Mixed Deck — All IEC Topics Flashcards

How many 90-degree bends are permitted between pull points in a conduit run?

Answer: Four 90-degree bends (360 degrees total)

NEC 358.26, 344.26, and related articles limit total bends between pull points to 360 degrees (four 90-degree bends).

The current a motor draws at the instant of starting when full voltage is applied, before the rotor begins to turn, is known as what?

Answer: Locked-Rotor Current (LRC)

Locked-Rotor Current (LRC), also known as Locked-Rotor Amps (LRA), is the inrush current drawn by a motor at startup when the rotor is stationary ('locked'). This current is typically 6 to 8 times the motor's normal full-load current and is a critical value for sizing short-circuit protection and motor controllers.

Under NEC Article 210, which branch circuit type is required for bathroom receptacles in a dwelling unit?

Answer: 20-ampere circuit dedicated to bathroom receptacles

NEC Section 210.11(C)(3) requires at least one 20-ampere branch circuit dedicated to bathroom receptacles in dwelling units.

The term 'effective ground-fault current path' as defined in the NEC is an intentionally constructed, permanent, low-impedance path that facilitates what?

Answer: The operation of the overcurrent protective device during a ground fault

An effective ground-fault current path is designed to carry enough fault current to quickly operate the overcurrent protective device and clear the fault.

When installing a panelboard in a residential garage, what NEC requirement applies?

Answer: Working space clearances of 36 inches depth must be maintained

NEC 110.26 requires a minimum of 36 inches of clear working space in front of electrical panels.

When installing a feeder to a detached garage with its own subpanel, which practice is critical for safety?

Answer: Running a separate equipment grounding conductor from the main panel and keeping the neutral and ground bars isolated in the subpanel.

In a subpanel located in a separate building, the grounded (neutral) conductor and the equipment grounding conductor must be kept separate. A separate equipment grounding conductor must be run with the feeder conductors to provide the effective ground-fault current path back to the main service. Bonding the neutral and ground at the subpanel would create objectionable current on the grounding conductors. A grounding electrode system is also required at the detached structure.

Ground-fault protection of equipment (GFPE) per NEC 230.95 is required on solidly grounded wye services of more than 150V to ground but not exceeding 600V phase-to-phase when the service rating is at least:

Answer: 800A

NEC 230.95 requires GFPE on services rated 800A or more on solidly grounded wye systems meeting the voltage criteria.

What is the maximum amp rating for a circuit breaker that can be installed on a 12 AWG copper circuit conductor connected to multiple receptacles?

Answer: 20-amp

Explanation: A 20-amp circuit breaker is the largest that can be installed on a 12 AWG copper circuit conductor. This is in accordance with the National Electrical Code (NEC) regulations for circuit protection, ensuring that the circuit is adequately protected from overcurrent conditions while using 12 AWG copper conductors.

When installing conductors in parallel (per NEC 310.10(H)), what is the minimum size conductor permitted to be paralleled?

Answer: No. 1/0 AWG

NEC 310.10(H)(1) requires that conductors installed in parallel must be 1/0 AWG or larger.

Per NEC 250.68(A), a grounding electrode conductor must be connected to the grounding electrode in what manner?

Answer: By pressure connectors, clamps, or other listed means

NEC 250.68(A) permits the grounding electrode conductor to be connected using listed pressure connectors, clamps, or other listed means; exothermic welding is not the only method.

At a marina, what is the maximum ground-fault protection (GFP) setting permitted for the main overcurrent device supplying a dock where shore power is provided to boats?

Answer: 100 mA

NEC 555.35(A)(3) requires that feeder and branch-circuit conductors installed on docking facilities be provided with ground-fault protection of equipment (GFPE) set to open at currents not exceeding 100 mA. Receptacles providing shore power have a lower 30 mA requirement.

A new electrical installation has just been completed. According to NEC 110.7, the completed wiring installation must be free from short circuits, ground faults, or any connection to ground that is not...

Answer: required or permitted by the Code.

NEC 110.7 states that completed wiring installations shall be free from short circuits, ground faults, or any connections to ground other than as required or permitted elsewhere in the Code. This is a fundamental safety requirement for all electrical systems.

A 45 kVA, single-phase, 240V/120V transformer is operating at full load. What is the rated primary current?

Answer: 187.5A

Primary rated current = kVA × 1,000 ÷ primary voltage = 45,000 ÷ 240 = 187.5A.

When must a lockout/tagout procedure be re-verified after it has already been established?

Answer: When the work scope changes or new hazardous energy sources may have been introduced

Lockout/tagout must be re-verified whenever the scope of work changes or new energy sources may have been introduced to the isolation.

Under NEC 110.16, electrical equipment in other than dwelling units must be marked to warn qualified persons of potential arc flash hazards. Where must this warning label be located?

Answer: On the equipment so it is visible before examination, adjustment, servicing, or maintenance

NEC 110.16 requires arc flash warning labels to be field-applied to the equipment so the label is visible before examination, adjustment, servicing, or maintenance.

Which of the following is NOT a primary function of an Equipment Grounding Conductor (EGC)?

Answer: To carry the unbalanced neutral current during normal circuit operation.

The Equipment Grounding Conductor (EGC) is a safety conductor and should only carry current during a ground-fault condition. The grounded conductor (neutral) is the conductor designed to carry the unbalanced current in a circuit during normal operation.

What is the maximum unbalanced load used to size the neutral conductor for a 120/240V single-phase service with a 100-ampere load on each hot leg and 80 amperes on the neutral?

Answer: 80 amperes

The neutral conductor must be sized for the maximum unbalanced load, which is 80 amperes in this scenario.

When NM cable passes through a floor, what protection is required?

Answer: The cable must be protected by a minimum 6-inch guard from the floor and a bushing at the top

NEC 334.15(C) requires NM cable passing through a floor to be enclosed in rigid metal conduit, IMC, Schedule 80 PVC, or equivalent protection for at least 6 inches above the floor, with a bushing at the top.

What is the total impedance of a series circuit with R = 6 Ω, XL = 10 Ω, and XC = 2 Ω?

Answer: 10 Ω

Z = √(R² + (XL - XC)²) = √(36 + (10-2)²) = √(36 + 64) = √100 = 10 Ω.

In a commercial repair garage, the area up to 18 inches above the floor is classified as a Class I, Division 2 location. Which wiring method is permitted for fixed wiring installed ABOVE this classified location?

Answer: Electrical Metallic Tubing (EMT)

NEC 511.7(A)(1) permits several wiring methods for fixed wiring above Class I locations in commercial garages, including metal raceways like RMC, IMC, or EMT. Non-metallic sheathed cables like NM and UF are not permitted for this application.