PLC Programming
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BACnet

Building Automation and Control Networks - ASHRAE standard for building automation and control systems.

Type: Mixed ProtocolSpeed: Varies by physical layerReleased: 1995Organization: ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers)
76.8 kbps (MS/TP) to 1 Gbps (BACnet/IP)
Bandwidth
Varies by network type
Max Nodes
Varies by physical layer
Max Distance
No
Real-Time

Protocol Overview

Building Automation and Control Networks - ASHRAE standard for building automation and control systems.

When to Use BACnet

Choose BACnet for commercial building automation, HVAC control, or any application requiring integration of diverse building systems.

Technical Specifications

Physical Layer

  • Physical Layer: Multiple (IP, MS/TP, PTP, LonTalk, ZigBee)
  • Cable Type: RS-485, Ethernet, or others
  • Topology: Bus, Star, Any IP topology
  • Power Over Cable: No

Data Layer

  • Data Link: BACnet protocol
  • Encoding: Binary or JSON (BACnet/SC)
  • Error Detection: Protocol specific
  • Frame Size: Protocol dependent

Performance

  • Scan Time: Application dependent
  • Deterministic: No
  • Real-Time: No

Certification

  • Certification Required: Yes
  • License Cost: BACnet Testing Laboratory (BTL) certification required
  • Version: BACnet 2020

Advantages & Disadvantages

Advantages

  • ✓Designed specifically for buildings
  • ✓Multi-vendor interoperability
  • ✓Flexible physical layers
  • ✓Rich object model for HVAC
  • ✓International standard (ISO 16484-5)
  • ✓Supports large distributed systems
  • ✓BACnet/SC adds modern security

Disadvantages

  • ✗Complex protocol stack
  • ✗Not suitable for high-speed manufacturing
  • ✗Limited real-time capabilities
  • ✗Implementation variations between vendors
  • ✗Requires expertise to configure properly

Common Use Cases & Applications

Commercial HVAC systems
Building automation
Energy management
Lighting control
Access control integration
Smart building systems

Industry Adoption

Adoption LevelVery High in building automation
Market Share60-70% of commercial building automation
Geographic PresenceWorldwide
Primary Industries
Commercial BuildingsHealthcare FacilitiesEducational InstitutionsGovernment Buildings

Supported Message Types

Who-Is
I-Am
Read Property
Write Property
COV Notifications
Alarms
Schedules

Supported PLC Brands

Johnson Controls
Siemens Building Technologies
Honeywell
Schneider Electric
Trane
Carrier

Quick Links

Alternative Protocols

  • Modbus
  • LonWorks
  • KNX

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