Building Automation Systems Flashcards

What does the acronym DDC stand for in building automation?

Answer: Direct Digital Control

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

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?

Answer: An alarm condition is triggered and a notification is generated

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

Which BAS network layer handles routing between multiple BACnet networks?

Answer: BACnet/IP with BBMD

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

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

Answer: Adjusting outdoor air intake based on occupancy measured by CO2 sensors

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

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

Answer: Automatically restart the controller if the program hangs or freezes

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

Which BAS sequence of operation step typically follows the morning warm-up mode?

Answer: Occupied mode

Morning warm-up pre-conditions the building before occupancy, after which the system transitions to occupied mode for normal operation.

What is the function of an actuator in a BAS-controlled HVAC system?

Answer: Convert an electrical control signal into mechanical movement

Actuators convert electrical signals from the DDC controller into physical movement to operate dampers, valves, or other mechanical components.