I want to install 3 1200 watt heat lamps on my outdoor patio. I am planning on installing a new circuit, since I have an open slot on my service panel (200 amp). I was going to run a 30 amp circuit with 10-2 NM wire. However, I'm not exactly sure how to place the outlets and if they should be 20 amp or not. I suppose I could come off the 10-2 with 12-2 at three different outlet sites. If all 3 heat lamps were on at the same time it would be 3600 watts, which would be 30 amps @120 volts. This would be pushing the 30 amp circuit since the total amps should be slightly less than the circuit. What should I do?

3 20 Amp circuits would work well. Contactor could allow 1 switch.
If allowed, it would need a 40 Amp circuit(#8's).
You can't put a 20 amp receptacle on a 40 amp breaker, hardwiring MAY be an option, I would wait for another reply to see if allowed.

I would suggest you reconsider your sizing.

Instead of bring 30 Amp off the main panel, I would suggest you bring 40 amp off the panel using 8/3 (40 amps) to a "B" panel. From the "B" panel to the bulbs, I would use three branch 15 amp branch circuits. Each bulb will actually draw only 10 amps. However, protecting a 30 amp circuit with a thirty amp breaker is asking for trouble.

Yipes. If you only have one slot open, your choices might include one or more of the following:

1. A sub-panel for this and additional circuits.

2. A lighting enclosure that you would build fed from a 40 A circuit would not be hard to do with DIN rail components.
a) DIN rail mounted contactor
b) DIN rail mounted 20 amp breakers
c) DIN rail mounted control transformer + fuse
d) Low voltage control circuit

3) Use a commercial lighting panel such as this one. http://www.amx.com/products/categoryRADIALightingSolutions.asp
It would allow dimming and be approved.

You can get extra space by adding 2 pole independent breakers that fit into a single slot.

You CANNOT have general purpose receptacles or residential lighting on a 30A (or larger) circuit. Period, end of story.

You have several choices, some of which have been stated.

Are these actually lights, or are they heating elements?
Can the units be hardwired?

My choice would be to find more room in your panel. See if it will accept twin breakers (skinnys, thins, whatever).
You will need three 15 or 20a circuits for this job.

If your panel does only have one space open, and it cannot accept twins, it may be time for a service upgrade.

Thanks for everyone's response. The 1200 watt heat lamps are halogen bulbs and I do have room for one twin breaker. I could run two 20 amp circuits and add the third light to an existing 15 or 20 amp circuit that is not being used to full capacity. The lamps come with plugs but could be hard wired.

You can combine 2 existing circuits to a twin and gain a slot. Just make sure the number of "poles" that the panel is allowed to have isn't exceeded.