Calculation sequence
Step-by-step method
- Sum appliance quantities times user-entered input ratings.
- Apply only the visible approved diversity factor.
- Divide by the user-entered heating value on the same HHV/LHV basis.
PlumbingIntermediateNatural and Fuel Gas
Fuel-Gas Load and Flow Calculator
Sum user-entered appliance loads and convert diversified load to ideal gas volume flow using a user-entered heating value.
Why it matters: Load inventory and heating-value conversion are distinct from pipe sizing, pressure drop, combustion, and code compliance.
Calculated result
Engineering evaluation
Ideal fuel-gas volume flow (Qᵍ)180 ft³/h
- Connected appliance load (Hᶜ)
- 180,000 Btu/h
- Diversified design load (Hᴰ)
- 180,000 Btu/h
Engineering interpretation
The entered load inventory represents 180000 Btu/h diversified load and 180 ft³/h ideal gas flow.
Important limitations
- Load/flow conversion only. This tool never sizes pipe, calculates pressure drop, establishes code compliance, or selects appliances, regulators, valves, vents, combustion air, or meters. Confirm fuel, HHV/LHV, standard conditions, altitude, utility data, and diversity authorization.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Hᶜ=n₁H₁+n₂H₂+n₃H₃
Hᴰ=D·Hᶜ
Qᵍ=Hᴰ/HV
Current substitution
Hᶜ=1×100000+1×80000+0×0=180000; Hᴰ=1×180000=180000; Qᵍ=180000/1000=180 ft³/h.
Equation legend
Inputs and calculated quantities
- n₁
- Appliance quantity row 1 — count
- H₁
- Appliance load row 1 — Btu/h or kW each
- n₂
- Appliance quantity row 2 — count
- H₂
- Appliance load row 2 — Btu/h or kW each
- n₃
- Appliance quantity row 3 — count
- H₃
- Appliance load row 3 — Btu/h or kW each
- D
- Approved diversity factor — 0–1
- HV
- Fuel heating value — Btu/ft³ or kWh/m³
- Qᵍ
- Ideal fuel-gas volume flow — ft³/h
- Hᶜ
- Connected appliance load — Btu/h
- Hᴰ
- Diversified design load — Btu/h
Applications
How this calculation is used
Building design
Document an appliance-load and ideal-flow screen.
Construction
Check appliance quantities, input ratings, and fuel basis.
Commissioning
Reconcile connected input ratings without sizing gas piping or selecting equipment.
Quality controls
Assumptions and limitations
Assumptions
- Entered values describe one documented system and use a consistent unit, energy, pressure, elevation, and measurement basis.
- Measurements are representative and synchronized where the calculation combines field readings.
Limitations
- This tool calculates load and ideal volume flow only. It never sizes pipe, calculates pressure drop, establishes code compliance, or selects appliances, regulators, valves, vents, combustion air, or meters.
- Pressure, temperature, compressibility, altitude, delivery pressure, diversity permission, and utility heating value require explicit project review.
Field use
Verification procedure
- Confirm the calculation boundary, source documents, formula symbols, and units.
- Record representative field values or approved project inputs and their sources.
- Review the result against the applicable code, criteria, manufacturer data, and measurement uncertainty.
Common engineering mistakes
- Combining values from different system boundaries, operating periods, temperature bases, or unit conventions.
- Treating a calculated screening value as a hidden pass/fail threshold or final design decision.
Technical basis
References and source standards
- NFPA 54, National Fuel Gas CodeFuel-gas load, system, and safety context; this library does not reproduce sizing tables or establish compliance.
- NIST SI and Unit Conversion GuidanceUnit symbols, pressure, flow, energy, temperature, and dimensional conversions used by the application.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement