Vent Proving Control for Gas Appliance Back Draft Prevention

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Solution Overview

Problem

Tightly sealed homes can lead to depressurization, causing gas-fired appliances' products of combustion to spill back into the home due to back drafting, which existing systems fail to address effectively, especially when cold air enters through the venting system.

Innovation Solution

A vent proving system that monitors vent gas temperature using a sensor and controller to determine back draft conditions, operating an electrical switch to adjust the vent damper and prevent gas burner operation if a back draft is detected, ensuring proper venting and safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If homes are sealed tighter to reduce air leakage, then energy efficiency is improved, but depressurization occurs causing back drafting of combustion products

Engineering Contradiction:

Improveenergy efficiencyVSAvoidback drafting

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The vent proving system performs preliminary verification of proper venting operation before allowing the gas burner to operate. The controller checks that the vent damper is in the correct position and that venting conditions are adequate prior to ignition, preventing back drafting from occurring in the first place rather than responding after it occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors vent damper position and venting conditions, providing feedback to the controller. Based on this feedback, the controller can adjust or prevent burner operation to maintain safe conditions, creating a closed-loop control system that adapts to changing pressure and drafting conditions.

Inventive Principle:

Principle #23Feedback

2Device complexity

If a thermal switch is used to shut off the boiler when drafting is blocked, then simple protection is provided, but it fails to detect back drafting caused by cold air entering through the vent

Engineering Contradiction:

Improvecontrol simplicityVSAvoiddetection accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The vent proving system introduces intermediate verification steps between the thermal switch and the burner control. Rather than relying solely on the thermal switch's temperature-based detection, the system uses additional sensors and control logic to verify venting conditions, creating a more reliable detection system that can distinguish between blocked vents and cold air infiltration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces or supplements the mechanical thermal switch with an electronic control system that uses electronic sensors and a microcontroller to monitor venting conditions. This electronic substitution provides more nuanced detection capabilities compared to the simple bimetallic thermal switch.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If the vent damper is opened when the gas burner is on, then proper venting is ensured, but latent heat is lost when the damper closes

Engineering Contradiction:

Improveventing safetyVSAvoidlatent heat loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The vent proving system verifies proper venting operation and damper positioning before allowing the burner to operate. By ensuring the damper is correctly positioned and venting is proven to be adequate prior to ignition, the system maintains safety while allowing the damper to close during operation to retain latent heat.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically controls the vent damper based on real-time verification of venting conditions. The damper opens only when venting is proven adequate, and closes when conditions are verified safe, creating a dynamic control strategy that balances safety requirements with energy conservation opportunities.

Inventive Principle:

Principle #15Dynamics

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

Prevents back drafting by selectively controlling the vent damper, ensuring safe operation of gas-fired appliances and preventing combustion products from entering the home, thereby maintaining indoor air quality and appliance efficiency.

Implementation Method 1

a sensor for sensing a variable in the vent representing air flow direction in the vent

Methodology Applied

Scientific EffectAir flow sensing:

Implementation Method 2

The controller determines if a back draft condition is present in the vent when the gas burner is on

Methodology Applied

Scientific EffectBack draft detection:

Data Source

PatentUS11262102B2Vent proving system

Publication Date: 2022.03.01 FIELD CONTROLS LLC

AI summary

A vent proving system is described for use with a gas fired appliance. The gas fired appliance includes a gas burner, a vent damper for selectively opening or closing an exhaust vent from the gas fired appliance and a relay control for operatively controlling the vent damper and the gas burner to open the damper if the gas burner is on. The vent proving system comprises a sensor for sensing a variable in the vent representing air flow direction in the vent. An electrical switch is connected in series between the relay control and the vent damper. A controller is operatively connected to the sensor, the electrical switch and to the relay control.