Size Natural Draught Purges with Absolute Certainty
Sizing purge openings incorrectly can lead to catastrophic ignition failures. Stop risking compliance on manual math and generic approximations. GasCalc transforms the strict geometric requirements of AS 3814 Clause 2.20.3.1 into a rapid, error-free digital workflow. Bring absolute certainty and audit-ready documentation to every Type B natural draught gasfitting project.
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Core Capabilities & Audit-Ready Reporting
Stop risking compliance failures on manual math and generic approximations. GasCalc provides indisputable mathematical proof of actual purge areas in the field.
Integrated Volume Calculators
Enter raw dimensions (length, width, height, or diameter) for both the combustion chamber and lateral flues. GasCalc handles the geometric formulas automatically to determine your exact purge volume (Vp).
AS 3814 & AS 1375 Interlock Detection
The tool automatically detects if your purge volume equals or exceeds 10 m³, instantly triggering mandatory safety warnings regarding door interlocks as legally required by AS 3814.
Precise Area Outputs
Automatically calculates the minimum required purge opening area in both square metres (m²) and square millimetres (mm²), applying the strict 0.2 multiplier dictated by the standard.
Data-Driven Compliance
Generates a complete, JSON-driven mathematical breakdown of the A ≥ 0.2 × Vp calculation for your commissioning report.
Inspector-Ready Output
Outputs crisp, vector-based PDF reports directly from the field, providing Technical Regulators with the exact mathematical proof they require for Type B appliance certification.
How the Calculator Works
Sizing purge openings incorrectly can lead to catastrophic ignition failures. GasCalc turns the strict requirements of AS 3814 Clause 2.20.3.1 into a simple, error-free workflow.
Map the Combustion Chamber
Define the main volume (Vc) of the appliance using either direct inputs or the built-in shape calculators for cylindrical and rectangular chambers.
Account for Lateral Flues
GasCalc prompts you to include any horizontal flue runs (Vf) where gas pooling and stratification might occur, ensuring a comprehensive purge volume (Vp).
Determine Opening Area
The app automatically calculates the minimum purge opening area in both m² and mm², applying the strict 0.2 multiplier dictated by the standard.
Legislative Framework
State & Territory Regulations
State legislation strictly enforces adherence to AS 3814 for all Type B appliance installations. Any natural draught purge system must mathematically prove that the purge opening area is sufficient to ventilate the combustion chamber and lateral flues prior to ignition.
AS 3814:2018 (Clause 2.20.3)
Mandates the minimum opening area of 0.2 m²/m³ of the purge volume, specifies the pre-purge period (not less than 5 minutes), and details strict interlock requirements for doors used for purging.
AS 1375:2023 (Clause 3.8.2)
Restricts natural draught purging to systems where ventilation reduces the mixture below the Lower Explosive Limit (LEL), and requires explosion relief hatches to be opened to initiate ignition.
GasCalc ensures all structural parameters are validated before establishing burner management settings.
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