Equipment Operation Flashcards

Pump cavitation is often heard as gravel-like noise. Which condition causes it?

Answer: Net positive suction head available falling below NPSH required

When NPSHa drops below NPSHr, liquid flashes to vapor at the impeller eye and the bubbles collapse violently.

What is the primary purpose of an economizer cycle on a rooftop unit?

Answer: Use cool outdoor air for free cooling when conditions allow

Economizers open outdoor air dampers to cool the building with outside air instead of mechanical refrigeration.

A building automation system shows a hot water reset schedule. What does it adjust?

Answer: Hot water supply temperature setpoint based on outdoor air temperature

Outdoor reset lowers supply water temperature as outdoor temperature rises, saving energy.

Which practice is required before performing maintenance on an energized-capable conveyor or fan under OSHA 1910.147?

Answer: Applying a personal lock and tag to each energy-isolating device and verifying zero energy

Lockout/tagout requires each authorized employee to isolate, lock, tag, and verify zero energy before servicing.

An air compressor's receiver tank should be drained regularly primarily to remove what?

Answer: Accumulated condensate and oil

Moisture condenses in receivers, and draining it prevents corrosion and carryover into the air system.

Belt-driven fans should be checked for proper tension. What is a common symptom of a belt that is too loose?

Answer: Squealing on startup and reduced airflow

Loose belts slip, producing squeal and lowering fan RPM and airflow.

What is the main function of a backflow preventer on a boiler makeup water line?

Answer: Prevent treated boiler water from contaminating the potable supply

Boiler water contains chemicals, so a reduced-pressure backflow assembly protects the potable system.