1. As for selection of the thermal relay with different rated current level, but with same adjusting range of thermal components:  For example, the thermal relay of JR16 series, in rated current of 20 A and 60 A, the setting value of thermal components has adjusting range of 14A ~16A, at this moment, the environmental temperature for the thermal relay and for the protected motor shall be checked. When the environmental temperature for the thermal relay is higher than that for the protected motor by 15 ℃ or more, the thermal relay with a size bigger shall be used; When the environmental temperature for the thermal relay is lower than that for the protected motor by 15 ℃ or less, the thermal relay with a size smaller shall be used; In addition, the loading of motor and the adjusting range for the thermal relay to be adjusted shall be considered too. 

2. Form of reset: The thermal relay can be generally reset manually and automatically. The conversion of this two kinds of resetting can be realized by the adjustment to the reset screw. When the thermal relay leaves the factory, it is generally set to automatically resetting state. When used, whether the thermal relay is set to manual reset state or automatic reset state shall depend on the specific situations of the control loop. In general,  the principle that after the protective device of the thermal relay acts, even though the thermal relay automatically resets, the protected motor shall not automatically restart, otherwise the thermal relay shall be reset to manual reset state. This is to prevent the motor starting repeatedly and damaging the equipment if the faults have not been eliminated. Such as: The thermal relay can be set to automatically resetting form for the control circuit generally with button to control its manually starting and manually stopping; For the automatically starting circuit controlled by automatic component, the thermal relay shall be set to manually resetting form. 

3. The relationship of the specifications of the relay and the installation location:  The star/triangle control position is different, so the specifications of the thermal relay selected is different too. 

4. Selection of connecting wires: If the connecting wires of the thermal relay are too thick or too thin, the normal working of the thermal relay will be affected, because the different thickness of the connecting wires will make the degree of heat dissipating capacity different and can affect the current heating effect of the thermal relay. The selection of connection wires with various specifications can refer to the manufacturer's instructions or the electrical manual. 

5. Adjustment of the setting current for overload protection of the motor which works in a short time repeatedly:  After many times of testing and adjusting in site, the reliable protection to the motor can be obtained. The method is that the setting current of the relay is firstly adjusted to be slightly lower than the rated current of the motor, and during running, if the relay is found to act frequently, then the setting value of the thermal relay is turned up gradually until the operation requirements are met.