I have a 220v heater that i would like to move 4-5ft further than the plug will allow. I saw some dryer extension cords that I think will work but a quick google of that seems to say don't do it. I don't particularly want to get an electrician to run an outlet closer to where I need it. I do plan to leave it unattended, mainly to warm the area up before I start working. Any alternatives / suggestions that are safe/legal, lol? Current cord is about 4ft long.