This is where I sat down and tried to figure out how a PID, a thermocouple, and a solid-state relay work. All were new to me, but they're pretty common equipment in the fancier homebrew setups where folks like to let automation give a helping hand. Actually, I would imagine that most folks are more like me and like to tinker and see if they can get something to do something that it normally wouldn't do. The PID for example is used in kilns. Here though, the goal is to have it keep a small tank of water at just the right temperature to keep another tank of water and grain at just the right temperature as it circulates through a closed loop in the smaller tank for a heat transfer. My testing was done with a lamp but the real circuit will power an element that normally goes in a home water heater. On the topic of wiring, you may note that I didn't use much (any) electrical tape or wire nuts in my quick test here. Don't try this at home. Like welding with galvenized pipe that I warned you against in the frame section of this project, death is practically on the front porch and knocking. My finished product will be done with much more care and safety.