BTU Calculation Formula:
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Definition: This calculator determines the BTU (British Thermal Unit) output required for a water heater based on flow rate and temperature rise.
Purpose: It helps HVAC professionals and homeowners properly size water heaters for residential and commercial applications.
The calculator uses the formula:
Where:
Explanation: The formula calculates the energy required to heat water by a certain temperature at a given flow rate.
Details: Correct BTU sizing ensures efficient water heating, prevents energy waste, and avoids undersized systems that can't meet demand.
Tips: Enter the water flow rate in GPM and desired temperature rise (°F). Both values must be > 0.
Q1: What is a typical temperature rise for water heaters?
A: Standard rise is 70°F (from 50°F groundwater to 120°F output), but this varies by climate and application.
Q2: How does flow rate affect BTU requirements?
A: Higher flow rates require proportionally more BTU output to maintain the same temperature rise.
Q3: What's the 500 constant in the formula?
A: It combines water's weight (8.33 lb/gal), minutes (60), and specific heat (1 BTU/lb°F), simplified to 500.
Q4: Should I add a safety factor?
A: Yes, consider adding 10-20% to the calculated BTU for peak demand and system efficiency.
Q5: How does this relate to tankless water heaters?
A: Tankless heaters are rated by maximum flow rate at a given temperature rise - this calculation determines the required rating.