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PEC: wiring methods and materials: board exam questions with solutions

On the RME exam under Philippine Electrical Code, Parts 1 and 2. Try each question before you open its solution.

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Build it in the lab

Wires and cables: types, sizes and pulling: the same circuits on a live bench, with meters you can move.

Questions

1. For a conduit containing three or more conductors (not a short nipple), what is the maximum percentage of its internal cross-sectional area the conductors may fill?

  1. 40%
  2. 31%
  3. 53%
  4. 60%
Show the answer and solution

Answer: A. 40%

Chapter 9, Table 1 limits fill to 53% for one conductor, 31% for two, and 40% for three or more.

Reference: PEC 2017 Part 1, Chapter 9, Table 1

2. A conduit has an internal cross-sectional area of 530 mm². Each insulated conductor to be installed has an overall area of 33.6 mm². What is the maximum number of these conductors permitted?

  1. 8
  2. 6
  3. 15
  4. 4
Show the answer and solution

Answer: B. 6

Allowable area at 40% fill = 0.40 × 530 = 212 mm². 212/33.6 = 6.31, so at most 6 conductors (round down).

Reference: PEC 2017 Part 1, Chapter 9, Table 1

3. Between two pull points (for example, box to box) in a run of rigid metal conduit or EMT, the total of all bends may not exceed:

  1. 180°
  2. 270°
  3. 360°
  4. 450°
Show the answer and solution

Answer: C. 360°

The raceway articles limit the bends between pull points to the equivalent of four quarter bends, 360° total, so conductors can be pulled without damage.

Reference: PEC 2017 Part 1, Art. 3.44 (RMC) and Art. 3.58 (EMT)

4. Why must all the conductors of an AC circuit, including the neutral and equipment grounding conductor, be run in the same metal raceway?

  1. To reduce the conduit fill percentage
  2. To allow smaller conductors to be used
  3. To permit splices inside the raceway
  4. To keep the magnetic fields cancelling so the metal raceway is not heated by induction
Show the answer and solution

Answer: D. To keep the magnetic fields cancelling so the metal raceway is not heated by induction

If the conductors of a circuit are separated, the net magnetic field around each conductor induces eddy currents and heating in the surrounding ferrous metal. Grouping them makes the fields cancel.

Reference: PEC 2017 Part 1, Art. 3.0 (Wiring Methods)

5. When calculating box fill, a box contains four equipment grounding conductors entering with different cables. How are they counted?

  1. All of them together count as a single conductor volume (based on the largest)
  2. Each counts as one conductor, four in all
  3. They are not counted at all
  4. Each counts as two conductors
Show the answer and solution

Answer: A. All of them together count as a single conductor volume (based on the largest)

All equipment grounding conductors in a box together count as one conductor volume allowance, based on the largest EGC present.

Reference: PEC 2017 Part 1, Art. 3.14 (Boxes: box fill calculations)

6. Where are splices and taps of conductors permitted in a conduit wiring system?

  1. Anywhere inside the conduit if taped
  2. Only in boxes, conduit bodies or other accessible enclosures
  3. Inside the conduit at any coupling
  4. Inside the wall cavity outside the raceway
Show the answer and solution

Answer: B. Only in boxes, conduit bodies or other accessible enclosures

Conductors in raceways must be continuous between outlets, boxes and devices. Splices go in boxes, conduit bodies or fittings that remain accessible.

Reference: PEC 2017 Part 1, Art. 3.0 (Wiring Methods)

7. What is the maximum conduit fill permitted when a single conductor or cable is installed in a conduit (not a short nipple)?

  1. 31%
  2. 40%
  3. 53%
  4. 60%
Show the answer and solution

Answer: C. 53%

Chapter 9, Table 1 allows 53% for one conductor, 31% for two and 40% for more than two.

Reference: PEC 2017 Part 1, Chapter 9, Table 1

8. Six current-carrying 3.5 mm² conductors are installed in one raceway. Each conductor's ampacity before adjustment (after temperature correction) is 30 A. Applying the adjustment factor for 4 to 6 current-carrying conductors, what is the adjusted ampacity?

  1. 30 A
  2. 21 A
  3. 15 A
  4. 24 A
Show the answer and solution

Answer: D. 24 A

The adjustment factor for 4 to 6 current-carrying conductors in a raceway is 80%. Adjusted ampacity = 30 × 0.80 = 24 A.

Reference: PEC 2017 Part 1, Art. 3.10 (Conductors for General Wiring: adjustment factors for more than three current-carrying conductors)

Other topics in the same subjects

PEC Part 1: general requirements · PEC: branch circuits, ampacity and protection · PEC: grounding and bonding · PEC: special occupancies and equipment

An independent, free reviewer: not affiliated with the PRC or the Boards. Subject weights and passing rules are from the PRC examination programs and the laws (RA 9292, RA 7920); check the current PRC program before you file. Code questions follow the Philippine Electrical Code 2017 Part 1; check them against your own copy of the Code.