On 11/14/2022 1:43 PM, Ed Cole wrote:
That is rated for 90A (in general). Resistance is 0.318 ohms/1000-feet so my 120-foot run has 0.0382 ohms. At 50A this results in a voltage drop of 1.9v. My service voltage is 243VAC.
It's important to realize that current on AC mains is FAR from being a sine wave. This has been true for at least 30 years, as loads have been strongly dominated by switch-mode power supplies in almost every piece of equipment wiring into or plugged into, the system, and square-wave modulated controllers for nearly all large loads, like motors and heating devices. Current flows in pulses, usually short ones, that recharge the input capacitors of associated power supplies.
The result of this is that both IR drop and the resulting heating are at least one-third greater than predicted by Ohm's Law applied to a sine wave. It is, therefore, very good engineering practice to oversize conductors, as you have done! Before we moved into the home we bought in NorCal, I had the outbuilding housing my shack rewired, and even though the runs from the panelboard are pretty short, had #10 pulled in for the 20A-240V circuit. Since I will never have more than one amp on at a time, I felt that 20A was sufficient. All of the 120V circuits are 20A, wired with #12, not oversized, since the only heavy load, 1 12A space heater, has its own circuit.
73, Jim K9YC 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
