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FTT-10 LONWorks Network Design Rules - LON Wiring Guidelines

Issue

Many LonWorks network installation problems can be avoided if the appropriate network design rules are followed when the network is being designed.

Environment

  • I/A Series MicroNet (LON) Controllers
  • Sigma MicroNet series LON Controllers
  • Vista
  • Xenta

Cause

The I/A Series MicroNet System Engineering Guide (F-26507) was written as a resource of information for installation of the I/A Series MNL-100, 200 & VAV controllers as well as  the Sigma MicroNet 440 and 620 controllers.  This document is no longer in print.  The Resolution, below, is a summary of the LON design rules presented in that document.

Resolution

FTT-10 LON network wiring must be installed using Echelon approved wire.  The most common type of wire used is described as Category 4  cable.  This wire is normally unshielded stranded twisted pair 22AWG (0.65mm).  An example of this wire is the W221P or W222P series cable from Connect-Air International.  This type of cable is normally available both in plenum rated and non-plenum rated types.  Consult the job specifications to determine if plenum rated or shielded cable is required.

The LON network can be wired using "Free Topology" or "Bus Topology" wiring segments.  

A.  BUS Topology Guidelines

  1. BUS Topology LonWorks wiring extends from device to device (daisy chain format) with no branches or stubs.
  2. A LON-TERM-2 terminator must be installed at each end of the LON bus.
  3. When using standard Category 4 LON cable with the recommended terminators, the bus may be up to 4593 feet (1400 meters) in length.
  4. When extending LON wire to the MN-Sx sensor base in a bus topology network, the sensor base must be wired as part of the daisy-chain and not as a stub connection.

B. FREE Topology Guidelines

  1. Free Topology imposes essentially no restrictions on the layout of the network -- some controllers may be wired point to point and others branching from a common point. 
  2. The free-topology LON network must be terminated at one point with a LON-TERM-1 terminator.
  3. When using standard Category 4 LON cable, the total wire length in a free topology LON network may not exceed 1641 feet (500 meters).  In addition, the longest wire path between any two controllers on a free topology LON network may not exceed 1312 feet (400 meters).

C. Common LON Network Wiring Guidelines

  1. LON wiring can not be part of an active bundled telephone trunk even if the telephone trunk is wired with Category 4 wire.
  2. Shielded Category 4 wire may be used in high EMI/RFI environments.  The shield must be wired continuously and grounded through a 470 Kohm resistor at one end.
  3. LON wiring must not be bundled with or housed in the same conduit as controller I/O and power wiring.

 D. LonWorks Network Wiring and Addressing Guidelines

  1. When the number of controllers on a LonWorks network exceeds 60, the network must be split into segments with not more than 64 controllers or devices per segment using LonWorks Repeaters or Routers. 
  2. When counting the controllers and devices on a LonWorks network segment, a LonWorks Network Interface Device and the repeater itself must be included in the device count in each segment.
  3. In a LonWorks network containing repeaters or routers, each LonWorks network segment must be properly terminated, as described above.
  4. Domain / Subnet / Node addressing is used when configuring the LON controllers.
  5. A LonWorks Subnet consists of a series of LonWorks controllers all configured within the same LON Subnet number.
  6. A single LonWorks Subnet can have a maximum of 127 device and controller Node addresses.  This Node address count includes the LonWorks Network Interface, all controllers on the subnet and repeater and / or router node addresses.  An allowance is typically made for additional addresses to be used by LonWorks tools connected to the Subnet.
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