Wiring Infrared Patio Heating Systems
You're stuck with the two-circuit approach, although I'd use a single 12/2/2 cable for the homerun for that
As it turns out, the NEC doesn't allow taps off 40 or 50A branch circuits to feed space-heating appliances in a dwelling unit (this is a combination of 210.19(A)(4) and 424.3(A)).  So, you're required to use the &quot;5 wire&quot; approach, running two 20A, 240VAC branch circuits to the switch box and thus onward to the heating appliance.  While you could use the approach of pairing 12/2s to make the homerun, I would use a single 12/2/2 cable for the NM leg of the circuit to avoid silly issues with circuits getting &quot;split&quot; across cables and thus violating Code.