SinfulDarkLord wrote:Of course on the drawing it says to hook it up to a 120V AC source, but the guy on youtube wired his to the terminals on the thermostat.
This would be either because the thermostat unit had a higher power rating or he was only using a small load (or enven possibly overloading the thermostat). Anyway the idea behind using a relay is to esentually upgrade your power handeling capacity. So the relay takes in the lower current that the thermostat provides and then provides a high current output to your heater.
Your diagram has both sides of the high current heater circuit going to pin 9. One of the wires needs to go to pin 10.