8. Relays and Solenoids
8.1 Circuit Transient Surges, Arc Suppression, and Voltage Surge Protection
Protective devices shall be used to limit surge current (back EMF). All relay and solenoid coils shall have built-in or exterior mounted circuitry to limit surges. Such circuitry (e.g., diodes, resistor, varistor, zener-zener) shall be located at the coil.
8.2 Continuous Current
Derating of continuous current is dependent upon the load type. If a relay is used to switch a combination of loads, the dominant load shall be used for derating purposes.
8.3 Coil Energizing Voltage
The voltage to energize or trigger the relay shall be at least 110% of the minimum rated energizing voltage.
8.4 Coil Dropout Voltage
The voltage to dropout or un-trigger a relay shall be less than 90% of the maximum rated coil dropout voltage.
8.5 Shock and Vibration
Special mounting considerations are necessary for mechanical relays in high temperature or vibration environments. Relays shall not unintentionally switch even during worst-case operating conditions.