Flue Gas Outlet Assembly Backdraft Prevention

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Solution Overview

Problem

Existing flue systems for fuel burning devices, such as tankless water heaters, are prone to backdraft issues, which can impair device operation and pose safety risks due to the inability of current non-return valves to effectively prevent the backflow of noxious flue gas.

Innovation Solution

An integral flue gas outlet assembly with a non-return valve system, including a bullet-shaped float valve and a door mechanism, is designed to prevent backdraft by allowing flue gas to flow only in one direction, while also incorporating a condensate drain assembly to manage condensate effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If after-market non-return valves are installed on the exhaust side, then backdraft mitigation is attempted, but incorrect installation risks eliminate effectiveness

Engineering Contradiction:

Improvebackdraft prevention reliabilityVSAvoidinstallation correctness

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The non-return valve is integrated into the flue gas outlet assembly as a built-in feature rather than requiring separate after-market installation. The valve mechanism is combined with the outlet structure, eliminating installation errors while maintaining backdraft prevention functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The float valve mechanism automatically responds to flue gas flow conditions without requiring external control or correct manual installation. The system self-regulates based on the presence and direction of flue gas flow, ensuring reliable operation regardless of installation variations.

Inventive Principle:

Principle #25Self-service

2Object-affected harmful factors

If air intake side non-return valves are used, then gas escape from air inlet is prevented, but flue gas backdraft into the device cannot be prevented

Engineering Contradiction:

Improvenoxious gas escape preventionVSAvoidbackdraft prevention capability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Instead of preventing gas escape from the air inlet, the valve mechanism is positioned and oriented to prevent flue gas from entering the device through the flue gas outlet. The non-return action is inverted to block the exhaust path rather than protect the intake path.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The float valve acts as an intermediary mechanism between the flue gas outlet and the internal device. It selectively blocks the outlet path based on flow conditions, preventing backdraft into the device while allowing proper exhaust operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If a float valve is positioned at the center of the flue gas inlet, then condensate drainage is simplified, but backdraft prevention effectiveness is reduced

Engineering Contradiction:

Improvecondensate drain assembly simplicityVSAvoidbackdraft prevention effectiveness

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The float valve is deliberately positioned asymmetrically at the periphery rather than the center of the flue gas inlet. This asymmetric placement creates an effective barrier to backdraft while the condensate drainage path remains functional through the peripheral positioning that maintains gravitational flow.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The float valve is positioned at a specific peripheral location where it provides maximum backdraft prevention effectiveness. This localized positioning optimizes the barrier function while the condensate drainage capability is maintained through the local geometry and gravity-driven flow in that specific region.

Inventive Principle:

Principle #3Local quality

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 backdraft into the fuel burning device and the surrounding space, ensuring safe operation and reducing the risk of hazardous conditions, while maintaining the system's venting performance and length.

Implementation Method 1

The float valve can include a bullet-shaped float. The float valve can be biased closed and can be configured to open to permit a flow of condensate from the condensate inlet to the condensate outlet upon a sufficient amount of condensate collecting proximate the float valve.

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Implementation Method 2

The door can be configured to bias closed and to open upon a flow of flue gas from the inlet chamber to the outlet chamber.

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Data Source

PatentUS20230213188A1Flue systems for fuel burning devices

Publication Date: 2023.07.06 RHEEM MFG CO

AI summary

An exemplary embodiment of the present disclosure provides a flue gas outlet assembly including a flue gas inlet configured to connect to an exhaust outlet of a fuel burning device, a flue gas outlet, and a flue pipe condensate drain assembly including a condensate inlet, a condensate outlet, and a float valve disposed between the condensate inlet and the condensate outlet, the float valve including a bullet-shaped float, wherein the float valve is biased closed and is configured to open to permit a flow of condensate from the condensate inlet to the condensate outlet upon a sufficient amount of condensate collecting proximate the float valve.