Wiring Calculator

Version 1.0  20 April 2015

Summary

This is a special purpose calculator which performs simple wiring calculations
for copper wires used in low voltage circuits. Given three of the four
quantities circuit length, current, wire cross section and voltage drop, the
Widget calculates the value of the fourth.

Output Mode

When the Widget is started, it displays a window with four fields. Enter data
into the three white fields, then press the RETURN or ENTER key. The Widget
computes the other value and displays it in the fourth field. Which of the four
values is to be computed can be set by clicking on the Output Mode menu button.

Units

The Widget uses two systems of units, SI Units (metres, amperes, square
millimetres and volts) and USA units (feet, amperes, American Wire Gauge and
volts). The system of units to be used can be chosen by clicking on the Units
menu button.

Temperature

The Temperature menu button can be used to specify the (maximum) operating
temperature of the copper wire (not the insulation). This is used to calculate
the resistivity of the copper (which increases as temperature increases).

Derating Constant

The Derating Constant menu button can be used to reduce the assumed current-carrying
capacity of a wire of specific cross section. This can be used in cases where
wires are in bundles or where ambient temperatures are higher than usual. The
Widget displays an alert when the Current field contains a higher value than the
Wire Cross Section (or AWG) would normally be expected to carry.

WARNING: The calculator was designed to calculate the voltage drop in low
voltage (12/24 volt) marine circuits where the voltage drop due to long wire
circuits is more often a problem than the current carrying capacity of the
wires. No attempt has been made to ensure that the results of any of the
Widget's calculations conform to current electrical codes, such as the NEC or
IEC codes. Users must check these and other safety matters for themselves.

NOTE: For a normal two-wire circuit with conductors of the same Cross Section
(Wire Size), the Circuit Length entered should be twice the length of the path
between the power source and the load, to equal the full circuit length.

License

The Wiring Calculator is Copyright © 2010,2015 Harry Whitfield (G6AUC).

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
St, Fifth Floor, Boston, MA 02110-1301 USA

Widget Concept, Coding and Documentation

Harry Whitfield <g6auc@arrl.net>
