HVAC Glossary: LonWorks

LonWorks represents a foundational open network protocol extensively utilized within the building automation sector, particularly for Heating, Ventilation, and Air Conditioning (HVAC) systems. Developed by Echelon Corporation, this technology facilitates seamless communication and interoperability among diverse devices from various manufacturers. Unlike some traditional protocols, LonWorks employs a peer-to-peer communication model, enabling direct interaction between control devices without a central master. This guide provides HVAC professionals with a deeply technical overview of LonWorks, covering its core concepts, architecture, applications, and practical considerations for implementation and troubleshooting.

Core Concepts and Terminology

Understanding LonWorks necessitates familiarity with its specialized terminology. The following definitions are crucial for comprehending the protocol's operation and application in HVAC environments.

Lon: Local Operating Network

Lon is an acronym for Local Operating Network, serving as the overarching term that encompasses all aspects of the LonWorks technology. It signifies a distributed control network designed for automation applications [1].

LonWorks Protocol

LonWorks refers to the comprehensive platform and protocol suite developed by Echelon Corporation. It defines how devices communicate, interoperate, and are managed within a network. The LonWorks FTT-10A configuration is a common variant specifically adapted for building communication systems, including HVAC [1].

LonTalk

LonTalk is the proprietary communication protocol used within LonWorks networks. It operates over various physical media, commonly a twisted-pair, transformer-isolated, free (open) network at a speed of 78 kbps. LonTalk enables devices to exchange data and commands efficiently and reliably [1].

LNS (LonWorks Network Service)

LNS, or LonWorks Network Service, is a software platform used for the setup, configuration, and management of LonWorks networks. It provides the necessary tools and services for commissioning devices, managing network variables, and maintaining network integrity [1].

LonMaker and IzoT CT

LonMaker was Echelon's original tool for network configuration and commissioning. It has since been succeeded by IzoT CT® (LonWorks Commissioning Tool), which offers enhanced capabilities for modern LonWorks implementations. These tools are essential for technicians to configure and manage LonWorks devices and networks [1].

SCPT (Standard Configuration Property Type)

SCPT stands for Standard Configuration Property Type. These are predefined data types used to configure LonWorks devices, allowing for standardized parameter settings across different manufacturers' devices. They are often referred to as Network Configurable Inputs (nci) [1].

SNVT (System Network Variable Type)

SNVT, or System Network Variable Type, defines standardized data formats for network variables. These variables facilitate interoperability by ensuring that devices from different vendors can understand and process the same type of data. Examples include SNVT_switch, SNVT_lev, and SNVT_count, which are further categorized as Network Variable Inputs (nvi) and Network Variable Outputs (nvo) [1].

Neuron ID and Neuron Chip

Each LonWorks device contains a Neuron Chip, an Echelon proprietary microprocessor that embeds a unique Neuron ID. This ID is a 48-bit unique identifier, ensuring that no two Neuron Chips worldwide share the same address. The Neuron Chip is the intelligence behind the LonWorks device, handling communication and control functions. Common Neuron Chips are identified as 3120 or 3150 [1].

Service Pin

The Service Pin is a physical or virtual switch on a LonWorks device. When activated, it broadcasts the device's Neuron ID to the LonWorks Network Service (LNS) tool, facilitating the commissioning process by allowing the LNS to discover and associate the device with its network profile [1].

Transceiver and Chip Set

A Transceiver is a component that connects the Neuron Chip to the physical network medium, such as a twisted pair. It provides the necessary electrical isolation and signal conditioning for reliable communication. Together, the Neuron Chip and the Transceiver form the Chip Set, which is fundamental to every LonWorks device [1].

LonWorks Network Architecture and Components

LonWorks networks possess distinct architectural characteristics that differentiate them from other common HVAC protocols. Understanding these differences is crucial for proper design, implementation, and maintenance.

Network Differences (compared to RS-485 protocols like Modbus or BACnet MS/TP)

Traditional RS-485 based protocols, such as Modbus or BACnet MS/TP, often require shielded, twisted-pair wiring with specific conductor counts (2 or 3). They also typically involve concepts like wire polarity and parity settings (e.g., 8EVEN1, 8NONE1). In contrast, early LonWorks implementations were designed for unshielded twisted-pair wiring, though specifications have evolved to include shielded types to mitigate noise issues. A key distinction is the absence of wire polarity in LonWorks, simplifying installation. Furthermore, LonWorks does not rely on predefined node IDs, device addresses, or network IDs that need to be manually entered, which can make initial setup more 'plug and play' [1].

Network ID and Commissioning

Unlike protocols where device addresses are static and tied to physical locations (e.g., AHU-1S always having address 0401S), LonWorks employs a unique Neuron ID for each chip. This Neuron ID is globally unique and is not user-configurable. During commissioning, a technician uses a service pin on the Lon device to broadcast its Neuron ID to the LonWorks Network Service (LNS) controller. The LNS then associates this unique Neuron ID with a specific Lon device and its equipment profile at the network level. This means that if a device fails and is replaced, the new device will have a different Neuron ID, requiring the LNS operator to re-commission the new device and associate its unique ID with the existing equipment profile. This network-level association provides flexibility but necessitates careful management during device replacement or troubleshooting [1].

External Interface File (XIF)

During the commissioning process, LonWorks tools require an External Interface File (XIF). This file, also known as a device mapping file, describes the capabilities and interface of a LonWorks device. XIF files are critical for enabling LonWorks network management tools to understand and interact with devices from various manufacturers. Technicians typically load XIF files supplied by the device manufacturer, or they can be extracted directly from the device itself. The proper use of XIF files ensures successful integration and interoperability within the LonWorks network [1], [2].

LonWorks in HVAC Applications

LonWorks has found widespread adoption in HVAC systems due to its open, interoperable, and distributed control capabilities. Its application spans various aspects of building automation, from individual equipment control to comprehensive building management systems.

Integration with Building Management Systems (BMS)

LonWorks devices are commonly integrated into Building Management Systems (BMS) to provide granular control and monitoring of HVAC equipment. This integration allows for centralized management of diverse systems, including air handling units (AHUs), variable air volume (VAV) boxes, chillers, boilers, and lighting. The peer-to-peer nature of LonWorks enables direct communication between these devices, facilitating efficient control strategies and reducing reliance on a central controller for every operation. This distributed intelligence enhances system reliability and responsiveness. For instance, a Daikin VRV system can be integrated with a BMS using LonWorks, alongside other open protocols like BACnet™ or Modbus® [1], [2].

Lon over IP

Lon over IP (LonIpNetwork) is an extension of the LonWorks protocol that enables communication over standard Ethernet networks, leveraging the CEA-852 tunneling standard. This is particularly useful in modern building automation where IP networks are ubiquitous. Instead of requiring a dedicated LonWorks adapter, Lon over IP utilizes the host device's Ethernet port. This allows for greater flexibility in network design and integration with existing IT infrastructure. A key component of Lon over IP is the Config Server, which manages and distributes routing information to all members of a LonIp channel, ensuring proper communication and device discovery across the IP network [2].

Practical Considerations for HVAC Professionals

For HVAC professionals, understanding the practical aspects of working with LonWorks systems is paramount for successful installation, commissioning, and maintenance.

Commissioning LonWorks Devices

Commissioning LonWorks devices involves several steps to integrate them into the network and ensure proper operation. This process typically includes:

• Device Discovery: Using tools like IzoT CT®, technicians discover LonWorks devices on the network. This can be initiated by activating the device's service pin, which broadcasts its unique Neuron ID [1].
• Binding: Once discovered, devices need to be bound to other devices or network variables to establish communication paths. This defines how devices interact and exchange data [2].
• Configuration: Devices are configured with specific parameters using SCPTs and SNVTs to match the application requirements. This may involve setting control logic, setpoints, or operational modes [1], [2].
• XIF File Management: Loading or extracting XIF files is crucial for the network management tool to correctly interpret and interact with the device. These files provide a blueprint of the device's capabilities and data points [1], [2].

Troubleshooting LonWorks Networks

Troubleshooting LonWorks networks requires a systematic approach, given their distributed nature. Common issues and considerations include:

• Network Wiring: While LonWorks is flexible, incorrect wiring (e.g., exceeding length limits, improper termination) can lead to communication errors. Verifying cable integrity and adherence to specifications is a primary step [1].
• Neuron ID Conflicts: Although Neuron IDs are unique, issues can arise if a device is replaced without proper re-commissioning, leading to the LNS associating the wrong Neuron ID with an equipment profile [1].
• Network Variable Issues: Incorrect SNVT types, binding errors, or misconfigured SCPTs can prevent devices from communicating or operating as intended. Tools like IzoT CT® are used to diagnose and correct these issues [1], [2].
• Lon over IP Connectivity: For Lon over IP implementations, network connectivity, firewall settings, and proper configuration of the Config Server are critical. NAT router port forwarding may also be necessary [2].

Frequently Asked Questions (FAQ)

Q1: What is LonWorks and how does it differ from other HVAC protocols like BACnet?

LonWorks is an open, peer-to-peer network protocol for building automation, allowing devices to communicate directly without a central master. It differs from protocols like BACnet, which can operate in a master-slave or peer-to-peer model, by its unique Neuron ID-based addressing and network variable concept, which simplifies interoperability across manufacturers [1].

Q2: What are the key components of a LonWorks network in an HVAC system?

Key components include Neuron Chips (the intelligent processors), Transceivers (for physical network connection), Service Pins (for device discovery), and network management tools like IzoT CT® (for configuration and commissioning). Devices communicate using standardized System Network Variable Types (SNVTs) [1].

Q3: How is a LonWorks device commissioned in an HVAC application?

Commissioning involves discovering the device (often via its service pin), associating its unique Neuron ID with an equipment profile in the LonWorks Network Service (LNS), binding it to other devices or network variables, and configuring its operational parameters using XIF files and network management tools [1], [2].

Q4: What is Lon over IP and when is it used in HVAC?

Lon over IP (LonIpNetwork) extends LonWorks communication over standard Ethernet networks using the CEA-852 tunneling standard. It is used when integrating LonWorks devices into existing IP infrastructure, providing greater flexibility and leveraging ubiquitous Ethernet connectivity, especially in larger or more distributed HVAC systems [2].

Q5: What are common troubleshooting steps for LonWorks networks in HVAC?

Common troubleshooting steps include verifying network wiring, checking for proper device commissioning and Neuron ID associations, diagnosing network variable binding and configuration errors, and ensuring correct Lon over IP connectivity, including Config Server setup and NAT router port forwarding where applicable [1], [2].