Michigan Low Voltage Practice key terms

In Michigan practice, circuits operating at 50 volts or less, such as communications, signaling, and control wiring, which fall under Article 725 and related articles rather than power wiring rules.

A circuit whose power source and wiring are not limited to Class 2 or 3 energy levels, so it must follow the stricter wiring methods of Part II of Article 725.

A circuit supplied by a listed Class 2 power source that limits energy to levels considered safe for fire and shock, allowing lighter wiring methods and fewer physical protections.

A circuit supplied by a listed Class 3 power source, with energy limits above Class 2 but still below Class 1, permitting reduced wiring methods while requiring more protection than Class 2.

A listed transformer, power supply, or battery arrangement whose output is tested and marked to stay within Class 2 voltage and current limits under any load condition.

A circuit that carries signals to operate equipment such as motors, contactors, or valves from a distance, governed by Article 725 when it operates at limited energy.

A circuit that activates an indicator, alarm, or annunciator in response to a condition, including fire alarm and security signaling covered by Article 760.

Wiring that connects initiating devices, control equipment, and notification appliances in a fire detection or alarm system, installed under Article 760 requirements.

The path connecting automatic detectors and manual pull stations back to the fire alarm control unit so the panel can register an alarm or supervisory condition.

The wiring that supplies horns, strobes, speakers, and similar devices so occupants are warned when the fire alarm system operates.

Premises wiring for telephone, data, and similar signals, covered by Article 800, which permits cable types and installation methods suited to low-energy communications.

A space used for air handling, such as above a suspended ceiling that serves as a return-air path, where cable jackets must meet low smoke and flame-spread requirements.

A vertical shaft or run between floors that carries cabling, requiring cable listings rated for vertical flame propagation when installed in that space.

An enclosed channel such as conduit, tubing, or wireway designed to hold and protect conductors and cables along a defined route.

The percentage of a raceway's cross-sectional area occupied by conductors, kept within code limits so cables can be pulled without damage and heat can dissipate.

The required fastening of cable and raceway at intervals and within specified distances of boxes, so wiring stays in place and strain is not transferred to terminations.

The calculation that limits how many conductors, devices, and fittings may occupy a box, based on conductor size and the volume marked on the enclosure.

An enclosure where conductors are spliced or where circuits branch, required to be accessible and sized so splices and devices fit without crowding.

A factory assembly of insulated conductors with an overall nonmetallic sheath, commonly called Romex, permitted only in specific locations under Michigan's adopted code.

Connecting electrical equipment and systems to the earth so fault current has a defined path and voltage on exposed metal parts is limited.

Joining metal parts together electrically so they remain at the same potential, preventing dangerous voltage differences between enclosures, raceways, and piping.

The conductor that connects the metal frames and enclosures of equipment to the grounding system, providing a low-impedance path for fault current.

A conductive object in direct contact with the earth, such as a ground rod or metal water pipe, that ties the grounding system to earth.

The conductor that links the grounding electrode to the service or system grounded conductor and equipment grounding conductors at the service point.

A conductor sized to carry fault current that ensures metal parts, such as a raceway and a box, are electrically joined so no voltage difference develops.

A device that trips when current leaks from the intended circuit path to ground, protecting people from shock in wet or otherwise hazardous locations.

A device that detects the signature of arcing in wiring and opens the circuit, reducing the chance that a damaged conductor starts a fire.

The clear space required in front of electrical equipment so a person can safely work on it without contacting live parts or obstructions.

A procedure that de-energizes equipment and applies locks and tags so power cannot be restored while someone is servicing the circuit.

Written authorization from the local enforcing agency allowing regulated electrical work to begin, based on an application describing the scope and location.

The agency's examination of submitted drawings and specifications before construction, confirming the proposed work will meet code before installation starts.

The inspection performed after framing and wiring are installed but before concealment, when boxes, cables, and grounding can still be examined and corrected.

The last inspection, done after devices, fixtures, and finishes are complete, confirming the finished installation is safe and matches the permitted scope.

A document issued by the building authority confirming a structure may be used for its intended purpose, typically after electrical final approval.

A Michigan credential authorizing a business to contract for electrical work, held by the qualifying master or journeyman who supervises the work.

A Michigan licensee who has completed required experience and examination and may perform electrical work under a master's or contractor's supervision.

A Michigan licensee qualified by experience and examination to supervise electrical work and to serve as the qualifying person for a contracting business.

A person registered in a supervised training program who may perform electrical work only under the direct oversight of a licensed electrician.