I just moved into this house and have found what I think is a 220 junction box in my bedroom it has 3 heavy gauge wires a White, Black and Bare (assuming this one is the ground) all of the other boxes have 110's 4 smaller gauge wires 2 ea. White and Black, am I right assuming that this is a 220?

Would not assume without checking with a volt meter.

Do u have any 220 breakers in panel box? If u do, shut them off one at a time and check the wires for voltage. It may be a 20 or 30 amp circuit that was used for AC at one time.

Chuck