Can you set an Oil/Wax Heater or Lye Tank at a particular set point and will it maintain that temperature?
Yes, your Oil/Wax Heater or Lye Tank, will maintain an even temperature by just setting the dial on the thermostat to a particular set point.
The temperature sensing bulb, is actually in the water jacket, not in the inner tank. The reason for this is because they are very fragile and sensitive. It is placed in the water jacket to protect the bulb and capillary tube from being hit by stirring or by liquids being poured in, etc. It is also surrounded by liquid making it more sensitive to changes in temperature.
The thermostat turns on and off with changes of + or -, 2 degrees Fahrenheit.
There will be a slight temperature variance between the inner tank and the water jacket but if you insulate it, the difference is very slight. No matter what type of tank you buy though, single or double jacketed, you always want to check the contents temperature and at first, make notes on the dial setting. This way you always know right where to set your thermostat. You can even place a mark at the setting or settings so that after a short while, you can just turn the knob to the mark.
Because it is a water jacketed tank, it will maintain a very constant and even heat. The jacket goes nearly all the way to the top of the inner tank so no matter how high the contents are that you are heating, the heat will be evenly distributed.