Can I Use a 120V Appliance with a 220V Socket?

Short answer: No

Longer answer: Unless you really, really, really, know what you're doing (and the fact that you're asking this question suggests you don't have solid, err, grounding in this), the answer is still no.

Chances are that the 240V outlet (you're talking the US here, right?) has three wires in it. The two flat parts of the outlet are both "live" at 120V, giving you 240V to the appliance.

There's a roundish third one which is a safety ground.

You might be tempted to build an adapter cable BUT this will mean using the "ground" as a neutral. DON'T.

Yes, you can maybe run a separate wire as the neutral, or might be able to take one of the hot wires and, both at the outlet and at the breaker box, convert them to a neutral, but again, this requires that you really, really, know the deal.

Have someone who knows a bit about electricity check to see what color the wires are in the outlet. If you have black, white, and red you CAN connect a 120 volt outlet to either black and white or red and white. If you have black and red only you cannot get 120 without rewiring (and remarking the red wire with white shrink tube on both ends) If you have black and white you can rewire it for 120. The wires will need to be moved in the panel. I would recommend getting a licenced electrician to do the job - but at least you do not need to have new wire pulled in.

Why not buy a 240v unit so you don't have to rework/run new wires?

That's probably the cheapest and easiest solution. As others have said, if it's a straight 240V circuit, no neutral, it would take changing the breaker to convert it to 120V. It's likely the only receptacle on that circuit, so there won't be a problem with other 240V receptacles also going to 120V. Changing the breaker and putting in a new breaker is not a big deal, but if you need an electrician to do it, it's probably going to cost more than a 240V AC.

There are ways but it may not meet code or could be dangerous. I'd either buy a 220V AC or have an electrician convert it to a 120 outlet the right way.

Do it right, not some half assed rig your neighbor can make for you.

The costs of having an electrician (depending on your area, of course) setting up a 120V outlet and then getting a commodity 120V unit is probably, once everything is totaled up, is likely to be about the same as getting the 240V unit.

At least in the US...

240V units are targetted more to the commercial market, may (or may not!) be better quality, but are certainly going to be more expensive....

I wouldn't rely on that. I've been to Habitat once and to Goodwill and the S. Army many times and don't remember ever seeing an AC.

Oh, absolutely there's no guarantee as to what you'll find and when/where. But I have bumped into 120V AC units at these places and... have even dropped my own with them when I upgraded.

Come to think of it I've seen them at pawn shops, too.

So yeah, it's worth looking around. Especially if you're in no hurry.

(Plus, natch, craigslist, ebay, etc.)

I'm having trouble finding a 220v "portable" air conditioner that's designed and priced for a bedroom-sized area. I was hoping there would be a converter box available that could make my American 120v appliance compatible with my American 220v socket.

You are talking portable AC that can be moved from room to room and not a window unit ? right ?

I am not sure why anyone would want to fool with those, but many must as there are many kinds for sale.

Shouldn't you be able to just plug it in ane standart 120 V receptical in the room ?

When we lived in Europe we used transformers to run American 120V appliances on German 220V power.

But one large enough to handle an AC unit is going to cost a lot, probably more than the AC unit, and they are massively heavy.

With German power we also had to worry about 50 Hz vs 60, but you're on American power so there should be no issue.

As said, a transformer for 220-to-120V would be the size of an AC & the price (or more)! Relatives in the UK had one so they could use a favorite American vacuum cleaner (Filter Queen). It was a big as the vacuum.

By "portable" A/C do you mean free-standing, or a window-mounted, unit ? how many BTUs are you looking for ?

Is there no standard 120 volt outlet nearby ? Even if a heavy duty extension cord is needed ?

Because they won't take them - particularly if over 3 years old.

I bet he has a black, white and bare wire in that box and the electrician may have reidentified the white but I wouldn't count on it. Black red and bare, 2 wire romex is so rare I doubt most people have ever even seen it. It still sounds like he should have a qualified person in that panel but the fix might be as simple as moving the white wire in the panel to the neutral bus and changing the receptacle.

It should be whatever their minimum trip charge is but that is easily around $100. I would call around.

I suspect there's a lot of local policy there, as I've personally handed over units that were five years old...

(and seen others for sale).

In any event, the bigger point still stands. A commodity 120V unit is _much_ cheaper than any 240V the original poster is likely to find.

That may just be a local thing. I have seen used window shakers here in thrift shops and pawn shops. I think they were $20-30 but I wasn't really paying that much attention. I gave one away with the shed I had converted into a play house for the kids and it may have been one of the first "she sheds" for the lady who bought it.

No one has yet commented that the stated 220/120V does not compute. Today in the USA it's 240 or 120V and when it was 220V, it was presumably

That is my strong suspiscion