Crankcase Heaters and Single Pole Contactor

So...I was talking to some people around the shop and we were discussing contactors, replacing them, etc. Nothing to bad. Then someone on the Tube of You commented about "back-feeding" circuits and that brought up crankcase heaters.
This is just a few minutes on crankcase heaters, why they use single pole contactors (mostly), and how they are actually pulling it off. It isn't perfect but something to think about as you are learning all these different components that you may come across in the hvac units you are working on out there in the field. I didn't put in a wiring diagram with this one so I hope it makes sense the way that I tried to put this out and show what is going on with the circuit. But, of course, I do try to chapter it out so you can skip around!

00:00 Intro
04:45 Crankcase Heater
08:18 Watts and Ohms Laws Calculations
09:56 Electrical Checks
13:00 Back-feeding Circuits
17:56 Unit On/Off, Crankcase Heater On/Off
19:00 Outro