A LONWORKS® Technology Demonstration Project

Introduction

Local Operating Network (LON) technology makes possible a new generation of smart, low-cost products that communicate with one another. The concepts presented in the previous LonWorks Tutorial are brought to life in an actual installation, a demonstration project in southern California.

The LonTalk® protocol is a serial protocol, meaning that LONWORKS nodes are daisy chained together on a single wire. It is designed from the viewpoint of the sensor level upwards through all the levels of the standard OSI reference model. This has benefits today in providing open, interoperable networks, and has benefits in the future when integrating control networks into the information highway. The promise of a completely open protocol is to make possible the kind of diverse and cost effective solutions that the IBM PC made possible in the computer industry.

Project Scope

IEC Intelligent Technologies was selected as the prime contractor for Southern California Edison's LONWORKS technology demonstration project. This project was meant to be more than a typical energy savings project, in that there was also a desire to show off the most attractive features of LONWORKS. LONWORKS was showcased as a robust, reliable technology that can do useful things today, while at the same time paying for itself through energy savings.

The main aspects of the project included control of the office lighting with passive infrared sensors, control of the HVAC system with temperature and pressure sensors, and a variable frequency drive. In order to document the project's energy savings, four electrical meters were installed.

One primary goal is to have the system operate with a minimum of human intervention. IEC's ICELAN-G and Intellect software products were used to install the network and provide a user interface.

In a conscious effort to showcase LONWORKS technology, the elements of this project were designed to highlight its advantages over competing technologies. Insofar as possible, LonTalk Nodes, the plug and play interoperability standard for LONWORKS were used. The ability to use multiple media, particularly the ability to communicate the LonTalk protocol over the building's existing power lines, was demonstrated through the use of routers. In all, equipment from eleven different manufacturers and services from an outside electrical contractor were used to demonstrate interoperability:

• Belimo
• Continental Controls
• Danfoss
• Echelon®
• HyCal
• IEC Intelligent Technologies
• Kniepkamp Engineering
• Leviton
• Pensar
• Precision Alarm Systems
• Sasco Data Systems

System Description

In principal, the wiring for some eighty nodes is very simple. The computer printer, copier, coffee pot and lights are controlled by LonTalk protocol signals carried over the electrical power lines. The passive infrared sensors, variable frequency drive, dampers and electrical meters were connected by twisted pair wiring to the control computer, a basic PC.

Lighting System

The lighting system consists of twenty-nine passive infrared sensors, and twenty lighting control nodes. The lighting control system uses FTT-10 transceivers for the passive infrared sensors and PLT-20 for the lighting control nodes. These transceiver types were selected to minimize installation costs. The wiring effort is reduced by taking advantage of the freeform topology scheme for flexibility in locating the PIR sensors and by taking advantage of the existing power line for the lighting nodes.

True peer-to-peer lighting control is implemented in IEC's design. The system uses LONMARK® compatible Precision Alarm Suppliers passive infrared (PIR) occupancy sensors, located in each private office, room or area separated by open office partitions. The PIR is also capable of sensing light level. This capability is utilized to minimize energy usage by energizing the light fixture only if ambient lighting is below the threshold. The threshold is programmable from the network. The PIR's are bound directly to IEC's LONMARK compatible digital output nodes that can control up to four individual light fixtures illuminating the area monitored by the PIR.

The digital output nodes are equipped with four digital output modules, each capable of switching up to 5A at 240VAC. The nodes are mounted in NEMA 1 enclosures. Each box mounted control node contains logical input network variables of SNVT_switch type for control of each individual fixture. In the event all monitored areas illuminated by the fixture are not occupied, the fixture will be turned off. IEC's Intellect Graphical User Interface (GUI) monitors the status of all PIRs and light fixtures and visually indicates the presence of an occupant in any area monitored by a PIR.

HVAC System

The HVAC system uses TP/XF-78 transceivers. A TP/XF-78 to FTT-10 router is used to isolate the HVAC system from the lighting control system. This minimizes the network traffic on both systems and provides optimum performance overall. TP/XF-78 is optimal for the HVAC because the network wiring is bus oriented, following the building ducting system. Only SNVT type data is used in controlling this subsystem.

A single rooftop unit (RTU) was retrofitted with a LONWORKS Variable Frequency Drive (VFD) node. IEC used a Danfoss LONMARK compatible VFD with TP/XF-78 transceivers to control the fan in the RTU. Commands are issued from IEC's Flexible I/O node that generates fan speed commands based on the compressor state and the duct static pressure. The RTU control algorithm ensures there is enough air flow to heat or cool the tenant area as well as maintain minimum flows during compressor operation. The heating/cooling decision is based on an average of network set points, and average network temperatures. The algorithm is designed to maintain minimum compressor off times as well as monitor duct temperature to ensure against the coils freezing. Selection of heating/cooling mode is included in the algorithm. Two of the four Form C relays on the Flexible I/O module are used to control the compressor state. All of the communication is based on the peer to peer distributed control concept. The MMI is used only to generate network setpoints and average network information.

A PID (proportional - integral - derivative) control loop positions the dampers in the HVAC system. Damper control is provided using IEC's Flexible I/O module with TP/XF-78 transceivers. The software on these modules is LONMARK compatible. The module controls damper position using its voltage output capability to command Belimo actuators. The control algorithm includes setpoint temperature and duct temperature to determine the required damper position. Each Flexible I/O module is capable of controlling two damper actuators. Temperature sensing inputs are received as a LonTalk message from the room temperature sensor.

IEC used a static pressure sensor to maintain a minimum flow when the compressor is turned off. The sensor output interfaces to one of the four analog inputs of the Flexible I/O module.

IEC used HyCal temperature/relative humidity sensors that are LONMARK compatible to provide temperature and relative humidity readings. The HyCal sensor is also on the TP/XF-78 channel. The outputs of the temperature sensor output are bound to the damper controller and are used to control damper position using a peer-to-peer implementation. Relative humidity is used for display on Intellect's Graphical User Interface.

User Interface

IEC's Intellect Graphical User Interface is a Windows based front end. Intellect provides the user a graphical interface and control feature set that allows the user to monitor and control the facility at the click of a mouse button. Intellect's feature list includes:

• Runs under Windows™ 3.1x, Windows for Workgroups, Windows 95 and Windows NT.
• Histories - User configurable record of building alarms kept on hard disk.
• Trend Logs - Record any system point at defined intervals and display in graphical or text format.
• Time of Day Schedules - Each point can be programmed to an individual schedule.
• Holiday and Advanced Scheduling - Override a previously defined Time of Day Schedule for the next day or years in advance.
• Point Memo - Document comments and special instructions for every point in the system.
• Notepad - Generic Windows Notepad.
• On-line Help.
• Point Overrides - Manual override of any point operation.
• User Activity Log - Records all major operator functions such as point enable/disable, point delete, parameter changes, operator log on, log off and system exit. Also records unauthorized actions. Each instance is recorded with the user and action performed and is time and date stamped.
• Equipment Runtimes - Reports hours of operation for energy usage calculations or preventative maintenance reports.
• Remote Access Capability via Modem.
• Multilevel, Configurable Password Protection and Point Segregation.
• If/Then Calculations - Mathematical, logical, and/or time based calculations for custom control strategies.
• Event Activated Messages.
• User Initiated Programs - User defined sequences of point commands. Multiple programs may be chained together or called by Time of Day programs.
• Time Initiated Programs - Time based execution of sequences of point commands.

IEC programmed additional features into Intellect to meet the requirements of this project. This includes providing power consumption data in graphical and numerical form for each electric sub-meter installed, with two separate sets of registers for each sub-meter, one cumulative power consumption register zeroed at system commissioning and another resetable by the tenant. In addition, a fourth pair of registers are supplied for the subtractive non-HVAC/non-lighting loads. This data is exportable to spreadsheets for tenant evaluation. The Intellect GUI provides a fifth set of registers that will impute a set of values for a system without controls. Register values are computed as follows:

• Non-Controlled Lighting Register computes non-lighting power consumption by calculating power usage assuming all lighting devices are powered on upon first occupancy of the tenant space and powered off on last occupancy on each day.
• Non-Controlled Lighting Register computes non-lighting power consumption by calculating power usage assuming all lighting devices are powered on upon first occupancy of the tenant space and powered off on last occupancy on each day.
• Non-Controlled Plug Load Register computes controlled plug load power consumption based on the controlled loads operating 24 hours a day.
• Controlled Plug Load Register computes power consumption based on the controlled loads actual powered-on time.

A graphical layout of the space including location of movable office partitions is provided with an icon located in each workspace indicating the presence of an occupant in each controlled space.

The Intellect GUI has a screen indicating the status of all HVAC sensors and actuators including all data output by room sensors, duct sensors, etc.

The Intellect GUI has screens displaying all meter and computed power consumption register data.

The INTELLECT software is running on a 486 DX 66 MHz PC with 16Mbytes RAM.

Network Installation

An important part of the economies of using LONWORKS is that the connections between sensors and control points is done in software, rather than running wiring between nodes. IEC used its ICELAN-G network configuration tool to perform this network configuration and "bindings". The graphical approach to ICELAN-G eased the installation process. A node is located and named on the ICELAN-G screen. The node is installed by pressing a service pin, entering a Neuron® ID, or utilizing the "wink" installation method.

Each node contains objects known as network variables. Connections are made by matching network variables to compatible variables on other nodes. ICELAN-G's graphical template binder feature made the installation quick and easy by creating templates of network variable connections for each subsystem. By dragging and dropping nodes into the templates, the node configuration process was automatically completed.

After network configuration was completed, the diagnostic features of ICELAN-G were used to determine if the nodes were operating properly. The NV browser was used for node configuration. ICELAN-G's as built documentation generator was used to create "as built" documentation of the LonTalk network. IEC used Echelon Corporation's Protocol Analyzer to measure network traffic statistics to determine if the network bandwidth was properly partitioned. Good network design made this a smooth process.

IEC wishes to acknowledge, with warm appreciation, the efforts of all the participating vendors that helped make this project a success. IEC wishes also to compliment Southern California Edison for conceiving and financing this project, without whose participation it would not have been possible.

Conclusion

LONWORKS has emerged as a comprehensive suite of hardware and software solutions that allows for the implementation of real projects that can be done today. Instead of resting on this accomplishment, the LONMARK association is working to bring about a true plug and play standard for the construction of interoperable networks. Many more projects that embody the concepts illustrated here have been completed and are in the planning stages. IEC Intelligent Technologies has the experience, personnel, and facilities to supply robust and cost effective LONWORKS solutions for your own applications. Please feel free to contact us if we may answer any questions or provide more information.