Even small air gaps cause hot spotting. Ground the equipment. It's common sense and a safe practice to electrically ground all equipment on which the heater is used. Grounding protects plant and personnel in case of any electrical failure in the heating system. Prevent excessive cycling.
Excessive cycling can be very detrimental to the life of a heater.
A solid state relay using SCRs operates on a one-second time base. This reduces the temperature difference between the overshoot and droop points and increases the life of the heater. For immersion applications of heaters. Make sure the sheath material and watt density ratings are compatible with the liquid being heated. Immersion heaters used in tanks should be mounted horizontally near the tank bottom to maximize convective circulation.