10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
These 10 free TBT questions are organized by exam domain, so you can see how each part of the Test and Balance Technician (TBT) blueprint is tested. Reveal the answer and explanation under each question.
A capture hood reads 330 cfm at a supply diffuser. A simultaneous, properly located duct traverse also reads 330 cfm. Removing the hood makes the traverse rise to 410 cfm; reseating the hood makes it fall again. Fan speed and damper positions remain fixed. What does this repeatable change establish?
Correct answer: C - The hood's added resistance is reducing the actual diffuser airflow.
A belt-driven fan delivers 10,000 cfm at 900 rpm and requires 5.0 bhp. A proposed sheave change would raise airflow to 12,000 cfm without changing the fan, air density, or system resistance. The motor's allowable continuous shaft output is 7.5 hp; disregard belt losses. Which prediction should govern approval of the change?
Correct answer: B - 1,080 rpm and 8.6 bhp; the motor capacity is insufficient.
Four supply terminals on one branch are ready for proportional balancing, with all terminal dampers fully open. Initial readings are: T-1, 300 cfm design and 270 cfm measured; T-2, 600 cfm design and 480 cfm measured; T-3, 200 cfm design and 210 cfm measured; T-4, 400 cfm design and 360 cfm measured. Which should be the fully open index terminal while the others are adjusted proportionally?
Correct answer: A - T-2
A pressure-independent VAV box is set for 800 cfm, but both the controller and an independent measurement show 520 cfm. The damper is physically fully open. Available pressure across the terminal is 0.12 in. w.g.; the manufacturer's minimum at 800 cfm is 0.30 in. w.g. What must be resolved before flow calibration is changed?
Correct answer: A - Restore the terminal's minimum required differential pressure, then retest airflow.
A chilled-water pump develops a gravel-like sound and unstable discharge pressure. Its speed and water temperature are unchanged. Pressure immediately upstream of the suction strainer is normal, but pump suction pressure is below its baseline and the strainer differential pressure has risen sharply. The finding that ties these observations together is:
Correct answer: D - A restricted suction strainer reducing available NPSH.
An air-conditioning unit with a thermostatic expansion valve and no liquid receiver is checked at a stable cooling load. Airflow across both coils is correct. Suction pressure is below the manufacturer's expected range, evaporator superheat is 24°F against an 8 to 12°F target, and condenser-outlet subcooling is 2°F against a 10 to 14°F target. The measurements have been verified. Which fault best fits the combined pattern?
Correct answer: D - Insufficient refrigerant charge in the system.
Air passes through a dry reheat coil with no mixing, leakage, or moisture exchange. As dry-bulb temperature rises at essentially constant pressure, which property pair is expected?
Correct answer: C - Relative humidity decreases, and dew point remains unchanged.
During a wet cooling-coil performance test, steady measurements taken immediately before and after the coil are 5,000 cfm at standard air density, dry-bulb temperatures of 80°F and 55°F, and enthalpies of 32 and 22 Btu/lb of dry air. The specified minimum total capacity at these test conditions is 200,000 Btu/h. Which result belongs in the report?
Correct answer: C - 225,000 Btu/h total cooling; the requirement is met.
For an airborne-infection-isolation room, the approved test requires room pressure 2.5 to 8 Pa below the corridor with the door closed and recovery within 30 seconds after the door closes. Pressure approaches zero during the door-opening test, then returns to 4.2 Pa below the corridor 12 seconds after closure. Inward airflow is confirmed at the door undercut with the door closed. How should this pressure-recovery test be recorded?
Correct answer: B - Record a passing pressure-recovery test and retain the measured pressure and recovery time.
An unoccupied laboratory is undergoing fume-hood commissioning. At the specified sash height, average face velocity is 105 ft/min, within the project's 95 to 115 ft/min range. Smoke escapes at one edge when a nearby supply diffuser operates, but containment improves when that diffuser's jet is temporarily diverted. Which correction is most directly supported by the test?
Correct answer: D - Redirect the supply jet, then retest the hood under normal operating conditions.
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