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Construction Electrician (309A) Red Seal Exam in Ontario

Certifying authority: Skilled Trades Ontario (STO). Last checked 2026-09-10.

Certification is required in Ontario

This trade is on Ontario’s compulsory list as Electrician — Construction and Maintenance (309A). Under Skilled Trades Ontario, workers must hold a valid Certificate of Qualification, a Provisional Certificate of Qualification, or a Registered Training Agreement; journeypersons must renew their C of Q each year. Official list PDF is dated Feb 2022; the count of 23 still matches the current STO page.

Source: Skilled Trades Ontario — Compulsory Trades (23 trades)

Preparing for the Construction Electrician (309A) exam in Ontario?

Start with 10 free interactive Construction Electrician (309A) questions with worked explanations, or take a full 100-question timed mock exam weighted to the official RSOS breakdown.

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Or unlock all Construction Electrician (309A) questions with the 7-Day Pass ($9.99) or 3-Month Pass ($69.99, Free-Until-You-Pass Guarantee).

Whether it is required or not, the exam itself is the same paper everywhere in Canada. What your province decides is whether you must hold the certificate, how you apply, and where you sit it.

The exam: 100 questions, 5 Major Work Activities

The Red Seal Occupational Standard sets the split below. It does not change by province.

Major Work ActivityWeightingQuestions
MWA A: Performs common occupational skills 11% 11 Qs
MWA B: Installs, services and maintains generating, distribution and service systems 28% 28 Qs
MWA C: Installs, services and maintains wiring systems 30% 30 Qs
MWA D: Installs, services and maintains motors and control systems 21% 21 Qs
MWA E: Installs, services and maintains signalling and communication systems 10% 10 Qs

Source: Red Seal Exam Breakdown — Construction Electrician (309A), red-seal.ca

Time allowed and pass mark

4 hours, and a 70% pass mark (70/100). These are set provincially rather than by the Red Seal standard, and the four hours is the same whether your paper is 100 or 150 questions.

Confirmed against Skilled Trades Ontario’s Exam Preparation Guide and SkilledTradesBC. Check your own authority before exam day.

Quick 3-Question Construction Electrician (309A) Readiness Check

Click any option (A–D) below to grade yourself immediately and view the worked explanation:

Sample Question 1 of 3
While preparing for an energized voltage verification inside a 600 V motor control centre at a commercial water treatment plant, a construction electrician reviews the workplace arc flash and shock risk assessment procedures before opening the hinged enclosure door. Which Canadian national consensus standard provides the technical guidance for electrical workplace hazard identification, arc flash boundaries, and shock protection selection?
A) CSA B44
B) CAN/ULC-S524
C) CSA Z462
D) CSA C22.2 No. 4
Correct answer: C

CSA Z462 (Workplace Electrical Safety) is the Canadian consensus standard governing electrical hazard assessment, shock approach boundaries, and arc flash PPE selection on jobsites. CSA B44 covers elevators, CAN/ULC-S524 covers fire alarm installation, and CSA C22.2 No. 4 is a product standard for switches.

Sample Question 2 of 3
When a new 1500 kVA distribution transformer at a plant in Becancour is energized with all its secondary loads switched off, the upstream breaker trips at once. A second attempt holds. The plant engineer is puzzled, since nothing is connected. What most likely causes this trip?
A) Magnetizing inrush current of several times the full-load current
B) Loss of the neutral connection on the secondary side
C) Load current drawn by the equipment connected downstream
D) A short circuit that exists inside all new transformers
Correct answer: A

On energization, a transformer core can draw a magnetizing inrush of roughly 8 to 12 times full-load current for a few cycles, depending on the point on the wave. Protection is set to ride through it. It is not load current or a permanent fault.

Sample Question 3 of 3
A monthly emergency lighting test at a factory in Cambridge has found two units with dim heads, which have been repaired. The local fire code asks for records to be kept, and the plant's maintenance schedule has a test log. What should be written in this log?
A) The date and the tester's name only, as repairs show on the unit's own label
B) The units found faulty only, as the ones that passed do not need any record
C) A general note saying that the test has been done, with no details about units
D) The date, the units tested, what was found and repaired, and the tester's name
Correct answer: D

A useful record shows the date, each unit, the findings and repairs, and who tested. Labels do not hold the history, passing units must also show as tested, and a general note gives no details.

Where you write it in Ontario

Booking is handled by Skilled Trades Ontario (STO); confirm current locations and dates with them.

Preparing for the Construction Electrician (309A) exam

Our Construction Electrician (309A) question bank is built to the official RSOS weighting above, with a worked explanation and code citation on every question.

Continue to Full 10-Question Interactive Construction Electrician (309A) Quiz → Take the full 100-question timed mock exam →

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