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Tankless Water Heater Sizing Formula:
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Tankless water heater sizing involves calculating the required flow rate (GPM) by summing the flow rates of all fixtures that might be used simultaneously. Proper sizing ensures adequate hot water supply without oversizing the unit.
The calculator uses the formula:
Where:
Explanation: The calculation sums the flow rates of all fixtures that might run simultaneously to determine the minimum required GPM capacity for the tankless water heater.
Details: Proper sizing ensures your tankless water heater can meet your household's hot water demands while maximizing energy efficiency and preventing unnecessary strain on the unit.
Tips: Enter the flow rates of all fixtures that might be used simultaneously, separated by commas. Typical fixture flow rates: shower (2.5 GPM), kitchen sink (1.5 GPM), bathroom sink (0.75 GPM), washing machine (2.0 GPM).
Q1: Why is proper sizing important for tankless water heaters?
A: Undersized units won't meet hot water demands, while oversized units are less energy efficient and more expensive to purchase and operate.
Q2: What factors besides flow rate should be considered?
A: Temperature rise (difference between incoming water temperature and desired output temperature) is equally important for proper sizing.
Q3: How do I determine fixture flow rates?
A: Check manufacturer specifications or use a flow meter. Older fixtures typically have higher flow rates than newer, water-efficient models.
Q4: Should I consider simultaneous usage patterns?
A: Yes, consider which fixtures are likely to be used at the same time (e.g., shower and kitchen sink during morning routine).
Q5: What about temperature considerations?
A: Colder incoming water temperatures require more heating capacity. The calculator provides flow rate requirements; temperature rise calculations are separate.