Understanding the Problem
Factories are hot, and in many cases very humid. This of course means there are potential problems with heating elements. The electric insulator in heaters, usually MGO (magnesium oxide), has a tendency over time to absorb moisture from the air. This occurs most often during down time on machines in damp environments or during long storage periods in stockrooms.
When full voltage is applied to a moisture-laden heater, fuses blow, circuit breakers trip, and voltage arcs to the sheath and destroys the heater.
Minimizing the Problem
Testing for the Problem
Solving the Problem
Another method for removing moisture is to run the heater at ½ voltage. This can work well but may take 12 - 24 hours, and Meg readings should always be taken before applying full voltage.
One of the relatively new devices on solid state controllers is a soft start feature. This is an excellent choice. Soft start applies varied voltage over time to slowly bring the heater up to temperature.