HVAC Building Automation Systems 3

Question 1

What does the acronym DDC stand for in building automation?

Accepted Answer

Direct Digital Control

Answer

DDC stands for Direct Digital Control, where microprocessor-based controllers directly regulate HVAC equipment.

Question 2

A BAS alarm is configured with a 'high limit' of 85°F for a space temperature sensor. What happens when the sensor reads 86°F?

Accepted Answer

An alarm condition is triggered and a notification is generated

Answer

When a monitored value exceeds its configured high limit, the BAS generates an alarm notification for operator response.

Question 3

Which BAS network layer handles routing between multiple BACnet networks?

Accepted Answer

BACnet/IP with BBMD

Answer

A BACnet Broadcast Management Device (BBMD) routes broadcast messages between BACnet/IP subnets across routed IP networks.

Question 4

What is 'demand-controlled ventilation' (DCV) in a BAS?

Accepted Answer

Adjusting outdoor air intake based on occupancy measured by CO2 sensors

Answer

DCV uses CO2 sensors as a proxy for occupancy to modulate outdoor air intake, reducing energy waste in partially occupied spaces.

Question 5

In a BAS, what is the purpose of a 'watchdog timer' in a DDC controller?

Accepted Answer

Automatically restart the controller if the program hangs or freezes

Answer

A watchdog timer resets the controller processor if the program stops responding, preventing lockups from causing equipment failures.

HVAC - Heating, Ventilation, and Air Conditioning Practice Test