Circulating electric heater

1, how to choose the circulating electric heater?
The selection of the circulating electric heater, maintenance must be in the field of electrical, mechanical and chemical aspects have certain experience, many big company or design institute the designers often artificially divided into groups of electrical, mechanical and heat transfer, on the design of the electric heater or select need at least one person was involved in. On a large scale, of course, powerful manufacturers can provide relevant technical support, professional design software, some manufacturers have been developed so that can't put the electric heater design as a too simple, also don't understand is too complicated.

2, the cause of circulating electric heater failure have those?
Usually the cause of damage of electric heater ? basically has the following five aspects