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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.
Description
40 Gallons for the first 2 people
10 Gallons for each additional person
20 Gallons for each bath after the first
(consecutive bath)
10 Gallons if dishwasher is used
20 Gallons if clothes washer is used
TOTAL
Heavy Usage Buffer
Use if family members take longer than average showers, etc.
First Hour Rating
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.
(continued)
Peak Hour Demand Worksheet
Installation & Operation Manual
Fill in the Blank
Gals.
Gals.
Gals.
Gals.
Gals.
Gals.
x 1.5
Gals.
Example
40
Gals.
20
Gals.
20
Gals.
10
Gals.
20
Gals.
110
Gals.
x 1.5
165
Gals.
19
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