Stoves and furnaces – Hot-air furnaces – Compressed air
Reexamination Certificate
2000-08-31
2001-05-08
Yeung, James C. (Department: 3743)
Stoves and furnaces
Hot-air furnaces
Compressed air
C126S080000, C126S312000
Reexamination Certificate
active
06227191
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to the field of high efficiency gas furnaces, and in particular to a high efficiency gas furnace that includes a draft inducer.
BACKGROUND OF THE INVENTION
In general terms, furnaces such as those commonly installed to heat homes operate by drawing air from the living area through the furnace, heating the air, and returning it to the living area. In some heating systems, the air drawn from the living area is also used for combustion before being vented to the outside. Other systems draw combustion air from the outside. Duct systems are generally used to move the air, both heated and unheated, from one location to another. A blower forces the air drawn from the living area for heating through at least one heat exchanger. Usually, more than one heat exchanger is utilized. The heat exchangers are heated by combustion product gases generated by burners in a burner assembly, with each burner aligned with the inlet to one heat exchanger. The burners allow combustion of the gas and direct heated flue gas into the heat exchangers.
The typical heat exchanger includes cells with a channel or pass formed in each cell to direct the flow of flue gas produced by combustion and can be formed from sheet steel (“clamshell” exchangers) or steel tubing (“tubular” exchangers). These cells are typically positioned side by side in a parallel manner and include a predetermined spacing to allow the blower air to flow around the cells. The blower air is thus heated as it circulates over the cells.
When the flue gasses exit the heat exchangers, they are gathered in a collector box. The flue gases are typically withdrawn from the collector box by a draft inducer and ducted to the outside via a flue vent.
Each burner-heat exchanger pair are referred to as a “cell.” The larger the furnace, the more cells it contains. Small furnaces typically contain a minimum of two cells. Draft inducers are sized to optimize combustion efficiency. A draft inducer sized for a two-cell furnace does not optimize combustion efficiency for a three-cell furnace, and vice versa. That is, a draft inducer sized for a three-cell furnace is too strong for a two-cell furnace and decreases the efficiency of the furnace. In a product line that includes two-cell through seven-cell furnaces, six different size draft inducers are needed. A need therefore exists to reduce the number of different size draft inducers required for the product line.
SUMMARY OF THE INVENTION
Briefly stated, a bypass hole is cut into a collector box cover to reduce the efficiency of a draft inducer fan when the fan is used with a furnace containing fewer burner-heat exchanger cells than the fan is optimally suited for. Thus the same inducer fan can be used for both a two-cell and three-cell furnace. A method for adjusting airflow in a draft inducer for a furnace includes collecting flue gasses from the heat exchanger cells, inducing a draft by moving the flue gasses from a collector box, through a housing, and out of an exhaust hole, and taking a portion of the flue gasses in the housing and re-entering the portion of flue gasses into the collector box instead of exhausting the portion of said flue gasses to the outside.
According to an embodiment of the invention, an apparatus for adjusting airflow in a draft inducer for a furnace includes a draft inducer, the draft inducer including a housing; a collector box for collecting flue gasses from a plurality of heat exchangers in the furnace; the collector box including a cover disposed adjacent the draft inducer housing; the cover having an inducer housing inlet; the draft inducer housing having an exhaust hole; moving means for moving the flue gasses from the collector box, through the housing, and out of the exhaust hole; and the cover having at least one bypass hole therein, whereby a portion of the flue gasses in the housing re-enter the collector box via the bypass hole.
According to an embodiment of the invention, an apparatus for adjusting airflow in a draft inducer for a furnace includes a draft inducer, the draft inducer including a housing; a collector box for collecting flue gasses from a plurality of heat exchangers;
a collector box cover disposed between the collector box and the draft inducer housing; the cover having an inducer housing inlet; the draft inducer housing having an exhaust hole; moving means for moving the flue gasses from the collector box, through the housing, and out of the exhaust hole; the cover having at least one bypass hole therein, whereby a portion of the flue gasses in the housing re-enter the collector box via the bypass hole; wherein a location of the bypass hole is offset from an end of any of the plurality of heat exchangers; wherein a location of the bypass hole is such that a positive pressure differential exists between the flue gasses in the draft inducer housing and the collector box; and wherein, when the furnace has a specified number of cells, each cell including one heat exchanger, and the moving means is optimized for the specified number of cells with a collector box cover having no bypass hole, the bypass hole optimizes the moving means for the furnace when the furnace has at least one less cell than the specified number of cells.
According to an embodiment of the invention, a method for adjusting airflow in a draft inducer for a furnace includes collecting flue gasses from a plurality of heat exchangers in the furnace; inducing a draft by moving the flue gasses from a collector box, through a housing, and out of an exhaust hole; and taking a portion of the flue gasses in the housing and re-entering the portion of the flue gasses into the collector box instead of exhausting the portion of the flue gasses.
REFERENCES:
patent: 2504315 (1950-04-01), Feuerfile
patent: 4289730 (1981-09-01), Tomlinson
patent: 5255665 (1993-10-01), Windon
patent: 5368010 (1994-11-01), Weber, III et al.
patent: 5941230 (1999-08-01), Rutz et al.
Carrier Corporation
Wall Marjama & Bilinski
Yeung James C.
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