Cabling Installation - Procedures

Transcription

1 Cabling Installation - Procedures Installing Twisted-Pair Media Topology: Ensure the topology chosen is appropriate for the transceiver in question: bus for TP/XF-1250 channels and either bus or free topology for TP/FT-10 channels. Cable Choice: Only use the transceiver manufacturer s recommended cable types. Do not mix cable types on the same segment, except where you are using stubs for TP/XF-1250 segments. In the case of link powered segments, ensure that the cable type chosen and the channel link power loading delivers the correct supply voltage to link powered devices over all temperatures. Cable Length: Bus Topology (TP/XF-1250 & TP/FT-10) Ensure that the cable length for the main run and stubs do not exceed the maximum recommended length. Free Topology (TP/FT-10) Ensure that the maximum total length of cable does not exceed the maximum recommended length for the cable type in question. Extending Distances: Only use physical layer repeaters or routers to extend segment lengths. Do not exceed one physical layer repeater per segment. Cable Termination: Use the correct segment termination method. Doubly terminate TP/XF-1250 and TP/FT-10 segments in bus topology. Use single point termination for TP/FT-10 segments in free topology. Only use the recommended termination network. Link Power Supplies: Locate the link power supply for a segment so that the voltage to link powered devices is kept within specification. Typically it helps to install the link power supply in the middle of the segment. Device Count and Distribution: For TP/XF-1250 and TP/FT-10 segments, ensure that the device count and distribution complies with that specified in the Junction Box and Wiring Guideline for Twisted Pair LONWORKS Networks and the transceiver user s guides. For TP/FT-10 segments using free topology, do not exceed the device count and maximum device-to-device distance. Cable Shield Termination: When using shielded cable, for all transceiver types, terminate the shield using the RC network shown below: Echelon Corporation 1

2 LONWORKS Network Design Twisted Pair Termination Circuit Ca 100µF 50Vmin Ra Cb 100µF 50Vmin Shielded Twisted Pair (STP) Rb Cc Shield Grounding Circuit Cc = 0.1 µf, 10%, Metalized Polyester, 100V Rb = 70kΩ, 1/W, ±5% Ground the cable shield at least once per segment, and preferably at each device. Grounding the shield at every device (using the shield grounding circuit shown) will assist in suppressing 50/60Hz standing waves. Building Entrance Protection: For inter-building communications, use shielded cable and lightning protection. The FTT-10A users guide provides full details. The following diagram illustrates the concept: Shielded Twisted Pair Net A Net B Shield Inside 1 2 Outside Gas Discharge Surge Protectors (Typically <5pF) Lightning Protector Protector Set (A set is two devices (separate) or a pair of devices in a single box). Building Wall C 1 2 < 300 pf = Single FTT-10A load < 150 pf = Single LPT-10 load C C 2 3 < 10pF Network Isolation Rating: If the network cabling requires a specific isolation rating, do not degrade the isolation rating by running network cabling in the same trunking or partition as other cables. Use a separate cable tray. Radiated Noise Sources: Avoid running network cabling in close proximity or in parallel to mains or other cabling which may be a noise source, i.e. mains cabling carrying high current triac controlled loads. RF & Magnetic Fields: Do not install devices close to high RF or high magnetic fields such as linear motors unless they are specifically designed to be

3 installed in such an environment. Testing: Once the segment cable and termination is in place, check the termination impedance using an AC bridge. The details of how to do this are covered in detail later in this chapter on page Once you have physically and logically installed all devices on each channel, use a protocol analyzer to check that the error rate is less than the acceptable limit for each channel type and that the actual throughput matches the For link power segments, check the supply voltage at the furthest devices from the link power supply and ensure that it meets the recommended limits when the devices are active and in worst case current consumption conditions. Installing Power Line Channels Legislation: Ensure that the transceiver choice meets local legislation. Pre-Installation Check: For commercial installations, verify that the installation is suitable for use with power line transceivers using PLCA-22 prior to physically installing the devices. This entails checking for injection loss, attenuation, signal-to-noise ratio, phase relationship, and error rates between all required points in the building. Details of how to perform these tests can be found in the relevant transceiver user s guide. Due to the nature of the mains network, carry out pre-installation tests over a suitable period to access the full building characteristics over all times of day and days of the week. For domestic installations, it may be unnecessary to perform a pre-installation check. Device Count and Distribution: With power line networks it is very difficult to provide general numbers for device counts and distribution since installation-specific factors affect these parameters; however, a maximum number of 500 devices per sub station would be starting point. Termination: In the case of unpowered media, long haul situations, or lightly loaded conditions, you may need to include bus topology termination for the segment. Details of suitable termination networks can be found in the relevant transceiver user s guide. Filtering: Due to the open nature of power line communications, you may need to filter the incoming mains supply to suppress unwanted incoming signals or to suppress local communication signals from escaping the building. You may also need to filter noise from old equipment that may be in use within the building. Commercial filters are available for this purpose. Noisy equipment should show up during the pre-installation check. Phase Coupling: If phase-to-phase communications are required, you will need to install some kind of phase coupling mechanism. Details of suitable coupling circuits may be found in the relevant transceiver user s guide or Echelon power Echelon Corporation 3

4 LONWORKS Network Design line application notes. Do not rely on the installations natural phase-to-phase signal coupling. Domain ID: Use a unique 6 byte domain ID for the network. Installing RF Media Other Media IP Channels Legislation: Ensure that the transceiver choice is meets local legislation and that any necessary licenses have been obtained. Pre-Installation Check: You may need to perform a pre-installation check to ensure that the transceiver will work over the required range and environment. If possible, find other local RF sources, such as paging systems, and ensure that they will not have any affect on the proposed installation. Installation: Only use the manufacturer s recommended aerial configurations. Domain ID: Use a unique 6 byte domain ID for the network. Installation: Follow the transceiver manufacture s specifications and advice with regard to media length and device distribution. Device Count and Distribution: Do not exceed the transceiver manufacturer s recommended device count and device distribution specifications. Physical installation: Do not install IP-based devices without first contacting the local IS administrator. Ensure that the maximum distance from the device to the hub, and maximum device-to-device distances are not exceeded. Address: Determine whether to use static or dynamic (DHCP) IP addressing. If in doubt, contact the local IS

5 Bandwidth: Ensure that, if necessary, the devices have their bandwidth clipped (QOS). Consult with the local IS administrator to see if this is necessary. Logical Connectivity: Contact the local IS administrator to have any intermediary firewalls or routers opened up. Echelon Corporation 5