I moved into an older house (built in 1955) and had to change the outlet for my electric dryer (built in 2005). Both the old and new outlets had four prongs, but they were arranged differently. After removing it from the wall, I noticed the old outlet only had three wires connected to it (no ground) - so that is how I wired the new one. The dryer works, but I don't know what risks I am running without a ground. ... Read this and 5 comments.