UFC 3 -520-01
June 10, 2002
EXAMPLE: Even if a larger conduit is required, an acceptable payback can be
achievable with a larger wire size. For this example, assume that a three-phase,
40 ampere lighting load operates for only 4,000 hours per year (which is about 11
hours per day) and is located 61 meters (200 feet) from the load center. As
shown below, the larger #6 AWG conductor pays for itself in 1.5 years.
Thereafter, the installation continues to save energy costs of over per year
compared to the smaller #8 AWG conductor.
Input Data
#8 AWG
#6 AWG
Conduit size
19.1 mm (0.75 inch)
25.4 mm (1 inch)
Conductor resistance (30 C)
0.1330
0.0839
Estimated power loss (3 phase)
638 W
403 W
Estimated wire cost
7
6
Estimated conduit cost
8
2
Incremental cost
3
Projected energy savings
940 kWh/year
Cost savings at
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.08 per kWh.2/year
Payback period
1.5 year
B-6.2
As the above e xamples illustrate, a significant energy savings can be realized
by increasing the conductor size to the next higher gauge size.
B-7
ADJUSTABLE SPEED DRIVE ECONOMIC EVALUATION .
B-7.1
If an ASD installation is considered on the basis of energy efficienc y, perform
an economic evaluation in accordance with the process shown in Figure B -4 .
B-9
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