I need to power up 4, 2kW, 120v lamps. The application is to heat something up. There will be 2 lamps on top (in a reflector) and 2 on the bottom. Driven by Eurotherm controllers through SSRs. In one reflector with 2 lamps, can I run 1 leg of 208 to each lamp and connect the other end of the lamp to neutral? I don't want to run 4 each 20 amp 120v circuits, just 1, 40 amp(?? ) 208v circuit. 8kW/208=38amps, should I size the breaker at 50amps?

I do not see how a 208 Volt 40 amp feeder will solve your problem trying to feed 4- 120 volt 2kW lamps, each will draw 16.6 amps each.

Your dealing with 120 volt loads, which needs one leg of a 208 volt system, plus the neutral, to deliver 120 volts.

You need 4- 120 volt circuits, and technically, if they will run more than 3 hours, because the load amps will exceed 80% of a 20 amp circuit by 0.666 amps, you would need to run 30 amp rated circuits.

The math works, but my concern would be the gauge of wire you use. Consider that 240v is just two phases of 120v in a single package. Right? If you bond all lamps to the same neutral wire, will the neutral be a sufficient gauge to carry that much current?? We're talking 70amps of current on a single neutral line. 8000w/120v. I don't have a code book handy, but that's a beefy wire.

I believe that because the 2 hot legs are out of phase by 120 degrees that the neutral does not need to be bigger than the hot. Can someone who really knows please confirm. Thanks

Good point on the phase.