Tankless Water Heater Calculator

Tankless Water Heater Flow Rate Formula:

\[ Q_{max} = \frac{Power}{\Delta T \times 8.34} \]

Maximum Flow Rate (Q_max):

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1. What is the Tankless Water Heater Calculator?

The Tankless Water Heater Calculator determines the maximum flow rate (Q_max) that a tankless water heater can deliver based on its power rating and the desired temperature rise. This helps in selecting the right unit for your household needs.

2. How Does the Calculator Work?

The calculator uses the tankless water heater flow rate formula:

\[ Q_{max} = \frac{Power}{\Delta T \times 8.34} \]

Where:

\( Q_{max} \) — Maximum flow rate (gallons per minute)
\( Power \) — Heating power in kW or BTU/h
\( \Delta T \) — Temperature rise in °F
8.34 — Conversion factor (lb/gal × BTU/lb·°F)

Explanation: The formula calculates how much hot water the unit can produce by dividing the available heating power by the energy required to heat each gallon of water by the desired temperature difference.

3. Importance of Flow Rate Calculation

Details: Proper flow rate calculation ensures your tankless water heater can meet simultaneous hot water demands from multiple fixtures (showers, sinks, appliances) without temperature fluctuations.

4. Using the Calculator

Tips: Enter the power rating of your tankless water heater (in kW or BTU/h), the desired temperature rise (difference between incoming cold water and desired hot water temperature), and select the appropriate power unit.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical temperature rise for tankless water heaters?
A: Typical temperature rise is 40-70°F depending on climate and season. In colder regions, incoming water temperature may be lower, requiring greater temperature rise.

Q2: How do I determine the right power rating for my home?
A: Consider simultaneous hot water usage. A 150,000-200,000 BTU/h unit can typically handle 2-3 fixtures simultaneously, while smaller units may serve single applications.

Q3: What flow rate do common fixtures require?
A: Showers: 1.5-2.5 GPM, Kitchen faucets: 1.0-2.2 GPM, Bathroom faucets: 0.5-1.5 GPM, Washing machines: 1.0-2.0 GPM.

Q4: Can I use this calculator for electric tankless water heaters?
A: Yes, but electric units typically have lower flow rates. Enter power in kW for electric models (1 kW = 3412 BTU/h).

Q5: What factors affect actual performance?
A: Incoming water temperature, water pressure, mineral buildup, altitude, and gas pressure can all affect real-world performance.