Calculating Tankless Water Heater Size

Tankless Water Heater Size Formula:

\[ Size = Peak Flow \times Temp Rise \times 500 / 60 \]

Size (BTU per hour):

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1. What is Tankless Water Heater Size Calculation?

The tankless water heater size calculation determines the required heating capacity in BTU per hour based on peak flow rate and desired temperature rise. Proper sizing ensures adequate hot water supply while maintaining energy efficiency.

2. How Does the Calculator Work?

The calculator uses the tankless water heater size formula:

\[ Size = Peak Flow \times Temp Rise \times 500 / 60 \]

Where:

\( Size \) — Required heating capacity (BTU per hour)
\( Peak Flow \) — Maximum flow rate (gallons per minute)
\( Temp Rise \) — Desired temperature increase (°F)
\( 500 \) — Constant factor for water heating calculation
\( 60 \) — Conversion factor from minutes to hours

Explanation: The formula calculates the energy required to heat water at a specific flow rate through a given temperature rise, accounting for water's specific heat capacity.

3. Importance of Proper Sizing

Details: Correct sizing is crucial for tankless water heaters. Undersized units cannot meet hot water demands, while oversized units waste energy and increase operating costs.

4. Using the Calculator

Tips: Enter peak flow rate in gallons per minute and desired temperature rise in °F. Consider simultaneous hot water usage when determining peak flow.

5. Frequently Asked Questions (FAQ)

Q1: What is peak flow rate?
A: Peak flow rate is the maximum gallons per minute of hot water needed during periods of highest demand, considering all fixtures that may be used simultaneously.

Q2: How do I determine temperature rise?
A: Temperature rise is the difference between your desired hot water temperature and the incoming cold water temperature. Typical rises range from 40°F to 70°F.

Q3: What factors affect sizing requirements?
A: Climate (groundwater temperature), number of bathrooms, fixture types, and simultaneous usage patterns all impact sizing requirements.

Q4: Can I use this for whole-house systems?
A: Yes, this calculation is suitable for whole-house tankless water heater sizing when accurate peak flow and temperature rise values are provided.

Q5: What about high-efficiency models?
A: While the basic calculation remains the same, consult manufacturer specifications for specific high-efficiency models as they may have different performance characteristics.