Operating instructions
METHOD B: “DETAILED” RESIDENTIAL
1) Record the total number of each type of fixture in column (c) of Worksheet 1. If a whirlpool (Jacuzzi) is
installed, record all fixtures EXCEPT the whirlpool faucet.
2) For each line multiply the quantity entered in column (c ) by the corresponding hourly usage in column
(b). Enter the result in column (d).
3) Total column (d). This is the PEAK HOUR DEMAND.
4) Multiply the Peak Hour Demand by 1.20. This is the ADJUSTED PEAK HOUR DEMAND.
5) If a new boiler is to be installed with the Maxi-Therm:
a) Go to Table 1 and select a Maxi-Therm which has a 135F First Hour Rating greater than or equal to
the Adjusted Probable Maximum Demand calculated above.
b) Use the appropriate graph in Figures 4a-4d to determine the boiler output needed to generate the
required First Hour Rating.
c) Determine the boiler size required to satisfy the space-heating requirement alone. Note the output of
this boiler.
d) Install the Maxi-Therm with a boiler having the larger of these two outputs.
6) If the Maxi Therm is to be installed with an existing boiler:
a) Go to Table 1 and select a Maxi-Therm which has a 135F First Hour Rating greater than or equal to
the Adjusted Probable Maximum Demand calculated above.
b) Use the appropriate graph in Figures 4a-4d to find the First Hour Rating that can be expected with
the boiler on the job.
c) If this First Hour Rating is unacceptable, the existing boiler is too small. Depending on hot water
usage pattern, the use of a larger Maxi-Therm may compensate for the undersized boiler. Consult a
Crown Representative for additional guidance.
7) If a whirlpool is installed, see Appendix A.
8) See the Zone Design section of this manual for circulator sizing and other information on designing the
Maxi-Therm zone.
EXAMPLE 1: A Maxi-Therm is to be installed with a new boiler. The residence has the following fixtures:
Bath #1: Bath #2:
7 GPM Shower Head 5 GPM Shower Head
Vanity Vanity
Kitchen: Laundry:
Kitchen Sink Clothes Washer
Automatic Dishwasher
The heat loss of the house is 80,000 BTU/hr
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