I'm pretty sure you are getting some bad information here.
I say this b/c I moved my Laundry Room into a portable shed outside the home. Had to run a 220 for the Dryer.
Then we wanted to put a 220 A/C w Heater so the shed is temp controlled.
I was told by an electrician, and my father-n-law who also runs wire, that I should NOT just tap into the 220 outlet and make another outlet for the A/C to plug into. I was told I would have ot run a completely new 220 line.
The reason;
1- Say it's a 50 Amp breaker and the dryer is taking up half that are more already, when the A/C kicks on *boom* Breaker Trips. Tripping breakers is a safety of course but not something you want to make a habit of and you better hope it does trip b/c if it doesn't you'll have a serious problem on your hands and you might find out once your box explodes and the house is on fire. Not being scary, I work with some electricians and they tell REAL stories all the time.
2- Now it is possible to have two 220 outlets off one line "IF" you have the proper size wire that will then allow you to put a 100 Amp breaker for that circuit.
What you need to do is simple. Call a local electrician, tell him what you want to do and see what he says or if he'll drop by and take a look.
*NOTE* I just hung the phone up with the head A/C Tech & Electrician for Fort Polk. He reassured me of all what I just posted.
Your case could be different, he's a nice fellow if you want his number PM me and you can call him yourself.
...and to be honest the LAST place I would look to for advice on Electricity is the INTERWEBZ
now in your situation you should run a 6-3 wire out to the shed to a small sub panel and then some 8-3 off of two 30amp breakers, one for the ac and one for the dryer.
