Basic mistakes made by heating devices users:

-using devices without checking what kind of medium they are designed to work in (water, air, oil, ice, acid)
-using standard heaters in stainless steel boilers, which results in a chemical process damaging a heater coating. In appliances made of stainless steel a specially designed heating element should be installed.
-no control of the level of water being heated. Evaporating water results in burnout of a heater. Immersion heaters have markings indicating minimal and maximal level of water they can work in. All other heaters must have their heating elements completely immersed underwater.

Under no circumstances must you allow an immersion heater to immerse underwater together with a cube it is mounted in!