Hot Water Heater Calculator

Hot Water Heater Size Formula:

\[ Size = Peak\ Demand \times \Delta T \times 500 / 60 \]

Size (BTU per hour):

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1. What is the Hot Water Heater Size Calculation?

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

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Size = Peak\ Demand \times \Delta T \times 500 / 60 \]

Where:

\( Size \) — Heating capacity in BTU per hour
\( Peak\ Demand \) — Maximum flow rate in gallons per minute
\( \Delta T \) — Temperature rise required in °F
\( 500 \) — Constant (8.33 lb/gal × 60 min/hr)
\( 60 \) — Conversion factor

Explanation: The formula calculates the energy required to heat water from incoming temperature to desired temperature at the peak flow rate.

3. Importance of Proper Sizing

Details: Correct sizing prevents undersizing (inadequate hot water) and oversizing (energy waste). Properly sized heaters provide consistent hot water while optimizing energy consumption and equipment lifespan.

4. Using the Calculator

Tips: Enter peak demand in gallons per minute and temperature rise in °F. Typical ΔT values range from 40°F to 100°F depending on incoming water temperature and desired output temperature.

5. Frequently Asked Questions (FAQ)

Q1: What is peak demand?
A: Peak demand is the maximum simultaneous hot water flow rate expected during highest usage periods, considering all fixtures and appliances.

Q2: How do I determine ΔT?
A: ΔT is the difference between desired hot water temperature and incoming cold water temperature. Typical values: 70°F for 120°F output with 50°F incoming water.

Q3: What are typical peak demand values?
A: Residential: 2-5 GPM; Commercial: 5-20 GPM depending on facility type and size.

Q4: Does this account for heat loss?
A: This calculation provides the heating capacity needed. Additional factors like pipe insulation and storage tank losses should be considered separately.

Q5: Can this be used for tankless water heaters?
A: Yes, this formula is particularly useful for sizing tankless water heaters where instantaneous heating capacity is critical.