Calculation results
Balanced combustion reaction
Combustion products
Scenario comparison
Save calculated cases and compare excess air, airflow, and fuel use.
| Scenario | Fuel | Excess air | Actual air | Fuel flow | Cost |
|---|---|---|---|---|---|
| No saved scenarios. | |||||
Recent calculation history
| Time | Fuel | Mode | Excess air | Lambda | Fuel flow |
|---|---|---|---|---|---|
| No calculations saved yet. | |||||
Formula used
The oxygen-only equation is an estimate. Analyzer readings must use consistent dry or wet conditions.
How to use this calculator
- Select the calculation mode and heater fuel.
- Enter heater output, efficiency, load, and operating count.
- Provide measured fuel flow or allow automatic estimation.
- Enter excess air, airflow, or flue-gas readings.
- Set site conditions and the preferred decimal precision.
- Calculate, review warnings, then export the results.
Example data
| Input | Example value | Purpose |
|---|---|---|
| Fuel | Propane | Sets combustion properties. |
| Rated output | 13 kW | Estimates fuel consumption. |
| Efficiency | 82% | Converts useful heat to fuel input. |
| Excess air | 25% | Sets actual combustion airflow. |
| Operating time | 5 hours | Estimates total fuel and cost. |
| Air temperature | 15°C | Converts standard airflow to actual airflow. |
Understanding the results
Stoichiometric air is the minimum theoretical combustion air. Excess air is supplied above that amount. Lambda shows the actual-to-theoretical air ratio.
Dry flue-gas values exclude water vapor. Wet values include combustion water. Mixing these bases creates inaccurate calculations.
High excess air may reduce useful efficiency. Low air may increase incomplete combustion risk. Burner adjustments require qualified testing and manufacturer guidance.
Safety and limitations
- Follow the heater manual and local safety requirements.
- Maintain required clearances from combustible materials.
- Never bypass flame, tilt, pressure, or oxygen safety controls.
- Do not adjust gas pressure using calculator results alone.
- Stop using heaters showing soot, unstable flames, or unusual odors.
- Use calibrated combustion instruments for commissioning work.
Frequently asked questions
What is excess air?
It is air supplied beyond the theoretical combustion requirement.
What does lambda mean?
Lambda is actual air divided by theoretical combustion air.
Can oxygen readings estimate excess air?
Yes, but oxygen-only calculations remain simplified estimates.
Why does dry basis matter?
Dry readings exclude water vapor and change gas percentages.
Can I calculate several heaters?
Yes. Enter the number operating under similar conditions.
Does altitude affect airflow?
Yes. Lower pressure increases the required actual air volume.
What is the equivalence ratio?
It is the inverse of lambda for this calculator.
Can this replace combustion testing?
No. Qualified testing is required for burner commissioning.
Can outdoor heaters operate indoors?
No. Outdoor heaters can create deadly carbon monoxide indoors.