Free CBO Practice Questions

Question 1

One office stays warm while neighboring zones served by the same air handler are comfortable. After 20 minutes of steady cooling, field measurements confirm the affected variable-air-volume (VAV) terminal's requested airflow and its reported room temperature of 78°F. Air enters the hot-water reheat coil at 55°F and leaves at 70°F, although the heating command is 0%. Where should troubleshooting begin?

Accepted Answer

At the terminal, by checking whether the reheat valve actually shuts.

Answer

At the air handler, by lowering its supply-air temperature setpoint.

Answer

At the zone sensor, by applying an offset to its temperature reading.

Answer

At the VAV controller, by raising its maximum cooling airflow setting.

Question 2

An occupied office building needs cooling on a humid morning. Its economizer uses differential enthalpy control. Verified readings are 70°F and 32 Btu/lb for outdoor air, compared with 76°F and 28 Btu/lb for return air. Select the correct operating state for these conditions.

Accepted Answer

Maintain required outdoor air and use mechanical cooling as needed.

Answer

Open the outdoor-air damper fully and stop mechanical cooling.

Answer

Close the outdoor-air damper and meet the load with mechanical cooling.

Answer

Maintain minimum outdoor air and stop cooling because outdoor air is cooler.

Question 3

Correcting an after-hours lighting schedule reduces monthly electricity use, but the demand charge does not change. The tariff bills the highest 15-minute average kW in each month, with no ratchet or minimum-demand provision. Rates are unchanged. Interval data show an unchanged midafternoon peak when cooling and other loads coincide. The results demonstrate:

Accepted Answer

The schedule reduced total energy use but did not lower the month's billing peak.

Answer

Lower billed demand obscured by the utility's charge for a historical peak.

Answer

A demand-meter fault because energy use and peak demand should fall together.

Answer

Load shifting without energy savings because the demand charge is unchanged.

Question 4

A carbon monoxide alarm sounds in a boiler-room corridor. Two employees nearby report headache and dizziness. A portable CO monitor reads 160 ppm at the exit. The operator is outside the affected area. What takes priority?

Accepted Answer

Evacuate the affected area and call emergency services from a safe location.

Answer

Enter the boiler room and check the flue connection before shutting down equipment.

Answer

Increase ventilation from the control station and wait for the reading to fall.

Answer

Compare the reading with an eight-hour exposure limit before deciding on evacuation.

Question 5

During filter rounds, an air handler's filter pressure drop has increased from 0.30 to 0.55 in. w.g., measured at the same airflow. The approved condition-based program calls for replacement at 0.90 in. w.g., or earlier if damage, moisture, airflow loss, or air-quality problems appear. None is present, and the next scheduled check is tomorrow. Which maintenance decision fits the findings?

Accepted Answer

Keep the unit operating and continue the scheduled condition checks.

Answer

Replace the filters now because the pressure drop has almost doubled.

Answer

Take the unit out of service because the rising pressure drop indicates blockage.

Answer

Increase fan speed now to restore the filters' original pressure drop.

Question 6

During a part-load test, a centrifugal supply fan draws 25.0 kW at full speed. Reducing its speed to 80% still satisfies measured zone-airflow and outdoor-air requirements. Assume friction losses dominate, damper positions remain fixed, and motor/drive efficiencies do not change. About how much input power should the reduced-speed test show?

Accepted Answer

12.8 kW

Answer

20.0 kW

Answer

16.0 kW

Answer

25.0 kW

Question 7

A meeting ran late, so the day operator used an authorized override to keep one floor's ventilation on. At 23:00 the floor is empty, another operator takes over, and the override is still active. The event has ended, and the approved unoccupied sequence provides all required protection. Which handoff instruction would prevent an unnecessary overnight run?

Accepted Answer

Restore automatic control, document the cleared override, and assign expiry times and owners to future overrides.

Answer

Leave the floor occupied overnight; have the day operator clear the override tomorrow.

Answer

Delete the event schedule; tell security to start ventilation manually for future meetings.

Answer

Turn the fan off at its local switch; leave the override for controls staff to review later.

Question 8

During a steam-trap survey, a contractor marks a trap 'failed open' because its outlet pipe is hot. The trap serves a heating coil with a changing load. There is no report of water hammer or loss of heat. What should the operator do with the replacement recommendation?

Accepted Answer

Record the diagnosis as unconfirmed; evaluate ultrasound and temperatures for the trap type and operating load.

Answer

Treat the hot outlet as proof of normal operation and close the survey finding.

Answer

Defer trap diagnostics until rising boiler fuel use confirms an energy penalty.

Answer

Isolate the heating branch and replace the trap before returning it to service.

Question 9

A commercial office with complete, verified property data receives an ENERGY STAR score of 82 in Portfolio Manager. The owner wants to announce that the building is '82% more efficient and ENERGY STAR certified.' Which statement can the operator support?

Accepted Answer

The building meets the score requirement, but completing certification is a separate step.

Answer

The building uses 82% less energy than an average office and qualifies for certification.

Answer

The score describes site energy use per square foot rather than relative performance.

Answer

The score proves compliance with ventilation standards and removes the need for verification.

Question 10

Adhesive odors begin after new flooring is installed in an occupied suite. Carbon dioxide is 740 ppm on a calibrated meter, and outdoor-air flow meets the suite's design requirement. The air handler uses MERV 13 filters. How should these findings be interpreted?

Accepted Answer

Ventilation meets design, but these readings do not exclude a chemical-emission problem.

Answer

The low CO2 concentration rules out a pollutant problem associated with occupancy.

Answer

The MERV 13 rating establishes effective removal of particles and adhesive vapors.

Answer

The design airflow establishes safe dilution even if the flooring's emissions have changed.

Free CBO Practice Questions

Domain 1: Maintain Energy Using Building Systems, Equipment, and Envelope to Minimize Energy Use 27% of exam

Question 1

Question 2

Question 3

Domain 2: Operate Energy Using Systems for High Performance 41% of exam

Question 4

Question 5

Question 6

Question 7

Domain 3: Perform Technical and Administrative Duties 17% of exam

Question 8

Domain 4: Maintain Indoor Environmental Quality to Standards 15% of exam

Question 9

Question 10

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