An LEC has left an ESA invoice unpaid for 45 days and now files a notification for a new commercial job. Under Rules 2-004 and 2-008, what follows?

ESA may refuse it, and the LEC may then do no further work

ESA may refuse it, but work may go on until the fees are paid

ESA must accept it and collect the fees separately

ESA may refuse it only once the fees are 90 days overdue

An office tenant has bought four products online that carry no approval mark of any kind and asks its LEC which of them may be used in its Ontario office, which has no hazardous locations. Under Rule 2-022, which product may be used without approval?

A battery-operated portable label maker for the mailroom

Under-cabinet LED lighting on a separate Class 2 power supply

A heated footrest on a separate Class 2 power supply

A battery-operated clamp meter marked Category III

An LEC pulls new RW90 conductors into an existing conduit that already holds conductors with 75 °C insulation. Under Rule 4-004, on what basis is the ampacity of all the conductors in the conduit determined?

The 75 °C rating of the lowest-rated conductors

The 60 °C column for every conductor in it

Each conductor's own insulation temperature rating

The 90 °C rating of the newly installed conductors

A feeder's phase conductors are RW90. To save cost, the contractor proposes a neutral of the same size with insulation rated 75 °C. Under Rule 4-016, is this permitted?

No; its rating may not be below the phase conductors'

Yes; a neutral carrying only unbalance may be rated lower

Yes; a neutral needs only the phases' voltage rating

No; a neutral in a raceway has to be bare instead

An owner asks for an additional supply service of the same voltage. Under Rule 6-102, which building may receive one?

A one-storey strip plaza whose stores each have their own entrance at grade

A three-storey building with shops below and offices above, each with its own entrance

A 40-unit apartment building, to separate the house loads from the suites

An office building, to supply a large new rooftop chiller plant

The steel reinforcing of a new building's concrete foundation, in contact with earth 1.5 m below grade, will serve as an in-situ grounding electrode. How does Rule 10-102 4) treat it?

It needs no approval mark, but needs earth contact equal to a manufactured one

It needs a certification mark, like any manufactured grounding electrode

It needs no approval mark, but must be backed up by two driven rods at least 3 m apart

It needs a field evaluation label before the connection is accepted

In a new strip plaza unit, a TECK90 cable rated for direct burial will run under the 125 mm concrete floor slab poured at grade to reach an island counter. Under Rule 12-012 9), on what condition may the cable lie directly beneath the slab instead of at Table 53 depth?

Its location and depth are permanently and legibly marked

It is bedded in screened sand at least 450 mm below the slab

It is covered with 38 mm treated planks under the slab

The slab is reinforced and at least 150 mm thick

A lighting contactor in a 347/600 V panel switches an office corridor's lighting circuit, and an upstream breaker is there to clear faults. Under Rule 14-012, what must the contactor's ratings be sufficient for?

The voltage and the load current it must interrupt

The voltage and 125 % of the connected lighting load

The voltage and the fault current available at it

The trip setting of the upstream breaker

A hospital renovation adds a fire pump with its own service box, located away from the other service boxes. Under Rule 32-306, what may be installed between that service box and the fire pump controller?

Only a labelled breaker, lockable closed, that carries locked-rotor current

A red disconnect, lockable in the ON position, identified as the pump supply

A fused switch lockable open, with fuses at 125 % of full-load current

A breaker set at the Table 29 maximum for the motor, lockable closed

Master Electrician Practice Questions: Section 1 OESC

Ten free practice questions on the Ontario Electrical Safety Code: Section 1 of the three sections of Ontario's Master Electrician licensing exam, which ESA, the Electrical Safety Authority, runs. They are original questions written by TicketPrep from the OESC rule numbers and the Ontario statutes, not questions from the exam. Each has four options and one correct answer, as every question in our bank does. Answer each one before opening the explanation. No account, no email.

01The questions

Procedural · Objective 1.1

An LEC has left an ESA invoice unpaid for 45 days and now files a notification for a new commercial job. Under Rules 2-004 and 2-008, what follows?
1. ESA may refuse it, and the LEC may then do no further work
2. ESA may refuse it, but work may go on until the fees are paid
3. ESA must accept it and collect the fees separately
4. ESA may refuse it only once the fees are 90 days overdue
Show the answer

A. Correct. Rule 2-008 lets ESA refuse a notification from anyone with fees or dues owing for more than 30 days, and Rule 2-004 3) says a contractor whose notification is refused must not proceed with any further electrical work.

Why not the others

B. Rule 2-004 3) says the opposite: once ESA refuses the notification under Rule 2-008, the contractor stops all further electrical work.

C. Rule 2-008 gives ESA the right to refuse, and fees owing for more than 30 days are one of its three grounds.

D. The ground in Rule 2-008 is fees owing for more than 30 days, so 45 days already qualifies.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rules 2-008, 2-004
Procedural · Objective 1.1

An office tenant has bought four products online that carry no approval mark of any kind and asks its LEC which of them may be used in its Ontario office, which has no hazardous locations. Under Rule 2-022, which product may be used without approval?
1. Under-cabinet LED lighting on a separate Class 2 power supply
2. A heated footrest on a separate Class 2 power supply
3. A battery-operated clamp meter marked Category III
4. A battery-operated portable label maker for the mailroom
Show the answer

D. Correct. Rule 2-022 1) bars using or selling electrical equipment that is not approved, but 2-022 2) exempts battery-operated portable equipment unless it is for a hazardous location or is a Category III or IV electrical test instrument (2-022 4)). A portable label maker in an office is neither, so it needs no approval.

Why not the others

A. Equipment connected to the output of a Class 2 power supply is generally exempt under Rule 2-022 2), but Rule 2-022 3) still requires approval for luminaires and for lighting equipment that incorporates LEDs, whatever their supply.

B. The Class 2 exemption in Rule 2-022 2) does not reach equipment that incorporates heating elements: Rule 2-022 3) keeps it under the approval requirement even when it is fed from a Class 2 or limited power supply.

C. Battery-operated portable equipment is generally exempt, but Rule 2-022 4) requires approval for a battery-powered electrical test or measuring instrument marked Category III or IV, as this meter is.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rule 2-022
Recall · Objective 1.2

An LEC pulls new RW90 conductors into an existing conduit that already holds conductors with 75 °C insulation. Under Rule 4-004, on what basis is the ampacity of all the conductors in the conduit determined?
1. The 60 °C column for every conductor in it
2. Each conductor's own insulation temperature rating
3. The 90 °C rating of the newly installed conductors
4. The 75 °C rating of the lowest-rated conductors
Show the answer

D. Correct. Rule 4-004 rates conductors of different temperature ratings in one raceway on the conductor with the lowest temperature rating, so the new RW90 conductors are rated as 75 °C conductors here.

Why not the others

A. 60 °C is the default for small unmarked terminations under Rule 4-006, not the rule for mixed ratings; Rule 4-004 uses the lowest insulation rating present, 75 °C.

B. Rule 4-004 does not let each conductor keep its own rating when ratings are mixed in one raceway; all are rated at the lowest rating present, 75 °C.

C. The newest or highest rating does not set the basis. Rule 4-004 uses the lowest rating present, 75 °C.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rule 4-004
Recall · Objective 1.2

A feeder's phase conductors are RW90. To save cost, the contractor proposes a neutral of the same size with insulation rated 75 °C. Under Rule 4-016, is this permitted?
1. Yes; a neutral carrying only unbalance may be rated lower
2. No; its rating may not be below the phase conductors'
3. Yes; a neutral needs only the phases' voltage rating
4. No; a neutral in a raceway has to be bare instead
Show the answer

B. Correct. Rule 4-016 requires an insulated neutral's insulation temperature rating to be not less than that of the ungrounded conductors, so with RW90 phase conductors the neutral must be rated 90 °C too.

Why not the others

A. Carrying only unbalanced current affects whether a neutral is counted for Table 5C (Rule 4-004), not its insulation. Rule 4-016 requires a rating not below the phase conductors'.

C. Voltage is not the only requirement. Rule 4-016 also sets the neutral's temperature rating at not less than that of the ungrounded conductors.

D. The reverse holds: Rule 4-016 requires neutrals to be insulated except where specific rules allow bare ones, and a service-raceway neutral must now be insulated.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rule 4-016
Calculation · Objective 1.3

A hospital wing measures 2500 m² on outside dimensions and includes a 200 m² operating suite (a high-intensity area). Heating comes from a central plant, and no other loads are included. What is the Rule 8-206 demand load?
1. 35 200 W
2. 41 300 W
3. 49 280 W
4. 56 000 W
Show the answer

C. Correct. Rule 8-206 1): 20 W/m² × 2500 m² + 100 W/m² × 200 m² = 70 000 W, or 28 W/m². Over 900 m², 8-206 2) b) gives 80 % × 28 W/m² × 900 m² + 65 % × 28 W/m² × 1600 m² = 20 160 W + 29 120 W = 49 280 W.

Why not the others

A. This leaves out the operating suite's 100 W/m². Rule 8-206 1) b) adds 100 W/m² for high-intensity areas on top of the 20 W/m² basic load over the whole building.

B. This uses the school factors of 75 % and 50 %. A hospital takes 80 % on the first 900 m² and 65 % on the area beyond it (Rule 8-206 2) b)).

D. This takes 80 % of the whole 70 000 W. The flat 80 % applies only to a building of 900 m² or less; above that, the area beyond 900 m² is taken at 65 % (Rule 8-206 2)).

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rule 8-206
Procedural · Objective 1.3

An owner asks for an additional supply service of the same voltage. Under Rule 6-102, which building may receive one?
1. A three-storey building with shops below and offices above, each with its own entrance
2. A one-storey strip plaza whose stores each have their own entrance at grade
3. A 40-unit apartment building, to separate the house loads from the suites
4. An office building, to supply a large new rooftop chiller plant
Show the answer

B. Correct. Rule 6-102 1) c) permits additional supply services for completely self-contained occupancies that are not one above the other and each have their own entrance leading directly to ground level. Where the service boxes are not grouped, 6-102 3) requires a diagram at each one showing where the others are.

Why not the others

A. The occupancies are stacked. Rule 6-102 1) c) requires self-contained occupancies that are not located one above the other, as well as a separate entrance to ground level for each.

C. Separating house and suite loads is not one of the Rule 6-102 1) cases (fire pumps, industrial or complex structures, side-by-side self-contained occupancies); the house loads are served from the building's one supply service.

D. A large load is not a reason for an additional supply service under Rule 6-102; only fire pumps, industrial or complex structures and side-by-side self-contained occupancies qualify. The chiller is supplied from the building's service.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rule 6-102
Recall · Objective 1.4

The steel reinforcing of a new building's concrete foundation, in contact with earth 1.5 m below grade, will serve as an in-situ grounding electrode. How does Rule 10-102 4) treat it?
1. It needs no approval mark, but needs earth contact equal to a manufactured one
2. It needs a certification mark, like any manufactured grounding electrode
3. It needs no approval mark, but must be backed up by two driven rods at least 3 m apart
4. It needs a field evaluation label before the connection is accepted
Show the answer

A. Correct. Rule 10-102 4) says an in-situ electrode is not electrical equipment for the purposes of Rule 2-024, so it needs no approval, but at 600 mm or more below finished grade it must expose to earth a surface area equal to that of a similar manufactured electrode.

Why not the others

B. Only manufactured electrodes are certified products. Rule 10-102 4) states that an in-situ electrode is not electrical equipment for Rule 2-024, so no approval mark applies to it.

C. Rule 10-102 1) lists in-situ electrodes as one of the three permitted kinds of grounding electrode in their own right; two rods 3 m apart are the manufactured-rod option of 10-102 2), not a required supplement.

D. Field evaluation is a route to approval for electrical equipment under Rule 2-024, and Rule 10-102 4) says an in-situ electrode is not electrical equipment for that rule.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rules 10-102, 2-024
Procedural · Objective 1.5

In a new strip plaza unit, a TECK90 cable rated for direct burial will run under the 125 mm concrete floor slab poured at grade to reach an island counter. Under Rule 12-012 9), on what condition may the cable lie directly beneath the slab instead of at Table 53 depth?
1. It is bedded in screened sand at least 450 mm below the slab
2. It is covered with 38 mm treated planks under the slab
3. Its location and depth are permanently and legibly marked
4. The slab is reinforced and at least 150 mm thick
Show the answer

C. Correct. Rule 12-012 9) lets direct-burial raceways and armoured or metal-sheathed cables run directly beneath a slab at grade at least a nominal 100 mm thick, provided the location and depth are marked conspicuously, legibly and permanently and the cable is not exposed to damage. The 125 mm slab qualifies.

Why not the others

A. Table 53 cover is the default, but Rule 12-012 9) is an alternative to it: an armoured cable suitable for burial may lie directly beneath a slab at grade at least 100 mm thick if its location and depth are permanently marked.

B. Treated planking is one of the mechanical protections of Rule 12-012 4), which only earns a 150 mm reduction in Table 53 cover. Under a slab of 100 mm or more, Rule 12-012 9) needs no planks; it needs the location and depth permanently marked.

D. Rule 12-012 9) needs a slab of at least a nominal 100 mm, so the 125 mm slab already qualifies, and reinforcement is not a condition. The deciding condition is a permanent, legible marking of the cable's location and depth.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rule 12-012
Recall · Objective 1.6

A lighting contactor in a 347/600 V panel switches an office corridor's lighting circuit, and an upstream breaker is there to clear faults. Under Rule 14-012, what must the contactor's ratings be sufficient for?
1. The voltage and 125 % of the connected lighting load
2. The voltage and the fault current available at it
3. The voltage and the load current it must interrupt
4. The trip setting of the upstream breaker
Show the answer

C. Correct. Rule 14-012 b) requires equipment that interrupts current at other than fault levels, such as a contactor switching a load, to have ratings sufficient for the voltage and for the current it must interrupt. The fault-current test of 14-012 a) applies to the breaker that clears faults.

Why not the others

A. No 125 % factor appears in Rule 14-012. It asks only that a load-switching device be rated for the voltage and the current it must interrupt.

B. Voltage plus available fault current is the test in Rule 14-012 a) for equipment that must interrupt fault current, here the upstream breaker. The contactor interrupts load current only (14-012 b)).

D. The breaker's trip setting is not what the contactor interrupts. Rule 14-012 b) asks for ratings sufficient for the voltage and the load current the contactor switches.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rule 14-012
Procedural · Objective 1.7

A hospital renovation adds a fire pump with its own service box, located away from the other service boxes. Under Rule 32-306, what may be installed between that service box and the fire pump controller?
1. A red disconnect, lockable in the ON position, identified as the pump supply
2. Only a labelled breaker, lockable closed, that carries locked-rotor current
3. A fused switch lockable open, with fuses at 125 % of full-load current
4. A breaker set at the Table 29 maximum for the motor, lockable closed
Show the answer

B. Correct. Rule 32-306 1) allows no device that can interrupt the fire pump circuit between the service box and the controller except a breaker labelled as the fire pump disconnecting means; 32-306 2) makes it lockable closed and 32-306 4) requires it to carry the pump's locked-rotor current indefinitely. Rule 32-304 permits the separate, remote service box.

Why not the others

A. A red disconnect lockable ON is the fire alarm supply rule (Rule 32-108 3)). For a fire pump, Rule 32-306 allows only a labelled breaker, lockable closed, that carries the locked-rotor current indefinitely.

C. A fused switch is a device that could interrupt the circuit and is not the labelled breaker Rule 32-306 1) allows, and a lock-open provision works against keeping the pump supplied.

D. A Table 29 setting is sized for ordinary motor protection and could trip on a long start. Rule 32-306 4) requires the fire pump breaker to carry the locked-rotor current indefinitely.

Source: ESA exam outline, Section 1: Ontario Electrical Safety Code; OESC Rules 32-304, 32-306

02Answer key

Question	Answer	Our objective
Q1	A	Objective 1.1
Q2	D	Objective 1.1
Q3	D	Objective 1.2
Q4	B	Objective 1.2
Q5	C	Objective 1.3
Q6	B	Objective 1.3
Q7	A	Objective 1.4
Q8	C	Objective 1.5
Q9	C	Objective 1.6
Q10	B	Objective 1.7

Want the rest of Section 1?

The full TicketPrep Master Electrician bank has 206 questions on the Ontario Electrical Safety Code and 550 across all three sections, covering every one of our 22 objectives, with every option explained the way the ten above are. Its timed 80-question mock exams score you on both of ESA's rules: 70 per cent overall and at least 60 per cent in each section. Try five more free in the quiz, no account, or get the whole bank for $69 one-time. All-Access ($119) covers the ME exam with all eighteen Red Seal trades, the Ontario G3 and 4th Class Power Engineering 4A and 4B.

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03What Section 1 covers

Section 1 of the ESA Master Electrician exam is the Ontario Electrical Safety Code. ESA's Information Package says it tests the latest version of the OESC and how well you use the Code as a reference tool. The current edition is the 29th, in force since May 1, 2025 (O. Reg. 449/24): CSA C22.1:24 with ESA's Ontario amendments. Our questions on it run from the Ontario administrative rules of Section 2 (notifications, connection authorizations, plan review, approved equipment) through conductor sizing, services and load calculations, grounding and bonding, wiring methods and voltage drop, protection, receptacles and motors, to the special sections such as hazardous locations, pools and hot tubs, Ontario's power-line rules and EV charging.

ESA publishes the three sections and their share of the exam, 33 per cent each, and the laws each one covers, but not how many questions each section has or which topics inside a section carry the most. The seven objectives below are TicketPrep's own, built from those lists, and the right-hand column is how many questions our bank holds on each objective, Standard and Advanced together, not a count from the exam.

Our objective	In our bank
Objective 1.1 Use the Ontario administrative rules and general requirements: definitions, notification of work, plan review, connection authorization, approval of equipment and the general installation rules of Section 2	33
Objective 1.2 Select and size conductors: ampacity tables, correction factors, termination temperatures, neutrals and identification (Section 4)	39
Objective 1.3 Lay out consumer's services and calculate service and feeder loads for dwellings and other occupancies (Sections 6 and 8)	40
Objective 1.4 Ground systems and bond equipment: electrodes, grounding conductors, system bonding and bonding-conductor sizing (Section 10)	24
Objective 1.5 Choose and install wiring methods: burial depth, raceway fill and supports, box fill and voltage drop (Section 12 and Rule 8-102)	24
Objective 1.6 Protect conductors and equipment and install receptacles, appliances and motors (Sections 14, 26 and 28)	28
Objective 1.7 Apply the special sections: hazardous locations, lighting, fire alarm and fire pumps, high voltage, heating, renewable energy and storage, pools, Ontario power lines and EV charging	18

04What the questions turn on

Ontario's own Section 2 runs on ESA's clock

Rule 2-004 has the contractor file a notification before the work starts, or within 48 hours after it starts when filing first is not practicable, so an emergency repair is no excuse to skip it. ESA also gets at least 48 hours' notice that the work is complete and ready for a connection authorization, longer in a remote spot an inspector cannot reach quickly. And nothing is closed in until it conforms and an inspector has authorized the concealment: the drywall date follows the inspection.

Ampacity is a choice of table, factor and column

Rule 4-004 sends you to a different ampacity table for conductors in free air than for conductors in a raceway, a cable or a cable tray, and how the cables are spaced and laid decides whether a correction factor for the number of conductors applies. Rule 4-006 then picks the temperature column from the rating of the terminations, not the insulation, so a 90 degree cable on 75 degree lugs is sized at 75 degrees. Most wrong answers come from the right table read in the wrong column.

A load calculation starts from the right floor area

For a single dwelling, Rule 8-110 counts the ground floor and the upper floors in full and a basement with enough headroom at a reduced share, while a low crawl space does not count at all; that area sets the basic load. An apartment unit's feeder has a minimum of its own under Rule 8-202, which can be larger than the sum of its loads. A school works from watts per square metre of its classroom and other areas under Rule 8-204, with a reduction once the building is large.

Voltage drop and taps turn on which current you use

When the load on a feeder is not known, Rule 8-102 checks the voltage drop at 80 per cent of the overcurrent device rating; where the devices were chosen under another section, as motor feeders are under Section 28, it uses the calculated demand instead, because a motor feeder's devices are deliberately oversized. A short tap without protection at its supply end, under Rule 14-100, must carry at least the rating of the panelboard it feeds, not just the load it serves today.

05The other sections

The Master Electrician exam has three sections, and you need at least 60 per cent in each one as well as 70 per cent overall to pass. Each section has its own page of free questions:

The Master Electrician practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it. TicketPrep is not affiliated with ESA or CSA Group, and no OESC text is reproduced here: the questions cite Rule numbers and explain the requirement in their own words.