AZ ROC R-11 Electrical cheat sheet

Ohm's law: E = I × R. Power: P = E × I = I²R = E²/R for resistive loads.

Single-phase power: P = V × I × power factor. Balanced three-phase power: P = √3 × line voltage × line current × power factor.

Approximate voltage drop: single-phase VD = 2 × K × I × L / circular mils; three-phase VD = √3 × K × I × L / circular mils.

A continuous load is expected to operate at maximum current for 3 hours or more; conductors and overcurrent devices are sized at 125% of the continuous load plus 100% of noncontinuous load.

In a balanced wye system, line voltage = √3 × phase voltage and line current = phase current. In a balanced delta system, line current = √3 × phase current.

Common systems include 120/240 V single-phase, 120/208 V three-phase wye, 277/480 V three-phase wye, and 240/480 V three-phase delta.

Conductor ampacity is limited by termination temperature ratings: 60°C, 75°C, or 90°C. The lowest-rated component in the circuit sets the final ampacity unless listed otherwise.

Box fill: each 14 AWG conductor counts as 2.00 cubic inches, 12 AWG as 2.25, 10 AWG as 2.50, 8 AWG as 3.00, and 6 AWG as 5.00.

In a three-phase wye circuit with linear loads, the neutral carries only unbalanced current; neutral current is zero when the load is balanced.

Nonmetallic-sheathed cable is permitted in many dry indoor locations but is not permitted in wet locations or where subject to physical damage.

EMT must be supported within 3 ft of each box and at intervals not exceeding 10 ft. Rigid metal conduit uses the same 10 ft support interval.

Conduit fill limits: 1 conductor = 53% of interior area, 2 conductors = 31%, and 3 or more conductors = 40%.

Ampacity derating for current-carrying conductors in a raceway: 4 to 6 conductors = 80%, 7 to 9 = 70%, and 10 to 20 = 50%.

NM cable must be secured within 12 in of each box and at intervals not exceeding 4.5 ft.

All junction boxes, outlet boxes, and switch boxes must remain accessible; boxes cannot be permanently covered by building finishes.

A listed expansion fitting is required where a raceway crosses a building expansion joint.

NEC Table 300.5 sets minimum burial cover; PVC raceways for 120/240 V circuits generally require at least 18 in of cover.

The grounded conductor and equipment grounding conductor must be separated downstream of the service disconnect; a subpanel neutral bar is not bonded to the enclosure.

Standard overcurrent device ratings include 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, and 100 A, continuing in standard steps above 100 A.

The next-higher-standard overcurrent device may be used only under NEC 240.4(B) conditions, generally when the device does not exceed 800 A and the conductor ampacity is adequate for the load.

A ground rod must be at least 8 ft long and driven to full length; multiple rods must be spaced at least 6 ft apart.

A metal underground water pipe grounding electrode must be supplemented by an additional electrode such as a ground rod.

Equipment grounding conductors are sized from NEC Table 250.122 based on the rating of the overcurrent device protecting the circuit.

GFCI personnel protection trips at approximately 5 mA of ground-fault current.

The grounded neutral conductor is not normally fused or switched; overcurrent protection is placed in the ungrounded conductors.

Ground-fault protection of equipment is required for certain 480Y/277 V services rated 1000 A or more under NEC 230.95.

Series-rated overcurrent combinations must be listed as a series-rated system; a breaker cannot be substituted unless the listing permits it.

Motor branch-circuit conductors are sized at 125% of the motor full-load current from NEC tables, not from the motor nameplate current.

Motor overload protection is generally sized at 115% to 125% of the motor nameplate full-load current.

Motor branch short-circuit and ground-fault protection is selected from NEC Table 430.52; an inverse-time breaker generally may not exceed 250% of full-load current.

A motor disconnecting means must be within sight of the motor and controller or capable of being locked open, unless the Code permits otherwise.

Motor overload protection protects the motor from sustained overload; branch-circuit short-circuit protection protects the circuit from fault current.

NEC motor full-load current tables are used for conductor and branch short-circuit sizing; nameplate current is used for overload sizing.

NEMA 1 enclosures are for indoor use; NEMA 3R is rainproof and weather-resistant; NEMA 4 is watertight; NEMA 12 is dusttight.

A motor controller may be remote if the disconnecting means is capable of being locked open and the installation complies with NEC 430.102.

Multi-speed motors require branch-circuit conductors and protection based on the highest rated winding current unless the Code specifies otherwise.

The National Electrical Code is a model code; the edition in force and any local amendments are established by the adopting jurisdiction and enforced by its authority having jurisdiction.

Arizona Revised Statutes Title 32, Chapter 10 governs contractor licensing and regulation by the Arizona Registrar of Contractors.

The Arizona Registrar of Contractors R-11 classification is an electrical contractor license covering electrical contracting within that classification's scope.

Arizona law generally prohibits offering or performing contractor work without a valid license; violations can lead to citations, cease-and-desist orders, and civil penalties.

Arizona does not issue a statewide journeyman electrician license; individual cities or towns may require their own electrician registration or license.

Arizona ROC rules require a written contract for residential work that states the scope, price, and payment schedule.

Arizona licensed contractors must include their ROC license number in advertising.

Local building departments issue permits and perform inspections; electrical work must pass the required inspections before being concealed or energized.

Arizona's preliminary 20-day notice is used by subcontractors and suppliers without a direct contract with the owner to preserve mechanics' lien rights.

Markup = (price − cost) / cost. Margin = (price − cost) / price. A 25% markup produces only a 20% margin.

Labor cost = quantity × labor unit hours per unit × loaded hourly rate, where the loaded rate includes wages, taxes, insurance, and benefits.

Material takeoffs add a waste factor; a common allowance for wire and small materials is 5% to 10%.

A change order documents added or deleted work and should be written and signed by the owner or authorized representative before the work proceeds.

Lockout/tagout isolates hazardous energy with a lock and tag before servicing equipment; only the person who applied the lock should remove it.

An assured equipment grounding conductor program tests temporary cords, receptacles, and tools for grounding continuity and records the tests at required intervals.

Arizona 811, formerly Arizona Blue Stake, must be contacted before excavation so underground utilities can be marked.

The critical path is the longest sequence of dependent project activities; any delay on that path delays project completion.

OSHA electrical construction safety requirements are in 29 CFR 1926 Subpart K, including minimum approach distances and temporary power rules.