They are identified by a coloured tracer on the casing of the wires. The red tracer goes to the top tag as you look at it, the black tracer to the bottom tag. These two would not be a disaster if they were reversed as it is an AC supply. Hoiwever, it is absolutely vital to fit the one with yellow/green tracer only to the earth tag in the middle. Any other connection on this wire will result in disaster. (at least a blown fuse or trip sw)
Hope this helps.
David Wright, July 2008
