So the situation is as follows: I've found an electric sauna heater I want to use in the detached, outdoor sauna I'm building. The outdoor sauna is 55' away from the house, so I'm planning to bury PVC conduit 18" deep for the wire runs.
A wall-mounted "power unit" which needs to go inside the house (sensitive electronics can't freeze, apparently) receives 240V power from the main breaker panel in the house. The power unit then sends 240V power out to the heater. A data cable also runs between the power unit and a digital control unit, installed inside the house to turn the sauna and sauna room lights on/off. A separate data cable runs from a temperature sensor in the sauna hot room back to the power unit as well. This temp sensor data cable will need to be buried in conduit for the run from the sauna to the house separate from the power cables, kept >2" away from the power cables per manufacturer. The power unit also has a connection that provides the power to a 120V light circuit, controlled by the digital control unit.
My questions:
So, because the power unit is protected by the double-throw breaker, and is providing power for both the 240V run to the sauna heater AND the 120V run to the lights, will this been seen as a single circuit going to an outbuilding? Or will this count as two separate circuits?
Assuming they count as one circuit and I'm allowed to send them both to the sauna building, will the 240V and the 120V wire runs out to the sauna be allowed to be in the same conduit? Or will I need to run three conduits? (One for the temp sensor data cable, one for the 120V light supply, and one for the 240V heater supply?)
Your thoughts are greatly appreciated!!
Best Answer
You'll need to run two conduits
The good news is that mixing 120 and 240V circuits in the same conduit is fine, and each of the mains circuits (light, aux, heater) in the mains conduit would be considered a "different use" for the purposes of NEC 225.30(D) since they're separately switched, so you can run all three mains circuits from the main building to the outbuilding instead of putting the power unit at the outbuilding. You should be able to run the A1/A2 (thermal protector) wires in this conduit as well, since they also run to the heater itself alongside the other mains wiring.
However, you'll need to run the temperature sensor cable in a separate conduit; I called Finlandia Sauna tech support, and they insisted that the temp sensor cable be separated from mains wiring, so I doubt the insulation on it is rated for running alongside mains, and the temperature sensor's housing may not be mains-legal either.