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I have a shallow well supplying utility water on a rural property. It's currently plugged into a standard 120v outlet. I'll be running a dedicated 240v circuit using 12/2 cable so I can use the pump's optional 240v mode. I'd like to use a common double-pole switch (four-way) to allow us to disable the pump when we're not on the property rather than always unplugging it.

Should I hard-wire the pump's cord into the switch in a junction box, or should I install an aftermarket 240v plug? If the latter, what plug type is appropriate?

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I'll be running a dedicated 240v circuit

...so turn off the breaker to the dedicated circuit.

a common double-pole switch (four-way)

...will almost certainly not be rated for the motor loading - that's going to take an uncommon switch or a contactor, but your dedicated circuit will have a common breaker that handles the load just fine.

I infer that the motor is 3/4 HP despite it being shy about that, since the amperage at 240VAC is similar to my own 3/4 HP (submersible) pump. So your switch will need to be rated for that motor loading (or more.)

Assuming any remotely normal pump set up, you can also switch off the pressure switch manually by flipping a lever on it.

If the pump is "Cord-and-Plug" connected with a flexible cord not suited for in-wall use a NEMA 6-15 or NEMA 6-20 would be a suitable plug/receptacle pairing depending on the breaker amperage, but you might want to consider a somewhat more secure pairing such as an L6-15 or L6-20 depending on the breaker amperage. However, the vast majority of well pump installations dispense with a plug/receptacle as an additional point of failure (and pointless expense for something that's not normally unplugged) and run cable or conduit all the way to the pump, so rather than change the cord end, you would remove the cord and wire from the junction box with a suitable cable or conduit (mine is MC, I'm not fond of rodent-chewed wires.)

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I'd like to use a common double-pole switch (four-way)

Those are completely different things. You just said "Toyota Prius pickup truck".

A common 4-way switch is a "reversing switch", it does not disconnect anything at all. It won't disconnect the motor; it won't even reverse a 1-phase motor, just cause a huge voltage spike if you tried lol.

A double-pole switch is exceedingly uncommon and I wouldn't expect a home store to stock one.

Regardless, you don't need a double-pole switch, a single-pole will suffice if it's rated for 240V. So you'll be up in the $10 "heavy duty" kinds.

to allow us to disable the pump when we're not on the property

I quite agree with Jeff, however. If your goal is an occasional disconnect, just flip the breaker off. I do that all the time with fridges and water heaters. Technically you should use a breaker rated "SWD" or "Switching Duty", but any new breaker should be (am I right ThreePhaseEel, does that apply to 2-pole breakers?)

Should I hard-wire the pump's cord into the switch in a junction box, or should I install an aftermarket 240v plug? If the latter, what plug type is appropriate?

GOOD question, many would misuse a 120V NEMA 5-15. Heck the entire nation of the Philippines does exactly that lol.

The correct plug-socket for a 240V-ground-not-neutral connection is the NEMA 6 family.

Doubling voltage halves current, so the correct plug is a NEMA 6-15. For sockets:

  • A 15A breaker requires 15A sockets (NEMA 6-15).

  • If the breaker is 20A, and there is only 1 socket (simplex), it must be NEMA 6-20.

  • If 20A and 2+ sockets, you can have any mix of 6-15 and 6-20 sockets.

Note how the 6-20 socket is keyed to accept a 6-15 plug. All these here are double (duplex) sockets, so one duplex 6-15 will work with both breaker sizes.

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  • I meant double-throw. Don't I need to switch both legs of the circuit? – isherwood Nov 20 '20 at 21:30
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    @isherwood I don't believe so, not if it's not a proper, Code required disconnect like you have next to an air conditioner. After all, baseboard heater thermostats only switch 1 pole. (even the 2-pole ones only switch one pole thermostatically; the other is only disconnected in the OFF position). – Harper - Reinstate Monica Nov 20 '20 at 22:20
  • All new breakers in the US (and most existing ones) are SWD – ThreePhaseEel Nov 21 '20 at 1:16
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If you want a plug & receptacle setup for 240V there are several common choices. NEMA 6-15 (15 amp) and 6-20 (20 amp) look very similar to the receptacles you're familiar with. They are keyed differently for 240V so you can't accidentally plug in a 120V appliance.

There are also locking plugs and receptacles, such as L6-15 (15 amp), L6-20. You've probably seen plenty of these locking plugs at outdoor events to supply electricity to booths and food vendors.

Note that your pump won't supply more water in 240V configuration than 120V.

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