or brick masonry heaters, although capable of providing efficient heat, tend to eliminate the esthetic value of the fireplace because the firebox is typically deep within a small opening. An alternate approach to the fireplace designed to include a baffle system through which combustion gases are circulated is the Finnish or fountain-style heater. This Technical Notes provides the information necessary to properly design and construct a fountain-style brick masonry heater or to modify conventional fireplace designs to incorporate baffle systems to allow the circulation of combustion gases.
The basic principles by which high efficiencies are obtained for heating the building interior and for the combustion of wood are the same as for the Russian-style brick masonry heater. Hot combustion gases circulating through the massive brick masonry heater, combined with properly controlled air intake for combustion, result in high efficiencies. The hot combustion gases are circulated through baffle chambers within the heater. The massive brick masonry is warmed and retains the heat. This warmed brick masonry radiates the heat long after the fire is extinguished. The basic concepts of design, construction and operation are simple, but there are several concerns which must be addressed to insure safety and durability.
GENERAL
Operation
The operation of both the fountain-style brick masonry heater and the contemporary-style heaters is quite similar. Both systems have unique operational advantages which are directly related to their design and the way in which combustion gases are circulated through the massive brick masonry assembly.
Typically, the combustion chamber or firebox is loaded with 10 lb (4.5 kg) to 20 lb (9.1 kg) of wood, after a fire with kindling is ignited. Once good combustion starts, the firebox doors or glass screens are closed and the air intakes adjusted to the proper setting so that good combustion continues. Unlike the Russian-style brick masonry heater, because of the design of the firebox, glass screens may be used on the fountain-style heater and the modified conventional fireplace. The glass screens or firebox doors used should be equipped with operable air inlets so that the air intake to the combustion chamber can be controlled. The metal firebox doors or glass screens selected for the firebox opening should be capable of withstanding the high temperatures in the combustion chamber. Temperatures of combusting wood will usually range from 1000°F (540°C) to 1500°F (820°C), and the temperature of the combustion gases near the fire usually ranges from about 800°F (430°C) to 1200°F (650°C). Thus, all components of the firebox should be capable of withstanding these temperatures.
The 10 lb (4.5 kg) to 20 lb (9.1 kg) of wood loaded in the firebox will burn for about 30 min when properly seasoned wood is used with adequate draft and combustion air. For maximum heating, the firebox should be reloaded with about 10 lb (4.5 kg) to 20 lb (9.1 kg) of wood every 30 min for a 2-hr period. This procedure usually results in enough heat being supplied by the brick masonry heater to keep a 2400 ft³ (68 m³) room warm for a period of 8 to 12 hr during the coldest months in severe climates, such as in Scandinavia. Under these severe climate conditions, the heater is usually operated for a 2-hr period twice a day, once in the morning and once in the evening. During the more moderate seasons, or in the more moderate climates, operating the heater once in the evening may be adequate to supplement the mechanical heating system to maintain See Reference 10.