I have a 20 amp breaker fed by 12/2 to junction box and am trying to run 3-6in cans, 110 cfm panasonic fan, and floor heat. The floor heat pulls a 5 amp load. The fan is a panasonic whisper.

Why the question, is the breaker tripping? Is this circuit in a bathroom and does it supply any receptacles at all?

Are you having a problem when every thing on the circuit is on?

Is this all there is on the circuit, because if there is nothing else, because if it is and the amperage needed by the fan is negligible, then you should be fine.

Do you know the amperage for the fan and lights?

FYI - only: I'd have to check the code book, but heating circuits are normally sized at 125% of the amperage.

5*1.25 = 6.25 amps.

No the breaker isn't tripping. Doing a remodel and my electrician said it was enough juice to run it all and well I had to make sure. Have not even turned the floor heat yet so I don't know if he's right. But after hearing from you I feel A little bit better.