LEP Philippines: Scenario-First Electrical Review Plan

The useful angle for reviewing the Licensed Electrical Practitioner credential in the Philippines is constraint-first problem solving: scenario-style items can embed several valid requirements — load classification, ampacity with derating, voltage drop, protection coordination — inside one fact pattern, and a calculation without a named governing constraint is only half a decision. This guide teaches the named concepts, two worked scenarios contrasting the plausible wrong move with the better decision, a decision table separating protection types, a documentation drill with a rubric, and an adaptable sequence. Start today by classifying every practice load as continuous or not, in writing, before computing anything.

Name the Load Type Before You Touch Any Formula

Classify each load as continuous or non-continuous and decide whether a demand factor applies before any arithmetic. These determinations set the target ampacity and protection value, so an unlabeled calculation usually needs full rework.

In common wiring practice, loads expected to run at maximum current for three hours or longer are treated as continuous, because conductor heat has time to accumulate and sizing rules respond by enlarging the minimum conductor and protection values. Non-continuous loads cycle or run briefly, and ordinary sizing applies. When a scenario states operating hours, shift schedules, or a phrase like 'runs continuously,' that sentence is the cue: classify the load in writing before computing a single value, since it changes both targets downstream.

Demand factors and the continuous-load adjustment are different tools pointing in opposite directions. A demand factor reduces connected load to the maximum demand a feeder or service is actually expected to carry — in a labeled illustration, 20 kW of connected load with a 0.7 demand factor becomes a 14 kW design demand. The continuous-load adjustment then enlarges that design value if the load runs continuously. Confusing the two, or applying them in the wrong order, either overstates or understates the conductor you need; label each factor on your worksheet.

Scenario 1: A Continuous Load on a Long Run

This scenario pairs the continuous-load enlargement with a voltage-drop check. The tempting single-step answer from the load current alone fails both gates, so run the sizing rules in order and record each one.

Worked example with illustrative values, not actual code tables: a workshop lighting load draws 30 A continuously, fed by a 60 m two-wire run at 230 V. The tempting move is to select a 30 A protection device and whatever conductor just carries 30 A. That skips the continuous-load rule: the minimum conductor ampacity becomes 30 × 1.25 = 37.5 A, and the protection must coordinate with that enlarged value. An answer computed directly from 30 A fails before any table is even opened.

Next comes the second gate. Suppose the conductor meeting 37.5 A has an example resistance of 2.0 Ω per 1,000 m: total loop resistance is 2 × 0.060 km × 2.0 Ω/km = 0.24 Ω, giving a drop of 30 A × 0.24 Ω = 7.2 V, about 3.1% of 230 V. If your code edition recommends roughly 3% for a branch circuit, this run fails the performance check even though ampacity passed. The better decision is the next larger conductor size, confirmed against that edition's actual tables, percentages, and conductor data.

Scenario 2: Motor Overload and Short-Circuit Protection Are Different Decisions

Overload and short-circuit protection serve different purposes and take different sizing sources. Treating them as one decision produces either nuisance tripping at start or silent overheating, so name which protection each number serves.

Worked example: a motor nameplate lists a full-load current of 28 A with a service factor of 1.15. A common wrong move is to set the overload relay and the branch-circuit short-circuit device from the same 28 A figure. The overload relay protects against sustained moderate overcurrent, so it is set near the nameplate value, adjusted for service factor and ambient conditions. The short-circuit device must instead remain closed through the large inrush present at every start, so motor-circuit provisions permit it far above running current.

The better decision keeps the two decisions separate: overload from the nameplate, short-circuit protection from the motor provisions of your code. Why it matters: one conflation produces opposite failures — a device sized only for running current trips on every start, while an overload set too high quietly allows overheating. On paper, name which protection each number serves before citing any table, and record whether the current value came from the nameplate or from a table.

Stack Derating Factors Against the Table, Not the Load

Correction factors multiply the table ampacity, not the load, and terminal temperature ratings cap which column you may claim. Fixing the order of operations here protects every downstream sizing result.

Derating factors multiply the table ampacity, never the load. Illustrative example: a conductor's base value in a 90°C column is 100 A; an ambient correction factor of 0.88 and a grouping factor of 0.80 for bundled conductors give 100 × 0.88 × 0.80 = 70.4 A effective. The failure pattern is arithmetic done on the wrong operand — dividing the load current by the factors, or applying them to the protection setting — which quietly inflates the margin you believe you have.

Column selection adds a second layer. Terminal and equipment temperature ratings commonly cap which column you may claim, so a 90°C-column value often cannot be used at a 75°C termination; verify the cap in your code edition. A reliable order of operations: take the base table value, multiply the correction factors, confirm the result meets the load-driven minimum, check the termination-rated column, then record which table, column, and factors you used. That written trail is what makes an answer defensible.

Treat Voltage Drop as a Separate Gate with Its Own Formula

Voltage drop is a performance gate separate from the thermal ampacity limit. Compute it for longer runs counting both conductors' length, record the percentage, and upsize when the recommendation for that circuit is exceeded.

Ampacity is a thermal limit protecting the conductor; voltage drop is a performance limit protecting the equipment. A run can satisfy the sizing tables and still deliver undervoltage at the load, which is why the two are separate gates rather than one calculation. For a two-wire circuit, count both conductors' length in the loop: drop in volts equals load current times the total loop resistance, and dividing by supply voltage converts it to the percentage form most recommendations use.

Equipment behavior explains the stakes. Motor torque varies approximately with the square of applied voltage, so a modest percentage drop can noticeably reduce starting torque; lamps dim; some electronics misbehave. Treat such relationships as reasoning aids only — the governing percentage for your scenario comes from the applicable code edition. Build the habit of computing drop for every run beyond a short length and recording the result even when it passes, so the check is visible on paper rather than assumed.

A Decision-Sheet Exercise That Forces Written Justification

Complete a one-page decision sheet per practice scenario: facts, classification, governing constraint, formula, cited table, result, residual checks, safety flags. Score against the rubric below and let blank lines direct your next review session.

Exercise: take ten practice scenarios — the free practice set on this site works as raw material — and complete one decision sheet per scenario, a single page listing the given facts, the load classification and its cue, the governing constraint named first, the formula, the table and column cited, the result, residual checks such as voltage drop, and any safety flags. Use illustrative numbers or your codebook's own tables; the goal is the written trail, not speed on the first pass.

Expect the first sheets to take several times longer than the later ones; the pattern should feel automatic somewhere around the sixth to eighth sheet. If the 'table cited' line stays blank, that is the signal to schedule code-navigation practice rather than more calculations. For scenarios involving troubleshooting energized equipment, the correct paper answer names the safety requirement — verifying absence of voltage, applying lockout/tagout, securing a permit — as a documented step; treat this as recognition, not a physical procedure to attempt unsupervised.

• Governing constraint stated in one sentence before any arithmetic appears on the page.
• Every number traceable to a named table and column, a given fact, or a labeled formula.
• Both gates shown: ampacity with correction factors, and voltage drop with the recorded percentage.
• Load classification written together with the scenario cue that supports it.
• Safety flags identified for energized-work or permit cues, and scope of practice noted where the scenario raises it.

An Adaptable Review Sequence Built Around Constraint-First Drills

Sequence your review as concept inventory, single-constraint drills, combined-gate problems, timed mixed sets, then code navigation. Readiness means stating the governing constraint first and completing sheets without rework — not any predicted score.

An adaptable sequence: start with a concept inventory — define each named concept above, its trigger cue, and the operand each factor applies to. Move to single-constraint drills, one check per problem, until the formulas are automatic. Then combine two gates per problem, then run timed mixed sets with decision sheets. Finish with code-navigation sessions in which you locate specific tables and provisions under time pressure. Shift emphasis toward whichever stage your rubric scores expose as weakest.

Readiness checks: you can state the governing constraint for an unfamiliar scenario before computing; you complete decision sheets without rework; you find cited tables quickly enough to keep pace; and you can explain aloud why the overload and short-circuit decisions differ. Self-check scores are learning milestones, not passing predictions. One administrative note: schedules, applications, requirements, and each credential's official scope are published by the Professional Regulation Commission at prc.gov.ph, which also cautions that it does not endorse review materials and warns against unofficial pages and fixers.

References and further reading

Use these references to explore the concepts and check the latest information from the relevant organizations.

• prc.gov.ph

Continue your preparation

• Licensed Electrical Practitioner Lep Philippines
• Study Guides