Willis Reader
11/10/17 12:30 p.m.

Winter is upon us.  Last night the temp dipped below freezing while I was working in the garage.  I like the cold and typically throw on my coveralls and keep working...however I need more motivation to get started than when it's warm.

My issue is only having a single 220 outlet in my garage.  I purchased a 220 v heater that I am hanging from the ceiling.  My air compressor is currently plugged into the outlet.  I'd like to plug them both in to....something....and then have a lever or switch activate whichever one I want to use.

My basement is finished.  Running another 220 line to my garage is out of the question...


I'm having trouble googling the right thing - which makes me think that this thing doesn't exist - which makes me think this is a bad idea.


Any options?

T.J. Melonhead
T.J. Melonhead MegaDork
11/10/17 12:50 p.m.

I had a similar issue when I installed a jet skit lift on my dock. I didn't want to run a new circuit from the subpanel out to the dock so I installed a switch that has on off position and from there I can power the jet skit lift or the boat lift, but not both at once. I used a switch that was designed for boats as a shore power switch. In my case, I was only dealing with 120 VAC circuits, so my actual switch wouldn't work for you, but it might get you in the right ballpark for an idea to start from.


Willis Reader
11/10/17 2:43 p.m.

That was helpful.  Thanks.


So what I found I need is a Double Throw Transfer Switch.  Yowsa....they are expensive.


I didn't really want to build a 2 prong extension cord, but that may be the cheaper option.

dculberson PowerDork
11/10/17 3:22 p.m.

Really all you need is a double throw two pole switch that can handle your current rating and some conduit and boxes. As long as you're not switching it while the devices are on you don't need anything really hard core. Dpdt switch (double pole double throw) rated for the highest load it will see and a box to fit it and boxes for each outlet and two 220v outlets coupled with some wire and you're set. 

wnick New Reader
11/11/17 10:07 a.m.

Willis is correct. A transfer switch is what you would need to handle the amperage. They are used for backup generators. No they are not cheap. The other option is bring your line side to a junction box, splice two sets of wires to feed the line side of two 2 pole single throw 20 or 30 amp switches(depending upon the load of the equipment). From the load side of the switches feed your equipment. Only turn on one switch at a time. 

You may have a problem with wire and break size if say the compressor requires a 20 amp feed and the heater requires a 30 amp feed. If you use a 30 amp/#10 wire the compressor will not be protected. If you use 20 amp/#12 wire the heater will trip the breaker or burn up the wire. 

Your best bet you be to feed and size the switches for 30 amps, from the load side of the compressor feed put in 20 amp fuses for each leg, then feed your compressor from there.

TasdevEngineer2of3 New Reader
11/26/17 8:50 p.m.

I used to have a similar problem with an air compressor and mig. Got tired of unplugging one to plug the other in as well it wears on the outlet. My solution - just installed another outlet/box a foot or so from and internally connected to the original. I was mindful of making sure that the switch on one device was off before the other was turned on. Did it this way for 10+ years and never had both on at once.

Now is it code to have two 220v outlets on the same circuit? Don't know and seems unlikely. But - it worked for me. May not work for you if you don't have a switch on your heater - but that could be added as well. Let your own good judgment guide you.


SVreX MegaDork
11/26/17 9:24 p.m.

You can plug 50 machines into the same circuit. It won't cause a problem if you only run 1 at a time. 

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