I am trying to install a tankless 220v hot water heater in my kitchen. There is a 220v outlet on the backsplash of the counter that was there when I moved in and have never used. I plan to use this as a 220v source. When I put the meter to the bare copper ground and 1 wire on the outlet I read 120v. I am guessing that both sides add up to 220V? Y/N? I am trying to establish that there is truly 220 here. Also, am I wrong to use this as a junction box for the heater? I intend on putting a blank plate over it so it won't be used for anything else later...