Temperature to CFM Calculator (Electric)

Temperature to CFM Calculator - Electric Heater Formula

Voltage (\( V \)):

Current (\( I \)):

Temperature Difference (\( TD \)):

1. What is Temperature to CFM Calculator?

Definition: This calculator computes the airflow (CFM, Cubic Feet per Minute) in an HVAC system for an electric heater or heat pump, based on voltage, current, and temperature difference.

Purpose: It is used by HVAC technicians to ensure proper airflow for efficient heating, critical for equipment performance and energy efficiency.

2. How Does the Calculator Work?

The calculator uses the following formula:

Electric Heater Formula:

\( CFM = \frac{V \cdot I \cdot 3.413}{TD \cdot 1.08} \)

Where:

\( CFM \): Airflow (Cubic Feet per Minute)
\( V \): Voltage (V)
\( I \): Current (A)
\( TD \): Temperature Difference (°F)
\( 3.413 \): BTUs per watt
\( 1.08 \): Standard air constant

Steps:

Enter the voltage, current, and temperature difference with their units (V/kV, A/mA, °F/°C).
Convert inputs to base units (V, A, °F).
Calculate the CFM using the formula.
Display the result with 2 decimal places and estimate CFM per ton.

3. Importance of CFM Calculation

Calculating CFM is crucial for:

HVAC Efficiency: Ensuring proper airflow for optimal heating performance.
Equipment Longevity: Preventing overheating or inefficiency due to inadequate airflow.
System Design: Matching airflow to system capacity (e.g., 400 CFM per ton for a 3-ton unit).

4. Using the Calculator

Example 1: An electric heater with 235 V, 49 A, and a 30°F temperature difference:

Voltage (\( V \)): 235 V
Current (\( I \)): 49 A
Temperature Difference (\( TD \)): 30°F
CFM: \( \frac{235 \times 49 \times 3.413}{30 \times 1.08} \approx 1212.04 \) CFM
CFM per Ton: \( \frac{1212.04}{3} \approx 404.01 \) CFM/ton (assuming 3 tons)
Result: \( CFM = 1212.04 \)

Example 2 (Celsius): An electric heater with 230 V, 50 A, and a 16.67°C temperature difference:

Voltage (\( V \)): 230 V
Current (\( I \)): 50 A
Temperature Difference (\( TD \)): 16.67°C = 30°F
CFM: \( \frac{230 \times 50 \times 3.413}{30 \times 1.08} \approx 1212.04 \) CFM
CFM per Ton: \( \frac{1212.04}{3} \approx 404.01 \) CFM/ton (assuming 3 tons)
Result: \( CFM = 1212.04 \)

Example 3: An electric heater with 240 V, 45 A, and a 25°F temperature difference:

Voltage (\( V \)): 240 V
Current (\( I \)): 45 A
Temperature Difference (\( TD \)): 25°F
CFM: \( \frac{240 \times 45 \times 3.413}{25 \times 1.08} \approx 1365.20 \) CFM
CFM per Ton: \( \frac{1365.20}{4} \approx 341.30 \) CFM/ton (assuming 4 tons)
Result: \( CFM = 1365.20 \)

5. Frequently Asked Questions (FAQ)

Q: What is CFM?
A: CFM (Cubic Feet per Minute) measures the volume of air moved by an HVAC system, critical for efficient heating.

Q: Why is temperature difference important?
A: The temperature difference between supply and return air determines how much heat is transferred, directly affecting the CFM calculation.

Q: What does the constant 3.413 represent?
A: The constant 3.413 is the number of BTUs per watt, used to convert electrical power to heat output.