Israel Electrician Licensing Exam common mistakes
Israel Electrician Licensing Exam · Understand the traps and how to avoid them.
When calculating voltage drop on a long feeder, the candidate uses the nominal current of the protective device instead of the design current Ib, or omits the 2× factor for a single-phase two-wire circuit and the √3 factor for a three-phase circuit, so the answer is off by a factor of two or more.
The voltage-drop formula is memorized as a single expression without the circuit-topology variants, and candidates confuse the rated current In of the breaker with the actual load current. Under time pressure they also forget that the tabulated mV/A/m values already embed the single-phase return path only for the two-core column.
What to do instead
Before computing, write the topology on the answer sheet (single-phase two-wire, three-phase, or three-phase with neutral) and select the matching formula from the table column. Use Ib for the load and verify Ib ≤ In ≤ Iz as a separate check. Practice five worked examples per topology until the factor selection is automatic.
The candidate sizes a cable from the tabulated current-carrying capacity alone and skips the correction factors for ambient temperature, grouping, thermal insulation, and installation method, so the selected cross-section is too small for the actual conditions.
Reference tables are studied as a lookup exercise and the derating factors appear as separate tables that are not mentally linked to the main selection step. Candidates also treat the installation method as a property of the room rather than of the route.
What to do instead
Adopt a fixed four-step routine: determine the installation reference method, apply Ca, Cg, and Ci to get Iz, then check Ib ≤ In ≤ Iz, then verify voltage drop and disconnection time. Write the applied factors and the resulting Iz on the working sheet so the examiner can follow the chain.
When asked about disconnection times and protective-device selection in a TN system, the candidate quotes the general 0.4 s or 5 s limit without checking the supply voltage and circuit type, and does not verify that the loop impedance Zs is low enough for the device's magnetic or instantaneous trip.
The time limits are memorized as isolated numbers, and the connection between Zs, the device's current-time curve, and the permitted disconnection time is not practiced. Candidates also mix up final circuits and distribution circuits.
What to do instead
For every disconnection question, state the system type, the circuit category, the applicable time limit, and then show the Zs calculation against the device's trip current from its curve. Build a one-page table linking device rating, curve, trip multiple, and maximum Zs, and rehearse it.
The candidate answers RCD questions by stating that a 30 mA device protects against all electric shock, without distinguishing additional protection from fault protection, without mentioning that a TN-C system cannot have the PEN conductor downstream of the RCD, and without noting that a 30 mA RCD does not remove the need for automatic disconnection.
The 30 mA figure is over-learned as a slogan. The role of the RCD in supplementary protection and the earthing-arrangement constraints on where it may be installed are understood only superficially.
What to do instead
For each RCD question, write three lines: what the device detects, what protection role it performs (fault, additional, or fire), and the earthing constraint on its position. Revise the TN-C, TN-S, TN-C-S, and TT differences with a sketch of each before attempting the question.
In questions on residual current devices and overcurrent protection coordination, the candidate selects a device by its rated current only and ignores the breaking capacity, the selectivity with the upstream device, and the discrimination between the service fuse and the main breaker.
Protection-device selection is learned as a rating-matching exercise, and breaking capacity and selectivity are treated as installation-level concerns rather than examinable design parameters.
What to do instead
When a device is proposed, check four properties explicitly: In against Ib, breaking capacity against the prospective short-circuit current at that point, trip curve against the load's starting current, and selectivity against the upstream device. State each check in one sentence in the answer.
The candidate performs an insulation resistance test and reports the raw reading without stating the test voltage, the minimum acceptable value, the need to disconnect sensitive equipment and electronics, and the requirement to test between all live conductors and between live conductors and earth.
Testing is studied as a list of instruments rather than as procedures with preconditions and acceptance criteria. Candidates also forget that a reading taken with equipment connected is meaningless.
What to do instead
For every test question, answer in a fixed template: purpose, instrument, test voltage, what is isolated or disconnected, the connections made, the acceptance criterion, and the interpretation of a failed result. Rehearse the template for insulation resistance, continuity, loop impedance, RCD trip time, and polarity.
Given a fault symptom such as a breaker tripping immediately on energization, the candidate jumps to replacing the breaker or the appliance instead of reasoning through the fault types: short circuit, earth fault, overload, or a faulty RCD, each of which produces a different tripping pattern.
Fault diagnosis is answered from experience with a single familiar case, and the discriminating evidence (trip timing, whether the RCD or the MCB trips, whether the fault appears only under load) is not systematically used.
What to do instead
Build a decision tree keyed on observable evidence: instantaneous trip on an MCB indicates a short or earth fault, delayed trip indicates overload, RCD-only trip indicates leakage, and intermittent trip indicates a loose connection or thermal fault. Then state the confirming measurement for each branch.
On motor questions, the candidate calculates slip or starting current using the wrong reference (synchronous speed instead of rotor speed, or full-load current instead of locked-rotor current) and ignores the effect of the starting method on the supply and on protection settings.
The formulas are recalled without the physical picture of the rotating field, and direct-on-line, star-delta, soft starter, and inverter starting are memorized as names rather than as different current and torque profiles.
What to do instead
Draw the speed-torque curve for each starting method and mark the operating point. Compute slip as (ns − n)/ns with ns from frequency and pole pairs. For protection, state how the setting must accommodate the starting current without tripping.
The candidate answers transformer questions by treating the transformer as ideal, so the secondary voltage is computed as turns ratio times primary voltage without accounting for regulation, and the current ratio is inverted or the kVA rating is treated as a kW rating.
Ideal-transformer relations are learned first and never replaced by the loaded model. The distinction between apparent power rating and real power delivered is also blurred.
What to do instead
For each transformer problem, state whether the question assumes an ideal transformer; if not, apply the voltage regulation as a percentage drop at the stated load and power factor. Always check the kVA-to-kW conversion with the load power factor before finalizing.
In safety questions, the candidate describes rescue and first-aid actions in the wrong order, for example touching or moving the casualty before isolating the supply, or starting CPR without ensuring the scene is safe and without calling for help.
First aid is revised as a list of steps without the underlying principle that rescuer safety precedes casualty care, and the specific hazard of a casualty still in contact with a live conductor is not emphasized in study.
What to do instead
Learn the sequence as a fixed chain: make the scene safe and isolate or separate the supply using an insulated object, call for help, assess responsiveness and breathing, then begin CPR or recovery position as indicated, and hand over to emergency services. Rehearse the chain aloud for electrical-contact, arc-flash, and fall-from-height scenarios.
The candidate cites SI 100 or SI 900 by number for a requirement without knowing which part or which standard actually governs the topic, and mixes Israeli requirements with remembered requirements from other national codes.
Standards are studied as titles rather than as scopes, and candidates who have seen foreign code material import requirements that differ from the Israeli code, especially in earthing arrangements and permitted wiring methods.
What to do instead
Maintain a one-page map of the standards: SI 100 for installation requirements, SI 900 for the application of residual current devices, and the relevant product and testing standards, each with a one-line scope note. When answering, name the standard and the requirement it imposes, and flag anything uncertain rather than guessing a clause number.
The candidate confuses earthing and bonding, describing main equipotential bonding as a means of fault current return, or omitting the requirement that bonding conductors connect extraneous conductive parts to the main earthing terminal.
The two functions are taught together and the distinction between protective earthing of exposed conductive parts and equipotential bonding of extraneous conductive parts is not sharpened. The purpose of bonding, equalizing potential to prevent touch voltage, is lost.
What to do instead
State the definition of each term before answering: earthing provides a fault current path, bonding equalizes potential between simultaneously accessible parts. For any question, identify whether the part is exposed or extraneous and which conductor is required, and sketch the main earthing terminal with its connections.
The candidate calculates load current for a three-phase installation using single-phase formulas, or sums the connected loads arithmetically without applying diversity, and then selects a supply capacity that is either grossly oversized or inadequate.
Maximum demand estimation is treated as simple addition, and the diversity factors for domestic and commercial installations are not practiced. The √3 factor is also dropped under time pressure.
What to do instead
Work in a fixed order: list the loads with their ratings, apply the diversity factor per load category, sum the diversified demand, convert to current using the correct three-phase or single-phase formula, and then check the result against the supply rating and the main breaker.
The candidate answers protection-against-electric-shock questions by naming the measure (for example, automatic disconnection) without stating the conditions that make it effective: the earthing system, the disconnection time, the loop impedance, and the supplementary measures required in special locations.
Measures are memorized as labels, and the conditions of effectiveness are treated as separate facts rather than as part of the measure itself. Special locations such as bathrooms and wet areas are especially weak.
What to do instead
For each protective measure, answer with the measure, its principle, the conditions for effectiveness, and the additional measures for special locations. Prepare a table of bathroom zones with the permitted equipment and the supplementary bonding or RCD requirements for each zone.