Tutorial #5b: Calculating

Press the Calculate button. The Pre-Calc Questions dialog box will appear.

Set up the box as shown here. The Remote Point 3 is the most geographically remote head in the system. Since we don t know if it is the most hydraulically remote, check the Auto Locate Remote Head option. The Source Point should default to the last node in the system which is 56. Node 56 should also appear as the City Supply node in the Water Supply information. Check Auto Adjust Fitting Lengths and Auto Peak Grid Calculation. The Auto Peak Distance will be 12 feet. Auto Change Peak Lengths should also be checked.

Press OK to execute. When complete, the Hydraulic Calculation dialog box will appear.

Press the Details button to expand the dialog. The program calculates the system in a series of passes until it is balanced. If you scroll down the list, you will see how the program changes the remote head and adjusts the remote area location (auto peaking) until the most remote area is found.

If you press the View button, the Calculation Summary will appear.

The first report is the Auto Peaking Summary. It shows how the remote area was shifted left and then right to determine which was the most demanding.

The remainder of the report shows head flow, system demand and pipe flow information.

You can also perform a Source Calculation. Check the box shown here before running the calculation.

The head flows will be based on the water supply rather than the minimum requirements.

In this example, Auto Peak Grid Calculation was selected in the Pre-Calc Questions dialog box. Auto Peaking is the process where the program moves the remote area and performs calculations on both sides of the existing remote area. In this way, the most demanding remote area can be found.

To Auto Peak, an Auto Peak Distance must be entered in feet. This is usually the distance between sprinklers on the branch lines. In this way, the remote area is moved over by one head in distance on both sides of the remote area. With the Auto Change Peak Lengths option checked, the pipe lengths in the System Piping tab will be adjusted if Auto Peaking finds a more demanding remote area.

Here is LINE 1 before running a calculation. The remote area is 6 feet from the Back Main (L6) and 78 feet from the Front Main (R78).

Here is a drawing showing the remote area location before the calculation.

Here is LINE 1 after running a calculation with Auto Change Peak Lengths checked and Perform Source Calc not checked.

The remote area has been moved so that the Back Main is 30 feet (L30) away and the Front Main is 54 feet away (R54). The remote area has been moved 24 feet to the right.

Here is a drawing showing the remote area location after the calculation.

NOTE: Auto-peaking is only recommended for typical systems where elevations and spacing between heads are the same. The auto-peaking process is merely sliding the remote area from side-to-side on the grid lines and not taking into account any variations within the grid line. On a non-typical grid, the remote areas should be manually peaked by creating multiple calculation files with each file representing a new remote area next to the previous one.*