Cold resistance determines the current surge at the moment of power-on, while hot power reflects the output capability during stable operation. When purchasing, suppliers should be asked to provide a Factory Inspection Report, in which the measured values of cold resistance, hot power, and insulation resistance are more meaningful for reference than the promised values in the specification sheet. If selection is based only on nominal power, differences in resistance wire material or winding process may cause the actual power to deviate from the design value, affecting the heating rate and temperature control accuracy.
The working voltage must not exceed 10% of the rated value. For a 380V system, for example, it should be controlled within 418V. Excessive voltage will accelerate oxidation of the resistance wire and shorten service life. It is recommended to install overvoltage protection or voltage stabilization devices in the distribution cabinet and to regularly check the supply voltage. For workshops with large grid fluctuations, models with a slightly higher rated voltage can be selected to leave a margin.
Common shell materials include stainless steel and galvanized sheet. Stainless steel has better corrosion resistance and is suitable for humid environments with slight acid or alkali gases; galvanized sheet has lower cost and is suitable for indoor working conditions that are dry and free of corrosive media. If the workshop has cutting fluid splashing or cleaning operations, stainless steel shells should be given priority. At the same time, the fit clearance between the shell and the heating ring body must be confirmed to avoid loosening caused by thermal expansion.
During installation, ensure that the inner wall of the heating ring fits evenly with the surface of the heated body; excessive clearance will reduce heat transfer efficiency. The terminal connections should be kept clean, and the tightening torque should meet the requirements of the manual. Regularly use a megohmmeter to check insulation resistance. If it is lower than 1MΩ, check for moisture or aging of the insulation layer. After shutdown, avoid immediately touching high-temperature surfaces to prevent burns.
