[Elecraft] Power Outlets for Ham Shacks

[Jim Brown]

On Sun, 18 Apr 2010 19:00:26 -0400, Bill Coleman wrote:

>There are hair dryers that draw more current than this. At 1500 watt draw is
>not unreasonable from a 120v outlet.

Yes and no. The current drawn by power supplies is NOT sinusoidal, it is a 
series of pulses at the positive and negative peaks of the 60 Hz sine wave to 
recharge the input filter capacitor. This causes the voltage drop in the 
wiring between the breaker panel and the outlet to be greater than would be 
predicted by Ohm's Law for a sine wave. This is true regardless of whether 
the power supply is a linear supply or a switching supply. 

In today's world, it makes good sense to over-size the conductors that feed 
ANY outlet, especially one that is likely to be heavily loaded. NEC (US 
electrical code) requires AT LEAST AWG #14 for a 15A outlet and #12 for a 20A 
outlet (and larger if the run to the outlet is long). Most of the cost of 
installing an outlet is labor. If you're going to add an outlet to your ham 
shack, I'd run #10 conductors (to reduce the voltage drop) and install a 20A 
breaker. 

Another point. Common neutrals should be avoided. That is, it is always best 
to run individual phase (hot) and neutral conductors to each outlet. 

You can read more about pulsed currents and the problems they cause in the 
Power and Grounding White Paper that's on my website. 

http://audiosystemsgroup.com/publish.htm 

73,

Jim Brown K9YC