MN Journeyman Electrician flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ohm's Law

E = I × R, where E is voltage in volts, I is current in amperes, and R is resistance in ohms. Combine with P = E × I to solve any two-variable problem.

Voltage Drop Formula

Single-phase: VD = 2 × K × I × L / CM. Use K = 12.9 for copper, 21.2 for aluminum. Three-phase multiplies by 1.732 instead of 2.

Series Circuit Characteristics

Current is identical through every element, voltages add, and total resistance equals the sum of resistances. A break anywhere stops current in the entire circuit.

Parallel Circuit Characteristics

Voltage is the same across all branches, branch currents add to total current, and total resistance is less than the smallest branch resistance.

Conductor Adjustment Table

Table 310.15(C)(1): 4-6 current-carrying conductors reduce ampacity to 80%, 7-9 to 70%, 10-20 to 50%, and 21-30 to 45%.

NM-B Cable Restrictions

Nonmetallic-sheathed cable is limited to normally dry locations. It is not permitted in wet locations, embedded in concrete, or in masonry voids, and must be protected from physical damage.

EMT Support Requirements

Electrical metallic tubing must be supported within 3 ft of each box and at intervals not exceeding 10 ft. The minimum trade size is 1/2 inch.

Box Fill Conductor Volumes

Article 314.16 volumes per conductor: 14 AWG = 2.00 cu in, 12 AWG = 2.25, 10 AWG = 2.50, 8 AWG = 3.00. Each device yoke counts as two of the largest conductor.

Raceway Fill Percentages

Chapter 9 fill limits: one conductor = 53% of interior area, two conductors = 31%, three or more conductors = 40%.

PVC Schedule 40 Supports

Support intervals: 3 ft for 1/2 through 1 inch trade sizes, 5 ft for 1 1/4 through 2 inch, and 6 ft for larger sizes.

Dwelling General Lighting Load

Dwelling units require 3 VA per square foot of floor area. Apply Table 220.42 demand factors: first 3,000 VA at 100%, next at 35%, remainder at 25%.

Small-Appliance Branch Circuits

At least two 20 A circuits are required for dwelling kitchen, pantry, and laundry areas. Each counts 1,500 VA in the load calculation.

Optional Dwelling Calculation

NEC 220.82: first 10,000 VA of the total load at 100%, the remainder at 40%, then add the larger of heating or air conditioning at 100%.

Range Demand Table

Table 220.55: a single range rated up to 12 kW may be calculated at 8,000 VA. Add 5% for each kW above 12 kW.

Standard OCPD Ratings

NEC 240.6(A) ratings include 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 125, 150, 200, 400, and 600 A. Devices must be selected from this list.

Next-Size-Up Rule

NEC 240.4(B) allows the next higher standard OCPD only when ampacity is not a standard rating, the device is 800 A or less, and the next rating does not exceed conductor ampacity.

Small Conductor Protection

NEC 240.4(D): 14 AWG copper is limited to 15 A, 12 AWG to 20 A, and 10 AWG to 30 A, unless a specific permission in 240.4(E) or (G) applies.

AFCI Requirement

NEC 210.12 requires arc-fault circuit-interrupter protection for 15 and 20 A branch circuits supplying outlets in dwelling living areas, bedrooms, closets, and hallways.

GFCI Locations

NEC 210.8 requires GFCI protection for 15 and 20 A, 125 V receptacles in bathrooms, garages, outdoors, unfinished basements, kitchens, laundry areas, and near sinks.

Grounding Electrode System

NEC 250.50 requires all available electrodes to be bonded together, including metal water pipe, building frame, concrete-encased electrode, ground ring, and rod electrodes.

Equipment Grounding Conductor Size

Table 250.122 sizes the equipment grounding conductor from the OCPD rating: 15 A = 14 AWG copper, 60 A = 10 AWG, 100 A = 8 AWG, 200 A = 6 AWG.

Grounding Electrode Conductor Size

Table 250.66 bases the grounding electrode conductor on the largest service conductor: 2 AWG or smaller = 8 AWG copper; 1/0-3/0 = 4 AWG; 250-500 kcmil = 2 AWG.

Single Rod Supplement

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

Main Bonding Jumper

The main bonding jumper connects the grounded service conductor to the equipment grounding conductor at the service. It is sized from Table 250.102(C)(1).

Motor Branch Conductor Size

Motor branch-circuit conductors must have ampacity at least 125% of the motor full-load current from Tables 430.248 through 430.250.

Motor Short-Circuit Protection

Table 430.52: inverse-time breaker = 250% of FLC, dual-element fuse = 175%, non-time-delay fuse = 300%. The next standard size up is permitted if needed.

Motor Overload Protection

NEC 430.32: overload devices are sized at 125% of FLA for motors marked 40°C or less temperature rise, and 115% for motors marked above 40°C.

Motor Disconnect Rating

The motor disconnecting means must be within sight of the motor and controller, lockable open, and rated at least 115% of the motor full-load current.

Transformer Current Formula

Primary current = kVA × 1,000 / primary voltage. For three-phase, divide by 1.732 × voltage. Secondary current uses the secondary voltage in the same formula.

Minnesota Code Adoption

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

Minnesota Licensing Board

The Minnesota Board of Electricity issues journeyman, master, and registered unlicensed electrician credentials and investigates complaints against licensees.

Minnesota Journeyman Requirements

A journeyman electrician license requires documented practical experience, typically four years or 8,000 hours, plus passage of the Board's journeyman examination.