CSLB C-10 Electrical Contractor flashcards

Multiwire branch circuits must have a means to simultaneously disconnect all ungrounded conductors at the panelboard where the circuit originates.

• Handle ties or common-trip breakers satisfy the requirement
• Prevents energized neutral hazards during single-pole servicing
• Applies wherever a shared neutral serves two or more ungrounded conductors

Memory trick: 'Tie the handles so both legs die together.'

Overcurrent protective devices (OCPDs) for continuous loads (operating for 3 hours or more) must be sized at not less than 125% of the maximum continuous load current.

• Applies to feeders and branch circuits (CEC 210.20(A), 215.2(A)(1)).
• Ensures the OCPD does not trip prematurely due to heating effects.
• The calculated value is then matched to the next standard OCPD size (CEC 240.6(A)).

Memory trick: Long run, add a quarter, then pick the next fuse.

A common type of electrical cable consisting of two or more insulated conductors and an insulated or bare equipment grounding conductor enclosed within a nonmetallic jacket, primarily used for interior wiring.

• Often referred to as 'Romex' (a brand name).
• Permitted in normally dry locations (CEC 334.10).
• Not permitted in damp/wet locations, direct burial, or exposed outdoors (CEC 334.12).

Memory trick: NM-B is for 'N-ice and M-ainly D-ry' inside walls.

An exception to AFCI requirements allows extending an existing unprotected branch circuit up to 6 feet without adding outlets, without requiring AFCI protection.

• Extension must be 6 feet or less
• No additional outlets may be added
• Recognizes impracticality of retrofitting AFCI on minor extensions

Memory trick: 'Six feet, no more outlets, no AFCI required.'

Sealing fittings in Class I, Division 1 locations must be installed within 18 inches of an enclosure containing arcing or sparking devices to prevent flame/gas propagation.

• 18 inches is the maximum allowed distance from the enclosure
• Seals prevent explosive gas migration through conduit
• Applies specifically to enclosures with switches, contacts, or similar arc-producing devices

Memory trick: 'Eighteen inches keeps the flame from finding a path.'

The section of the California Electrical Code that provides general requirements for conductors used in electrical wiring, including their types, insulation, operating temperatures, and ampacity ratings.

• Contains tables for conductor ampacities (e.g., Table 310.16).
• Addresses correction factors for ambient temperature and number of current-carrying conductors.
• Specifies conductor marking requirements and uses.

Memory trick: Loads, Protection, Conductors, Motors - each has its own Code book.

Determining the minimum required internal area of a conduit to ensure the total cross-sectional area of all conductors installed does not exceed the maximum allowable fill percentage (e.g., 40% for 3+ conductors).

• Prevents overheating of conductors and allows for easier pulling.
• CEC Chapter 9, Table 1 specifies the fill percentages.
• CEC Chapter 9, Table 5 lists conductor areas.

Memory trick: Conductor Area divided by Percent, tells the Conduit's size.

Determining the reduction in voltage along a conductor due to resistance, ensuring it remains within acceptable limits (typically 3% for branch circuits per CEC 210.19(A)(1) FPN No. 4).

• Voltage drop (VD) is proportional to current, length, and conductor resistivity.
• Inversely proportional to conductor circular mil (CM) area.
• Formula: VD = (2 * K * I * L) / CM for single-phase circuits.
• K is the resistivity constant for copper (12.9) or aluminum (21.2) at 75°C per CEC Chapter 9, Table 8.

Memory trick: Kilo-current-length over Circular-Mils, watch the drop.

Choosing the appropriate conduit material and type based on location, environmental factors, mechanical protection requirements, and code compliance for service entrance conductors.

• Service entrance conduits require robust mechanical protection.
• Underground conduits must be rated for direct burial or encased in concrete.
• RMC offers highest mechanical protection, followed by IMC, then PVC Schedule 80/40.

Memory trick: Protection and Environment dictate your Conduit's path.

Feeder conductors supplying multiple motors must be sized for the sum of all motor full-load currents plus 25% of the largest motor's FLC.

• Formula: Sum(FLC) + 0.25 x largest FLC
• Uses Table 430.250 for FLC values, not nameplate current
• Applies to feeders, not individual motor branch circuits

Memory trick: 'Add them all, then boost the biggest by a quarter.'

For hermetic refrigerant motor-compressors, if a branch-circuit selection current is marked on the nameplate, it must be used in place of rated-load current for all branch-circuit sizing calculations.

• Branch-circuit selection current is always ≥ rated-load current when both are marked
• Used for conductor ampacity, disconnect, and controller sizing
• Found in Article 440, which governs air-conditioning and refrigeration equipment

Memory trick: 'When selection current is marked, it always wins the sizing game.'

A lighting and appliance branch-circuit panelboard may contain a maximum of 42 overcurrent protective devices, not including the main, per NEC 408.36.

• Applies to panelboards where more than 10% of OCPDs are 30A or less with a neutral connection
• Main breaker/lugs are not counted toward the 42-circuit limit
• Rule prevents overloaded, hard-to-label panelboards

Memory trick: 'Forty-two and no more' keeps the panel door closing.

A standard electrical blueprint symbol, typically a receptacle icon with an adjacent triangle containing a 'G' or 'GF', indicating a Ground-Fault Circuit Interrupter protected receptacle.

• GFCI receptacles provide personnel protection against electric shock.
• Required in specific locations like bathrooms, kitchens, outdoors, and garages (CEC 210.8).
• The symbol is critical for proper material takeoffs and installation planning.

Memory trick: Receptacle's mark tells its special function.

Graphical representations used on construction drawings to denote various electrical components, devices, and wiring methods.

• Standardized by industry organizations (e.g., ANSI, IEEE, NEMA).
• Essential for interpreting electrical plans and performing material takeoffs.
• Symbols can have modifiers (e.g., subscripts, additional lines) for specific characteristics.

Memory trick: Shape and Subscript tell the tale of the device.

NEC 410.16 sets minimum clearances between luminaires and closet storage space based on fixture type to prevent contact with combustible stored items.

• Surface-mounted incandescent (enclosed lamp): 12 inches
• Recessed incandescent/fluorescent (enclosed lamp): 6 inches
• Surface-mounted fluorescent: 6 inches

Memory trick: 'Surface incandescent needs a foot of room.'

Selecting the appropriate conductor size to ensure the voltage drop along the circuit does not exceed a specified percentage (e.g., 3%) for efficient operation and compliance with CEC recommendations.

• CEC FPN No. 4 to 210.19(A)(1) recommends 3% for branch circuits and 5% total for feeder + branch.
• Involves using the voltage drop formula (CM = (2KL * I) / VD) and conductor properties tables.
• Must also consider conductor ampacity and load type (continuous/non-continuous, motor/non-motor).

Memory trick: K-I-L-L the V-D, find the C-M, then pick the A-W-G.

Equipment intended to interrupt fault current must have an interrupting rating not less than the available fault current at its line terminals.

• Applies to breakers, fuses, and switches
• Rating must be ≥ calculated available fault current
• Undersized AIC ratings risk explosive equipment failure

Memory trick: 'Never let the breaker's muscle be smaller than the fault's punch.'

Calculating the current (amperes) in a 3-phase circuit given the power (watts) and line-to-line voltage, using the formula I = P / (V * √3).

• Applies to balanced 3-phase loads.
• √3 (square root of 3) is approximately 1.732.
• Power (P) must be in watts (W) and voltage (V) in volts (V).

Memory trick: Power is Root-Three times Voltage, Current, and Power Factor.

The maximum number of conductors allowed within Flexible Metal Conduit (FMC) based on conductor size, insulation type, and conduit trade size, specified in NEC Annex C.

• FMC is often used for short, flexible connections to equipment or lighting.
• Due to its flexible nature, FMC's internal dimensions can vary slightly, so Annex C tables are critical.
• The insulation type of the conductors significantly impacts the conductor area and thus the fill.

Memory trick: FMC fill: 'Flexible' 'Means' 'Careful' 'Counts' from the 'Table'.

The maximum number of conductors allowed in Electrical Metallic Tubing (EMT) based on conductor size, insulation type, and conduit trade size, specified in NEC Annex C.

• NEC Annex C tables provide pre-calculated maximum conductor counts for various conduit types.
• These tables simplify conduit fill calculations, replacing the need for individual area calculations.
• Always ensure the conductor insulation type (e.g., THHN, THWN) matches the table used.

Memory trick: EMT fill: 'Easy' 'Measurement' 'Table' for 'Conductor' 'Counts'.

Special provisions in the NEC allow for smaller service entrance conductors for dwelling units than would typically be required for a general 200A load, due to inherent diversity of loads.

• NEC 310.12 (formerly 310.15(B)(7)) provides specific tables for dwelling service conductors.
• This table applies to 120/240V, 3-wire, single-phase dwelling services.
• It accounts for the diversity of loads in a typical home, reducing the required conductor size.

Memory trick: Dwelling service: 'Special' rules 'Reduce' conductor 'Size'.

A method of determining the minimum required lighting load for a given occupancy type and floor area, using unit load values from NEC Table 220.12.

• NEC Table 220.12 provides unit load values in VA per square foot for various occupancy types.
• The calculated general lighting load is used for service and feeder sizing.
• This is a minimum load; actual lighting loads may be higher depending on design.

Memory trick: Lighting load: 'Area' times 'Unit' equals 'Total' VA for the building.

Calculating voltage drop in three-phase systems requires using a specific formula that accounts for the three-phase nature of the power, ensuring stable voltage delivery.

• The three-phase voltage drop formula includes the square root of 3 (√3).
• K-factor for copper is 12.9, for aluminum is 21.2.
• Conductor ampacity must also be checked against NEC Table 310.16.

Memory trick: Three phases, three steps: Ampacity, Voltage Drop, and then you're set!

Standardized graphical representations used on blueprints to depict electrical components, devices, and systems.

• Symbols provide a universal language for electricians and designers.
• Understanding symbols is crucial for accurate material takeoffs and installation.
• Variations exist, but many core symbols are widely recognized, often defined in a legend.

Memory trick: Lighting symbols: 'Shapes' and 'Letters' tell you 'Where' and 'What'.

A standardized VA value assigned to each general-purpose receptacle outlet for load calculation purposes, ensuring adequate circuit capacity.

• NEC 220.14(I) specifies 180 VA per single or multiple receptacle on a single yoke.
• This value is used when the actual load is unknown or for general branch circuit calculations.
• It helps prevent circuit overloading by providing a baseline load assumption.

Memory trick: Receptacle loads: 'Every' outlet 'Adds' a 'Standard' amount.

The process of selecting the appropriate Rigid Metal Conduit (RMC) size to safely contain a specified number and size of conductors, adhering to NEC fill percentages.

• RMC has larger internal diameter compared to other conduits of the same trade size.
• Conductor areas are found in NEC Chapter 9, Table 5.
• Conduit fill percentages (e.g., 40% for 3 or more conductors) are in NEC Chapter 9, Table 1.

Memory trick: RMC: 'R'eal 'M'etal 'C'onduit, 'R'eally 'M'ust 'C'alculate 'Fill'.

A 20A, 120V circuit dedicated to supplying receptacle outlets in kitchen, pantry, dining room, and similar areas for small appliances.

• NEC requires at least two 20A small-appliance branch circuits for dwelling unit kitchens.
• These circuits serve countertop receptacles, dining area receptacles, and typically exclude lighting or other fixed appliances.
• Each circuit is typically assumed to serve multiple receptacles, but the exact number isn't rigidly defined by NEC.

Memory trick: Kitchen outlets: 'Two' circuits, 'Many' spots for small appliances.

A specific minimum VA load mandated by the NEC for each dedicated laundry branch circuit in dwelling units, ensuring adequate capacity for laundry appliances.

• NEC 210.11(C)(2) requires at least one 20A branch circuit for the laundry area.
• NEC 220.52(B) specifies a minimum calculated load of 1500 VA for this circuit.
• This load is applied even if the actual washing machine draws less, or if a gas dryer is used (which still requires a 120V receptacle for its motor/controls).

Memory trick: Laundry load: 'One' circuit, 'Fixed' VA 'Minimum'.

Standardized graphical representations used on blueprints to depict automatic or manual devices that control electrical circuits or equipment.

• Symbols for control devices help identify their function and location.
• Understanding these symbols is essential for proper installation and troubleshooting.
• The legend on blueprints provides specific interpretations for symbols used.

Memory trick: Control symbols: 'Shapes' and 'Arrows' tell you 'How' it controls.

Voltage drop over a conductor is calculated by determining the total resistance of the conductor over its full length (out and back) and then applying Ohm's Law (Vd = I * R).

• R_total = (resistance per 'X' feet) * (total length / 'X' feet).
• For single-phase, total length is 2 * one-way length.
• For three-phase, total length is √3 * one-way length (often simplified to just one-way length for resistance calculation if using K factor).
• Vd = I * R_total.

Memory trick: Resistance per Foot times Total Feet gives Total Resistance, then Ohm's Law!

In an ideal transformer, the ratio of primary to secondary voltage is inversely proportional to the ratio of primary to secondary current.

• Vp/Vs = Is/Ip (Voltage ratio is inverse of current ratio).
• Np/Ns = Is/Ip (Turns ratio is inverse of current ratio).
• Ip = primary current, Is = secondary current.
• Assumes 100% efficiency (ideal transformer).

Memory trick: Voltage goes down, Current goes up, Power stays equal, don't mess it up.

In a Wye (star) three-phase connection, the line-to-line voltage is √3 times the line-to-neutral voltage, and phases share a common neutral point.

• Vll = √3 * Vln.
• Vln = Vll / √3.
• Provides a neutral point for single-phase loads.

Memory trick: Wye is 'Y' for 'Why' the Lines are Longer than Neutral!

The National Electrical Code (NEC) limits the total number of bends in a conduit run between pull points (e.g., boxes, conduit bodies) to not more than the equivalent of four quarter bends (360 degrees total).

• Maximum of 360 degrees of bends between pull points.
• A 90-degree bend is a quarter bend.
• Applies to all types of conduit (EMT, IMC, RMC, PVC, etc.).
• Prevents excessive strain on conductors during pulling and simplifies installation/removal.

Memory trick: Four quarters make a whole circle, that's your bend limit, no more hurdle.

The ratio of the primary voltage to the secondary voltage in a transformer is equal to the ratio of the number of turns in the primary winding to the number of turns in the secondary winding.

• Formula: Vp/Vs = Np/Ns.
• Ideal transformers assume no losses.
• Used for stepping up or stepping down voltage.

Memory trick: Volts and Turns go together, but Current is backwards!

In a Delta (mesh) connection, the line current is √3 times the phase current (IL = √3 × Iph), and the line voltage equals the phase voltage (VLL = Vph).

• Commonly used for high power transmission and distribution.
• Provides three-phase power without a neutral.
• Line currents are displaced by 30° from phase currents.

Memory trick: Delta Current: Line is Root-3 times Phase.

Ohm's Law states that resistance (R) is equal to voltage (V) divided by current (I), expressed as R = V/I.

• Resistance is measured in ohms (Ω).
• Voltage is measured in volts (V).
• Current is measured in amperes (A).
• This fundamental law relates voltage, current, and resistance in DC circuits and resistive AC circuits.

Memory trick: V over I times R, the Ohm's Law, is clear.

The total resistance of resistors in parallel is calculated by summing the reciprocals of individual resistances and then taking the reciprocal of that sum.

• 1/Rt = 1/R1 + 1/R2 + ... + 1/Rn
• Total resistance is always less than the smallest individual resistor.
• Current divides among parallel branches.

Memory trick: Parallel paths means reciprocal sums, making total smaller.

Voltage drop is the reduction in electrical potential along the length of a conductor due to its resistance. It is calculated using Ohm's Law (V = I * R).

• Calculated as Vd = I * Rconductor.
• High voltage drop leads to reduced efficiency and performance.
• NEC limits maximum permissible voltage drop for feeders and branch circuits.

Memory trick: Voltage 'Drops' when Current 'Runs' through Resistance.

Apparent power (S) in a three-phase circuit is the product of the line voltage, line current, and the square root of 3, expressed in volt-amperes (VA) or kilovolt-amperes (kVA).

• Formula: S = √3 * V_L * I_L (for VA) or S = (√3 * V_L * I_L) / 1000 (for kVA).
• V_L is line-to-line voltage, I_L is line current.
• Apparent power includes both real and reactive power.
• Power factor and efficiency are not directly used to calculate apparent power itself.

Memory trick: Apparent is Hypotenuse, Real is Adjacent, Reactive is Opposite.

The National Electrical Code (NEC) recommends maximum voltage drops of 3% for feeders and 3% for branch circuits (total 5% from service to farthest outlet) to ensure efficient operation and prevent equipment damage.

• 3% maximum for feeders.
• 3% maximum for branch circuits.
• Total maximum of 5% from service entrance to the farthest outlet.
• Recommendations are not mandatory unless adopted by local jurisdiction or specified by equipment manufacturer.

Memory trick: Three for Branch, Three for Feed, Five for Total, a good electrical deed.

The turns ratio of an ideal transformer relates the number of turns in the primary and secondary coils to their respective voltages and currents.

• Vp/Vs = Np/Ns (Voltage ratio equals turns ratio).
• Is/Ip = Np/Ns (Current ratio is inverse of turns ratio).
• Np = number of turns in primary coil.
• Ns = number of turns in secondary coil.

Memory trick: Voltage and Turns go hand-in-hand, Current is the inverse demand.

The formula P = V * I calculates the electrical power consumed by a resistive load, where P is power in watts, V is voltage in volts, and I is current in amperes.

• Applies to DC circuits and purely resistive AC circuits.
• Power is measured in watts (W).
• Voltage is measured in volts (V).
• Current is measured in amperes (A).

Memory trick: Volts times Amps gives you Watts of Power.

In a parallel circuit, components are connected across the same two points, sharing the same voltage. The total resistance is always less than the smallest individual resistance.

• Formula: 1/Rt = 1/R1 + 1/R2 + 1/R3 + ...
• Voltage is the same across all parallel components.
• Current divides among the branches.

Memory trick: Parallel is 'P' for 'Product-over-Sum' (for two) or 'Reciprocal Sum' (for many).

The formula I = P / V calculates the current in a circuit when the power consumed and the voltage supplied are known.

• Current (I) is measured in amperes (A).
• Power (P) is measured in watts (W).
• Voltage (V) is measured in volts (V).
• This is a rearrangement of the basic power formula P = V * I.

Memory trick: Power over Voltage gives Current's flow.

In a Wye (star) three-phase connection, the line-to-line voltage is √3 times the phase voltage, and the line current is equal to the phase current.

• V_L = √3 * V_P (Line voltage equals √3 times phase voltage).
• I_L = I_P (Line current equals phase current).
• Provides a neutral point for single-phase loads.
• Commonly used for distribution systems (e.g., 208Y/120V).

Memory trick: Wye is Root 3, Delta is Direct.

In an ideal transformer, the ratio of primary current to secondary current is inversely proportional to the ratio of primary voltage to secondary voltage (or directly proportional to the turns ratio of secondary to primary).

• Formula: Vp/Vs = Is/Ip (or Ip = (Vs * Is) / Vp).
• Assumes 100% efficiency (no losses).
• If voltage steps down, current steps up (and vice versa).

Memory trick: Power In = Power Out; Voltage and Current swap their ratios!

Reactive power in a three-phase system is the portion of apparent power that does not perform useful work; it is measured in volt-amperes reactive (VAR).

• Calculated as Q = √3 * V * I * sin(θ).
• Power factor (PF) = cos(θ).
• Represents energy stored and returned to the source.

Memory trick: Power Triangle: Real is horizontal, Reactive is vertical, Apparent is the hypotenuse.

The total current in a series circuit is the same through all components and is calculated by dividing the total voltage by the total equivalent resistance.

• Rt = R1 + R2 + R3 + ...
• I_total = V_total / R_total
• Current is constant throughout the series circuit.

Memory trick: Series: Sum Resistance First, then Ohm's Law for Current.

In a parallel resistive circuit, the reciprocal of the total equivalent resistance is equal to the sum of the reciprocals of the individual resistances.

• Formula: 1/Rt = 1/R1 + 1/R2 + ... + 1/Rn.
• The total resistance in a parallel circuit is always less than the smallest individual resistance.
• For two resistors: Rt = (R1 * R2) / (R1 + R2).
• Voltage is the same across all branches.

Memory trick: Reciprocal sum for parallel, less than the smallest for all.

Real power (P) in a three-phase purely resistive circuit is calculated as the product of the square root of 3, line voltage, line current, and a power factor of 1 (since it's purely resistive).

• Formula: P = √3 * V_L * I_L * PF (where PF = 1 for purely resistive).
• Measured in watts (W) or kilowatts (kW).
• V_L is line-to-line voltage, I_L is line current.
• Purely resistive loads have a power factor of 1.

Memory trick: Root three Volts Amps Power Factor, that's the real power factor.

The actual power consumed by a single-phase AC load, calculated as Voltage × Current × Power Factor.

• P = V × I × PF
• Power factor (PF) represents the efficiency of power usage.
• Measured in watts (W) or kilowatts (kW).

Memory trick: Single phase, V-I-PF, just multiply.

The actual power consumed by a three-phase load, measured in watts (W) or kilowatts (kW), considering voltage, current, and power factor.

• Calculated as P = √3 × V × I × PF.
• Power factor (PF) accounts for reactive power.
• Represents the useful work done by the circuit.

Memory trick: Real Power is Root-3 times Voltage, Current, and Power Factor.

In a series circuit, components are connected end-to-end, forming a single path for current. The total resistance is the sum of the individual resistances.

• Formula: Rt = R1 + R2 + R3 + ...
• Current is the same through all components.
• Voltage drops across each resistor add up to the source voltage.

Memory trick: Series is simply SUMS: sum the resistance, sum the voltage drops.

Ohm's Law states that the current (I) in a circuit is equal to the voltage (V) divided by the resistance (R).

• I = V / R
• Fundamental to circuit analysis.
• Applies to DC circuits and resistive AC circuits.

Memory trick: Current 'I' is Voltage 'V' over Resistance 'R'.

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Resistance (R) is calculated by dividing voltage (V) by current (I).

• Formula: R = V / I.
• Units: Resistance in Ohms (Ω), Voltage in Volts (V), Current in Amperes (A).
• Always ensure current is in Amperes before calculation.

Memory trick: V over I times R, V over I times R, V over I times R. That's Ohm's Law for me!

The maximum number of conductors permitted in a conduit based on conductor type, size, and conduit size, as specified in NEC Chapter 9 Tables C.1 through C.12.

• Prevents overheating and facilitates conductor installation.
• Tables are specific to conduit type (EMT, RMC, PVC) and conductor type (THHN, XHHW).
• Fill percentage limits apply if not using tables (e.g., 40% for 3+ conductors).

Memory trick: NEC Tables C: Conductor Count, Conduit Choices.

Real power in a single-phase resistive circuit is the actual power consumed by the load, converted into heat or useful work. It is measured in Watts (W).

• Calculated as P = V * I.
• For purely resistive loads, power factor is 1.
• Represents the power doing useful work.

Memory trick: Power is like a 'VIP' - Voltage x Current gives Watts.

Resistance can be calculated from power and voltage using R = V² / P, or by first calculating current (I = P/V) and then applying Ohm's Law (R = V/I).

• P = V × I, P = I² × R, P = V² / R
• Can derive resistance if power and voltage are known.
• Applies to DC circuits and resistive AC circuits.

Memory trick: Power's Voltage-Squared over Resistance, or first find Current.

Evaluating megohmmeter readings to determine the health and integrity of electrical insulation, typically using industry rules of thumb or specific standards.

• Higher resistance is better
• Readings depend on voltage and equipment type
• Trends over time are important

Memory trick: Resistance Rule: 1 Megohm per 1000V + 1 MΩ is a good start!

A precise method for measuring the resistance of a grounding electrode to earth using three test probes, commonly known as the Three-Point Test.

• Requires disconnecting the electrode from the system.
• Uses two auxiliary electrodes (current and potential).
• Measures earth resistance by varying the distance of the potential probe.

Memory trick: Fall of Potential: The Gold Standard for Ground.