Five free practice questions on maintenance and repair: block E of the Red Seal 308A Sheet Metal Worker exam, about 7 of its 120 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A transverse joint on a low-pressure rectangular supply duct rattles and whistles. On one side of the joint the drive cleat has worked partly out of its edges. What is the repair?
- Wrap the loose joint with cloth duct tape to stop the leak.
- Drive the cleat home, bend its ends over and seal the joint.
- Add a hanger on each side of the joint, tight to the duct.
- Replace the drive cleat with a Pittsburgh lock on that side.
Show the answer
B. Correct. A drive cleat slides over the folded edges of the two duct ends, and its ends are bent over so it cannot creep out under vibration. Driving it fully home and bending the ends closes the joint mechanically; sealing it then stops the whistle at the gap.
Why not the others
A. Cloth duct tape over a loose joint leaves the cleat free to keep creeping out, and its adhesive dries and lets go on metal duct. The joint is closed mechanically first, then sealed with a duct sealant.
C. Hangers carry the duct's weight; they do not close a joint whose cleat has slid out, so the leak and whistle stay. The cleat is driven home, its ends bent over and the joint sealed.
D. A Pittsburgh lock is a longitudinal seam formed along a duct section's corners; it is not used to join two sections end to end. This transverse joint is closed with its drive cleat, driven home and bent over.
Source: Red Seal Occupational Standard, sub-task E-19.02
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On a scheduled service, the stainless baffle filters from a restaurant's kitchen exhaust hood are coated with hardened grease. Which cleaning method suits them?
- Vacuum them with a brush attachment and refit them.
- Blow them out with compressed air and refit them.
- Soak them in a hot degreasing solution and rinse them.
- Pressure wash them with cold water alone and refit them.
Show the answer
C. Correct. Hardened grease has to be dissolved, and soaking in a hot degreasing solution reaches into the folds of the baffles; the rinse then carries off the loosened grease and the cleaner before the filters are refitted. Clean baffles keep grease out of the exhaust duct and fan.
Why not the others
A. Vacuuming picks up dry, loose dirt such as lint on a coil face. Hardened grease stays stuck to the baffles; it has to be dissolved by soaking in a hot degreaser.
B. Compressed air moves loose, dry dust; it does not lift hardened grease, and it can spray grease droplets around the kitchen. Greasy baffles need a degreaser, by soaking.
D. Cold water does not dissolve grease; under pressure it skims the surface and leaves the hardened layer in the folds. A hot degreasing solution does the work, then a rinse.
Source: Red Seal Occupational Standard, sub-task E-18.02
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An uninsulated galvanized supply duct carrying cooled air through a humid crawlspace is wet over its whole outer surface and drips onto the floor. Its joints were sealed and pass a smoke test. What is causing the water?
- Condensate from the coil is being carried along inside it.
- Cooled air is escaping through its seams and joints.
- It is colder than the dew point of the air around it.
- Its air velocity is too high for the duct's size.
Show the answer
C. Correct. Metal carrying cooled air runs colder than the dew point of humid surrounding air, so moisture condenses over its whole outer surface (sweating). The repair is insulation with a continuous, sealed vapour retarder on the outside, so the humid air cannot reach the cold metal.
Why not the others
A. Water carried inside would gather at low points and weep through joints there, and these joints are sealed; it would not wet the whole outside of the duct. The outer surface sweats because it is below the air's dew point.
B. The joints pass a smoke test, so air is not escaping. A leak would also wet only the area around the leaking seam, not the whole surface; this is condensation on cold metal.
D. Velocity does not wet the outside of a duct; the metal's temperature against the surrounding air's dew point does. Insulating with a vapour retarder stops the sweating.
Source: Red Seal Occupational Standard, sub-task E-19.01
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On a scheduled inspection of a rooftop unit's belt-drive supply fan, which reading is taken with the fan running, before it is locked out?
- The pulley alignment.
- The motor winding resistance.
- The belt deflection.
- The motor amp draw.
Show the answer
D. Correct. Running current exists only with the motor under load, so it is read with a clamp-on ammeter while the fan runs, without opening any connection, and compared with the nameplate full-load amps and the last reading. Then the fan is locked out for the hands-on checks.
Why not the others
A. Pulley alignment is checked across the pulley faces with a straightedge or laser, which means hands on the drive; it is a lockout check, made after the running readings are taken.
B. Winding resistance is a dead test: it is read only with the motor locked out and isolated from its supply, never on a running motor. It comes after the running readings.
C. Belt deflection is measured by pressing on the belt span, which puts hands at the drive's nip points; it is done under lockout with the guard off, after the running readings.
Source: Red Seal Occupational Standard, sub-task E-18.01; CSA Z460
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A belt-drive exhaust fan's motor has failed, and a replacement of the same horsepower and voltage is being ordered. Which other nameplate rating decides whether the fan keeps its old airflow on the existing pulleys?
- Its service factor.
- Its frame size.
- Its rated rpm.
- Its enclosure type.
Show the answer
C. Correct. On the same pulleys, fan speed = motor rpm × motor pulley diameter ÷ fan pulley diameter, and airflow follows fan speed, so a motor rated slower turns the fan slower and the airflow falls in the same proportion. Frame, service factor and enclosure matter for fit, overload margin and surroundings.
Why not the others
A. The service factor is the overload margin the motor can carry continuously. It does not set the speed at which the motor turns the pulley; the rated rpm does.
B. Frame size sets the mounting dimensions and shaft size, so it decides whether the motor bolts onto the base and takes the pulley. It does not set the speed; the rated rpm does.
D. The enclosure type (open drip-proof, totally enclosed and so on) suits the motor to its surroundings, such as a wet or dusty airstream. It has no effect on speed; the rated rpm decides that.
Source: Red Seal Occupational Standard, sub-task E-19.02
02Answer key
| Question | Answer | Sub-task |
|---|---|---|
| Q1 | B | Repairs worn or faulty components |
| Q2 | C | Services components |
| Q3 | C | Diagnoses system faults |
| Q4 | D | Performs maintenance inspections |
| Q5 | C | Repairs worn or faulty components |
03What block E covers
Keeping installed systems working: scheduled inspections of fans, drives, filters, grilles and dampers, servicing filters, belts, pulleys, access door gaskets and kitchen hood baffles, and finding and repairing faults, from low airflow, banging panels and sweating duct to musty odours, crushed flex, worn pulleys, failed motors, leaking coils and slipped damper actuators.
The Red Seal Occupational Standard names this block “Performs maintenance and repair”. It carries 5.8% of the exam, about 7 of the 120 questions, split across two tasks. The share column is each task's weight within the block, as the standard publishes it.
| Task and its sub-tasks | Share of block |
|---|---|
| Performs scheduled maintenance Performs maintenance inspections; Services components | 38% |
| Repairs faulty systems and components Diagnoses system faults; Repairs worn or faulty components | 62% |
04What the questions turn on
A filter drop only climbs
A loading filter's resistance only rises, so a reading below the clean-filter figure points to torn, missing or bypassed filters. Filters reaching final drop in half the manual's interval call for a shorter interval written into the schedule.
Pressure drops locate the fault
With less air flowing, every component's drop should fall, so a coil whose drop has doubled is restricted. One outlet down while its neighbours hold their readings puts the fault between the trunk and that outlet, such as crushed flex.
Pulleys and motors set fan speed
Fan speed is motor rpm times motor pulley diameter over fan pulley diameter, and airflow follows it. Closing an adjustable pulley's flange raises its pitch diameter. Static pressure varies as the square of the speed ratio.
Moisture problems start at a surface
Duct carrying cooled air below the dew point of humid air sweats, and needs insulation with a sealed vapour retarder. Wet, mouldy porous liner is cut out and replaced, not cleaned, once the moisture source is fixed.
05The other blocks
The 308A exam has five blocks. Each has its own page of free questions:
The 308A Sheet Metal Worker practice exam 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.