My questions involve how a 240v fan-forced wall-mounted heating circuit works when controlled by a single pole thermostat and how to safely test its line and load wires. I understand that both the feed white and black wires are hot, and that one of those wires bypasses the thermostat and feeds directly into the heater while the other wire connects to the thermostat. This means that the heater always has at least 110v of juice going into it, whether the thermostat is on or off. I'm assuming the heater has some sort of electronics that keep it from running until voltage jumps up from 120v to 240v (when the thermostat is switched on). Is that right?
I now want to correctly identify which wire is the supply (from the breaker box) coming into the thermostat and which is the load (going to the heater). I would like to use my little 2-wire circuit tester light to do this test. Though only made for 120v 20A circuits I am assuming I can safely test for the presence of a current by connecting to either a white or black lead wire and a ground wire, rather than the other white or black wire (which could potentially also be carrying a current). Is this assumption correct?
Finally, can someone tell me if its true that there is no circuit (the flowing in and out of electricity) with these wall mounted heating units? If both wires going to the heater are sending in current, and there is no neutral wire returning current, then there isn't a circuit in the heater. All the juice going to the heater is turned into heat - there is absolutely nothing to return - therefore no neutral. If that's the case, then if the heater fails, doesn't that mean that the entire heater becomes an electrified 240 volt death machine when the temperature drops?
Sorry for the long post - I looked for definitive answers on this topic before posting but couldn't find any. I need answers to these questions before I feel comfortable continuing with my project.
Thanks!
--Brian