MN Journeyman Electrician cheat sheet

Ohm's law: E = I × R; power P = E × I = I²R = E²/R. Use 12.9 Ω·cmil/ft for copper and 21.2 Ω·cmil/ft for aluminum at 75°C in voltage-drop calculations.

Voltage drop (single-phase): VD = 2 × K × I × L / CM. Three-phase: VD = 1.732 × K × I × L / CM, where L is one-way length in feet and CM is circular mils.

Branch-circuit voltage-drop recommendation in NEC 210.19(A) informational note: total drop on feeder plus branch circuit should not exceed 5% of nominal voltage.

Conductor circular mils: 14 AWG = 4,110; 12 AWG = 6,530; 10 AWG = 10,380; 8 AWG = 16,510; 6 AWG = 26,240; 4 AWG = 41,740; 3 AWG = 52,620; 2 AWG = 66,360; 1 AWG = 83,690; 1/0 = 105,600; 250 kcmil = 250,000.

Ampacity correction and adjustment are separate multiplier steps: ambient-temperature correction (Table 310.15(B)(1)) and conductor-count adjustment (Table 310.15(C)(1)); apply both when both conditions exist.

Table 310.15(C)(1) adjustment factors: 4-6 current-carrying conductors = 80%; 7-9 = 70%; 10-20 = 50%; 21-30 = 45%; 31-40 = 40%; 41 and above = 35%.

Series circuit: current is the same through every element, voltages add, total resistance adds. Parallel circuit: voltage is the same across branches, currents add, total resistance is less than the smallest branch.

For a resistive load, a 10% drop in applied voltage reduces power by about 19% (P varies as the square of voltage). Motor torque also varies roughly as the square of voltage.

Balanced three-phase: line current equals phase current in wye; line voltage equals 1.732 × phase voltage in wye. In delta, line voltage equals phase voltage and line current equals 1.732 × phase current.

NM-B cable is permitted only in normally dry locations and must be protected where subject to physical damage; it is not permitted in wet locations, in masonry voids, or embedded in concrete.

Nonmetallic-sheathed cable in thermal insulation: 334.80 requires the 60°C ampacity column unless the conductor is listed and identified for the higher temperature, and the 90°C column may be used only for derating starting ampacity.

EMT: minimum trade size is 1/2 inch; supports required within 3 ft of each box and at intervals not exceeding 10 ft. IMC and RMC support intervals are also 10 ft.

PVC Schedule 40 support intervals: 3 ft for 1/2-1 inch trade sizes, 5 ft for 1 1/4-2 inch, and 6 ft for larger sizes.

Box fill (314.16): each 14 AWG conductor = 2.00 cu in, 12 AWG = 2.25, 10 AWG = 2.50, 8 AWG = 3.00. One equipment grounding conductor counts as a single conductor; each device yoke counts as two of the largest conductor in the box.

Standard box volumes: 4 × 1 1/4 square = 18.0 cu in; 4 × 1 1/2 square = 21.0; 4 × 2 1/8 square = 30.3; 4 11/16 × 1 1/2 square = 29.5; 4 11/16 × 2 1/8 square = 42.0.

Raceway fill: 1 conductor = 53% of interior cross-sectional area, 2 conductors = 31%, 3 or more = 40%.

Bending radius for exposed and concealed conductors: one-shot and full-shoe bends must not be less than the values in Chapter 9 Table 2; for shielded cable the minimum is 12 times the cable diameter.

Cable tray, busway, and conductor identification: grounded conductor must be white or gray, equipment grounding conductor green or green with yellow stripes, and the high-leg of a 4-wire delta must be orange (or other permitted marking).

Standard branch-circuit ratings: 15, 20, 30, 40, 50, and 60 A for general-purpose circuits; 15 or 20 A circuits must use 14 or 12 AWG copper minimum.

Small-appliance branch circuits: at least two 20 A circuits required in a dwelling kitchen, laundry, and pantry area; each counts 1,500 VA in the load calculation.

Laundry branch circuit: one 20 A circuit required, counted at 1,500 VA. Bathroom receptacle circuits must be 20 A and may not serve other outlets.

General lighting load for dwellings: 3 VA per square foot. Apply demand factors from Table 220.42: first 3,000 VA at 100%, 3,001-120,000 VA at 35%, remainder at 25%.

Standard service calculation method (Article 220 Part III): add general lighting, small appliance, laundry, and fastened-in-place appliance loads, then apply demand factors, then add the largest motor at 25%.

Optional method (220.82) for a dwelling: first 10,000 VA of total load at 100%, remainder at 40%; add heating or air conditioning (larger of the two) at 100%.

Demand factor for 4 or more fixed appliances (Table 220.53): 75% of the total connected load.

Range demand (Table 220.55): one range up to 12 kW may be calculated at 8,000 VA; add 5% per kW above 12 kW.

Service-entrance conductors must have ampacity not less than the calculated load, and the service disconnecting means must be rated at least the calculated load and not less than 60 A for a one-family dwelling.

Standard OCPD ratings (240.6(A)): 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000 A.

Next-size-up rule (240.4(B)) applies only when the conductor ampacity does not correspond to a standard rating, the OCPD does not exceed 800 A, and the next higher standard rating does not exceed the ampacity of the conductor.

240.4(D) small-conductor limits: 14 AWG copper = 15 A, 12 AWG copper = 20 A, 10 AWG copper = 30 A, unless permitted by 240.4(E) or (G).

Overcurrent device must be sized to protect the conductor at its ampacity after adjustment and correction; the device is selected from the standard ratings, generally rounding down.

Series-rated systems: the load-side breaker must be listed for use with the line-side device; a marked series combination rating may allow a lower interrupting rating on the load side.

Fuse and breaker interrupting rating must be at least the available fault current at the line terminals, unless the device is series-rated or protected by an upstream device.

GFCI protection is required for 15 and 20 A, 125 V receptacles in bathrooms, garages, outdoors, unfinished basements, kitchens, laundry areas, and within 6 ft of sinks (210.8).

AFCI protection is required for 15 and 20 A branch circuits supplying outlets in dwelling living areas, bedrooms, closets, hallways, and similar rooms (210.12).

Supplementary overcurrent protection does not replace branch-circuit or feeder protection; it protects only the equipment it serves.

Service grounding electrode system (250.50): all available electrodes must be bonded together, including metal water pipe, metal frame of the building, concrete-encased electrode, ground ring, and rod or pipe electrodes.

Grounding electrode conductor sizing (Table 250.66) is based on the largest ungrounded service conductor: 2 AWG or smaller = 8 AWG copper; 1/0-3/0 = 4 AWG; 250-500 kcmil = 2 AWG; over 1,100 kcmil = 3/0 AWG.

Equipment grounding conductor sizing (Table 250.122) is based on the rating of the overcurrent device: 15 A = 14 AWG copper; 20 A = 12 AWG; 60 A = 10 AWG; 100 A = 8 AWG; 200 A = 6 AWG; 400 A = 3 AWG; 600 A = 1 AWG.

A single rod, pipe, or plate electrode with resistance over 25 Ω must be supplemented by an additional electrode (250.53(A)(2)).

Bonding jumpers around water meters and at metallic piping must be sized per Table 250.102(C)(1); the main bonding jumper is sized from Table 250.102(C)(1) based on the service conductor size.

Receptacle grounding: grounding-type receptacles must be connected to the equipment grounding conductor; replacing a nongrounding receptacle requires a GFCI or an equipment grounding conductor run to the outlet.

Metal raceways and enclosures must be bonded at both ends and must be electrically continuous; a bonding jumper is required around expansion joints, concentric knockouts, and similar fittings.

Ground-fault protection of equipment (230.95) is required for solidly grounded wye services over 150 V to ground and more than 1,000 A, with a maximum setting of 1,200 A and a time delay.

Motor branch-circuit conductor ampacity is at least 125% of the motor full-load current from Tables 430.248-430.250, and the overload device is sized from the motor nameplate service factor and temperature rise.

Motor branch-circuit short-circuit and ground-fault protection (Table 430.52): inverse-time breaker = 250% of FLC; dual-element fuse = 175%; non-time-delay fuse = 300%. Next-size-up is permitted if the listed device is not sufficient.

Motor overload protection (430.32): 125% of FLA for a motor with a marked temperature rise of 40°C or less, or 115% for a marked rise over 40°C.

Motor disconnecting means must be within sight of the motor and controller and must be capable of being locked in the open position; the disconnect must be rated at least 115% of the motor FLC.

Transformer overcurrent protection (450.3): primary-only protection at 125% of primary current for transformers over 1,000 V, and 125% for transformers 1,000 V or less when the secondary is protected at 125% or less.

Transformer ampacity: primary current = kVA × 1,000 / primary voltage; secondary current = kVA × 1,000 / secondary voltage. For three-phase, divide by 1.732 × voltage.

Heretically sealed transformer: the disconnecting means must be within sight of the transformer, and the transformer must be located in a ventilated area unless listed for the location.

Special equipment: 680 pools and spas require bonding of metallic parts and an equipotential bonding grid; 690 solar PV systems require rapid shutdown and listed DC-rated disconnects.

Motor control centers and combination starters must have a disconnect within sight of the controller; a controller may be a manual or magnetic starter listed for the application.

Minnesota adopts the National Electrical Code through Minnesota Rules Chapter 1315; the adopted edition is enforced with state amendments published by the Minnesota Department of Labor and Industry.

Electrical work in Minnesota requires a license issued by the Minnesota Board of Electricity: journeyman, master, or registered unlicensed electrician working under supervision.

A journeyman electrician license requires documented hours of practical experience (typically 4 years or 8,000 hours) and passage of a Board examination; a master license requires additional experience and a master examination.

License renewal in Minnesota occurs on a two-year cycle and requires continuing education hours; the specific hour count and approved course categories are set by the Board.

Electrical permits must be obtained from the local authority having jurisdiction before work begins; the Board of Electricity regulates licensing while local building officials inspect and enforce the code.

Minnesota amendments address items such as the state's adoption of NFPA 70 with state-specific amendments, licensing of electrical contractors, and bonding and grounding requirements for specific installations.

Only a licensed electrical contractor may contract for electrical work; a journeyman may perform the work under the contractor's license, and an unlicensed registered electrician works under direct supervision.

Violations of the licensing statute may result in fines, license suspension or revocation, and civil penalties; the Board has authority to investigate complaints and hold hearings.

Minnesota requires that a master electrician or licensed contractor be responsible for the work; the responsible licensed individual must be identified on the permit application.

Ohm's law: E = I × R; power P = E × I = I²R = E²/R. Use 12.9 Ω·cmil/ft for copper and 21.2 Ω·cmil/ft for aluminum at 75°C in voltage-drop calculations.

Voltage drop (single-phase): VD = 2 × K × I × L / CM. Three-phase: VD = 1.732 × K × I × L / CM, where L is one-way length in feet and CM is circular mils.

Branch-circuit voltage-drop recommendation in NEC 210.19(A) informational note: total drop on feeder plus branch circuit should not exceed 5% of nominal voltage.

Conductor circular mils: 14 AWG = 4,110; 12 AWG = 6,530; 10 AWG = 10,380; 8 AWG = 16,510; 6 AWG = 26,240; 4 AWG = 41,740; 3 AWG = 52,620; 2 AWG = 66,360; 1 AWG = 83,690; 1/0 = 105,600; 250 kcmil = 250,000.

Ampacity correction and adjustment are separate multiplier steps: ambient-temperature correction (Table 310.15(B)(1)) and conductor-count adjustment (Table 310.15(C)(1)); apply both when both conditions exist.

Table 310.15(C)(1) adjustment factors: 4-6 current-carrying conductors = 80%; 7-9 = 70%; 10-20 = 50%; 21-30 = 45%; 31-40 = 40%; 41 and above = 35%.

Series circuit: current is the same through every element, voltages add, total resistance adds. Parallel circuit: voltage is the same across branches, currents add, total resistance is less than the smallest branch.

For a resistive load, a 10% drop in applied voltage reduces power by about 19% (P varies as the square of voltage). Motor torque also varies roughly as the square of voltage.

Balanced three-phase: line current equals phase current in wye; line voltage equals 1.732 × phase voltage in wye. In delta, line voltage equals phase voltage and line current equals 1.732 × phase current.

NM-B cable is permitted only in normally dry locations and must be protected where subject to physical damage; it is not permitted in wet locations, in masonry voids, or embedded in concrete.

Nonmetallic-sheathed cable in thermal insulation: 334.80 requires the 60°C ampacity column unless the conductor is listed and identified for the higher temperature, and the 90°C column may be used only for derating starting ampacity.

EMT: minimum trade size is 1/2 inch; supports required within 3 ft of each box and at intervals not exceeding 10 ft. IMC and RMC support intervals are also 10 ft.

PVC Schedule 40 support intervals: 3 ft for 1/2-1 inch trade sizes, 5 ft for 1 1/4-2 inch, and 6 ft for larger sizes.

Box fill (314.16): each 14 AWG conductor = 2.00 cu in, 12 AWG = 2.25, 10 AWG = 2.50, 8 AWG = 3.00. One equipment grounding conductor counts as a single conductor; each device yoke counts as two of the largest conductor in the box.

Standard box volumes: 4 × 1 1/4 square = 18.0 cu in; 4 × 1 1/2 square = 21.0; 4 × 2 1/8 square = 30.3; 4 11/16 × 1 1/2 square = 29.5; 4 11/16 × 2 1/8 square = 42.0.

Raceway fill: 1 conductor = 53% of interior cross-sectional area, 2 conductors = 31%, 3 or more = 40%.

Bending radius for exposed and concealed conductors: one-shot and full-shoe bends must not be less than the values in Chapter 9 Table 2; for shielded cable the minimum is 12 times the cable diameter.

Cable tray, busway, and conductor identification: grounded conductor must be white or gray, equipment grounding conductor green or green with yellow stripes, and the high-leg of a 4-wire delta must be orange (or other permitted marking).

Standard branch-circuit ratings: 15, 20, 30, 40, 50, and 60 A for general-purpose circuits; 15 or 20 A circuits must use 14 or 12 AWG copper minimum.

Small-appliance branch circuits: at least two 20 A circuits required in a dwelling kitchen, laundry, and pantry area; each counts 1,500 VA in the load calculation.

Laundry branch circuit: one 20 A circuit required, counted at 1,500 VA. Bathroom receptacle circuits must be 20 A and may not serve other outlets.

General lighting load for dwellings: 3 VA per square foot. Apply demand factors from Table 220.42: first 3,000 VA at 100%, 3,001-120,000 VA at 35%, remainder at 25%.

Standard service calculation method (Article 220 Part III): add general lighting, small appliance, laundry, and fastened-in-place appliance loads, then apply demand factors, then add the largest motor at 25%.

Optional method (220.82) for a dwelling: first 10,000 VA of total load at 100%, remainder at 40%; add heating or air conditioning (larger of the two) at 100%.

Demand factor for 4 or more fixed appliances (Table 220.53): 75% of the total connected load.

Range demand (Table 220.55): one range up to 12 kW may be calculated at 8,000 VA; add 5% per kW above 12 kW.

Service-entrance conductors must have ampacity not less than the calculated load, and the service disconnecting means must be rated at least the calculated load and not less than 60 A for a one-family dwelling.

Standard OCPD ratings (240.6(A)): 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000 A.

Next-size-up rule (240.4(B)) applies only when the conductor ampacity does not correspond to a standard rating, the OCPD does not exceed 800 A, and the next higher standard rating does not exceed the ampacity of the conductor.

240.4(D) small-conductor limits: 14 AWG copper = 15 A, 12 AWG copper = 20 A, 10 AWG copper = 30 A, unless permitted by 240.4(E) or (G).

Overcurrent device must be sized to protect the conductor at its ampacity after adjustment and correction; the device is selected from the standard ratings, generally rounding down.

Series-rated systems: the load-side breaker must be listed for use with the line-side device; a marked series combination rating may allow a lower interrupting rating on the load side.

Fuse and breaker interrupting rating must be at least the available fault current at the line terminals, unless the device is series-rated or protected by an upstream device.

GFCI protection is required for 15 and 20 A, 125 V receptacles in bathrooms, garages, outdoors, unfinished basements, kitchens, laundry areas, and within 6 ft of sinks (210.8).

AFCI protection is required for 15 and 20 A branch circuits supplying outlets in dwelling living areas, bedrooms, closets, hallways, and similar rooms (210.12).

Supplementary overcurrent protection does not replace branch-circuit or feeder protection; it protects only the equipment it serves.

Service grounding electrode system (250.50): all available electrodes must be bonded together, including metal water pipe, metal frame of the building, concrete-encased electrode, ground ring, and rod or pipe electrodes.

Grounding electrode conductor sizing (Table 250.66) is based on the largest ungrounded service conductor: 2 AWG or smaller = 8 AWG copper; 1/0-3/0 = 4 AWG; 250-500 kcmil = 2 AWG; over 1,100 kcmil = 3/0 AWG.

Equipment grounding conductor sizing (Table 250.122) is based on the rating of the overcurrent device: 15 A = 14 AWG copper; 20 A = 12 AWG; 60 A = 10 AWG; 100 A = 8 AWG; 200 A = 6 AWG; 400 A = 3 AWG; 600 A = 1 AWG.

A single rod, pipe, or plate electrode with resistance over 25 Ω must be supplemented by an additional electrode (250.53(A)(2)).

Bonding jumpers around water meters and at metallic piping must be sized per Table 250.102(C)(1); the main bonding jumper is sized from Table 250.102(C)(1) based on the service conductor size.

Receptacle grounding: grounding-type receptacles must be connected to the equipment grounding conductor; replacing a nongrounding receptacle requires a GFCI or an equipment grounding conductor run to the outlet.

Metal raceways and enclosures must be bonded at both ends and must be electrically continuous; a bonding jumper is required around expansion joints, concentric knockouts, and similar fittings.

Ground-fault protection of equipment (230.95) is required for solidly grounded wye services over 150 V to ground and more than 1,000 A, with a maximum setting of 1,200 A and a time delay.

Motor branch-circuit conductor ampacity is at least 125% of the motor full-load current from Tables 430.248-430.250, and the overload device is sized from the motor nameplate service factor and temperature rise.

Motor branch-circuit short-circuit and ground-fault protection (Table 430.52): inverse-time breaker = 250% of FLC; dual-element fuse = 175%; non-time-delay fuse = 300%. Next-size-up is permitted if the listed device is not sufficient.

Motor overload protection (430.32): 125% of FLA for a motor with a marked temperature rise of 40°C or less, or 115% for a marked rise over 40°C.

Motor disconnecting means must be within sight of the motor and controller and must be capable of being locked in the open position; the disconnect must be rated at least 115% of the motor FLC.

Transformer overcurrent protection (450.3): primary-only protection at 125% of primary current for transformers over 1,000 V, and 125% for transformers 1,000 V or less when the secondary is protected at 125% or less.

Transformer ampacity: primary current = kVA × 1,000 / primary voltage; secondary current = kVA × 1,000 / secondary voltage. For three-phase, divide by 1.732 × voltage.

Heretically sealed transformer: the disconnecting means must be within sight of the transformer, and the transformer must be located in a ventilated area unless listed for the location.

Special equipment: 680 pools and spas require bonding of metallic parts and an equipotential bonding grid; 690 solar PV systems require rapid shutdown and listed DC-rated disconnects.

Motor control centers and combination starters must have a disconnect within sight of the controller; a controller may be a manual or magnetic starter listed for the application.

Minnesota adopts the National Electrical Code through Minnesota Rules Chapter 1315; the adopted edition is enforced with state amendments published by the Minnesota Department of Labor and Industry.

Electrical work in Minnesota requires a license issued by the Minnesota Board of Electricity: journeyman, master, or registered unlicensed electrician working under supervision.

A journeyman electrician license requires documented hours of practical experience (typically 4 years or 8,000 hours) and passage of a Board examination; a master license requires additional experience and a master examination.

License renewal in Minnesota occurs on a two-year cycle and requires continuing education hours; the specific hour count and approved course categories are set by the Board.

Electrical permits must be obtained from the local authority having jurisdiction before work begins; the Board of Electricity regulates licensing while local building officials inspect and enforce the code.

Minnesota amendments address items such as the state's adoption of NFPA 70 with state-specific amendments, licensing of electrical contractors, and bonding and grounding requirements for specific installations.

Only a licensed electrical contractor may contract for electrical work; a journeyman may perform the work under the contractor's license, and an unlicensed registered electrician works under direct supervision.

Violations of the licensing statute may result in fines, license suspension or revocation, and civil penalties; the Board has authority to investigate complaints and hold hearings.

Minnesota requires that a master electrician or licensed contractor be responsible for the work; the responsible licensed individual must be identified on the permit application.