Michigan Low Voltage Practice cheat sheet

Michigan adopts the NFPA 70 National Electrical Code through the Michigan Electrical Code, administered by the Bureau of Construction Codes; local amendments are published in the Michigan Administrative Code.

Article 720 covers circuits under 50 volts; Article 725 covers Class 1, 2, and 3 remote-control and signal circuits, and Article 800 covers communications circuits - scope determines which article governs.

Class 2 and Class 3 circuits are limited by Tables 725.121(A) and (B), which cap voltage and power (for example 100 VA for Class 2, 100 VA for Class 3) based on the power source and circuit class.

Article 725 Class 1 vs Class 2/3 is decided by the power source and wiring method, not by the load: a Class 2 source remains Class 2 even if the load is a 120 V device through a listed relay.

Low voltage does not mean unregulated: Chapter 3 wiring methods (300.15 boxes, 300.22 plenum rules, 310 ampacity) still apply to Class 1 circuits and to Class 2/3 where the article says so.

Article 800 communications circuits (phone, data, CATV, fiber) have separate requirements from Article 725; mixing them in one raceway or box requires compliance with the stricter applicable rules.

Article 760 fire alarm circuits split into NPLFA (non-power-limited) and PLFA (power-limited); PLFA wiring must be listed for the purpose and separated per 760.139.

Article 725.3 lists cross-references: Class 2/3 circuits in ducts, plenums, or hazardous locations must also meet Articles 300, 430, and 500-series requirements.

CL2, CL3, CM, CMR, CMP, and CATV/communication cable suffixes indicate listing: the P suffix (plenum) is required in ducts and plenums per 300.22(C); R (riser) is required in vertical shafts.

Box fill for low voltage is governed by the box's listing and 314.16 where applicable; Class 2/3 splices must be in a listed enclosure or box, not free-air, unless the cable is listed for the purpose.

Support intervals: CL2/CL3 and communications cables are generally supported every 4.5 ft (1.4 m) and within 12 in. of boxes unless the article specifies otherwise (for example 800.24, 725.24).

Cable through bored holes in framing must be at least 1-1/4 in. from the nearest edge of the stud, or protected by a listed steel plate per 300.4.

Separation: Class 2/3 conductors must be separated from power conductors by at least 2 in. (50 mm) or by a barrier, unless the Class 2/3 circuit is installed using a Chapter 3 method (725.139).

Sleeves and raceways: low voltage cable may occupy a raceway with power conductors only if the cable is listed for the purpose and the raceway is sized per Chapter 9 fill tables.

Firestopping: penetrations of fire-rated assemblies by low voltage cable must be sealed with a listed firestop system per the building code; the electrical code does not waive this requirement.

Exterior and wet locations require a wiring method listed for wet locations (for example UF, or cable with a W suffix); indoor-rated CL2 cable is not permitted outdoors in wet locations.

Article 250 applies to grounding and bonding of power systems; low voltage systems that are separately derived or that interface with power circuits must follow 250.30 and 250.50 requirements.

Class 2 and Class 3 circuits are generally not required to be grounded, but if the system is grounded, the grounded conductor must be bonded to the equipment grounding conductor at the source only (single point).

Communications systems grounding follows Article 800, Part IV: the communications bonding conductor must be bonded to the building's grounding electrode system or to the nearest accessible point of the power grounding system.

Grounding electrode conductor sizing for communications and low voltage systems is based on Table 800.156 (or the applicable article) and is sized to the largest conductor served.

Bonding jumpers must be listed for the purpose, and connections must be made with listed connectors; solder-only connections are not permitted for grounding and bonding.

Equipment grounding conductors must be sized per Table 250.122 based on the overcurrent device protecting the circuit; for low voltage circuits, the equipment grounding conductor may be reduced per the applicable article.

Touch potential and step potential are reduced by equipotential bonding of metallic raceways, cable trays, and equipment; single-point grounding of shielded cable reduces ground loops.

Ground fault circuit protection: low voltage circuits are generally not required to have GFCI protection, but the power source feeding them may require it per 210.8 if the source is in a dwelling unit location.

Article 725 Class 1 circuits use Chapter 3 wiring methods and are permitted to share raceways with power conductors if the Class 1 circuit is supplied by a power source and the conductors are listed for the voltage.

Article 760 fire alarm: NPLFA (non-power-limited) circuits must be installed in metal raceways or listed fire alarm cable and separated from power conductors per 760.139; PLFA circuits use listed PLFA cable.

Article 800 communications: primary protectors are required where conductors enter a building and are exposed to lightning or contact with power conductors above 300 V; the protector must be listed and bonded.

Article 820 CATV and Article 830 network-powered broadband have separate requirements; coaxial cable shield must be grounded at the building entrance per 820.93.

Control circuits: Article 430 Part VI governs motor control circuits; a Class 1 remote-control circuit may be tapped from the motor branch circuit only if the tap rules in 430.72 are met.

Signaling circuits: Article 725 covers Class 1, 2, and 3 signaling; Article 760 covers fire alarm; Article 800 covers communications; the system function determines the article, not the voltage.

Power-limited fire alarm circuits must be separated from Class 1 and power circuits by at least 2 in. or by a barrier, and must not be installed in the same raceway with power conductors unless listed for the purpose.

Access control, CCTV, and intrusion detection systems typically fall under Article 725 Class 2/3 and must use listed CL2/CL3 cable and listed enclosures.

Electrical work in Michigan requires a permit from the local enforcing agency (city, village, or township) unless the work is exempt under the Michigan Electrical Code; permits are required for new circuits and for alterations.

Licensing: electrical contractors must be licensed by the Michigan Department of Licensing and Regulatory Affairs (LARA); journeyman and master electricians are licensed by examination and must complete continuing education for renewal.

Low voltage work is generally regulated: a permit and inspection are required for low voltage installations, and the installer must hold the appropriate electrical license or work under a licensed contractor.

Inspection sequence: rough-in inspection before covering, final inspection after completion; the enforcing agency must be notified when work is ready for inspection.

Plan review may be required for commercial and multi-family projects before a permit is issued; the local enforcing agency sets the threshold.

Fees are set by the local enforcing agency and are typically based on the valuation or the number of fixtures/circuits; permits must be posted or available on the job site.

Stop-work orders may be issued for work without a permit or work not conforming to the code; the enforcing agency has authority to disconnect and require correction.

Licensing reciprocity: Michigan has limited reciprocity with other states; verify with LARA before relying on an out-of-state license.

Michigan adopts the NFPA 70 National Electrical Code through the Michigan Electrical Code; local amendments appear in the Michigan Administrative Code and are enforced by the Bureau of Construction Codes.

Article 720 covers circuits under 50 volts; Article 725 covers Class 1, 2, and 3 remote-control and signal circuits; Article 800 covers communications circuits.

Class 2 and Class 3 circuits are limited by Tables 725.121(A) and (B), which cap voltage and power based on the power source and circuit class.

Class 1 vs Class 2/3 is determined by the power source and wiring method, not by the load; a Class 2 source remains Class 2 through a listed relay.

Low voltage is still regulated: Chapter 3 wiring methods (300.15 boxes, 300.22 plenums, 310 ampacity) apply to Class 1 circuits and to Class 2/3 where the article requires.

Article 800 communications circuits have separate requirements from Article 725; mixing them in one raceway or box requires compliance with the stricter applicable rules.

Article 760 fire alarm circuits split into NPLFA (non-power-limited) and PLFA (power-limited); PLFA wiring must be listed for the purpose and separated per 760.139.

Article 725.3 lists cross-references: Class 2/3 circuits in ducts, plenums, or hazardous locations must also meet Articles 300, 430, and 500-series requirements.

CL2, CL3, CM, CMR, CMP, and CATV suffixes indicate listing: the P suffix (plenum) is required in ducts and plenums per 300.22(C); R (riser) is required in vertical shafts.

Box fill for low voltage is governed by the box listing and 314.16 where applicable; Class 2/3 splices must be in a listed enclosure or box, not free-air, unless the cable is listed for the purpose.

Support intervals: CL2/CL3 and communications cables are generally supported every 4.5 ft (1.4 m) and within 12 in. of boxes unless the article specifies otherwise (for example 800.24, 725.24).

Cable through bored holes in framing must be at least 1-1/4 in. from the nearest edge of the stud, or protected by a listed steel plate per 300.4.

Separation: Class 2/3 conductors must be separated from power conductors by at least 2 in. (50 mm) or by a barrier, unless the Class 2/3 circuit is installed using a Chapter 3 method (725.139).

Sleeves and raceways: low voltage cable may occupy a raceway with power conductors only if the cable is listed for the purpose and the raceway is sized per Chapter 9 fill tables.

Firestopping: penetrations of fire-rated assemblies by low voltage cable must be sealed with a listed firestop system per the building code; the electrical code does not waive this requirement.

Exterior and wet locations require a wiring method listed for wet locations (for example UF, or cable with a W suffix); indoor-rated CL2 cable is not permitted outdoors in wet locations.

Article 250 applies to grounding and bonding of power systems; low voltage systems that are separately derived or that interface with power circuits must follow 250.30 and 250.50 requirements.

Class 2 and Class 3 circuits are generally not required to be grounded, but if the system is grounded, the grounded conductor must be bonded to the equipment grounding conductor at the source only (single point).

Communications systems grounding follows Article 800, Part IV: the communications bonding conductor must be bonded to the building's grounding electrode system or to the nearest accessible point of the power grounding system.

Grounding electrode conductor sizing for communications and low voltage systems is based on Table 800.156 (or the applicable article) and is sized to the largest conductor served.

Bonding jumpers must be listed for the purpose, and connections must be made with listed connectors; solder-only connections are not permitted for grounding and bonding.

Equipment grounding conductors must be sized per Table 250.122 based on the overcurrent device protecting the circuit; for low voltage circuits, the equipment grounding conductor may be reduced per the applicable article.

Touch potential and step potential are reduced by equipotential bonding of metallic raceways, cable trays, and equipment; single-point grounding of shielded cable reduces ground loops.

Ground fault circuit protection: low voltage circuits are generally not required to have GFCI protection, but the power source feeding them may require it per 210.8 if the source is in a dwelling unit location.

Article 725 Class 1 circuits use Chapter 3 wiring methods and are permitted to share raceways with power conductors if the Class 1 circuit is supplied by a power source and the conductors are listed for the voltage.

Article 760 fire alarm: NPLFA (non-power-limited) circuits must be installed in metal raceways or listed fire alarm cable and separated from power conductors per 760.139; PLFA circuits use listed PLFA cable.

Article 800 communications: primary protectors are required where conductors enter a building and are exposed to lightning or contact with power conductors above 300 V; the protector must be listed and bonded.

Article 820 CATV and Article 830 network-powered broadband have separate requirements; coaxial cable shield must be grounded at the building entrance per 820.93.

Control circuits: Article 430 Part VI governs motor control circuits; a Class 1 remote-control circuit may be tapped from the motor branch circuit only if the tap rules in 430.72 are met.

Signaling circuits: Article 725 covers Class 1, 2, and 3 signaling; Article 760 covers fire alarm; Article 800 covers communications; the system function determines the article, not the voltage.

Power-limited fire alarm circuits must be separated from Class 1 and power circuits by at least 2 in. or by a barrier, and must not be installed in the same raceway with power conductors unless listed for the purpose.

Access control, CCTV, and intrusion detection systems typically fall under Article 725 Class 2/3 and must use listed CL2/CL3 cable and listed enclosures.

Electrical work in Michigan requires a permit from the local enforcing agency (city, village, or township) unless the work is exempt under the Michigan Electrical Code; permits are required for new circuits and for alterations.

Licensing: electrical contractors must be licensed by the Michigan Department of Licensing and Regulatory Affairs (LARA); journeyman and master electricians are licensed by examination and must complete continuing education for renewal.

Low voltage work is generally regulated: a permit and inspection are required for low voltage installations, and the installer must hold the appropriate electrical license or work under a licensed contractor.

Inspection sequence: rough-in inspection before covering, final inspection after completion; the enforcing agency must be notified when work is ready for inspection.

Plan review may be required for commercial and multi-family projects before a permit is issued; the local enforcing agency sets the threshold.

Fees are set by the local enforcing agency and are typically based on the valuation or the number of fixtures/circuits; permits must be posted or available on the job site.

Stop-work orders may be issued for work without a permit or work not conforming to the code; the enforcing agency has authority to disconnect and require correction.

Licensing reciprocity: Michigan has limited reciprocity with other states; verify with LARA before relying on an out-of-state license.