1. What is a Rinnai Tankless Water Heater Sizing Calculator?

Definition: This calculator helps determine if a Rinnai tankless water heater can meet your household's hot water demand based on fixture counts.

Purpose: It ensures you select a properly sized tankless water heater to avoid running out of hot water during peak usage.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total flow rate (gallons per minute)
• \( Q_i \) — Flow rate of each fixture

Explanation: The calculator sums the flow rates of all potentially simultaneous hot water fixtures to determine peak demand.

3. Importance of Proper Sizing

Details: Undersized tankless heaters can't keep up with demand, while oversized units waste energy. Proper sizing ensures continuous hot water and energy efficiency.

4. Using the Calculator

Tips: Enter the number of each fixture type that might run simultaneously. Default values represent a typical medium-large household.

5. Frequently Asked Questions (FAQ)

Q1: Why is 7.5 GPM significant?
A: 7.5 GPM is the typical maximum flow rate for medium-large households. The Rinnai RU199iN handles up to 9.9 GPM with some temperature rise.

Q2: What if my total exceeds 7.5 GPM?
A: Consider installing multiple units or a higher-capacity model like the Rinnai V Series.

Q3: Do I need to count every fixture in my home?
A: No, only count fixtures that might run simultaneously during peak usage times.

Q4: What temperature rise should I expect?
A: A 7.5 GPM unit typically provides about 45°F temperature rise (from 50°F groundwater to 95°F output).

Q5: How does cold weather affect sizing?
A: In colder climates with lower groundwater temperatures, you may need a higher-capacity unit or multiple heaters.