high combustion and operating temperatures. A load of wood of forty to sixty pounds is easily ignited with the aid of the forced draft from a small starter·-fire of kindling, and will be completely burned in less than two hours. During steady-state operation combustion temperatures will be in excess of 1300° Fahrenheit, and at this temperature fuelwood exhibits a delaytime of about 1/10 of a second in order to achieve virtually complete combustion of all volatile gases, producing only heat, carbon dioxide, water vapor, and fly ash. No creosote. Coupled to the combustion chamber of the furnace is an air-to-liquid heat-exchanger. A heavy investment of engineering time has produced a highly efficient heat-exchange design capable of dropping the exhaust _gas temperature from 1300- • 1400° to 150-300° Fahrenheit. The heat exchanger is in turn connected to a large (600 to 3000 gallon) insulated water storage tank. Heat is produced during steady-state operation at the rate of 120,000 to 140,000 BTU per hour, is captured by the heat exchanger and transferred to the insulated water srnrage by means of a small circulating pump. The pump is turned on when the furnace is fired and maintains a constant circulation between the Jetstream's heat-exchange tubes and the storage tank. As outlined so far, the system is closed and non-pressurized, and the water contains .chemicals designed to prevent corrosion in the furnace boiler. If the water storage tank were stripped of its insulation, it would provide a gentle heat similar to that of the "Russian fireplace-stove," which uses thousands of pounds of masonry as a massive heat-sink. Those interested in active solar applications will recognize at this point how easily the Jetstream system can be integrated into an active solar installation. • But there is more to the J etstream system as envisioned by its designers. Depending on the type of structure to be heated, the system can take different forms from this point on. For hot-air heat in an existing structure, a liquid-to-air heat exchanger is used to draw off heat in small amounts from liquid A 40" by 12¼" diameter-....,,,..--. vertical loading fuel tube. Water jacketed to inhibit burning outside of combustion zone. A 50-gallon hydronic ---- ., December 1980 • RAIN Page 9 storage and se'nd it into an existing hot-air furnace ductwork system for distribution throughout the structure. If hot-water heat is de;ired, a liquid-to-liquid heat exchanger is connected to a non-pressurized system. If the Jetstream is to be installed in new construction, the furnace can go either way. At this po!nt the flexibility of the J etstream system becomes increasingly apparent, for it can heat a structure of any . size with high efficiency up to its limits of about 120,000 BTU's per hour, and can be easily used to heat large quantities of water as well as air for domestic purposes or for special applicati_ons such as hot tubs, swimming pools, and laundromats. The manufacturer supplies only the basic furnace and an optional digital readout panel to monitor temperatures at different locations throughout the system, such as firebox, exhaust stack, and water temperature at different locations. ,Fiberglass or steel storage tanks, due to their size and weight, are best sought out locally to avoid high shipping costs, and the same applies to the substantial quantity of hardware needed to complete a J etstream system installation, such as pumps, copper piping, a small expansion tank, electrical wire and hardware, etc. The manufacturer does supply a l00~page installation and operations manual which goes into great detail and is of considerable help in assembling and de-bugging a Jetstream system as it is tailored to t~e individual requirements of its owner. In addition, the manufacturer selects Jetstream dealers for their knowledge of the system, its appiications, their ability to supervise installations, and to troubleshoot and provide maintenance help at a later date. Wood, as a renewable resource, has always. been an excellent heat energy s.ource. Unfortunately, it carried with it inherent problems like air pollution, and chimney fires caused by creosote buildup. Finally, with the Jetstream, these problems are virtually eliminated and a·safe and sensible future for wood-burning is assured.DD ethousing for combustion air and exhaust draft. To Home heat exchanger. -f-t-H"ltlH::::lz~it:~"1-----Fire tu:~~~~:~:~; Preheated charge air----- introduces combustion air under pressure. Wood burns in refractory combustion chamber where high temperatures (1200-2000°F) and turbulent, forced preheated combustion air produce optimum combustion environment. Insulating cement for heat retention and structural integrity. inserts. --1----Return water from heat storage. ~-----ttigh temperature turbulent tunnel provides ignition of any unburned residues. Y...-----Hiigh temperature, durable castable refractory. Jetstream System Diagram 1. High efficiency Jetstream Furnace releases energy from wood and transfers it to heat storage. 2. Heat energy stored in insulated storage tanks. 3. Home draws automatically from heat storage as required, for home heat or domestic hot water.
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