HVAC Commercial HVAC Systems

Question 1

What is a 'Variable Air Volume' (VAV) system and how does it differ from a 'Constant Volume' (CAV) system?

Accepted Answer

VAV varies supply air volume to each zone while maintaining constant supply temperature; CAV delivers constant air volume at varying temperatures

Answer

VAV varies supply air temperature; CAV varies supply air volume

Answer

VAV uses variable speed drives on chillers; CAV uses fixed-speed chiller compressors

Answer

VAV serves commercial buildings; CAV serves residential buildings only

Question 2

What is a 'chilled water system' in commercial HVAC?

Accepted Answer

A central system where a chiller produces chilled water distributed to air handling units throughout the building

Answer

A system using ice storage for overnight thermal banking

Answer

A domestic cold water system integrated with HVAC

Answer

A system using well water for direct cooling of air

Question 3

In commercial HVAC, what is a 'cooling tower' and what process does it use to reject heat?

Accepted Answer

A heat rejection device that cools condenser water by evaporating a portion of the water into the air stream

Answer

A tall air handler that provides cooling to upper floors

Answer

A refrigerant condenser mounted on the building's cooling tower

Answer

A thermal storage vessel that holds chilled water

Question 4

What is a 'packaged rooftop unit' (RTU)?

Accepted Answer

A self-contained HVAC unit on the roof containing all heating and cooling components, serving commercial spaces through ductwork

Answer

A chiller unit installed on the roof for large commercial buildings

Answer

A rooftop air handler connected to a remote chiller plant

Answer

A solar-powered supplemental cooling unit

Question 5

What is an 'air handling unit' (AHU)?

Accepted Answer

A large central air treatment and distribution unit that conditions and circulates air throughout the building via ductwork

Answer

The thermostat and control panel for a commercial system

Answer

The chiller plant serving the building

Answer

A local zone terminal unit like a VAV box

Question 6

What is a 'building automation system' (BAS)?

Accepted Answer

An integrated control system that monitors, controls, and optimizes all building mechanical systems including HVAC, lighting, and elevators

Answer

A computerized fire safety and emergency system

Answer

A remote monitoring service provided by equipment manufacturers

Answer

A building security access control system integrated with HVAC

Question 7

What is 'economizer' mode in a commercial air handling system?

Accepted Answer

Using outdoor air for free cooling when outdoor conditions are cool enough, reducing or eliminating mechanical cooling requirements

Answer

Operating the chiller at part-load for reduced energy consumption

Answer

Reducing ventilation below minimum rates during unoccupied periods

Answer

Variable frequency drive operation of supply fans at reduced speed

Question 8

What is 'commissioning' of a commercial HVAC system?

Accepted Answer

A systematic quality-assurance process verifying that HVAC systems are installed and operating as designed to meet the owner's project requirements

Answer

The initial start-up of equipment by the manufacturer's representative

Answer

Annual maintenance contracts for commercial equipment

Answer

The process of obtaining building permits for HVAC installation

Question 9

In commercial HVAC, what does the term 'tons of refrigeration' mean?

Accepted Answer

A unit of cooling capacity equal to 12,000 BTU/hr (the heat needed to melt one ton of ice per day)

Answer

The weight of refrigerant in the system in tons

Answer

The cooling capacity rated in metric tonnes

Answer

A measure of the chiller's physical weight

Question 10

What is 'heat recovery' in commercial HVAC and provide an example?

Accepted Answer

Recovering heat from the condenser to preheat domestic hot water instead of rejecting all heat to a cooling tower

Answer

Using waste heat from lighting systems to reduce heating loads

Answer

Recovering heat from occupants to eliminate the need for heating

Answer

Using economizer mode to recover heat in winter for reheating