First a little background: The previous owner of my house replaced the typical California wall furnace with a direct vent heater. Think of those log stoves you'd expect to see in a cabin, just burning natural gas instead. Now I'm planning on putting a ceiling fan in the room that has the heater. Since the heater doesn't have any sort of fan, I thought it'd be spiffy to wire up the fan to turn on when the switch was on, or when the thermostat turned the heater on. Thus, in the last few days I started the researching what would be needed to do this.
A little while back, I'd also picked up some 20/2 bell wire so I could properly mount the transformer for my doorbell. The previous owner had buried the transformer in the wall. Running the numbers, I found that the 20/2 wire would work for the fan's relay circuit. However, the wire doesn't have any of the required markings for class two cable. When I went looking for specs on the wire, I was finding that it's apparently 30V 60C rated. Doing some more digging, it seems that most wire sold for doorbells at the big box stores is rated less than 60V.
So my question, aren't doorbell circuits considered class 2 and required to have 150V minimum ratings by NEC 725.179(G)? Or is there an exception that I missed?
I agree. I've never paid attention to those code provisions before, but I see no reason why a doorbell circuit wouldn't be required to comply with all of the Class 2 or 3 provisions including conductor insulation ratings.