Limit switch control method for a two-stage furnace
First Claim
1. A method of operating a gas furnace of the type having a control system for selectively operating in either of two stages of operation and a gas valve which is responsively operable in either a low or high fire mode comprising the steps of:
- determining whether, when the control system is calling for a low fire mode, the gas valve is in a high fire mode; and
responsively restricting the control system to operation in a high fire only mode.
3 Assignments
0 Petitions
Accused Products
Abstract
A two-stage gas furnace control system automatically shifts into a high fire only mode if, in two consecutive low fire heating cycles a limit switch is tripped to indicate that a gas valve is stuck in a high fire condition. In this way, continued operation is allowed to proceed in a safe manner. Provision is also made to lock out the system from further operation if, while in the high fire only mode, the limit switch is tripped in a predetermined consecutive number of cycles or if, while in a preemptive low fire only mode, the limit switch is tripped.
38 Citations
13 Claims
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1. A method of operating a gas furnace of the type having a control system for selectively operating in either of two stages of operation and a gas valve which is responsively operable in either a low or high fire mode comprising the steps of:
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determining whether, when the control system is calling for a low fire mode, the gas valve is in a high fire mode; and responsively restricting the control system to operation in a high fire only mode. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a gas furnace system of the type having a gas valve which is operable to either a high fire or a low fire condition in response to a control system, a method of operating the system comprising the steps of:
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determining whether the gas valve is in a high fire condition when the control is calling for low fire condition; and responsively restricting the control system to high fire operation. - View Dependent Claims (8, 9, 10)
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11. A method of operating a furnace system of the type having a limit switch for sensing the temperature in a circulating air chamber around the heat exchanger and for responsively shutting down portions of the system when the temperature reaches a predetermined limit, including the steps of:
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sensing, in consecutive heating cycles, when the temperature in the circulating air chamber reaches the predetermined limit; counting the number of times when the predetermined temperature is reached in consecutive heating cycles; and when said number reaches the predetermined level, shutting down the system from further operation. - View Dependent Claims (12, 13)
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Specification