## LonWorks Protocol Basics for BAS LonWorks (Local Operating Network) is a peer-to-peer networking protocol widely used in building automation, particularly in older commercial and institutional facilities. ## LonWorks Overview ### What is LonWorks? LonWorks is a complete networking platform that includes: | Component | Description | |-----------|-------------| | Protocol | LonTalk communication protocol | | Neuron Chip | Embedded processor with protocol stack | | Transceivers | Physical layer interfaces | | Network Management | Tools for commissioning and maintenance | ### Key Characteristics | Feature | Description | |---------|-------------| | Topology | Peer-to-peer (any device can talk to any) | | Media | Twisted pair, power line, IP, fiber | | Addressing | Neuron ID (unique 48-bit) + logical address | | Data Model | Standard Network Variable Types (SNVTs) | ## Network Architecture ### Physical Topologies **Free Topology (FT-10):** - Most common in BAS - Bus, star, or combination - Up to 64 devices per segment - 2700m maximum length (with repeaters) **Twisted Pair (TP/XF-1250):** - Higher speed (1.25 Mbps) - Shorter distances - Stricter topology requirements ### Logical Architecture ```mermaid graph TD DOM["LonWorks Domain
(Site Level)"] subgraph S1["Subnet 1 (Segment)"] N1["Node 1
(Controller)"] N2["Node 2
(Controller)"] N3["Node 3
(Sensor)"] end subgraph S2["Subnet 2 (Segment)"] R1["Router to Subnet 1"] end IP852["IP-852 Router
(to Enterprise Network)"] DOM --> S1 DOM --> S2 DOM --> IP852 ``` ## Network Variables (NVs) ### What are Network Variables? Network variables are the data points that devices share on the network: | Property | Description | |----------|-------------| | Name | Identifier (e.g., nviSpaceTemp) | | Direction | Input (nvi) or Output (nvo) | | Type | SNVT (standardized) or UNVT (proprietary) | | Binding | Connection to other device NVs | ### Standard Network Variable Types (SNVTs) ASHRAE/ANSI defines standard types: | SNVT | Type | Description | |------|------|-------------| | SNVT_temp_p | Temperature | °C × 100 (0.01°C resolution) | | SNVT_lev_percent | Level | 0-100% (0.5% resolution) | | SNVT_switch | Binary | On/off with value and state | | SNVT_hvac_mode | HVAC Mode | Off, Heat, Cool, Auto, etc. | | SNVT_occupancy | Occupancy | Occupied, Unoccupied, Bypass, Standby | **Reference:** ANSI/CEA-709.1 (LonWorks Protocol Standard) ### Bindings Devices communicate by binding output NVs to input NVs: ```mermaid graph LR VAV["VAV Controller"] RS["Room Sensor"] NVO["nvoEffSetpt
(output)"] NVI["nviSetpoint
(input)"] VAV --> NVO NVO <-->|binding| NVI NVI --> RS ``` ## Common BAS Applications ### Typical LonWorks Equipment | Equipment | Manufacturer Examples | |-----------|----------------------| | VAV Controllers | TAC, Honeywell Excel | | Unitary Controllers | Carrier Comfort Network | | Rooftop Units | Trane Tracer | | Lighting Controls | Lutron, Leviton | | Meters | Continental Controls | ### System Architecture Example ```mermaid graph TD BL["Building Level"] IPR["LonWorks IP Router"] S1["Subnet 1: VAV Controllers
(Floor 1)"] S2["Subnet 2: VAV Controllers
(Floor 2)"] S3["Subnet 3: AHU Controllers"] S4["Subnet 4: Lighting System"] BL --> IPR IPR --> S1 IPR --> S2 IPR --> S3 IPR --> S4 ``` ## Integration with Other Systems ### LonWorks to BACnet **Gateway approach:** - LonWorks points mapped to BACnet objects - Gateway handles protocol translation - Maintains SNVT-to-BACnet object mapping **Dual-protocol devices:** - Many modern controllers support both - Native translation in device - Simpler architecture ### LonWorks to Niagara Niagara provides LonWorks integration via: - LON driver (requires LON interface) - Point discovery and binding - SNVT interpretation - Scheduling and control ## Commissioning Tools ### LonMaker Primary commissioning tool: - Network design and documentation - Device installation and replacement - Binding creation and management - Network diagnostics ### Other Tools | Tool | Purpose | |------|---------| | NodeUtil | Basic device configuration | | LonScanner | Network traffic analysis | | Echelon i.LON | IP integration and management | ## Network Management ### Device States | State | Description | |-------|-------------| | Unconfigured | New device, no network assignment | | Configured | Assigned to subnet/node | | Hard-offline | Intentionally disabled | | Soft-offline | Communication lost | ### Service Pin Physical button on device for: - Identifying device to commissioning tool - Initiating device replacement - Forcing unconfigured state ## Troubleshooting ### Common Issues | Problem | Possible Cause | |---------|----------------| | Device offline | Wiring, power, address conflict | | No communication | Binding missing, routing issue | | Incorrect values | SNVT mismatch, scaling issue | | Slow response | Network congestion, wink storms | ### Diagnostic Steps 1. **Verify physical layer** - Check wiring and termination 2. **Check device status** - Use network management tool 3. **Verify bindings** - Ensure connections are correct 4. **Monitor traffic** - Look for errors or congestion 5. **Check routing** - Verify router configuration ## Migration Considerations ### Why Migrate from LonWorks? | Factor | Consideration | |--------|---------------| | Vendor support | Declining LonWorks focus | | Integration | BACnet/IP more common | | Tools | LonMaker licensing complexity | | Skills | Fewer techs trained on LON | ### Migration Approaches 1. **Overlay** - Add BACnet supervisor, keep LON field devices 2. **Gateway** - Protocol translation at building level 3. **Gradual replacement** - Replace LON devices with BACnet over time 4. **Full replacement** - Complete system changeout ## Best Practices ### Network Design - Keep subnet sizes reasonable (32-50 devices) - Plan router placement for efficient traffic - Document all bindings - Use consistent naming conventions ### Maintenance - Maintain network database backup - Document device locations - Keep spare devices configured - Train staff on basic troubleshooting ## References - **ANSI/CEA-709.1** - LonWorks Protocol Standard - **LonMark International** - Interoperability guidelines - **Echelon Corporation** - Technical documentation

lonworks

LonWorks Protocol Basics for BAS