It appears the thermostat of our 240 volt baseboard heaters are wired with 12/2 cable only, no ground. Is this the norm? Safe? Or do I need to replace this with grounded wire? Grounded 12/2 is used everywhere else in the circuit. Thank in advance.

If your heaters are for less than 20 Amps, then 12/2 is the correct AWG.

Neutral (white) is used as a hot leg. Practice dictates that the white conductor be marked to show that it is not being used as a Neutral. I usually would use red tape on both ends of the conductor and also on any visible parts of the cable so that it cannot be confused as a neutral leg.

Usually a 12/2 cable will have a bare ground wire in it. Just as it is possible that the manufacturer is providing the grounding means elsewhere in the circuit. Best suggestion I can make is to check the specs on the equipment.

So, the stats are wired with two wire cable?

Since the baseboard heaters are controlled by the stats, now the issue is where is the feed, and is there a ground in that cable. If the feeder goes to the heater first, and that is 3 wire, at least the heater is grounded.

I am not too worried about the stats having no ground, assuming the stats are all plastic.

However, if the stats have any exposed metal, the stats should be grounded.

Thanks guys, I'm sure the 12 AWG is OK for the heaters, my concern was the ungrounded cable going to the stat. Since the stats are metal I'm going to change that to 12/2 with ground. Thanks again for the help.