When should the radiator fan turn on?

As I noted earlier I got a 2000 Sunfire with a bad engine. I got the engine swapped out and started, but when checking it out, I noted the engine ran at 195 with out having the thrmostat open. It finally let go at around 210 degrees , but still did not cycle. The fan works because it runs when first starten and when the A/C is on. I am wondering if I have a real problem or am just being a nervous nellie. How hot does the car have to get before the cooling fan kicks in? Any help would be greatly appreciated. Thanks a bunch!