1. What is a First Hour Rating Calculator?

Definition: This calculator determines the First Hour Rating (FHR) of a water heater, which measures how many gallons of hot water the heater can supply in one hour.

Purpose: It helps homeowners and professionals select the appropriately sized water heater for their needs.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( FHR \) — First Hour Rating (gallons/hour)
• \( T \) — Tank Capacity (gallons)
• \( R \) — Recovery Rate (gallons/hour)

Explanation: The formula accounts for 70% of the tank's capacity plus the heater's recovery rate in one hour.

3. Importance of First Hour Rating

Details: FHR helps determine if a water heater can meet peak demand periods, ensuring adequate hot water supply during times of high usage.

4. Using the Calculator

Tips: Enter the tank capacity in gallons and the recovery rate in gallons per hour. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is only 70% of tank capacity used?
A: This accounts for the fact that the bottom portion of the tank contains cooler water that hasn't been fully heated yet.

Q2: How do I find my water heater's recovery rate?
A: Check the manufacturer's specifications or energy guide label on your water heater.

Q3: What's a good FHR for a family of four?
A: Typically 50-70 gallons per hour, depending on usage patterns and appliances.

Q4: Does this work for tankless water heaters?
A: No, tankless heaters are rated differently by their flow rate and temperature rise.

Q5: Should I round up when sizing my water heater?
A: Yes, it's recommended to round up to the nearest standard size for better performance during peak demand.