RCDD Building Automation and Intelligent Building Systems 2

Question 1

Which standard defines the BACnet data communication protocol for building automation and control networks?

Accepted Answer

ANSI/ASHRAE 135

Answer

BACnet is defined by ANSI/ASHRAE Standard 135 and is also published internationally as ISO 16484-5.

Question 2

What is the default UDP port used by BACnet/IP?

Accepted Answer

47808

Answer

BACnet/IP uses UDP port 47808 (0xBAC0) by default.

Question 3

A BACnet/IP network spans several IP subnets and devices need to exchange broadcast messages such as Who-Is. What device or function is required?

Accepted Answer

BACnet Broadcast Management Device (BBMD)

Answer

A BBMD forwards BACnet broadcasts across IP subnets because routers do not pass local broadcasts.

Question 4

BACnet MS/TP networks use which physical layer?

Accepted Answer

EIA-485 (RS-485)

Answer

MS/TP (Master-Slave/Token-Passing) runs over an EIA-485 twisted-pair bus.

Question 5

What is the recommended topology for an EIA-485 field bus serving BAS controllers?

Accepted Answer

Daisy-chain with termination at both ends

Answer

EIA-485 is designed as a daisy-chained bus terminated at each end to prevent signal reflections.

RCDD - Registered Communications Distribution Designer Practice Test