[Elecraft] [KPA500] 240V connection advice

[Jim Brown]

On Mon,7/11/2016 1:42 PM, Matt Murphy wrote:
> I was thinking of making a cable by modifying an IEC power cord (with C13
> connector) by connecting the two wires to the two hots of a NEMA 10-30
> plug, and ignoring the neutral plug AND ignoring the ground wire in the IEC
> power cord.

Hi Matt,

Good engineering practice as well as all building codes in NA require 
that two hots be used to power 240V equipment, and that a green wire be 
run with the two hot conductors and bonded to the equipment enclosure. 
It is both illegal and very bad practice to use neutral as a ground, or 
to bond neutral to ground anywhere but the main entry panel.

I suspect that outlet you have is for an old laundry appliance. If you 
can get at the wiring to re-run it, you should pull in a new run to 
replace the old one. You should NOT use that outlet without that green 
wire run from the panel with the "hot" (phase) conductors.

What WOULD be safe is to rewire the existing wiring on both ends so that 
the wire currently connected to neutral in the panel is moved to the 
ground bus in the panel, the existing outlet replaced with a 240V 
outlet, and that former neutral, now used as the green wire, is 
connected to the round "ground" pin in the new outlet. And to satisfy 
code, put a piece of green electrical tape on that green wire on both 
ends to identify it.

If the circuit is protected by a pair of 20A breakers and the conductor 
size is #12 or larger, I suggest that you use a 20A outlet, which allows 
you to connect both 15A and 20A plugs.

73, Jim K9YC