You could run the low voltage with the line voltage if you use "line
voltage" conductors, which will probably be rated 600 volts, and although
'THHN is often bantered about as the conductor of choice, keep in mind it is
not rated for wet locations. Most, but not all conductors have multiple
ratings, so for wet locations be sure it has a letter "W" in it like THWN



"Howard" wrote in message
...
I'm replacing an old heat pump installation which had the thermostat
wiring and the 220V romex all within the same plastic conduit whip
going from disconnect to the condenser unit.

I understand thisn't acceptable per current code. I need a couple
clarifications.

1. Can std. Romex wire be used in a conduit or does it need to be
individual wires? (ie THHN)
2. It appears that thermostat wiring is permitted within a conduit if
it's insulation is rated for the same voltage as the high voltage
circuit. (ie CL1 220V). However can std. thermostat wire (ie 18/4)
be contained in it's own small conduit within the main conduit??