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

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