Full Product Manual

Table Of Contents
Calculate System Run Time Page 45
EXAMPLE
You determine that the water requirement for the base plants in your
hydrozone is 0.2 inches per day based on the formula in Chapter 4 and
Appendix B. The adjusted EDR is 0.58 inches per hour.
Divide the water requirement by the adjusted EDR to determine the system
run time. The system run time is 0.34 hours.
Then you multiply the hours by 60 to find the run time in minutes:
0.34 Hours x 60 minutes = 21 minutes per day
To calculate the system run time for densely planted base plants, use the follow-
ing variation of the general formula:
Run Time Per Day (hours) = Water Requirement (inches per day)
Adjusted EDR (inches per hour)
In Chapter 4, you calculated the water requirement in gallons per day for sparse
plantings. To calculate the system run time for sparse plantings, the formula is:
Run Time Per Day (hours) = Water Requirement (GPD)
Flow (GPH)
Sparse Planting
Most irrigation controllers are set in minutes, so you must convert to minutes by
multiplying run time (in hours) by 60.
EXAMPLE
Assume you have determined that the water requirement for your base plant is
1.4 gallons per day. You have selected two single-outlet 2.0-GPH emitters to
water each plant. To calculate the system run time, you first calculate the
adjusted flow:
4.0 GPH (2 emitters @ 2.0 GPH)
× .90 = 3.6 GPH
Then divide the water requirement (1.4 GPD) by adjusted flow (3.6 GPH) and
round to two decimal places:
1.4 GPD
÷ 3.6 GPH = 0.39 Hours
Then you multiply the hours by 60 to find the run time in minutes:
0.39 Hours x 60 minutes = 23 minutes per day
Be sure to total the flows of all emitters used to irrigate a single base plant. Also,
since the flow amounts are based on 100% application efficiency, you must adjust
the result for the application efficiency of your system. To do this, multiply the
total flow and the application efficiency (percentage) that you recorded on your
Site Data Worksheet. The result is the “adjusted flow.” Most irrigation controllers
are set in minutes, so you must convert to minutes by multiplying Run Time (in
hours) by 60.
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