Bosch SST150-40 Installation And Operating Manual page 22

Installation & Operating Manual
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 STS tank
must be equal to or exceed the total fi rst hour
requirements.
Peak Hour Demand Worksheet
Description
40 Gallons for the fi rst 2 people
10 Gallons for each additional person
20 Gallons for each bath after the fi rst
(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 23 & 24 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 fl ow needed
between the Indirect Water Heater and Boiler.
2 2 |
Fill in the Blank
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x 1.5
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Indirect Fired Water Heaters Installation and Operating Manual
Example
Gals. 40 Gals.
Gals. 20 Gals.
Gals. 20 Gals.
Gals. 10 Gals.
Gals. 20 Gals.
Gals. 110 Gals.
x 1.5
Gals. 165 Gals.