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