Electrical Glossary

Discrimination

Ensuring that when a protective device clears a fault, as few circuits as possible (ideally only the affected circuit) are disconnected. In the case of cascaded protective devices such as MCBs or Fuses, there must be sufficient difference in their trip rating such that only one one nearest the fault trips. (with cascaded RCDs discrimination is usually achieved by have devices with progressively faster response times as you move further from the circuits origin).

Whole House RCD

A deprecated way of installing an RCD such that a single low trip threshold device (typically 30mA) protects all the circuits in a property. While counter to the advice given in the present wiring regulations. installations of this type are still commonly found.