Fan Air Heater Calculator

Enter Fan And Heater Data

Airflow

Airflow Unit

Inlet Air Temperature (°C)

Target Outlet Temperature (°C)

Installed Heater Power (kW)

Heater Efficiency (%)

Fan Motor Heat Added To Air (W)

Duct And Casing Loss (%)

Daily Runtime (hours)

Energy Price Per kWh

Air Density (kg/m³)

Specific Heat (J/kg·°C)

Room Volume (m³)

Single Phase Voltage (V)

Three Phase Voltage (V)

Power Factor

Example Data Table

Case	Airflow	Inlet	Outlet	Efficiency	Approximate Input
Small duct heater	600 m³/h	12 °C	30 °C	98%	3.7 kW
Workshop warm air	1,200 m³/h	15 °C	35 °C	98%	8.6 kW
Large fan heater	2,500 m³/h	10 °C	32 °C	95%	20.3 kW

Formula Used

Volumetric flow: Q is converted to m³/s.

Mass flow: ṁ = ρ × Q.

Temperature rise: ΔT = outlet temperature − inlet temperature.

Useful heat: P_air = ṁ × C_p × ΔT.

Required heater input: P_input = (P_air × loss multiplier ÷ efficiency) − fan heat.

Single phase current: I = W ÷ (V × PF).

Three phase current: I = W ÷ (√3 × V × PF).

How To Use This Calculator

Enter the fan airflow and choose the matching unit.
Enter inlet air temperature and target outlet temperature.
Add heater efficiency, duct loss, and fan motor heat.
Enter installed heater power to compare capacity margin.
Enter runtime and energy price for daily cost.
Press calculate, then review the result above the form.
Use the CSV or PDF button to save the result.

Fan Air Heater Calculation Guide

Why Heater Sizing Matters

A fan air heater is a simple heating device, yet its sizing can be tricky. The fan moves air across a heating element. The air gains heat as it passes through the unit. The main question is clear. How much heat is needed to raise the air temperature?

Core Physics

This calculator uses airflow, air density, specific heat, and temperature rise. These values define the useful heat added to the air. It also adds practical allowances. Losses can occur in ducts, casing surfaces, and mixing zones. Efficiency also matters. A small change in airflow can change the heater rating quickly.

Airflow And Temperature

Airflow is the strongest driver. Doubling airflow doubles the heat needed for the same temperature rise. Temperature rise works the same way. A ten degree rise needs twice the heat of a five degree rise. That is why fan data and target temperature must be entered carefully.

Advanced Input Values

Density and specific heat are included for advanced work. Standard air is often close to 1.2 kg per cubic meter. Specific heat is often near 1005 joules per kilogram degree Celsius. Real sites may differ. High altitude, humidity, and high temperature can shift these values.

Capacity Review

Installed heater power is also useful. It shows whether the selected heater can meet the target. The margin value helps compare required power with available power. A negative margin means the heater may not reach the target outlet temperature.

Electrical Planning

The current estimates support electrical planning. They do not replace code checks. Cable size, breaker rating, duty cycle, and safety controls must be reviewed by qualified personnel. Thermal cutouts and airflow switches are important in many heater systems.

Running Cost

The running cost estimate is helpful during design. It uses heater input power, daily runtime, and energy price. This gives a clear daily energy cost. Longer operation or higher temperature rise can increase cost fast.

Practical Checks

Use the result as a planning guide. Check the fan curve. Confirm the actual airflow after filters, coils, and duct pressure losses. Keep the heater clean. Make sure the element is rated for the airflow. Good airflow protects the heater and improves comfort.

For best results, test inlet and outlet temperatures after installation. Record values during steady operation. Then adjust set points, airflow, or capacity safely later.

FAQs

1. What does a fan air heater calculator estimate?

It estimates heat power, airflow conversion, temperature rise, current, energy use, and running cost. It helps compare required heater size with installed heater capacity.

2. Why is airflow important?

Airflow controls how much air must be heated each second. Higher airflow needs more heater power for the same outlet temperature.

3. What air density should I use?

A common planning value is 1.2 kg/m³. Use measured or site-specific density for high altitude, unusual humidity, or high temperature conditions.

4. What specific heat value is typical for air?

Many air heating estimates use about 1005 J/kg·°C. Adjust this value if you have a project specification or measured air property data.

5. Why include duct and casing loss?

Some heat can escape before reaching the target space. A loss allowance makes the heater input estimate more realistic for field installations.

6. Can fan motor heat reduce heater demand?

Yes, if motor heat enters the air stream. The calculator subtracts that added heat from the required heater input.

7. Are the current values final electrical ratings?

No. They are planning estimates. Final wiring, breaker size, overload protection, and controls must follow local electrical rules and equipment data.

8. Why is my capacity margin negative?

A negative margin means installed power is below calculated demand. Increase heater size, reduce airflow, reduce target temperature, or improve efficiency.