WI Electrician cheat sheet

Ohm's law: E = I × R; power P = I × E = I²R = E²/R.

Series circuit: current is the same everywhere; resistances add; voltage divides in proportion to resistance.

Parallel circuit: voltage is the same across all branches; branch currents add; total resistance is less than the smallest branch resistance.

Three-phase power: P = √3 × E_line × I_line × power factor for a balanced load.

Conductor ampacity is adjusted for ambient temperature and for more than three current-carrying conductors in a raceway or cable.

Voltage drop for a single-phase two-wire circuit: VD = 2 × K × I × L ÷ CM, where K is the resistivity constant and CM is circular mils.

Box fill is computed by counting each conductor, each device yoke, and each equipment grounding conductor, then comparing to the box's cubic-inch capacity.

Motor branch-circuit conductors are sized at not less than 125 percent of the motor full-load current rating.

Service and feeder calculations begin with the calculated load; the service disconnect rating must be at least the calculated load and the service conductors must carry it.

Standard overcurrent device ratings follow the standard ampere-rating table; the next higher standard rating may be used only where the calculated load does not exceed the device rating.

For a single-family dwelling, the general lighting load is computed at 3 VA per square foot of floor area, then demand factors are applied.

Feeder and service neutral loads may be reduced for household electric ranges and similar appliances where the maximum unbalanced load is less than the branch-circuit rating.

Grounding electrode conductor size is selected from the table keyed to the largest service conductor; it is not sized by overcurrent device rating.

A grounded (neutral) conductor may serve as the equipment grounding conductor only in existing installations of the type permitted by the Code for the specific wiring method.

Interrupting rating of overcurrent devices must be at least the available fault current at the point of application.

Conductor fill in a raceway is limited to 40 percent for three or more conductors; 53 percent for one conductor; 31 percent for two conductors.

Small-appliance branch circuits: at least two 20-ampere circuits for the kitchen, pantry, and dining area receptacle outlets.

Laundry branch circuit: at least one 20-ampere circuit for the laundry receptacle outlet(s).

Bathroom receptacle outlets must be supplied by at least one 20-ampere branch circuit, and that circuit may not supply outlets outside the bathroom.

Ground-fault circuit-interrupter protection is required for receptacle outlets in bathrooms, garages, outdoors, kitchens (countertop surfaces), and unfinished basements.

Arc-fault circuit-interrupter protection is required for most 120-volt, 15- and 20-ampere branch circuits supplying outlets in dwelling units.

Receptacle spacing in habitable rooms: no point along the floor line may be more than 6 feet from a receptacle outlet.

Receptacles in a dwelling unit must be of the grounding type, and the grounding contacts must be connected to an equipment grounding conductor.

A 125-volt, single-phase, 15- or 20-ampere receptacle outlet in a dwelling unit must be tamper-resistant where required by the Code for the location.

Motor disconnecting means must be located within sight of the motor controller and must open all ungrounded conductors.

Motor overload protection is sized to the motor's nameplate full-load current and service factor; it is separate from branch-circuit short-circuit and ground-fault protection.

Motor branch-circuit short-circuit and ground-fault protection may be a nontime-delay fuse, time-delay fuse, instantaneous trip circuit breaker, or inverse-time circuit breaker, each sized by a percentage of full-load current.

A controller must be capable of starting and stopping the motor it serves and must have a horsepower rating not less than the motor.

Flexible cord and cable connections to motors must be suitable for the environment and must include an equipment grounding conductor.

Class I locations are those in which flammable gases or vapors may be present; equipment must be marked for the class, division, and group.

A motor circuit's conductors are sized at 125 percent of the motor full-load current, and the overload device protects the motor, not the conductors.

Phase converters and variable-frequency drives require conductors and overcurrent protection sized per the manufacturer's instructions and the Code.

SPS 316 adopts the National Electrical Code with Wisconsin amendments; where the state rule and the NEC differ, the state rule governs.

Electrical work in Wisconsin requires a permit from the local municipality or the Department of Safety and Professional Services where no local program exists.

Licensed electricians must be credentialed by the Department; journeyman and master electrician credentials are separate categories.

Inspections are performed by the authority having jurisdiction, and work must be inspected before being concealed.

The Department may adopt fee schedules and administrative procedures for permits, inspections, and credentials.

Electrical installations must comply with the adopted edition of the NEC as amended by SPS 316, including local ordinances that are more stringent.

Unsafe or noncompliant installations may be ordered corrected, and the Department may pursue enforcement action against unlicensed practice.

Ampacity tables are based on an ambient temperature of 30 degrees C for conductors in free air and on the table's stated conditions for raceways.

Equipment grounding conductors must be sized per the table keyed to the rating of the overcurrent device protecting the circuit.

A junction box must be accessible; boxes must be supported and have sufficient volume for the conductors and devices.

Receptacle outlets on a 20-ampere branch circuit must be rated 20 amperes or be a 15-ampere receptacle protected by the branch-circuit overcurrent device.

Switches must be connected to the ungrounded conductor, not the grounded conductor, so the fixture is de-energized when the switch is open.

Cable assemblies installed in exposed locations must be protected from physical damage where subject to damage.

The neutral conductor of a multiwire branch circuit must be sized to carry the maximum unbalanced load and must not be opened by a single-pole switch.