On June 5, 2017 at 13:40, Proggieus said...
actually you can if the low voltage is controlling the high voltage and the low voltage wiring has the same insulation rating as the HV wiring
Not if the LV is a class 2 or 3 circuit (which is most certainly will be). Just because you run 18 THHN for your LV does not change the fact it is a Class 2 or 3 circuit - and there for illegal under NEC. 725.136
You can have class 2 or 3 wiring with class 1 HV in the same 'enclosure' providing proper spacing and partitions are in place. Maybe that is what you are getting confused on, as that section talks specifically about class 2/3 circuits controlling class 1 HV circuits.
