If the relay is used at a voltage and current no higher than the minimum load, the contact resistance will increase and the signal may not be correctly transmitted. This happens because stabilization of the contact surface (accomplished by electrically and mechanically eliminating minute substances generated on the contact surface by opening/closing the contacts) with the minimum load probably will not occur.

In addition, even if the load is within the maximum ratings, care should be taken to ensure that the current does not drop below the minimum load ratings after opening or closing the contacts.
 

The switching life of a relay can be improved by providing a protection circuit that suppresses transient current and voltage spikes applied to the contacts when the contacts are opened or closed.

It is important to select the correct protection circuit suitable for the contact load.
 

With an inductive load, when the contacts are opened to break the circuit, a counter electromotive force as shown in Fig. 1 is generated, causing an electric discharge between the contacts. This discharge energy accelerates metal dislocation and wear on the contact surface. A protection circuit is therefore necessary to absorb this counter electromotive force. Table 1 shows guideline circuit examples and circuit constants. Never use a connection with a capacitor only as shown in Table 2.
 

The breakdown voltage of a non-polar capacitor should be 300 V or higher.

Some loads, such as halogen lamps, have a low initial resistance so that an inrush current 10 times as high as the steady-state current may flow through the relay on power application. A high inrush current may also flow when the relay is used to switch loads such as motors and capacitors. In these cases, a current-limiting resistor may be connected in series with the contacts to keep the inrush current limited (refer to Fig. 2).
 

When the stray line capacitance is large, the inrush current that is generated from it may pose a problem. As shown in Fig. 3, the electric charge of the line capacitance is discharged directly through the contacts when the contacts are closed. The smaller the characteristic cable impedance and the longer the cable, the greater wear on the contacts.

It may be necessary to connect a current-limiting resistor or surge suppressor in series with the contacts as a protection circuit.