 Safety  Protective devices - devices designed to automatically limit or shut off the flow of electricity in the event of a ground-fault, over-load or a short circuit in the wiring system

 Fuses An "over-current" device that is placed in a circuit to protect the circuit from excessive spikes in current They automatically open or break the current path when the amount of current becomes excessive Can be fixed by replacing with a new fuse Use the size and type of fuse that is recommended by the manufacture Never use anything other than a fuse to complete a circuit (wire, foil, solder) Replace with the correct current rating or smaller Replace with the correct voltage rating or higher

 Circuit breakers An "over-current" device that is placed in a circuit to protect the circuit from excessive spikes in current They automatically open or break the current path when the amount of current becomes excessive They can be fixed by resetting the circuit breaker

 Ground-fault-circuit-interrupters (GFCI) The GFCI is designed to shut off electrical power with in as little as 1/40th of a second  It works by comparing the amount of current going to the equipment against the current returning from the equipment  If the difference exceeds 6mA the GFCI stops current quickly enough to prevent electrocution The GFCI is often found in wet locations such as bathrooms or kitchens The GFCI can be fixed by resetting the GFCI

 Surge protectors/suppressors Also called surge arrestors Limits surge voltages (spikes) to prevent damage to equipment power supplies  Used at power service-entrances to protect against lightning strikes  Also as an adapter that plugs into the wall to interface with equipment Protects sensitive computerized equipment

 Wire Sizing  Two methods or standards for wire sizing  Based on the diameter or size of the wire  AWG  American wire gauge  Range is from #40, the smallest, to #4/0 (four aught), the largest

kcmil  Thousands of circular mils  One inch = 1000 mils  Circular mils of a wire equal the diameter of a single strand multiplied by the number of strands  Starts at 250 kcmil and increases to 2000 kcmil  Larger size wire is measured in this way  Picks up where AWG stops

 Grounding Definition - system of conductors that provide a current path from electrical circuits or equipment to earth Purpose - to protect the operator and patient from electrical shock

Terms  Grounding conductor » Green wire or green with one or more yellow stripes » Not used as the normal current carrying wire » Fault condition current carrying wire only » Must be of sufficient size to carry enough current to trip a protective device Characteristics  Grounded conductor must be a solid wire (uninterrupted) from the transformer to the disconnecting means  Grounding conductor and grounded conductor may be tied together at disconnecting ends (common) or run individually