A question about the external condensors - are they supposed to be
screwed into the floor/roof? I'm planning on placing it on a flat roof
so I can't screw it down.


Mine just sits on the patio. I haven't bothered to bolt it down. It's very
heavy; you may need a small crane or something to get it up to a roof. Also
consider the noise they produce, as it may upset the neighbours.

S.