how big does a relay have to be before it is a contactor?

[keithkyll]

Correct Keith - apart from the small European ones that pivot - they call them contactors. Not in my mind - has to be double break.

When I said most were double break, I was thinking the exception was these from Potter Brumfield, now Tyco. I see that it's called a relay, so I guess contactor does mean double break.
It's easy to see the floating contact construction, and how it would pivot to break a weld, even though it's only a single break.