Metasys Network Technical Manual Network Communications Section Technical Bulletin Issue Date 636 1199 N2 Communications Bus lntroduction Page 3 • Application Details *3 • Theory of Operation *5 • Components *8 • Planning Considerations *10 • Design Considerations *11 • Maximizing Your System’s Efficiency • Specifications 13 *15 Installation Procedures 17 • Preliminary Information 17 • Sample Layouts 18 • Wiring--NCU/NEU to N2 Bus 24 • Wiring--ASCs to N2 Bus 27 • Ins
Troubleshooting Procedures *51 • Overview • Checking for Good Wire Runs 51 • Checking for Proper Termination 52 • Checking the End-of-Line Device Settings 52 • Checking for Proper Channel Selection 52 • Checking the N2 Device 52 • Checking the Number of Defined N2 Devices 52 • Checking the Length of N2 Bus • Checking for “T” or “Y” Connections 53 • Checking for a Ground Loop 53 • Checking the Repeater 53 • Checking the Surge Protector 53 • Checking the Communication Term
Introduction Application Details The N2 Communications Bus is a local network that links controllers and point interfaces to the Network Control Module (NCM). The N2 Bus uses a master/slave protocol, in which the master device, the NCM, initiates all communication with the N2 Bus devices. These N2 Bus devices include the Digital Control Modules (DCMs), Point Multiplex Modules (XBN, XRE, XRL, XRM), and all Application Specific Controllers (ASCs).
The N2 is based on Opto-22 Optomux protocol, which was designed for industrial applications, and is a proven communication network. The N2 Bus follows the electrical characteristics of Electronics Industry Alliance (EIA) Standard RS-485. It is optically isolated between itself and other devices (except UNT100/101, VAV100/101, and Companion Personal Computer), assuring reliable operation and noise immunity. The NCM101/102 provides two bus channels: Channel A and Channel B.
N2 Bus TBC N2 Bus TBC TBC DCM XM NCM XM DCM DCM XM DCM Base Frame Base Frame Base Frame 5-slot NCU 2-slot NEU 1-slot NEU External Wiring Internal Wiring ASC (ILC Shown) INOUTCON Figure 2: Internal and External N2 Bus Connections Theory of Operation The N2 Bus has three different types of communication, four priority levels, and a specific method of data transmission.
Priority Levels There are four priority levels assigned to N2 devices: 0, 1, 2, and 3, where 0 is the highest. The priorities establish how often a device is to be polled. For example, a Priority 2 device will be polled more often than a Priority 3 device. How often a device will be polled depends on its assigned priority. You set the priority level when defining the N2 device. We recommend the priority levels remain the system defaults (e.g., DCMs at Priority 1 and ASCs at Priority 3).
To take this example one step further, suppose a point object at an N2 device changes state and needs to notify you at the OWS. As mentioned before, the NCM continually polls all N2 devices over the N2 Bus for changes in status. When a change occurs, the NCM will be sent that change when it polls the N2 device. The NCM then formats a Change-of-State (COS) message and sends it over the N1 LAN to the OWS (and other devices in the NCM’s routing table for that particular COS message).
The components of the N2 Bus are the N2 Bus Submodule (NCM101/102 only), communication terminal board, repeater, enclosure, fiber optic modem (optional), cable, and surge protector. Components N2 Submodule (NU-N2B101-0)--The N2 Submodule is a small plug-in unit for the NCM101 and NCM102. (The NCM401 can also use this submodule if for some reason it is no longer used as a migration NCM.) It is an interface device that the NCM101/102 requires to communicate over the N2 Bus.
R S.I. TECH MINI OPTICAL BIT-DRIVER MODEL 2110 T Fiber Optic Modems (S.I. Tech 2110)--These are communication devices that provide conversion between standard N2 signals (RS-485) and fiber optic signals. Note that one pair of modems is needed for each conversion between the standard N2 cable and fiber cable. Note: We recommend that you use only the S.I. Tech 2110 fiber modems on the N2 Bus.
Planning Considerations This section describes briefly what you need to know when planning to install the N2 Bus. Space The N2 Bus requires no additional space than is provided within the NCU and NEU enclosures. The N2 Bus repeater should be installed in an inconspicuous location accessible to building maintenance personnel. To meet NEC requirements, the repeater must be installed in an enclosure, and the line (120 VAC) and low voltage (N2 Bus) must be separated by two inches.
Design Considerations This section describes briefly what you need to know when designing an N2 Bus installation. A properly installed N2 Bus consists of an electrically continuous line of cable (unbroken) from one end of the system to the other. Selecting the Right Cable For most N2 Bus installations, the most practical choice is solid, two twisted pair unshielded telephone cables.
General • Each NCM can support one or two N2 Bus. The devices that you place on the N2 Bus must be daisy-chained devices, which include: NCM, DCM, XBN, XRE, XRL, XRM, IAC, ILC, AHU, UNT, VAV, VMA, LCP, IFC, D600, repeater, and surge protector. For more information on using two N2 Buses, refer to Dual N2 Bus Application Note (LIT-6363145) under Application Notes: Network Communications in this manual. Number of Devices • Currently, up to 100 devices can be connected to an NCM, including repeaters.
• The maximum distance between two fiber modems is 2012 m (6600 ft). If your application requires lengths beyond 2012 m (6600 ft), contact S.I. Tech for information about their “high power” option. • You may also use optical fiber on the N2 Bus. (A pair of fiber modems is required for conversion.) Duplex optical fiber is needed, either 50 (3.0 dB/km), 62.5 (4.0 dB/km), or 100 (5.0 dB/km) micrometers. The 62.5 size is preferred.
• Monitor Your System’s Improvement Estimating Your System’s N2 Traffic Move the LCPs and DX9100s to a separate N2 Bus, as described in the Dual N2 Bus Application Note (LIT-6363145) in the Metasys Network Technical Manual (FAN 636). If problems occur with throughput once the system is operational, monitor the N2 network traffic using N2/L2/S2 Statistics. This gives an estimate of the network activity to help you to determine if additional steps are required.
Specifications Table 3: Specifications Category Specification Product Name N2 Communications Bus Error Checking Module 256 Checksum Address Range of Devices 1 to 255* Number of N2 Devices Up to 100 (60 to 200 TC-9100s) Signaling Method Baseband, 9600 baud, ASCII/Hexadecimal character Surge Protection Tested to pass IEEE 587 and 472 waveforms Termination Method Network of voltages, biases, and resistors that are switch selectable.
Network Communications—N2 Communications Bus
Installation Procedures Preliminary Information There are a few considerations that you should be aware of when installing N2 Bus wiring throughout a building: • Follow all National Electrical Code (NEC) and local code restrictions. • Do not exceed the device maximums given in this document. • Be careful when pulling N2 wire. This is especially true if you are using 24 or 26 AWG wire, which breaks easily when pulled. Plenum grade wire is the best choice for pulling through tight areas.
Sample Layouts Six sample layouts of the N2 Bus are shown in Figures 4 through 9. Also shown are the proper End-of-Line (EOL) termination points. The layouts are: • standard N2 layout • N2 layout with NCU in the middle • N2 layout with a repeater • N2 layout with branched repeaters • N2 layout with fiber modems • N2 layout with branched fiber modems Figure 4 shows a network with two OWSs and two NCUs. One separate N2 Bus segment is externally wired from each NCU.
Figure 5 shows an NCU in the middle of the single N2 Bus segment. The N2 Bus in this network continues to function logically as a single bus.
Figure 6 shows a repeater lengthening the N2 Bus. The configuration has two segments.
Figure 7 shows the N2 Bus branching from multiple repeaters. The branch can be at either Side A or B. Multiple branches off one side are also allowed, as long as the device and distance limitations are followed. This network shows three segments.
Figure 8 shows the standard N2 Fiber layout. Notice two S.I. Tech 2110 modems are needed for each conversion to fiber: one to convert the standard N2 signals to optics, and the other to convert optics to the standard N2 signals. N2 Bus To Local N2 Devices TBC EOL=Out S.I.Tech 2110 T N C M To Local N2 Devices R NCM's EOL=In Fiber Cable T R S.I.Tech 2110 NCU Note: For end-of-line termination rules, see the Setting Terminations section of this document.
Figure 9 shows a branched N2 Fiber layout. Any path from the NCM to an N2 device cannot go through more than two pairs of 2110 modems (i.e., cascaded modems). This is because the 2110 modems delay the N2 Bus signal, and the N2 can only compensate for two of these delays; therefore, up to two pairs of 2110 modems can be cascaded in series. This configuration is shown in the middle of Figure 9. N2 Bus EOL=Out TBC S.I.Tech S.I.Tech 2110 2110 T N C M T R NCM's EOL=In T R EOL=In S.I.
Wiring-NCU/NEU to N2 Bus 24 The N2 Bus is wired to the communication terminal board of the NCU or NEU using the terminal block labeled TB1. Wire the N2 Bus as shown in Figure 10 (TBC801) or Figure 11 (TBC821). Be sure to follow these rules: • Always make sure the input wires you connect to the N2 terminals are twisted together and the output wires from the N2 terminals are twisted together. This is shown in Figures 10 and 11.
HRD GND 6 SFT GND 4 Two Twisted Pair Telephone Cable 3 SFT GND Twisted 5 2 IN (-) 1 IN (+) OUT (+) REF-IN REF-IN REF-OUT REF-OUT Twisted 3-wire Twisted Cable HRD GND SFT GND 6 4 3 SFT GND 5 2 IN (-) 1 Note: Coax connectors are not on BSF121. Twisted OUT (-) IN (+) OUT (+) REF-IN REF-OUT N1 LAN Coax Connectors Twisted Notes: TB2 TB1 We recommend stranded 22 AWG or heavier wire. Experience has shown that solid 24/26 AWG wire is prone to breakage during installation.
TBC821 TB2 6 3 6 5 4 2 3 TB1 5 1 4 2 1 Notes: Two Twisted Pair Telephone Cable Twisted Twisted T UNUSED REF-IN IN (+) IN (-) UNUSED REF-OUT OUT (+) OUT (-) We recommend 22 AWG or heavier wire. Experience has shown that 24/26 AWG wire is prone to breakage during installation. If shielded wire is used, wire shield to SFT GRD (soft ground) terminal for devices other than the NCM. 1 4 SFT 2 5 GND HRD SFT GND GND 3 6 = Tape Back 3-wire Twisted Cable one location, preferably at the NCU.
Wiring--ASCs to N2 Bus The N2 Bus is wired to the dedicated terminal block on each ASC. For details, refer to the technical bulletin for the particular ASC. Installing the Repeater You can use the N2 Bus repeater in three different configurations: station, branch, or star. As these configurations show in Figures 12, 13, and 14, the maximum N2 Bus length from the NCU to the farthest device cannot be longer than 4572 m (15,000 ft). This is the farthest distance the N2 Bus signal can travel.
Figure 13 shows the branch configuration, with multiple repeaters wired together and a separate branch of N2 devices off each repeater.
Figure 14 shows the star configuration, in which the first three repeaters are installed in a central location and each device is wired from each repeater. NCU Central Location Note: NCM's EOL In Maximum cable distance between two repeaters is 1524 m ( 5000 ft). There is no rule for minimum distance between repeaters. 1524 m (5000 ft) 0.
The instructions for installing the repeater include setting the baud rate, wiring the N2 Bus, and wiring the power. Refer to Figure 15. Follow these steps: 1. Set the baud rate to 9600 baud by placing Switch 6 in the On position. Place all other switches in the Off position.
Installing the Fiber Modems The 2110 fiber modems can be installed in any location on the N2 Bus. Just as only two repeaters can be cascaded on the N2 Bus, only two pairs of 2110 modems can be cascaded. The first installation step is to route the optical fiber and connect each modem to the ends of the fiber. The second step is to connect the N2 Bus on both sides of the modems. Routing and Connecting the Fiber Cables To route and connect the fiber cables follow these steps and refer to Figure 16: 1.
Fiber Modem Between Two Segments If you need to place the 2110 modem between two segments of N2 Bus, wire a stub length of six inches or less as shown in Figure 17 and terminate the two pairs of N2 Bus cable at the end of the stub length. N2 + N2 REF Use wire nuts to join N2 cable to stub length. Maximum stub length is six inches. S.I.Tech 2110 T To NCM N2 Bus R To N2 Devices S.I.Tech 2110 T R Fiber Cable T R S.I.
In order to properly terminate the N2 Bus, you need to know the two types of terminating devices. They are: Setting Terminations • Switch-Terminating--device has an EOL switch or jumper; includes the NCM, DCM, XBN, XRE, XRL, XRM, ILC, IFC, D600, and repeater. • Self-Terminating--device has termination built-in; includes AHU, LCP, UNT, and VAV. Figure 18 shows four examples of how to properly terminate.
• To set the EOL jumpers on the repeater, refer to Table 4 and Figure 15. Remove the cover of the repeater to get at the EOL jumpers. Note: Sides A and B have separate EOL settings. Determine the settings individually. Table 4: EOL Settings for Repeater Side Jumpers Instructions Side A J1 and J2 If at end-of-line, install both jumpers over Pins 1 and 2 (EOL In). If not at end-of-line, install both jumpers over Pins 2 and 3 (EOL Out).
Optional Shield REF Fold back and tape. 9-pin Connector N2 - N2 + Solder jumper wires between Pins 3-7 and Pins 8-9.
Installing the Surge Protector Surge protection is strongly recommended if the N2 Bus is wired between buildings. The protection is provided by a voltage surge suppressor/protector, which is installed on the N2 Bus near the N2 device. Example applications are shown on Figures 21 and 22. Figure 22 shows extra protection with the installation of one suppressor near the first N2 device and another at the point where the N2 Bus enters the building.
A S C N E U Surge Protector A S C N C U N2 Bus Surge Protector Surge Protector N2 Bus N E U N2 Bus N2 Bus protect2 Figure 22: Extra Surge Protector Installation The recommended surge protector is the Transient Eliminator, model TE/JC04C12, manufactured by Advanced Protection Technologies (APT). The device protects the N2 Bus from indirect lightning. It shunts both common and normal mode voltage surges to ground repeatedly without damage to N2 Bus components.
Table 6 lists the specifications of the surge protector.
The surge protector consists of two sections: the terminal block and the main assembly. These sections separate to make the unit easier to install and replace. Refer to Figure 23. Surge Protector Unprotected Side Protected Side HRD GND HRD GND SFT GND SFT GND N2 REF N2 REF N2- N2- N2+ N2+ Main Assembly Keypin Between Terminals 1 and 2 Terminal Block protectr Figure 23: Sections of Surge Protector How the Surge Protector is wired depends on which device requires protection.
4. Connect the protector to earth ground with 12 AWG stranded green wire as shown in Figures 24 through 30. The total length of ground wire cannot exceed 4.57 m (15 ft) which means an earth ground must be available within 4.57 m (15 ft) of the N2 device. (Your installation design will have to accommodate this requirement.) For NCUs/NEUs, you may use the hard ground termination on the Communications Terminal Board (TBC), as long as the ground wire is 4.57 m (15 ft) or less to earth. 5.
NCU/NEU - Unshielded N2 Bus Building One Building Two Metal Enclosure Metal Enclosure Protected NCU N2+ N2REF SFT GRD HRD GRD N2 Bus HG Unprotected Unprotected + 2 Surge 4 Protector R 6 8 10 1 3 5 7 9 N2 Bus + R Protected N2 Bus + + 1 Surge 2 - 3 4 Protector R R 5 6 7 8 10 9 NEU N2+ N2N2 REF SFT GRD HRD GRD HG HG HG HG Notes: For surge protector's hard ground, use 12 AWG stranded wire, 4.57 m (15 ft) maximum length.
AHU/LCP/UNT/VAV - Unshielded N2 Bus Building One Building Two Metal Enclosure Metal Enclosure NCM ASC REF N2N2+ N2 Bus ASC REF N2N2+ HRD GRD REF N2N2+ HG HG HG Metal Enclosure Protected N2 Bus N2+ N2REF ASC Metal Enclosure Unprotected + 2 Surge 4 Protector R 6 8 10 1 3 5 7 9 Unprotected N2 Bus + R Protected + 1 Surge 2 3 Protector 4 R 5 6 7 8 9 10 + R N2 Bus HG HG HG HG Notes: For the surge protector's hard ground (HG), use 12 AWG stranded wire, 4.57 m (15 ft) maximum length.
AHU/LCP/UNT/VAV - Shielded N2 Bus Building One Building Two Metal Enclosure Metal Enclosure NCM ASC N2 Bus REF N2N2+ ASC REF N2N2+ HRD GRD REF N2N2+ SG SG HG HG Metal Enclosure Metal Enclosure SG Protected N2 Bus N2+ N2REF ASC Unprotected + 2 Surge 4 Protector R 6 S 8 10 Unprotected N2 Bus + 1 3 R 5 S 7 9 Protected + 1 Surge 2 3 Protector 4 R 5 6 S 7 8 9 10 + R S N2 Bus HG HG HG HG SURGE3 Notes: For surge protector's hard ground (HG), use 12 AWG stranded wire, 4.
IAC/IFC/ILC - Unshielded N2 Bus Building One NCM** IAC, IFC, or ILC* REF N2N2+ N2 Bus REF N2N2+ HRD GRD HG Building Two ** Standard, Fire, or Security NCM. Metal Enclosure Protected N2+ N2REF IAC, IFC, or ILC* N2 Bus Metal Enclosure Unprotected Unprotected + 2 Surge 4 Protector R 6 8 10 1 3 5 7 9 + R N2 Bus Protected + 1 Surge 2 3 Protector 4 R 5 6 7 8 9 10 + R N2 Bus N2+ N2REF HG HG HG HG HG Notes: For the surge protector's hard ground (HG), use 12 AWG stranded wire, 4.
IAC/IFC/ILC - Shielded N2 Bus Building One NCM** IAC, IFC, or ILC* REF N2N2+ N2 Bus REF N2N2+ HRD GRD HG Building Two SG Metal Enclosure Metal Enclosure SG Protected N2 Bus N2+ N2REF IAC, IFC, or ILC* Unprotected Unprotected N2 Bus + + 2 Surge 1 4 Protector 3 R R 5 6 S S 7 8 9 10 Protected + 1 Surge 2 3 Protector 4 R 5 6 S 7 8 9 10 + R S N2 Bus HG HG HG IAC, IFC, or ILC* N2+ N2REF HG SG HG Notes: For the surge protector's hard ground (HG), use 12 AWG stranded wire, 4.
N2 Repeater - Unshielded N2 Bus Building One Metal Enclosure NCM ASC REF N2 Bus REF N2N2+ HRD GRD N2N2+ Building Two HG Metal Enclosure Protected Unprotected Side A COMD D N2 Bus D D COM Side B Side B Repeater + 2 Surge 4 R Protector 6 8 10 1 3 5 7 9 Unprotected Protected N2 Bus + R + + 1 Surge 2 3 Protector 4 R R 5 6 7 8 9 10 N2 Bus N2+ N2REF HG HG HG Notes: For surge protector's hard ground (HG), use 12 AWG stranded wire, 4.57 m (15 ft) maximum length.
N2 Repeater - Shielded N2 Bus Building One Metal Enclosure NCM N2 Bus ASC REF N2N2+ HRD GRD REF N2N2+ Building Two SG N2 Bus Metal Enclosure Protected Side A Unprotected N2 Bus COM D D D D COM Side B Repeater + R S 2 Surge 4 Protector 6 8 10 1 3 5 7 9 + R S Unprotected N2 Bus + R S SG HG Protected N2 Bus 1 Surge 2 + 3 Protector 4 R 5 6 S 7 8 9 10 ASC N2+ N2REF HG HG HG Notes: For surge protector's hard ground (HG), use 12 AWG stranded wire, 4.57 m (15 ft) maximum length.
Setting the Channel Switch (NCM 101/102 Only) The Channel Select switch is located on the front of the N2 Submodule (Figure 31). It configures the NCM to use one of two channels for the N2 Bus, Channel A or Channel B. The switch corresponds to the terminal block on the communication terminal board to which N2 Bus wiring is terminated. Channel A corresponds to TB1 and Channel B with TB2.
Commissioning Procedures Overview Commissioning the N2 Bus includes checking and modifying the wiring between all N2 devices. Troubleshooting involves performing one or more steps to isolate and correct a communication problem.
To add a DCM or XM to a new NEU, connect the N2 Bus to the new NEU via the respective communication terminal board. Install the device into a proper, available slot in the NEU. If this device is not the end-of-line device, set the EOL switch to Out. If this device is the end-of-line device, set the EOL switch to In. To add an ASC to the N2 Bus, wire the bus to the designated N2 Bus terminals. If the ASC is an ILC and it is not the end-of-line device, set the EOL switch to Out.
Troubleshooting Procedures Overview The N2 Bus is a reliable communications bus. However, there are situations in which communication problems may occur. Under most circumstances, you can detect a problem by examining the XMIT and RECV LEDs on the N2 device. If they are not flickering, or are flickering irregularly, the bus is not working properly. You may also refer to the N2 Bus Statistics window under NC Diagnostics at the OWS. (Examine the Number of Retries figure.
Checking for Proper Termination To verify proper cable termination, examine all N2 Bus wiring. There must not be any breaks in the three signal lines, and the wires must be connected to their proper terminals. Lightly tug on each wire to ensure that it is secure. Also, the polarity of the wiring must be consistent throughout the system. In addition, make sure the ribbon cable that connects the communication terminal board to the base frame is secure.
Checking the Length of N2 Bus The N2 Bus may not communicate because the length of the bus is too long. The recommendation is 1524 m (5000 ft) for each segment and a maximum distance of 4572 m (15,000 ft) from the farthest N2 device. Checking for “T” or “Y” Connections The N2 Bus is strictly a daisy-chained bus in which multiple devices are connected in series. You cannot cut the bus between two devices, add a T or Y connection, and then connect another device from the connection.
Checking the Communication Terminal Board Communication may fail if one or more of the fuses on the communication terminal board blows. The TBC801 has six fuses that protect the components of the NCU/NEU from high voltages and power surges. (Note that the TBC821, the improved version of the TBC801, uses thermistors instead of fuses, which provide overload protection and are also resettable, so that the TBC will work again after it cools off.
TBC801 Base Frame Leads from Continuity Tester or Ohmmeter tbcfuse Figure 32: Checking Fuses on the Communication Terminal Board Checking Communication Faults You can use an oscilloscope to pinpoint communication faults over the N2 Bus. The procedure requires a 2-channel scope with an A minus B function or an A plus B with B inverted function. Follow these steps: 1. Plug the scope into a grounded electrical outlet. 2. Set both channels to 2 volts per division.
3 to 10 V pp (including +0.5 VDC Bias) 0 V- Ch 1 = 2 V/div. T/div 0.5 mS scopesg Figure 33: N2Bus Signal as Measured with Oscilloscope 6. Connect Channel B to the N2- wire and connect Channel A to the N2+ wire. Connect the oscilloscope ground lead to the N2 Reference wire. 7. Compare the signal you measure with the waveform in Figure 33. They should resemble the figure. A signal outside this range indicates that the N2 Bus is not functioning properly.
Ordering Instructions Johnson Controls Code Numbers Vendor Code Numbers Table 8: Johnson Controls Code Numbers Description Product Code Number N2 Submodule NU-N2B101-0 Enclosure for N2 Repeater BZ-1000-7 or AS-ENC100-0 Table 9: Vendor Code Numbers Description Model Number Manufacturer N2 Bus Repeater 4683-TTM-1 (115 VAC) 4683-TTM-2 (230 VAC) Acromag Transient Eliminator Surge Protector TE/JC04C12 Advanced Protection Technologies Fiber Modem Model 2110 Mini Bit-Driver Point to Point S.I.
Repair Parts If the communication terminal board or N2 Submodule is defective, replace it. Refer to the Warranty section of the Standard Terms page in your current Cost Schedule for information on returning defective material. If the surge protector is defective, contact the manufacturer for warranty and replacement details. (See Table 9.) The following table contains the current Metasys order numbers.
Notes Network Communications—N2 Communications Bus 59
Notes Controls Group 507 E. Michigan Street P.O. Box 423 Milwaukee, WI 53201 60 Network Communications—N2 Communications Bus www.johnsoncontrols.com FAN 636 Metasys Network Technical Manual Release 10.0 Printed in U.S.A.
