Exam Cheat Sheet · Quick Reference
South Carolina Residential Electrical
South Carolina · PSI Services Contractor
Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.
Total questions
60
Passing score
74%
Exam time
180 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
South Carolina State Portion 60 questions
General Electrical Knowledge
13 Q · 22%
Calculate voltage, current and resistance in series, parallel and combination circuitsCalculate power used in a circuitUnderstand and apply fundamental ac theoryCalculate voltage drop for branch circuits or feedersTroubleshoot and test systemsUnderstand and apply definitionsInstall smoke alarmsRead and interpret blueprints and drawingsPerform quantity take-offsEnsure structural requirements not compromised
Services, Feeders, and Branch Circuits
15 Q · 25%
Install servicesInstall feedersInstall branch circuitsInstall temporary installationsInstall motors used in dwellingsInstall three-phase service
Overcurrent Protection
5 Q · 8%
Understand and apply knowledge of NEC overcurrent protection requirements
Grounding and Bonding
6 Q · 10%
General requirementsUse tables to obtain the required sizes of grounding electrode conductorUse tables to obtain the required sizes of equipment grounding conductor
Conductors and Cables
5 Q · 8%
Install underground conductors and cablesPerform vertical installationsSelect a conductorArmored Cable Type ACMetal-Clad Cable Type MCNonmetallic-Sheathed Cable Type NM, NMC, NMSService Entrance Cables: Type SE and USEUnderground Feeder and Branch Circuit Cable Type UF
Raceways and Boxes
4 Q · 7%
Understand and apply general raceway requirementsUnderstand and apply general box requirementsInstall RMC (rigid metal conduit)Install EMT (electric metallic conduit)Install IMC (intermediate metal conduit)Install RNC (rigid non-metallic conduit)Install FMC (flexible metal conduit)Install LFMC (liquid-tight flexible metal conduit)Install FMT (flexible metallic tubing)Calculate area of raceway and number of conductors (conduit fill)Install outlet, device, pull and junction boxesCalculate box volume and fill
Lighting
4 Q · 7%
Install fixturesGround fixturesInstall fixture wiringUnderstand fixture construction requirementsInstall fluorescent fixturesInstall recessed fixturesInstall switches
Specialty – pool/spa, garages, generators, wheelchair lifts
4 Q · 7%
Install wiring for pools, spas and hot tubsInstall bonding and grounding for swimming pool, hot tub and spa bonding and all associated equipmentInstall pool, spa and hot-tub lightingInstall generatorsInstall wheelchair liftsInstall equipment in garages
Safety
4 Q · 7%
Understand Responsibility for Providing Personal Protective EquipmentPrepare Emergency Action PlansEnsure Safety Training is Conducted when NeededEnsure First Aid Kit is Available per RequirementsEnsure Personal Protective Equipment is Used CorrectlyUse All Tools and Equipment in Accordance with RequirementsUtilize Ladders in Accordance with RequirementsMaintain Material Safety Data Sheets (MSDS)Provide Fall Protection
Key Distinctions
Motor nameplate amperesvsFull-load current (NEC tables)
Overload heater elements are sized from the nameplate amperes, while branch-circuit conductors, switch ratings, and short-circuit protection are sized from NEC full-load current tables.
NEC Handbook, Section 430.32Main bonding jumpervsSystem bonding jumper
The main bonding jumper is used only at the service, while the system bonding jumper connects the grounded circuit conductor to the EGC at a separately derived system such as a transformer.
NEC Handbook, Article 100 (Definition: Bonding Jumper, System)Single-phase ampere formulavsThree-phase ampere formula
Single-phase: I = (kW × 1000) ÷ (E × PF); three-phase adds the factor 1.73 (√3) in the denominator: I = (kW × 1000) ÷ (E × PF × 1.73).
NEC Handbook, Section 220.5(A)THHN insulationvsTHW insulation
THHN is rated 90°C for dry and damp locations only, while THW is rated 75°C and is approved for both dry and wet locations.
NEC Handbook, Section 310.104, Table 310.104(A)Type NM cablevsType USE cable
NM cable is permitted inside one- and two-family dwellings and attached/detached garages, while USE cable is for underground use only and is not permitted for interior wiring.
NEC Handbook, Section 334.10(1)Flexible metal conduit (FMC)vsLiquidtight flexible metal conduit (LFMC)
FMC is not permitted in wet locations, whereas LFMC is permitted for direct burial where listed and marked for the purpose.
NEC Handbook, Section 348.12Equipment grounding conductor (EGC) sizingvsGrounding electrode conductor (GEC) sizing
EGC size is based on the rating or setting of the overcurrent device ahead of the equipment, while GEC size is based on the size of the largest ungrounded service conductor.
NEC Handbook, Section 250.122 / Table 250.122Power-limited fire alarm (PLFA) circuitsvsSmoke alarm branch circuits (120 V)
PLFA circuits must be separated from electric light and power conductors unless specific exceptions apply, while single- and multiple-station smoke alarms in dwellings are supplied by standard 120-volt branch circuits not subject to Article 760.
NEC Handbook, Section 760.136(A)Conductor ampacity > 800 A overcurrent devicevsConductor ampacity ≤ 800 A overcurrent device
When the overcurrent device exceeds 800 A, conductor ampacity must equal or exceed the device rating; the next-higher-standard-size allowance of 240.4(B) does not apply above 800 A.
NEC Handbook, Section 240.4(C)Parallel circuit resistancevsSeries circuit resistance
In a parallel circuit the total resistance is always less than the resistance of any individual branch because additional paths reduce overall opposition, whereas in a series circuit resistances add together.
NEC Handbook, Section 90.1 (Ohm's Law principles); parallel circuit theory as applied in electrical installations2/0 AWG THW copper (200 A dwelling service)vs3/0 AWG THW copper (standard ampacity table)
For a 3-wire, single-phase dwelling unit service, the 83% allowance permits 2/0 AWG THW copper for a 200 A service, rather than the 3/0 AWG that standard ampacity tables would otherwise require.
NEC Handbook, Section 215.2(A)(3)Open conductors (temporary wiring)vsComplete metallic raceway (temporary wiring)
When temporary branch circuits supplying receptacles are run as open conductors, a separate equipment grounding conductor is required; a complete metallic raceway can itself serve as the EGC.
29 CFR 1926, §1926.405(a)(2)(ii)(B)Key Terms
Ampacity correction factor base temperature NEC Handbook, Section 310.15(B), Table 310.16 notes
Per NEC 310.15(B) and Table 310.16, ampacity values are based on a standard ambient temperature of 30°C (86°F); correction factors must be applied when ambient differs from this value.
Dwelling unit lighting load (minimum) NEC Handbook, Table 220.12
Per NEC Table 220.12, the minimum general lighting load for dwelling units is 3 volt-amperes per square foot, calculated from outside dimensions excluding open porches and garages.
Conductor fill adjustment factor (4–6 conductors) NEC Handbook, Table 310.15(C)(1)
Per NEC Table 310.15(C)(1), when 4 through 6 current-carrying conductors occupy a raceway, the tabulated ampacity must be multiplied by 0.80 (80%).
Lighting demand factor — first 3,000 VA NEC Handbook, Table 220.42
Per NEC Table 220.42, the first 3,000 VA (or less) of a dwelling unit's lighting load is calculated at a 100% demand factor; VA from 3,001 to 120,000 uses 35%.
Maximum overcurrent protection — 14 AWG copper NEC Handbook, Section 240.4(D)
Per NEC 240.4(D), the maximum overcurrent protective device for 14 AWG copper conductors is 15 amperes.
Bonding jumper screw identification NEC Handbook, Section 250.28(B)
Per NEC 250.28(B), when a main bonding jumper or system bonding jumper is a screw only, it must be identified with a green finish that is visible with the screw installed.
Earth as ground-fault current path NEC Handbook, Section 250.4(A)(5)
Per NEC 250.4(A)(5), the earth shall not be considered an effective ground-fault current path because its resistance is too high to reliably operate overcurrent devices.
AC system grounding voltage range NEC Handbook, Section 250.20(B)
Per NEC 250.20(B), alternating-current systems of 50 volts to 1000 volts are required to be grounded under specified conditions.
Grounded conductor minimum size (supply > 1100 kcmil Cu) NEC Handbook, Section 250.102(C) / Table 250.102(C)(1)
Per NEC Table 250.102(C)(1) Note 1, when ungrounded supply conductors exceed 1100 kcmil copper, the grounded conductor or bonding jumper must have an area of at least 12½% of the largest ungrounded supply conductor.
Box fill — No. 14 AWG conductor NEC Handbook, Section 314.16(B)
Per NEC Table 314.16(B), each No. 14 AWG conductor requires a 2.0 cubic-inch volume allowance in a box fill calculation.
Box fill — No. 6 AWG conductor NEC Handbook, Section 314.16(B), Table 314.16(B)
Per NEC Table 314.16(B), each No. 6 AWG conductor requires a 5 cubic-inch volume allowance in a box fill calculation.
Maximum bends between pull points (RMC) NEC Handbook, Section 344.26
Per NEC 344.26, a run of rigid metal conduit must not exceed the equivalent of four quarter bends (360 degrees total) between pull points such as boxes or conduit bodies.
FMC fastening requirement NEC Handbook, Section 348.30(A)
Per NEC 348.30(A), flexible metal conduit must be securely fastened within 12 inches (300 mm) of each box, cabinet, conduit body, or other termination.
Working space width (panelboard) NEC Handbook, Section 110.26(A) and (B)
Per NEC 110.26(A)(2), the minimum width of working space in front of electrical equipment is 30 inches (762 mm), and that space must not be used for storage.
K value for copper conductors (voltage drop) NEC Handbook, Chapter 9, Table 8
In voltage-drop calculations where inductance is negligible, the resistance constant K for copper conductors at 75°C is 12.9 ohms per circular mil foot; for aluminum at 75°C, K = 21.2.
Inverse time breaker maximum — single-phase motor NEC Handbook, Table 430.52
Per NEC Table 430.52, the maximum rating for an inverse time circuit breaker protecting a single-phase motor branch circuit is 250% of the motor's full-load current.
Formulas to Know
Single-phase current (kW known)
I = (kW × 1000) ÷ (E × PF)Three-phase current (kW known)
I = (kW × 1000) ÷ (E × PF × 1.73)Multi-motor feeder ampacity (NEC 430.24)
Feeder ampacity = (125% × FLC of largest motor) + sum of FLC of all other motorsConductor ampacity adjustment (conduit fill)
Adjusted ampacity = Base ampacity × Adjustment factor (e.g., 0.80 for 4–6 conductors)Energy saved by lamp replacement
Watts saved = Old lamp wattage − New lamp wattageOperating cost of electrical appliance
Cost = (Watts × Hours used × Rate per kWh) ÷ 1000Voltage drop (DC or single-phase AC, inductance negligible)
VD = (2 × K × I × L) ÷ CM [K = 12.9 for Cu at 75°C; L = one-way length in feet; CM = conductor area in circular mils]Dwelling service conductor ampacity allowance
Minimum allowable ampacity = Service rating × 83% (3-wire, single-phase dwelling)