Tankless Water Heater BTU Calculator

BTU Calculation Formula:

\[ Q = \dot{m} \times c \times \Delta T \]

BTU Required (BTU/h):

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1. What is a Tankless Water Heater BTU Calculator?

Definition: This calculator estimates the BTU (British Thermal Unit) requirement for tankless water heaters based on flow rate and temperature rise.

Purpose: It helps HVAC professionals and homeowners determine the appropriate size for tankless water heater installations.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Q = \dot{m} \times c \times \Delta T \]

Where:

\( Q \) — BTU per hour required (BTU/h)
\( \dot{m} \) — Mass flow rate (lb/h)
\( c \) — Specific heat capacity of water (1.0 BTU/lb·°F)
\( \Delta T \) — Temperature rise needed (°F)

Explanation: The flow rate multiplied by specific heat and temperature rise gives the energy required to heat the water.

3. Importance of BTU Calculation

Details: Proper BTU estimation ensures adequate hot water supply, energy efficiency, and prevents undersizing or oversizing the water heater.

4. Using the Calculator

Tips: Enter the flow rate in pounds per hour, specific heat capacity (default 1.0 BTU/lb·°F for water), and desired temperature rise. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How do I convert GPM to lb/h?
A: Multiply gallons per minute by 500 (1 GPM ≈ 500 lb/h for water).

Q2: Why is specific heat capacity 1.0?
A: Water's specific heat is 1 BTU/lb·°F, but you can adjust for other fluids.

Q3: What's a typical temperature rise?
A: For shower use, typically 50-70°F rise from groundwater temperature.

Q4: How does elevation affect the calculation?
A: Higher elevations may require adjustment for lower boiling points.

Q5: Should I add a safety factor?
A: Consider adding 10-20% to the calculated BTU for peak demand periods.