How to Switch Power Between 2 Devices Using 1 Power Source

Question

Location: US Residential.

I have a line already which can support up to 25A 2 pole (in breaker panel) I have 2 devices, each rated 220/240V 2-pole. However, at any given time only 1 I need to run. For example: summer : Device SUMM, winter : Device WINT.

Thus I am looking for [??] which when installed into this power line can effectively switch between SUMM and WINT.

Notes: Both SUMM and WINT can be directly wired using a J-box. Notes: Both devices are residential rated and so sustained current or temp. ratings are fine. Notes: I have seen switches do this but flipping them from devices SUMM or WINT usually causes a transient surge / a small flash and that's something I'd like to avoid. In my naive mind, I feel such a surge/flash will not occur if the devices happen to have their own power switch and are switched off before transferring. Of course another option would be to flip the breaker off, transfer and switch the breaker on. I am fine with that approach. My breakers are QO.

Answer 1

Fundamentally, what you need is a 3-way switch. A 3-way switch is normally used in pairs so that you can turn a light on or off at any time from two different locations (e.g., top and bottom of a staircase). A 3-way switch can also be used to switch power between two devices. If the devices you were trying to switch were 120V (hot/neutral, switch the hot wire only), you'd be done.

But you are using 240V devices with two hot wires. So you really want to switch both wires. That gets a little harder to find. What you are specifically looking for is:

• Double Pole - that switches two wires at once
• Double Throw - two different positions, each allowing power to a different place
• 25A or higher rating

Here is an example Leviton 1288 from Home Depot:

Answer 2

You need to use a 2 pole, 3 Way, Centre Off Rotary Selector Switch of adequate rating.

Answer 3

Since you are not being specific about what your loads are, I cannot tell you about any rules which might apply to specific types of loads.

Generally, if there is no probability of simultaneous use they can simply be tied together with no need for an interlock switch. You already do this in your kitchen with your plug-in coffeemaker, microwave and griddle, of which you only use one at a time.

Answer 4

There is nothing keeping you from plugging many 15A devices into a series of 15A outlets on a 15A circuit, but the breaker will keep you from overloading. (Assuming the breaker functions as intended, if course.)

So technically, if each device has its own power switch and you know not to turn them on simultaneously, you don't need a selection switch except for convenience.

Caveat: Hardwired is a different kettle of worms.

Answer 5

Put a breaker in your panel that can handle both loads at once even though it will likely not happen.

Run a heavy cable to a junction box near your panel.

Run two smaller gauge cables from the junction box to match the load for each draw!

No need to ever think about a switch between seasons!