CITS Electrician (Theory) common mistakes
CITS Electrician (Theory) · Understand the traps and how to avoid them.
When calculating voltage drop for a branch circuit, the candidate uses the nominal current (e.g., 15 A breaker rating) instead of the actual load current, or uses the one-way circuit length rather than the total conductor length (out and back).
Textbook examples often simplify with full-load current and round-trip length, but candidates forget that voltage drop depends on the actual current drawn by the load and the total resistance path. They also confuse the 'length of run' with the 'length of conductor'.
What to do instead
Always identify the load current from the appliance nameplate or the calculated demand, and double the one-way distance for the conductor length in the formula VD = 2 × L × R × I (for single-phase). Practise with real-world scenarios where the load is less than the breaker rating and the run is long.
Incorrectly sizing the equipment grounding conductor (EGC) by matching it to the overcurrent device rating rather than to the phase conductor size, or using Table 250.122 without checking the minimum size requirements for specific equipment.
Candidates memorise 'ground wire must be sized per Table 250.122' but forget that the table is based on the rating of the overcurrent device, not the conductor ampacity. They also overlook that for feeders and services, the EGC may be required to be larger if the phase conductors are increased for voltage drop.
What to do instead
Review NEC Table 250.122 and the rules in 250.122(B) regarding proportional sizing when conductors are upsized. Work through examples where the overcurrent device is 200 A but the phase conductors are 4/0 for voltage drop, and determine the correct EGC size.
When selecting a conductor for a given load, the candidate uses the 60°C column of Table 310.16 regardless of the terminal temperature ratings, or ignores the adjustment factors for ambient temperature and number of current-carrying conductors in a raceway.
Many candidates default to the 60°C column because it is conservative, but they fail to check the actual termination ratings (which may be 75°C) and then forget to apply correction and adjustment factors, leading to undersized conductors or incorrect ampacity calculations.
What to do instead
Always start by checking the termination temperature rating (110.14(C)) and use the corresponding column. Then apply ambient temperature correction (Table 310.15(B)(2)(a)) and conductor adjustment for bundling (Table 310.15(C)(1)). Practise with multi-conductor feeders in high-temperature environments.
During troubleshooting, the candidate immediately replaces a blown fuse or tripped breaker without performing any diagnostic tests (e.g., insulation resistance, continuity, or load current measurement) to identify the root cause.
Under exam pressure, candidates jump to the 'obvious' solution, forgetting that a fuse blowing indicates an underlying fault. They also may not have practised a systematic troubleshooting sequence.
What to do instead
Follow a structured approach: isolate the circuit, test for voltage, then test insulation resistance and continuity to locate faults. Memorise the sequence: verify power, check protective devices, test for shorts/ground faults, then measure load current. Use practice scenarios that require identifying the cause before resetting.
When installing a raceway, the candidate ignores the fill requirements of Chapter 9, Tables 1 and 4, and instead uses a 'rule of thumb' like 'no more than 40% fill' without verifying the actual conductor dimensions and raceway type.
Candidates often rely on memory of '40% fill' but forget that the 40% applies only to over two conductors, and that different raceway types have different fill tables. They also may not account for conductor insulation thickness.
What to do instead
Always use the specific table for the raceway type (e.g., Table 1 for EMT) and calculate the total conductor area from Chapter 9, Table 5. Then compare to the allowable fill percentage (53% for one conductor, 31% for two, 40% for over two). Practise with mixed conductor sizes and types.
When determining the minimum ampacity for a service or feeder, the candidate applies the demand factors from Article 220 before calculating the total connected load, or misapplies the optional method versus the standard method.
Candidates confuse the sequence: first calculate the total load, then apply demand factors. They also may not recognise when the optional method (220.82 or 220.84) is permitted and how it differs.
What to do instead
Review Article 220 carefully: for standard method, compute general lighting, small appliance, laundry, and other loads, then apply demand factors as specified. For optional method, ensure the dwelling meets the criteria. Work through examples comparing both methods.
In motor branch-circuit calculations, the candidate uses the motor's nameplate current (FLA) for sizing the overload protection, but uses the same value for sizing the branch-circuit conductors and short-circuit protection, instead of using Table 430.250 for conductor sizing and Table 430.52 for short-circuit protection.
Candidates often treat motor loads like standard appliances and use the nameplate current for all calculations, not realising that the NEC requires different values for different purposes (e.g., 125% of FLC for conductors, 125% of FLA for overloads, and Table 430.52 for branch-circuit protection).
What to do instead
Memorise the steps: determine motor FLC from Table 430.250 (not nameplate), size conductors at 125% of FLC (430.22), size overload protection per 430.32 based on nameplate FLA, and size short-circuit protection per Table 430.52. Practise with various motor types and sizes.
When applying the requirements for Ground-Fault Circuit-Interrupter (GFCI) protection, the candidate only considers bathrooms and kitchens, but misses other locations such as laundry areas, outdoors, garages, and unfinished basements, or fails to recognise that GFCI protection is required for receptacles that are easily accessible and within 6 feet of a sink.
Candidates rely on outdated or incomplete knowledge of GFCI requirements, which have expanded over recent NEC editions. They may not have studied the specific sections (210.8, 210.8(A), etc.) in detail.
What to do instead
Create a checklist of all GFCI-required locations from Article 210.8, including dwelling units, and update for the latest edition. Use flashcards for each location and test yourself on scenarios like a receptacle in a garage or near a laundry sink.
The candidate fails to properly document an electrical installation or maintenance procedure, omitting critical details such as the test results, the specific NEC references used, or the as-built conditions, leading to incomplete or non-compliant documentation.
Candidates focus on technical calculations and forget that proper documentation is part of professional practice. They may not understand what constitutes a complete record for inspections or maintenance.
What to do instead
Study the requirements for documentation in NFPA 70B and local regulations. Practise writing a sample maintenance record that includes: date, equipment ID, tests performed (with values), pass/fail criteria, and corrective actions. Include references to the applicable NEC articles.
When performing insulation resistance testing (megger test), the candidate does not discharge the circuit after testing, or fails to isolate the equipment properly, leading to inaccurate readings or safety hazards.
Candidates may not have hands-on experience with insulation testers and forget the importance of discharging capacitive circuits. They also may not follow lockout/tagout procedures.
What to do instead
Always follow the manufacturer's instructions: isolate and lock out, connect the tester, apply voltage for the specified time, then discharge the circuit through the tester before disconnecting. Practise with a mock circuit and emphasise safety steps.