The problem is that the outlet temperature of the electric heater E-404 should be controlled at 120 degree , and the internal over temperature alarm temperature should be set to 200 degree . During the heating process, if the outlet temperature did not reach the control temperature, the internal temperature quickly reached the alarm temperature, causing the electric heater to automatically stop heating. At this time, the internal temperature still remained for a period of time before it could drop below the set value. After on-site reset, the heating was restarted, In order to maintain the heating process of the electric heater, it is necessary to frequently reset and start it on site, resulting in the following problems: 1) Large fluctuations in heating temperature, difficulty in ensuring outlet temperature, poor regeneration effect, and affecting product quality. 2) Due to frequent start-up of the electric heater, it needs to be reset and started every 5-10 minutes, resulting in frequent action of the control components of the electric heater and affecting the service life of the electrical components. 3) The operator's labor intensity is high. Due to the need for operators to reset and restart the electric heater on site every time it shuts down for self-protection, the labor intensity is high, which is not conducive to safety production.

Since the discovery that power sources can undergo thermal effects through wires, many inventors around the world have been engaged in the research and manufacturing of various electric heating appliances. The development and widespread application of electric heating, like other industries, follow this pattern: gradually promoting from advanced countries to countries around the world; Gradually developing from cities to rural areas; From collective use to family and then to individuals; The product has evolved from low-end to high-end. Most of the budding electric heating appliances in the 19th century were inferior, first appearing as electric heating appliances for daily life. In 1893, the prototype of the electric console first appeared and was used in the United States, followed by the use of electric stoves in 1909, which placed electric heaters in the stove, meaning that heating was transferred from firewood to electricity, that is, from electrical energy to thermal energy.