I currently use a little 28 qt. cooler as my mash tun, but I am thinking about using a 30 qt. aluminum turkey fryer pot instead. I have three kettles (1 SS, 2 Al) and two burners.
I like the cooler for the mash tun because it is fairly well insulated and allows me to maintain a consistent temperature over the hour or so it is in service. However, the biggest problem I have is trying to adjust the temperature if I miss my target mash temp. Having to add hot or chilled water to the mash tun is a pain.
Since I have an extra aluminum kettle on my hands I'm thinking about how I could use it for my mash tun instead of the cooler. I would like to install a small water heater element (2,000w, 120v, $10 at Home Depot) in the bottom of it. I would still heat my strike and sparge water with one of my propane burners, but the electric element would allow me to add heat if it gets too cool without adding more water. And since it's aluminum, if it's too hot by a degree or two when I dough in I would guess it will shed the extra heat pretty quickly.
This seems like a pretty easy project, especially if I don't bother with adding an automatic thermostat. But, before I get started, I thought I'd see if anyone had done this before and/or if anyone thinks having a heating element in contact with the grain bed would be a bad idea.