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I have one 30A 120V single phase circuit and three 30A 120V single phase loads. How do I switch between the three, i.e one is on and the other two are off?

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    Would it be acceptable for the loads to be cord and plug connected? If so, install a 30 ampere receptacle, and install a 30 ampere cord and plug on each device. Then simply plug in the device you want to use. – Tester101 Aug 17 '14 at 14:54
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    How about a 30a 3 position rotary switch? I don't know if this particular switch is rated for use in home wiring, it's from a marine supplier (though it is UL rated). – Johnny Oct 17 '14 at 2:48
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    If you go with a multiposition switch, make sure it operates as break-before-make. – keshlam Dec 16 '14 at 4:05
  • I think Johnny has your solution. A little pricey but if it does what you want then it may be worth the price. – ArchonOSX Dec 11 '15 at 14:16
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The 3 position switch Johnny pointed out is listed to UL 508 for industrial control devices, so it should be acceptable for switching some general-use receptacles around. (You'd be creating a tiny industrial control panel under Article 409 of the NEC -- your average junction box + cover combo meets NEMA 1, and there are provisions in the Code for an industrial control panel that's protected by the upstream breaker.)

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Can they be prioritized? If so, magnetic motor starters could be used, such that the highest-priority load drops the other two starters out of circuit, and the middle-priority load drops the least-priority load out of circuit. BUT... momentarily, all three COULD be energized at once unless you used break-before-make starters and drove each actual load from its own motor starter.

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