1. What is the BTU to GPM Formula?

The BTU to GPM formula calculates the flow rate required in a hydronic heating or cooling system based on the heating/cooling load and temperature difference. It's essential for sizing pumps and designing HVAC systems.

2. How Does the Calculator Work?

The calculator uses the BTU to GPM formula:

Where:

• \( GPM \) — Flow rate in gallons per minute
• \( BTU/hr \) — Heating or cooling load in BTU per hour
• \( \Delta T \) — Temperature difference in degrees Fahrenheit
• \( 500 \) — Constant factor (1 BTU/lb·°F × 8.34 lb/gal × 60 min/hr)

Explanation: The formula converts thermal energy transfer rate to water flow rate, considering water's specific heat capacity and density.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate calculation is crucial for proper system design, energy efficiency, and ensuring adequate heat transfer in hydronic systems.

4. Using the Calculator

Tips: Enter BTU/hr value (heating/cooling load) and temperature difference (°F). Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the 500 constant derived from?
A: The constant 500 comes from water's specific heat (1 BTU/lb·°F) × water density (8.34 lb/gal) × minutes per hour (60 min/hr).

Q2: Can this formula be used for other fluids?
A: This specific formula is designed for water. For other fluids, you would need to adjust the constant based on the fluid's specific heat and density.

Q3: What is a typical ΔT for hydronic systems?
A: Typical ΔT values range from 10°F to 20°F for heating systems and 8°F to 12°F for chilled water systems.

Q4: How accurate is this calculation?
A: The calculation is theoretically accurate for water at standard conditions. Actual system performance may vary due to piping losses and other factors.

Q5: When is this formula most commonly used?
A: This formula is widely used in HVAC design for sizing pumps, heat exchangers, and piping systems in both residential and commercial applications.