Installation & Operation Manual
20
8
Performance data
How to properly Size Your Indirect Water Heater
Use the First Hour Rating (FHR) to properly size your Indirect Water Heater. The First Hour Rating is the amount of hot
water in gallons the heater can supply per hour (starting with a tank full of hot water), depending on tank capacity, source of
heat, and the size of the burner.
Estimate your peak hour demand as follows:
•
Determine what time of day (morning, noon, evening) you use the most hot water in your home. Keep in mind the
number of people living in your home.
•
Use the worksheet below to estimate your maximum usage of hot water during this one hour of the day -- this is your
peak hour demand.
Note:
The worksheet does not estimate total daily hot water usage.
The worksheet example shows a total peak hour demand of 165 gallons; therefore, this household would need a water heater
with a First Hour Rating of no less than 165 gallons.
Fixture Count Guide
To quickly estimate the minimum gallons of hot water required based on a family size number of baths and hot water
appliances the First Hour Rating of the Squire must be equal to or exceed the total first hour requirements.
Peak Hour Demand Worksheet
Description
Fill in the Blank
Example
40 Gallons for the first 2 people
Gals.
40
Gals.
10 Gallons for each additional person
Gals.
20
Gals.
20 Gallons for each bath after the first
(consecutive bath)
Gals.
20
Gals.
10 Gallons if dishwasher is used
Gals.
10
Gals.
20 Gallons if clothes washer is used
Gals.
20
Gals.
TOTAL
Gals.
110
Gals.
Heavy Usage Buffer
Use if family members take longer than average showers, etc.
x 1.5
x 1.5
First Hour Rating
Gals.
165
Gals.
Proceed to pages 21 – 23 of this manual to locate your Indirect Water Heater and Boiler in the sizing charts. Using the First
Hour Rating calculated in this worksheet, locate your Indirect Water Heater and Boiler along with your First Hour Rating.
This will also determine the flow needed between the Indirect Water Heater and Boiler.
