WireGauge Calculator V1.0

Yet another useless tchachke from the sclerotic mind of
William T. Hubbard
ThermoSight, inc.
Mercer Island, WA
15 Sept, 2005

Purpose: The purpose of this program is to determine the maximum distance one may run a power line predicated on wire gauge and load current. The applied voltage is required input only for the purpose of determining maximum acceptable voltage drop.

Background: This program began life as a page on PELCO's website ...
( http://www.pelco.com/support/tools/wiregacalc.aspx ) That page provided exactly the information I needed in a moment of desperation. Later, I returned to the page, reviewed the code to analyze the algorithm, modified it, and re-cast it in the form of a C++ .NET program.

Algorithm: This is a very simple algorithm based on Ohm's Law which simply determines the length of a given power line over which the voltage drop produced by a specified load current equals 5 percent of the applied voltage. The resistance of the line is predicated on wire gauge, and a table relating resistance and gauge may be found in the Handbook of Electronic Tables and Formulas for American Wire Gauge, in which, resistance is stated in units of Ohms per 1000 ft.

It is unclear to the authors why the handbook uses gauge in determining resistance but apparently fails to take material into consideration (i.e. for any given gauge, wouldn't a gold wire offer less resistance than a carbon wire?)

This program uses an equation similar to:

DistFt = (50  Eapp) / (OhmsPerK  LoadAmps)

where:

DistFt =

Maximum distance in feet of the selected gauge line one may use to convey the load current without violating industry guidelines.

Eapp =

applied voltage.

OhmsPerK =

resistance in ohms per 1000 feet of wire.

LoadAmps =

Load current in Amps (even though the user entry is in milliamps!).

Instructions: Select exactly ONE option in the Voltage Selection and Wire Gauge Selection checkboxes. Then enter the load current, IN MILLIAMPS, and click on the button labeled "Calculate distance in feet".

The authors wish to both acknowledge and thank the Lund Instrument Engineering Co. for their assistance in the form of the following page ....
http://www.powerstream.com/Wire_Size.htm

bill & Brooke hubbard
ThermoSight, inc.
Mercer Island, WA
14 September, 2005