Stoves and furnaces – Hot-air furnaces – Compressed air
Reexamination Certificate
2001-02-12
2004-01-13
Bennett, Henry (Department: 3743)
Stoves and furnaces
Hot-air furnaces
Compressed air
C137S177000, C137S396000, C137S624110, C137S624140, C431S119000
Reexamination Certificate
active
06675795
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a freeze resistant method for draining furnace condensate in low temperature environments.
Condensing furnaces are designed to be installed indoors where there is little chance of freezing. Condensing furnaces often employ a condensing heat exchanger which recovers additional heat from the system by condensing water vapor from combustion gases. The liquid condensate, primarily water with a temperature exceeding 100° F., is normally drained away from the furnace and disposed. The flow rate of the condensate is quite small, around four to eight pounds per hour for a typical residential gas furnace. Therefore, the condensate drains out of the system very slowly, and thus cools down rapidly. This makes it difficult to operate a condensing furnace in low temperature environments due the tendency of this liquid condensate to subsequently freeze. If the condensate freezes before being removed from the system, the frozen condensate can block the flow of the flue path, causing damages to the furnace or posing a safety risk.
For the above reasons, condensing furnaces are not designed to operate outdoors. However, they are often installed in unheated spaces where temperatures may drop below freezing. Electrical heating tape can be utilized to prevent freezing, but there are several disadvantages to utilizing this method. Heat tape is expensive and has poor reliability. Additionally, there are safety concerns with utilizing heat tape.
Hence, there is a need in the art for a freeze resistant method for draining furnace condensate in low temperatures.
SUMMARY OF THE INVENTION
The present invention relates to a freeze resistant method for draining furnace condensate in low temperature environments.
In the preferred embodiment, a condensate reservoir is connected to a condensing heat exchanger of a condensing furnace. The condensing heat exchanger recovers heat from the system by condensing water vapor from combustion gases, producing a liquid condensate which accumulates in the condensate reservoir.
In one embodiment, a condensate line connects the discharge inducer fan to the side of the outlet of the condensate reservoir. The inducer provides a source of suction on the condensing heat exchanger and assists in pulling the flow of the combustion products through the system. During operation, the inducer produces a positive pressure along the condensate line, creating a back pressure on the outlet of the reservoir. This prevents draining of the condensate reservoir and allows the fluid to accumulate. When the system and the inducer are shut off, the positive pressure placed on the outlet of the reservoir is removed, allowing the liquid condensate to quickly flush from the reservoir.
By rapidly flushing the still warm liquid condensate out of the system with a high rate of flow, the amount of condensate remaining in the system after operation and exposed to cold conditions can be minimized. As the liquid condensate is rapidly flushed from the condensate reservoir, it travels to a condensate trap and is then drained. The liquid condensate can either drain into an outdoor unheated space or into an adjacent indoor heated space.
In an alternative embodiment, a valve is positioned proximate to the output of the condensate reservoir. The valve is opened when the liquid condensate is to be flushed, allowing rapid expulsion of the liquid condensate from the system. Alternatively, closing and opening this valve has the same function of applying and removing back pressure from the inducer.
In another alternative embodiment, the condensate reservoir is integrated as a part of the condensing heat exchanger, rather than a separate component located proximate to the condensing heat exchanger.
In another feature, controls are employed to regulate the amount of liquid condensate in the condensate reservoir and to prevent overflow. A control regulates the “on” time of the system. The system would automatically shut off and the reservoir drains after a specified period of time had elapsed. In another embodiment, a level detector can be employed. When a high level of liquid condensate is detected in the reservoir, the system would be interrupted to purge the reservoir. After flushing, the system then resumes.
Accordingly, the present invention provides a freeze resistant method for draining furnace condensate in low temperatures environments.
These and other features of the present invention will be best understood from the following specification and drawings.
REFERENCES:
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patent: 4682579 (1987-07-01), Bigham
patent: 4729328 (1988-03-01), Shellenberger
patent: 4856550 (1989-08-01), Smelcer
patent: 5115798 (1992-05-01), Moore et al.
patent: 5531241 (1996-07-01), Rasmussen
patent: 81826 (1983-06-01), None
Swieczkowski Robert Henry
Videto Brian David
Barrow James G.
Bennett Henry
Carrier Corporation
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