This gold plating also prolongs the shelf life of the relay. However, high currents will destroy this gold plating, so that a relay contact cannot be used for low current switching after it has been used for high current switching. The numbers behind DC and AC refer to the type of load switched by the output contacts of the relay. DC1 and AC1 refer to resistive loads. DC13 and AC15 refer to inductive loads, such as a relay coil, motor, or solenoid.
Inductive loads cause large surge currents when the load is switched on.
For this reason, contacts are rated for lower amperages for inductive loads than for resistive loads. NEMA 12 Enclosures are intended for indoor use primarily to provide a degree of protection against dust, falling dirt and dripping non-corrosive liquids. NEMA 13 Enclosures are intended for indoor use primarily to provide a degree of protection against dust, spraying of water, oil and non-corrosive coolant. IP65 Figure 6 stands for protection against dust. No dust can enter a housing with a low pressure of 20 mbar.