Xylem BMAID R4 - Manual (Page 11)

PAGE 11
Residential Water Systems
CentriPro
uSING two DIffErENt CablE SIzES
Customers sometimes desire to use two or more wire sizes on a pump installation. This is acceptable as long as
the maximum cable length ratings are not exceeded. The data below describes how to safely accomplish the
task. The cable lengths in the wire sizing charts represent 100% of the allowable length for each wire size. Never
use more than 100% of any length shown in the table.
The Three-Wire, Single Phase Motor Wire Chart will be used in this example. See page 8.
Installation Data:
• 2 HP, 230V, 1Ø, 3-Wire Motor
• 150 Ft of #12 wire buried between the home (service entrance) and the well
• Pump is set at 340 feet
• Total wire length is 490 feet
Refer to 3-Wire Motor Lead Length Chart
• Select row for 2 HP, 230V, 1Ph Motor
• Maximum wire lengths are:
• #12 - 286’ • #10 - 456’ • # 8 - 722’
• Allowable Drop Cannot Exceed 100% of Any Length or Combination of Lengths
The existing 150 feet of #12 underground wire uses 150’/286’ = 52.4% of the allowable length.
100% - 52.4% = 47.6% of another wire available to use. Which wire will use ≤ 47.6% of its allowable length to
run 340’.
340’/456’ = 74.5% of #10 - 74.5% + 52.4% = 126.9% - over 100% is not allowable
340’/722’ = 47.1% of #8 - 47.1% + 52.4% = 99.5% which is allowable
On this application we can use 150’ of #12 with 340’ of #8.
The formula is: Actual Length 1
+
Actual length 2
≤ 1 or ≤ 100%
Maximum Allowed Maximum Allowed
Using this formula it is possible to size wire using 2 or more different wire sizes.