Method and system for vented rollout switch
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Solution Overview
Problem
Gas furnaces face issues with rollout conditions due to cracked or occluded heat-exchange tubes, leading to damage and nuisance tripping of temperature-sensitive rollout switches, which can be caused by space constraints and the flame not being drawn to the switch, as well as high temperatures triggering false shutdowns.
Innovation Solution
A rollout shield with strategically placed vents adjacent to the rollout switch, providing a path for the rollout flame and secondary combustion air, helps in attracting the flame to the switch, increasing the likelihood of proper tripping during rollout conditions while reducing nuisance tripping during normal operation by maintaining the switch below threshold temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rollout switch is positioned away from the gas burner to avoid high temperatures, then nuisance tripping is reduced, but the switch may not detect rollout conditions accurately
Solution Approach 1:
The rollout shield creates different thermal zones: a cooler zone where the switch is positioned (through the switch aperture) and a hotter zone near the gas burner. The local quality of the shield structure provides thermal protection to the switch while maintaining the ability to detect rollout flames that extend into the shield area.
Solution Approach 2:
The switch aperture provides a three-dimensional pathway for flame detection without requiring the switch to be in direct contact with the high-temperature zone. This dimensional approach allows the switch to detect rollout conditions through the aperture while being positioned in a cooler region.
2Productivity
If space constraints are present in the furnace, then the rollout shield and switch positioning options are limited, but proper rollout detection is still required
Solution Approach 1:
The rollout shield serves multiple functions: it provides thermal protection for the rollout switch, defines the rollout detection zone, and structures the venting pathways. This multi-functionality reduces the need for additional separate components, maintaining furnace compactness while ensuring proper rollout detection capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents furnace damage by ensuring accurate detection of rollout conditions and reducing false shutdowns, allowing for reliable operation and extended component lifespan by ensuring the rollout switch is tripped by the high-temperature flame rather than ambient air, thus maintaining proper gas furnace operation.
Implementation Method 1
The at least one vent is disposed on at least two sides of the rollout switch... provide a path for a rollout flame to the rollout switch
Implementation Method 2
providing a path for a rollout flame and secondary combustion air... attracting the flame to the switch
Data Source
AI summary
A furnace includes a gas burner exposed to a heat-exchange tube. An inducer is fluidly coupled to the heat-exchange tube and configured to induce draft air through the heat-exchange tube. A regulator is fluidly coupled to the gas burner. A rollout shield is disposed adjacent to the gas burner. A rollout switch is disposed in the rollout shield. The rollout switch is electrically coupled to the regulator. At least one vent is formed through the rollout shield adjacent to the rollout switch. The vent provides a path for a rollout flame to the rollout switch. The at least one vent is disposed on at least two sides of the rollout switch.