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
•
Installing the Repeater
•
Installing the Fiber Modems
31
•
Setting Terminations
33
•
Installing the Surge Protector
*36
•
Setting the Channel Switch (NCM 101/102 Only)
*48
*27
Commissioning Procedures
49
•
Overview
49
•
Checking N2 Bus Installation
49
•
Modifying N2 Bus Installation
49
*Indicates those sections where changes have occurred since the last printing.
© 1999 Johnson Controls, Inc.
Code No. LIT-636018
1
www.johnsoncontrols.com
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 Terminal Board
54
•
Checking Communication Faults
*51
*53
*55
Ordering Instructions
57
•
Johnson Controls Code Numbers
57
•
Vendor Code Numbers
*57
•
Repair Parts
*58
* Indicates those sections where changes have occurred since the last printing.
2
Page
Network Communications—N2 Communications Bus
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).
Figure 1 shows an example of several devices connected to the N2 Bus.
Note that the N2 Bus is wired in a daisy-chained fashion, in which
multiple devices are connected in series. The N2 Bus can use either solid
or stranded wire. It can also use optical fiber when special fiber modems
are used. Choices include:
•
3-wire twisted cable
•
two twisted pair telephone cable
•
two twisted pair cable with a shield
•
duplex optical fiber (requires pair of fiber modems)
N1 LAN
NCU
N2 Bus
NEU
ASC
(ILC Shown)
NEU
N2EXAMPL
Figure 1: Example of an N2 Bus Layout
Network Communications—N2 Communications Bus
3
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.
Channel A is typically used for the N2 Bus. Channel B is used for the L2
Bus, including connection to C210 and C260 application specific
controllers.
For the NCM200, the N2 Bus interface is built-in and the L2 Bus interface
is provided by installing an L2 Bus submodule in the NCM’s
communications submodule slot.
The N2 Bus carries all communication between the NCM and the N2
devices. The types of data that go across the bus include:
•
commands from the NCM to an N2 device
•
data requests from the NCM to an N2 device
•
responses from an N2 device to the NCM, including identification,
changes-of-state, advisories, and requested data values
•
complete databases for N2 devices
•
time synchronization message from NCM
The N2 Bus connects an NCM to other N2 devices either internally or
externally. Internally, devices in the Network Control Unit (NCU) are
connected to the N2 Bus via the base frame on the NCU (Figure 2).
Connection occurs when you plug an N2 device into the NCU. No manual
wiring is required.
Externally, N2 devices are connected to the N2 Bus via the terminal block
on the device or the Communication Terminal Board (TBC) if the
connection is at an NCU or Network Expansion Unit (NEU). Connection
occurs when you terminate the N2 wires between the terminal blocks and
TBCs. Refer to Figure 2.
4
Network Communications—N2 Communications Bus
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.
Communication
Types
The N2 Bus features three different types of communication, which may
come from either an NCM or any user interface device: offline poll,
online poll, and general communication. The NCM initiates all
three communication types.
•
Offline Poll--a request from the NCM to re-establish communication
with an offline device. This type of poll occurs continually between the
NCM and each offline N2 device that is defined in the NCM database.
An offline device is polled once after every complete scan of all online
devices. Once communication is established, the NCM begins sending
online polls to the device.
•
Online Poll--a request from the NCM to the N2 device for any status
changes. The NCM polls devices continually, according to the priority
levels assigned to the devices. Polling is interrupted momentarily when
a command is issued through general communication.
•
General Communication--commands and requests that come from
application programs or operator devices. These can occur anywhere
on the network. This type of communication takes precedence over
polling. After general communication finishes, polling of online and
offline devices resumes.
Network Communications—N2 Communications Bus
5
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). However, you may assign higher priorities to a limited
number of devices if your application requires faster response times. For
details, refer to Guidelines for Efficient Operation Technical Bulletin
(LIT-636341) under the Appendix tab of this manual.
Data
Transmission
Figure 3 illustrates how a data request from an Operator Workstation
(OWS) travels over the N1 Local Area Network (LAN) and the N2 Bus.
Figure 3 shows that the request is made at the OWS:
1.
The request is created at the OWS.
2.
The message is transmitted over the N1 LAN to the NCM that has this
object defined. The NCM reformats the message.
3.
The NCM sends the message over the N2 Bus to the appropriate
device to obtain the requested information. The N2 device responds.
4.
The NCM sends the data to the requesting OWS.
5.
If the N2 device in the request loop is offline, the NCM notifies the
OWS.
Operator
Workstation
NCM
N2 Device
1
N1 LAN
2
5
3
4
N2 Bus
DATAREQ
Figure 3: Data Request from OWS
6
Network Communications—N2 Communications Bus
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).
Network Communications—N2 Communications Bus
7
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. The N2 Submodule is required for every NCM101/102 that
communicates with any N2 device, regardless of whether the N2 device is
within the same NCU or remote from the NCU.
Note: The NCM200 contains a built-in N2 interface and the NCM401
does not use the N2 Bus Submodule when the NCM401 is used for
migration applications.
TB2
1
2
5
3
1
4
TB1
6
2
4
5
3
6
Communication Terminal Board (TBC821)--This module is the
termination point for the N2 Bus and L2 Bus. (The old TBC model,
TBC801, also terminates the N1 LAN via two coax connectors. It is shown
in Figure 10.) It allows an NCM to communicate with NEUs and ASCs.
The board is factory mounted, and is located in the upper left corner of the
5-slot and 2-slot unit, and on the left side of the 1-slot unit. Every NCU
and NEU contains a communication terminal board.
Repeater (4683-TTM-1/2)--The N2 Bus repeater isolates and boosts the
power of the N2 Bus signal, which extends the range and increases the
number of devices that can reside on the N2 Bus. You need a repeater only
when the N2 Bus must be extended beyond 5000 feet or beyond
50 devices. The repeater actually creates a new N2 Bus segment.
(A segment is an electrically continuous daisy-chained cable between
repeaters or repeaters to End-of-Line [EOL].) In addition, the repeater
electrically isolates the two segments.
Enclosure (BZ-1000-7 or AS-ENC100-0)--This metal box is used to
house the N2 repeater. Because 120 VAC is terminated to the repeater via
three wires, not a plug, you must install the repeater in an enclosure to
meet National Electrical Code (NEC) requirements.
8
Network Communications—N2 Communications 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. These modems were tested as fully functional with
the Metasys system and found to be transparent to Metasys
system operation and functions. Other modems are available, but
because design changes were made to the 2110 to make it
compatible with the Metasys Network, other modems may not
work.
Power Supply (S.I. Tech 2121)--Resembling a calculator power
supply, this component provides power to the 2110 optic converter.
Each 2110 modem requires one 2121 Power Supply.
9-Pin Connector Kit (Male)--This kit is required to construct a 9-pin
connector and hood for terminating the N2 Bus cable to the 9-pin female
connector on the 2110 fiber modems. (The modems do not have a 3-point
terminal block for the N2 as do other N2 devices.) The connector kit needs
to use D-style connectors (solder style).
Cable--The N2 Bus can use either a solid or stranded type of the
following wires: 3-wire twisted cable; two twisted pair telephone cable;
and two twisted pairs with a shield. Duplex optical fiber can also be used.
Surge Protector (TE/JC04C12)--The surge protector guards the
N2 Bus from most induced voltage transients resulting from natural or
man-made disturbances. It is recommended if the N2 Bus is to be wired
between buildings.
In addition to these components, internal N2 Bus circuitry is included on
the boards of all N2 devices and on the NCU and NEU base frames.
Network Communications—N2 Communications Bus
9
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. The recommended
enclosure is the BZ-1000-7. Another option is to use the AS-ENC100-0
enclosure with the repeater’s cover removed. The 2121 power supply is a
calculator-type supply. See Table 1 for dimensions of these devices.
If you are using optical fiber, consider the minimum bend radius of the fiber
cable you are using. While handling the cable, do not bend it at right angles.
A minimum radius of cable must be maintained. (Refer to the fiber cable
manufacturer’s guidelines for the bend specification.) Adhering to the
bending rules may dictate where you can locate the units and how large an
enclosure must be used to install the units and still adhere to the rules.
Table 1: Device Dimensions
Environment
Device
Dimensions
N2 Bus Repeater
177.8 H x 109.2 W x 53.3 D mm (7.0 x 4.30 x 2.10 in.)
BZ-1000-7 Enclosure
259 H x 249 W x 76 D mm (10.2 x 9.8 x 3.0 in.)
AS-ENC100-0 Enclosure
173 H x 185 W x 119 D mm (6.8 x 7.3 x 4.7 in.)
2110 Fiber Optic Modem
76 H x 44.5 W x 16 D mm (3.0 x 1.75 x 0.625 in.)
2121 Power Supply
38 H x 51 W mm (1.5 x 2.0 in.)
The operating environment for the N2 Bus and its components must
maintain temperatures within the range of 0 to 50°C (32 to 122°F) while
maintaining relative humidity at a value of 10 to 90% (non-condensing).
The operating environment for the repeater must maintain temperatures
within the range of 0 to 70°C (32 to 158°F) while maintaining relative
humidity at a value of 0 to 95% (non-condensing).
If the N2 Bus is installed in an area of the country that often experiences
thunderstorms and the N2 Bus is wired between the buildings, surge
protection or optical fiber for the bus is recommended. Refer to Installing
the Surge Protector in the Installation Procedures section of this
document.
Power
10
The repeater requires an external source of 115 VAC at 0.05A
(or 230 VAC at 0.03A) at a frequency of 60 Hz (or 50 Hz). The
recommended power supply for the 2110 fiber modem is the
S.I. Tech 2121. It converts either 110/220 VAC 60/50 Hz to 12 VDC
(8 watts). The power supply requires an electric wall outlet nearby.
Network Communications—N2 Communications Bus
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. If you have existing stranded
cable, you can use it, but you may find that the strands become a nuisance
when wiring the cable. However, stranded wire is stronger than solid wire,
since it is not as prone to breakage during installation.
For N2 Bus installations where the very high noise exists (e.g., gas ignition
systems, radar or magnetic resonance imaging equipment, factory floor, or
outdoors), shielded wire or optical fiber is best. Of the two, fiber is by far
the better, but the more expensive. It offers extended N2 distances and
excellent immunity to electrical noise, lightning, and various other
building noises. It may be buried underground between two buildings, so
that the N2 Bus can be extended in a campus-type installation.
N2 Bus Rules
Table 2 summarizes the rules and maximums allowed for installing the
N2 Bus. You may wish to photocopy this table and keep it handy. These
statements are explained in following sections.
Table 2: N2 Bus Rules
Category
Rules/Maximums Allowed
General
One or two N2 Bus per NCM
Only daisy-chained devices
Number of Devices
100 devices per NCM (60 to 200 TC-9100s)
50 devices per repeater
Two repeaters cascaded
Line Length and Type
1524 m (5000 ft) between NCM to farthest N2
device before repeater is needed
4572 m (15,000 ft) from NCM to farthest N2
device (three segments of 5124 m [5000 ft] each)
2012 m (6600 ft) between two fiber modems
Cable
26 AWG twisted pair or larger
(solid or stranded 22 AWG or heavier
recommended)
Terminations
Two switched EOL per segment (preferred)
One switched EOL per segment (required)
Network Communications—N2 Communications Bus
11
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 actual number of devices is dependent on the features
and point count used in the NCM.
•
Special rules apply to the TC-9100 controller, where the maximum
number of devices can be from 60 to 200, dependent on the software
configuration in the NCM.
•
Up to 50 daisy-chained devices are allowed before a repeater is
needed. Add a repeater to the bus when you reach 49 devices. Count
each repeater as one device.
•
Any path from the NCM to an N2 device cannot go through more than
two repeaters or two pairs of fiber modems (i.e., cascaded
repeaters/modems). This is because the repeater/modem delays the
N2 Bus signal between Sides A and B. The N2 Bus can compensate
for only two of these delays; therefore, up to two repeaters or two pairs
of fiber modems can be cascaded in series. These configurations are
shown in Figures 12, 13, and 14. Note that the signal from the NCM
only passes through two repeaters or two pairs of modems to any N2
device.
•
For additional information on the maximum number of devices and
priority assignments, be sure to read Guidelines for Efficient Operation
Technical Bulletin (LIT-636341) under the Appendix tab of this
manual.
Line Length and Type
12
•
A maximum of 1524 m (5000 ft) of daisy-chained cable is allowed
before a repeater is needed. Add a repeater to the bus when you reach
1524 m (5000 ft).
•
The maximum distance from an NCM to the farthest device, even
through repeaters, is 4572 m (15,000 ft).
•
You may use 18 through 26 AWG twisted pair wire; however,
Johnson Controls recommends 22 AWG or heavier, because lighter
wire breaks easily when stripped and installed.
Network Communications—N2 Communications Bus
•
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.
Terminations
Each N2 device should be properly terminated as described in the Setting
Terminations section.
System
Expansion
Over time, the control needs of a building may require modifications to the
N2 Bus installation. For details, refer to the Modifying the N2 Bus
Installation section later in this document.
Maximizing
Your System’s
Efficiency
With the introduction of the NCM200 and NCM300, a larger allocated
memory capacity allows for increased database sizes per NCM. This
means you can add more elements to your system.
There is probably enough allocated memory for your database, but the
N2 Bus does have a finite bandwidth. Excessive traffic could slow down
the system despite adequate memory. Use generally accepted estimating
practices, then follow the guidelines below to maximize N2 operation.
Lab and Central Plant Controller (LCP) and DX9100 devices function
differently than other Metasys controllers. Therefore, if you use these
devices and have throughput problems, follow the suggestions below to
ensure that Metasys operates with maximum efficiency.
•
•
•
•
•
Priority One--Reduce the number of commands going to LCP or
DX9100 devices from GPL processes. If a process has 30 or more
consecutive commands or if the process is executed faster than every
20 seconds, you either:
increase the period length of the process or make it run on triggers
only, or
place delays between consecutive commands
Use Metasys Release 6.00 or later software to take advantage of
improvements in LCP/DX9100 message processing.
Reduce online polling by reducing the polling priority to Level 3 for all
devices on the N2 network.
Get offline devices back online as soon as possible. Refer to the
device’s technical bulletin in the Metasys Network Technical Manual
(FAN 636) for details.
Reduce the number of Analog Data (AD) and Binary Data (BD)
associated input points.
Network Communications—N2 Communications Bus
13
•
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.
The number of messages allowed on the N2 Bus differ depending on the
ASC firmware revision.
A maximum of 1100 messages per minute are allowed on the N2 Bus
unless it is connected to one of the following controllers (in which case
900 messages per minute are allowed):
•
Air Handling Unit (AHU) Version C02 or lower
•
One Unitary (UNT) Controller Version B02 or lower
•
Variable Air Volume (VAV) Controller Version A02 or lower
Refer to the following steps to determine the average rate at which
messages are traveling over the N2 Bus:
1.
Using the N2/L2/S2 Statistics window, track the number of polls,
commands, and offline polls for a five minute period during peak
usage.
To do this, clear the statistics and reread them after the five minute
period. (Refer to Using Diagnostics in the Operator Workstation
User’s Manual [FAN 634] for detailed instructions on using the
Statistics window.)
2.
Using the statistics from the five minute period, multiply the number
of offline polls by four (since offline polls take four times longer to
complete), add it to the total number of commands and polls, and
divide the total by five to calculate the total number of polls per
minute.
commands + polls + 4 (offline polls) = number of polls per minute
5
14
Network Communications—N2 Communications Bus
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.
Note: ASCs are self-terminating and therefore do not
require End-of-Line (EOL) resistors.
Transmission Media
3-wire twisted cable (26 AWG or larger; 22 AWG
recommended)
Two twisted pair telephone cable
Two twisted pair cable with a shield
(All cables listed above can be solid or stranded.)
Optical Fiber
Physical Configuration
Daisy-chained
Distance Between
Devices
Up to 1524 m (5000 ft)
Line Length
Up to 4572 m (15,000 ft) (one repeater per 1524 m
[5000 ft] or 50 devices)
Standard Components
N2 Bus Submodule (NCM-101/102 only)
Communication Terminal Board
Cable
Optional Vendor
Components
N2 Repeater:
Acromag 4683-TTM-1 (115 VAC) or
Acromag 4683-TTM-2 (230 VAC)
Note: Repeater required for N2 to support more than
50 devices or runs over 5000 feet.
Surge Protector: Advanced Protection Technologies
Transient Eliminator® TE/JC04C12
Fiber Modem:
S.I. Tech 2110 and S.I. Tech 2121
Power Supply
9-pin Male Connector Kit (required by 2110 modem)
* If you have VMAs on the N2 trunk, do not use addresses 254 or 255.
Network Communications—N2 Communications Bus
15
16
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.
Network Communications—N2 Communications Bus
17
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.
N1 LAN
N1
EOL
In
N1
EOL
Out
Operator Workstation
5-slot NCU
N2 Bus
N2
EOL
Out
N1
EOL
Out
N2
EOL
In
NCM's
N2
EOL 1-slot NCU
In
N2 Bus
N1
EOL
In
Operator
Workstation
ASC
(UNT Shown)
ASC
(ILC Shown)
Self
Termination
N2
EOL
Out
1-slot NEU
2-slot NEU
One
N2
EOL
In
LAYOUT1
Figure 4: Standard N2 Layout
18
Network Communications—N2 Communications Bus
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.
N1
EOL
In
N1 LAN
N1
EOL
In
5-slot NCU
Operator Workstation
N1 and
All N2
EOLs
Out
N2 Bus
Operator Workstation
N2 Bus
1-slot NEU
N2
EOL
Out
5-slot NEU
One
N2
EOL
In
ASC
(ILC Shown)
N2
EOL
Out
ASC
(UNT Shown)
Self
Termination
LAYOUT2
Figure 5: N2 Bus Layout with NCU in the Middle
Network Communications—N2 Communications Bus
19
Figure 6 shows a repeater lengthening the N2 Bus. The configuration has
two segments.
N1 LAN
N1
EOL
In
N1
EOL
In
N1
EOL
Out
NCM's
N2
EOL
In
Operator Workstation
5-slot NCU
Operator Workstation
1-slot NEU
N2
EOL
Out
A
Repeater
Side A=N2 EOL In
Side B=N2 EOL In
B
1-slot NEU
EOL
Out
ASC
(ILC Shown)
EOL
Out
N2 Bus
2-slot NEU
One
EOL
In
LAYOUT3
Figure 6: N2 Bus Layout with a Repeater
20
Network Communications—N2 Communications Bus
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.
N1 LAN
N1
EOL
In
N1
EOL
In
5-slot NCU
N1 EOL
Out
NCM's N2
EOL In
Operator Workstation
Operator Workstation
1-slot NEU
N2
EOL
Out
Note: Since the repeater delays the N2 Bus signal
between Sides A and B, a maximum of
two repeaters can be cascaded (connected in series).
A
A
Repeater
Side A=N2 EOL Out
Side B=N2 EOL In
1-slot NEU
1-slot NEU
B
N2
EOL
Out
Repeater
Side A=N2 EOL In
Side B=N2 EOL Out
B
N2
EOL
In
ASC
(ILC Shown)
A
B
ASC
(ILC Shown)
N2
EOL
Out
N2
EOL
Out
N2 Bus
2-slot NEU
All N2
EOLs
Out
Repeater
Side A=N2 EOL Out
Side B=N2 EOL In
N2 Bus
2-slot NEU
One
N2
EOL
In
A
Repeater
Side A=N2 EOL In
Side B=N2 EOL In
LAYOUT4
B
Figure 7: N2 Bus Layout with Branched Repeaters
Network Communications—N2 Communications Bus
21
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.
EOL=In
N2 Bus
To Remote
N2 Devices
N2FIBER1
Figure 8: N2 Bus Layout with Fiber Modems
22
Network Communications—N2 Communications Bus
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.Tech
2110
T
R
2110
EOL=In
To Local
N2 Devices
N2 Bus
Fiber
Cable
S.I.Tech
2110
EOL=In
To Remote
N2 Devices
R
T
S.I.Tech
2110
To Local
N2 Devices
2110
T
Fiber
Cable
T
R
EOL=Out
S.I.Tech
R
Fiber
Cable
S.I.Tech
NCU
EOL=Out
EOL=In
N2 Bus
To Remote
N2 Devices
R
Fiber
Cable
Notes: Only two pairs of fiber modems
can be cascaded.
For end-of-line terminations,
see the Setting Terminations
section of this document.
T
R
S.I.Tech
2110
EOL=In
N2 Bus
N2FIBER2
To Remote
N2 Devices
Figure 9: N2 Bus Layout with Branched Fiber Modems
Network Communications—N2 Communications Bus
23
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. Also, keep these wires
twisted up to within an inch or two of the actual screw terminals.
•
To maintain consistency throughout the system, it is best to use the
same color wires for the N2 Bus (e.g., always use the orange/white
wire for N2+ and the white/orange wire for N2-). This should ensure a
working N2 Bus the first time it is wired, and make troubleshooting
easier should a problem occur.
•
If the N2 wire has three conductors, terminate the third wire (and any
spare conductors) to REF, not to SFT GRD. Use the SFT GRD for a
shield only.
•
Shielded cable is generally not required, except in very high noise
environments, such as near gas ignition systems and radar or magnetic
resonance imaging equipment. If you must use shielded wire:
-
At each N2 device that does not have its own soft ground terminal
(e.g., ASCs), wire the shield to a 560 pF (1 Kv ceramic) capacitor
that is wired to earth ground. (If a 560 pF capacitor is not readily
available, one in the range of 560 to 1000 pF can be used.) At the
NCU and NEU, a capacitor is not needed, since the soft ground
termination at the TBC provides the required capacitance.
-
At only one NCU or NEU on the N2 Bus, wire the shield to earth
ground at the TBC.
Network Communications—N2 Communications Bus
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.
If shielded wire is used, wire shield to SFT GRD
(soft ground) terminal. To hard ground N2 Bus,
wire shield to HRD GRD (hard ground). N2 Bus
should be hard grounded at only one location,
preferably at the NCU.
Wires that are labeled "OUT" and "REF OUT"
are only used if the N2 Bus must continue
to another device.
For two twisted pair cable, terminate one pair
to (+) and (-). Terminate the other pair by
terminating one wire to REF and folding back and
taping the remaining wire.
tbcwire
Figure 10: Wiring N2 Bus to the Communication Terminal Board (TBC801)
Network Communications—N2 Communications Bus
25
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. To hard ground
N2 Bus, wire shield to HRD GRD (hard ground).
Wires that are labeled "OUT" and "REF OUT"
are only used if the N2 Bus must continue
to another device.
For two twisted pair cable, terminate one pair
to (+) and (-). Terminate the other pair
by terminating one wire to REF and folding back
and taping the remaining wire.
IN (+)
Twisted
1
REF-IN
IN (-)
2
OUT (+)
Twisted
REF-OUT
SFT
GND
3
4
SFT
5 GND
HRD
GND
6
OUT (-)
TBCWIRE2
Figure 11: Wiring N2 Bus to the Communication Terminal Board
(TBC821)
26
Network Communications—N2 Communications Bus
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. Note, however, that the grand total of all N2 Bus
segments can be much longer than 4572 m (15,000 ft). For example, in
Figure 13, the grand total is 7315 m (24,000 ft); however, the longest
single run is 4115 m (13,500 ft).
The station configuration, shown in Figure 12, has repeaters wired in
between the devices.
NCU
4572 m (15,000 ft)
NCM's
EOL In
50 Devices
1524 m (5000 ft)
N2 Bus
or
A
A
B
ASC
Repeater
Self
NEU
NEU
NEU
A: EOL In
Termination
EOL Out
EOL Out EOL Out B: EOL In
NEU
EOL Out
B
Repeater
ASC
NEU
A: EOL In NEU
EOL Out
EOL In
B: EOL In EOL Out
REPEATCN
Figure 12: Repeater Station Configuration
Network Communications—N2 Communications Bus
27
Figure 13 shows the branch configuration, with multiple repeaters wired
together and a separate branch of N2 devices off each repeater.
NCU
NCM's
EOL In
305 m
(1000 ft)
305 m
(1000 ft)
N2 Bus
762 m
(2500 ft)
152 m
(500 ft)
A: EOL Out
B: EOL In
EOL Out
NEU
Repeater
Repeater
914 m
(3000 ft)
1524 m
(5000 ft)
EOL Out
305 m NEU
(1000 ft)
A: EOL Out
B: EOL In
Repeater
1524 m
(5000 ft)
A: EOL In
B: EOL In
Repeater
1219 m
(4000 ft)
EOL In
EOL In
NEU
EOL In
EOL Out
305 m ASC
(1000 ft)
A: EOL In
B: EOL In
NEU
Note: Branches can be at
Side A or B.
REPEATC2
NEU
Figure 13: Network Branch Configuration
28
Network Communications—N2 Communications Bus
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)
0.9 m
(3 ft)
N2 Bus
A: EOL Out
B: EOL In
Repeater
1524 m
(5000 ft)
EOL In
1523 m
(4997 ft)
B: EOL In
B: EOL In
Repeater
Repeater
1524 m
(5000 ft)
A: EOL In
A: EOL Out
A: EOL Out
B: EOL Out
Repeater
1524 m
(5000 ft)
A: EOL In
1524 m
(5000 ft)
EOL In
EOL In
Self
Termination
B: EOL In
Repeater
1-slot NEU
1524 m
(5000 ft)
1-slot NEU
Self
Termination
1-slot NEU
ASC
(UNT Shown)
REPEATST
ASC
(UNT Shown)
Figure 14: Repeater Star Configuration
Network Communications—N2 Communications Bus
29
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.
J4
J3
N2 Bus Repeater
3 21
N2 Bus Side B
Com
D
D
REF-OUT
N2 OUT(-)
N2 OUT(+)
3 21
J1
J2
N2 Bus Side A
Com
D
D
REF-IN
N2 IN(-)
N2 IN(+)
Baud Rate
Switches
EOL
Jumpers
Side B
(Out)
EOL
Jumpers
Side A
(In)
120 VAC
G
W
N1
GND
LO
HI
Note: For two twisted pair cable,
terminate one pair to (+)
and (-), and the other pair
to REF.
REPEATIN
Figure 15: Installing the Repeater
2.
Mount the repeater in an enclosure, such as the BZ-1000-7. Mount the
enclosure in an appropriate location.
3.
Wire the repeater between two segments of the N2 Bus. If you are
using this repeater in a branch, the side with the branch will have
double the amount of wires terminated.
4.
Connect the power wires to the repeater.
For more details on installing the repeater, refer to the manufacturer’s
literature.
30
Network Communications—N2 Communications Bus
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.
Route the optical fiber in a manner that is required for the application.
2.
Connect the fiber cable from the T (Transmit) output of the modem
nearest to the NCM to the R (Receive) input of the modem near the
N2 devices.
3.
Connect the fiber cable from the T (Transmit) output of the modem
near the N2 devices to the R (Receive) input on the modem nearest to
the NCM.
4.
Plug in the power supply for each modem.
N2 Devices
Side
NCM
Side
N2 Bus
R
MINI OPTICAL BIT-DRIVER
MODEL 2110
Optical Fiber
R
S.I. TECH
MINI OPTICAL BIT-DRIVER
MODEL 2110
S.I. TECH
T
N2 Bus
T
CONNECT
Figure 16: Connecting the 2110 Modems
Connecting
Modems to
N2 Bus
Connecting the N2 Bus to the 2110 modem is accomplished by soldering
the N2 wires to pins on the 9-pin connector, which also configures the
modem as an end-of-line device. To connect the bus, go to the Setting
Termination on Fiber Modems section in this document.
Network Communications—N2 Communications Bus
31
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.Tech
2110
STUBCONN
To N2 Devices
Figure 17: Connecting 2110 Modem in Between
Two N2 Bus Segments
32
Network Communications—N2 Communications Bus
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.
(A)
T
(B)
T
SW
TERM
SW
TERM
SW
TERM
T
SELF
TERM
(C)
SW
TERM
SELF
TERM
(D)
T
T
SW
TERM
Key:
SELF
TERM
SELF
TERM
SELF
TERM
SW
TERM
SW
TERM
SW TERM = Switch-terminating devices. Includes NCM, DCM, XMs, ILC, IFC, D600, and repeater.
SELF TERM = Self-terminating devices. Includes AHU, LCP, UNT, and VAV.
T = End-of-line termination must be switched in.
EOLTERMS
Figure 18: Setting EOL Terminations
Rules
Follow these rules:
•
Set the EOL to In for any switch-terminating device with one N2 cable
connected, since this is an end-of-line device.
•
For each N2 Bus segment, at least one switch-terminating device must
have its EOL set to In. This is typically the NCM or a repeater.
However, the N2 Bus will be less susceptible to noise if the ends of
each segment have a switch-terminating device with its EOL set to In.
•
For a multislot NCU or NEU that is at the end of line, any one of the
EOL switches on any of the components can be set to In. However, to
maintain consistency, you may want to always use the EOL switch on
the N2 device that is located in the right-most (highest numbered) slot
in the NCU/NEU.
Network Communications—N2 Communications Bus
33
•
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).
If not at end-of-line and repeater is only switch-terminating
device on segment, install both jumpers over Pins 1 and 2
(EOL In).
Side B
J3 and J4
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).
If not at end-of-line and repeater is only switch-terminating
device on segment, install both jumpers over Pins 1 and 2
(EOL In).
Setting
Termination on
Fiber Modems
The 2110 modem does not have an EOL jumper to set. The EOL selection
is instead accomplished by properly terminating the N2 wires to the 9-pin
connector. Soldering the wires to specific pins and soldering two jumper
wires configures the modem as an end-of-line device. (For a summary,
refer to Table 5.)
Modem Set EOL=In
To set the modem as an end-of-line device, wire the 9-pin connector using
solder connections as shown in Figure 19.
34
Network Communications—N2 Communications Bus
Optional
Shield
REF
Fold back
and tape.
9-pin Connector
N2 -
N2 +
Solder jumper wires between Pins 3-7 and Pins 8-9.
eol-in
Figure 19: Modem’s Cable Connector: EOL Set to In
Modem Set EOL=Out
To set the modem with the end-of-line selection set to Out, wire the 9-pin
connector using solder connections as in Figure 20:
Optional
Shield
N2 +
Fold Back
and Tape
N2 -
REF
9-pin Connector
eol-out
Figure 20: Modem’s Cable Connector: EOL Set to Out
Table 5: EOL Connections Summarized
N2 Bus Signal
For EOL Selection
For Non-EOL Selection
N2 +
Terminal 7, Jumper 7 - 3
Terminal 3
N2 -
Terminal 8, Jumper 8 - 9
Terminal 9
REF
Terminal 1 or 5
Terminal 1 or 5
SHIELD
Tape Back
Tape Back
Network Communications—N2 Communications Bus
35
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
N2 Bus
N
E
U
N2 Bus
N2 Bus
protect1
Figure 21: Surge Protector Installation on N2 Bus
36
Network Communications—N2 Communications Bus
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.
!
CAUTION: The device is capable of protecting the N2 Bus from
indirect lightning strikes, not direct lightning
strikes. A direct strike may cause actual damage to
the bus cable or surrounding property. An indirect
lightning strike may cause induced voltage transients
that could cause electronic malfunction without
visible damage to equipment if the equipment was
not protected.
Use the surge protector with the standard N2 Bus wiring. Do not use it
with any other type wiring, such as leased line. If you need surge
protection for other wire types, contact APT or another transient noise
protection company.
Network Communications—N2 Communications Bus
37
Table 6 lists the specifications of the surge protector.
Table 6: Surge Protector Specifications
Category
Specification
Product Name
Transient Eliminator
Generic Name
Surge Protector
Model Number
TE/JC04C12
Design
Three stage solid-state design using both metal oxide
varistors and silicon avalanche diodes for suppression
Response Time
Less than one nanosecond
Maximum Impulse
Current
(8/20 ms current impulse)
10 kA per conductor
Maximum Energy
Dissipation
80 Joules per conductor (10/1000 us)
Maximum Operating
Voltage
12 VDC
Protection
Common and normal modes
Suppression Voltage
Levels (Common mode)
100 kHz ringwave @ 200A:
100 kHz ringwave @ 500A:
3 kA combination wave:
Negligible Insertion
Losses
At 9600 baud or lower
Maximum Number of
Protectors Allowed on
N2 Bus
No maximum; use as many as necessary and practical
Maximum Length of
N2 Bus Between
Two Buildings Using
Protector
1524 m (5000 ft) (standard N2 Bus specification)
Other Mechanical
Features
Encapsulated in Ceramgard for insulation and
environmental protection.
Two part design for easy connection and replacement of
protective device to base using edge connector.
Durable UL Recognized plastic enclosure material.
Dimensions (H x W x D)
63.5 x 50.8 x 25.4 mm (2.5 x 2.0 x 1.0 in.)
15.8 volts
16.8 volts
20.8 volts
One pair of surge protectors is required whenever the N2 Bus is routed
outside between two buildings. The ATP recommends that the protector is
installed close to the N2 device that first receives the bus wires from the
outside. For extra protection, you are allowed to install another protector
on the same N2 segment at the entrance or exit of the building. However,
it is very important that the protector be installed near the first N2 device,
because, if it were installed at the entrance of the building only, transients
may be introduced inside the building farther down the line, thereby
risking damage to the N2 device.
The protector does not require that you use any special type of wire for the
N2 Bus, such as double-shielded twisted cable. Just use the standard
recommended twisted cable types.
38
Network Communications—N2 Communications Bus
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. Refer to Figures 24 through 30 for the wiring diagrams for all
the various N2 devices. Also, follow these general steps:
1.
Mount the device per local codes and install in an enclosure
(if necessary) as close as possible to the N2 device. Any electrical box
with a cover is acceptable. Bond the enclosure to the N2 device by
connecting the two with conduit that carries the N2 cable.
Note: For extra protection, you may as an option, install a second
protector at the point where the N2 Bus enters the building.
Also, install that unit in a separate enclosure (if necessary).
2.
Connect the N2 segment from the outside to the unprotected side of
the device. If possible, run the segment inside metallic conduit, since
the conduit acts like a shield for lightning.
3.
Connect the N2 segment that will go to the N2 device to the protected
side of the device. Keep this segment away from the unprotected
segment.
Network Communications—N2 Communications Bus
39
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.
For hard-ground installation, connect the shield to Pin 9.
For soft-ground installation, connect the shield to Pin 7.
For more details on installation, refer to the specific manufacturer’s
literature.
40
Network Communications—N2 Communications Bus
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.
Make sure wires entering surge protector's enclosure are not close to wires leaving enclosure.
NCU/NEU - Shielded N2 Bus
Building One
Building Two
Metal Enclosure
Metal Enclosure
NCU
N2+
N2REF
SFT GRD
HRD GRD
Protected Unprotected
N2 Bus
Unprotected Protected
N2 Bus
+
+ 2
Surge 1
4 Protector 3
R
R
5 S
6
S
7
8
9
10
N2 Bus
+
+
1 Surge 2
3 Protector 4 R
R
5
6
S
S
7
9
NEU
N2+
N2N2 REF
SFT GRD
HRD GRD
8
10
HG
HG
HG
HG
Notes: At NCU, wire shield to HRD GND connection.
For surge protector's hard ground, use 12 AWG stranded wire, 4.57 m (15 ft) maximum length.
Make sure wires entering surge protector's enclosure are not close to wires leaving enclosure.
SURGE1
Figure 24: Installing Surge Protector for NCU/NEU
Network Communications—N2 Communications Bus
41
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.
Make sure wires entering surge protector's enclosure are not close to wires leaving the enclosure.
SURGE2
Figure 25: Installing Surge Protector for AHU/LCP/UNT/VAV
42
Network Communications—N2 Communications Bus
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, 4.57 m (15 ft) maximum length.
Soft ground (SG) the N2 Bus shield within one inch of entering the enclosure with a 560-1000 pF capacitor.
Make sure wires entering surge protector's enclosure are not close to wires leaving the enclosure.
Figure 26: Installing Surge Protector for AHU/LCP/UNT/VAV
Network Communications—N2 Communications Bus
43
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, 4.57 m (15 ft) maximum length.
Make sure wires entering surge protector's enclosure are not close to wires leaving the enclosure.
* The IAC, IFC, and ILC must each be on a separate N2 Bus.
Figure 27: Installing Surge Protector for IAC/IFC/ILC
44
IAC, IFC, or
ILC*
Network Communications—N2 Communications Bus
SURGE4
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, 4.57 m (15 ft) maximum length.
Soft ground (SG) the N2 Bus shield within one inch of entering the enclosure with a 560-1000 pF capacitor.
Make sure wires entering surge protector's enclosure are not close to wires leaving the enclosure.
SURGE5
* The IAC, IFC, and ILC must each be on a separate N2 Bus.
** Standard, Fire, or Security NCM.
Figure 28: Installing Surge Protector for IAC/IFC/ILC
Network Communications—N2 Communications Bus
45
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.
Make sure wires entering surge protector's enclosure are not close to wires leaving the enclosure.
Figure 29: Installing Surge Protector for N2 Bus Repeater
46
ASC
Network Communications—N2 Communications Bus
HG
SURGE6
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.
Soft ground (SG) the N2 Bus shield within one inch of entering the enclosure with a 560-1000 pF capacitor.
Make sure wires entering surge protector's enclosure are not close to wires leaving the enclosure.
SURGE7
Figure 30: Installing Surge Protector for N2 Bus Repeater
Network Communications—N2 Communications Bus
47
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.
NCM-101/102
(Inside Front Door)
N2 Submodule
Channel
Select
A
B
End-of-Line
Termination
Channel
Switch
A: TB1 (N2 Bus)
B: TB2 (L2 Bus)
End-of-Line
Switch
CHANNLSW
Figure 31: Channel Select Switch on N2 Submodule
Channel A is typically used for Metasys family N2 Bus devices. Channel B
is most often for wiring the L2 Bus devices, such as the C210 and C260
application specific controllers, to the Metasys Network. This document
discusses Channel A only. For details on Channel B, refer to the technical
documents for the C210A and C260A application specific controllers in the
Application Specific Controllers Technical Manual (FAN 636.3).
Set the switch to Position A for the N2 Bus to use Channel A.
Note: Channel selection for the NCM200 is automatic, since it has the
N2 Bus integrated.
48
Network Communications—N2 Communications Bus
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.
Checking N2
Bus Installation
Checking the N2 Bus installation involves verifying the:
•
N2 Bus installed according to the rules described in the Installation
Procedures section of this document
•
N2 Bus polarity and wiring for all devices
•
installation of N2 Bus repeaters, if any are used
•
positions of all end-of-line switches and jumpers
•
N2 Bus signal between N2+ and REF is 2.45 to 2.98 VDC, and
between N2- and REF is 2.06 to 2.54 VDC
•
Bias voltage approximately +0.4 VDC while no transmitters are active
A few of these problems can be detected with a Digital Voltmeter (DVM).
Ordinarily, this is the only equipment you’ll need.
Modifying N2
Bus Installation
Modifying the N2 Bus includes adding, deleting, or relocating an N2
device. These modifications can be performed while the bus is operating.
Note: When you are modifying the N2 Bus, remember to follow the
N2 Bus rules as outlined in Table 2.
Adding an N2
Device
An N2 device can be added between two other N2 devices or at the end of
the bus.
Follow these steps to add an N2 device:
1.
Define the new N2 device in the system software. Refer to the
Operator Workstation User’s Manual (FAN 634).
2.
To add a DCM or XM to an existing NCU/NEU, simply install the
device into a proper, available slot. If this device is not the end-of-line
device, set the EOL switch to Out. If this device now becomes the
new end-of-line device, set the EOL switch to In, and change the EOL
switch of the previous end-of-line device to Out.
Network Communications—N2 Communications Bus
49
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. If the ILC now becomes the new end-of-line
device, set the EOL switch to In, and change the EOL switch of the
previous end-of-line device to Out.
Deleting an
N2 Device
Follow these steps to delete an N2 device:
1.
Delete the removed N2 device from system software. Refer to the
Operator Workstation User’s Manual (FAN 634).
2.
To delete a DCM or XM from an installed NCU/NEU, simply remove
the device from the slot. If the EOL switch on this device was set to
In, set the EOL switch of the previous device to In.
To delete an ASC that is between two other N2 devices, disconnect
the In and Out sections of N2 wires at the ASC to be deleted. Connect
the two sections of the same color wire so as to follow proper polarity
(i.e., N2+ IN to N2+ OUT, N2- IN to N2- OUT, REF IN to REF OUT).
To delete an ASC that is at the end of line, disconnect the N2 wiring
from the ASC and disconnect only the N2 OUT wiring from the
upstream device.
Relocating an
N2 Device
A DCM or XM can be moved to a different NCU/NEU or a different slot
in the same NCU/NEU. Also, an ASC can be moved to a different location
on the N2 Bus.
To relocate a DCM or XM to a different slot or different NCU/NEU:
1.
Remove the device from the slot.
2.
Install the device in the desired slot or NCU/NEU.
3.
Change the EOL switches as required.
To relocate an ASC to a different spot on the N2 Bus:
50
1.
Disconnect the N2 Bus wiring.
2.
Install the ASC in its new position.
3.
Change the EOL switches as required.
Network Communications—N2 Communications Bus
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.)
The most likely problems with a malfunctioning N2 Bus are:
•
broken or frayed wire
•
improper bus termination
•
incorrectly set end-of-line switches or jumpers
•
improper channel switch selection
•
defective N2 device
•
too many N2 devices defined
•
N2 Bus is too long
•
N2 Bus has “T” or “Y” connections installed
•
ground loop present on N2 Bus
•
defective repeater
•
defective surge protector
•
communication terminal board failure
A few of these problems are detected with a Digital Voltmeter (DVM),
and you can use an oscilloscope to pinpoint communication faults over the
N2 Bus.
Checking for
Good Wire
Runs
The wire used for the N2 Bus must be free of broken or frayed sections.
If any of the three signal lines is broken or frayed, the devices that are
located after the break will report offline. To check for the defective part
of the cable, start at the device that physically precedes the first offline
device. The problem is likely in the cable between the last online device
and the first offline device.
Network Communications—N2 Communications Bus
51
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. To check the cable, unscrew
and pull out the communication terminal board. A single mounting screw
holds the communication board in place. Press the cable into place, and
reinsert the communication board. Remember to screw the board back into
place.
Checking the
End-of-Line
Device Settings
For every N2 Bus segment, you must have one or two devices set as
end-of-line. One device is set if the devices at both ends are
self-terminating ASCs. Two devices are set if the devices at both ends are
switch-terminating devices. (For details, refer to the Setting Terminations
section in this document.) If you set the end-of-line terminations
incorrectly, the N2 Bus may have signal reflections that will interfere with
communication. If you set more than two devices per segment as
end-of-line, the N2 Bus may be loaded down, reducing the total number of
devices that can be connected. Verify that the correct devices are set as
end-of-line.
Checking for
Proper Channel
Selection
(NCM101/102 only.) The channel switch on the N2 Bus Submodule must
be placed in Position A, the channel over which the N2 devices
communicate. The submodule is installed in one of the NCM submodule
ports.
Checking the
N2 Device
The N2 device, if internally shorted, can bring down the N2 Bus.
However, this situation is rare. If you suspect this problem, you’ll need to
disconnect each N2 device one at a time and observe when the bus comes
back online. What is more common is for an N2 device to report offline.
The most common reason is an incorrect address setting. The setting must
match what is set at the NCM.
Checking the
Number of
Defined
N2 Devices
If you have too many devices defined and connected to the bus, the
N2 Bus may not communicate. The maximum number of devices
recommended on the N2 Bus is 100 (NCM101/102, NCM401, and
NCM200). For TC-9100 devices, the maximum may be from 60 to 200.
However, depending on how you use these devices, the actual maximum
may be lower. When you reach the maximum number, you’ll need to
connect the remaining devices to a different N2 Bus on a different NCM.
52
Network Communications—N2 Communications Bus
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.
If you do this, signal reflections will result, disturbing normal N2
communication. Make sure no such connections exist.
Checking for a
Ground Loop
The N2 Bus must be properly grounded at only one location, preferably at
the NCU. If grounded at two or more locations, a ground loop will be
introduced that will disrupt normal N2 communications.
Checking the
Repeater
The N2 Bus wiring at the repeater must be properly and securely
connected. Refer to the Installing the Repeater section in this document
for details. The device itself, if defective, can cause N2 communication
problems. For troubleshooting information, refer to the manufacturer’s
literature.
Checking the
Surge
Protector
The surge protector may cause N2 communication problems. First, make
sure the surge protector is wired correctly, especially the hard and soft
grounds (Refer to Figures 24-30.) An easy way to tell if the unit is
defective is to simply disconnect the hard ground wire on the protected
side of the surge protector. If communication is restored, the unit is
defective and should be replaced.
Another way is to disconnect the surge protector from the N2 Bus and tape
the loose ends of the bus together, making sure you maintain proper
polarity. If N2 Bus communication resumes, the surge protector is
defective.
The surge protector is not field-serviceable. If found defective, the entire
unit must be replaced.
Network Communications—N2 Communications Bus
53
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.) The
Fuses F1, F2, and F3 protect TB1; Fuses F4, F5, and F6 protect TB2.
If any of these fuses blows, you need to replace the board.
Table 7: Communication Terminal Board
Terminal Screw
N2 Bus Wire
Fuse
1
N2(+)
F2
2
N2(-)
F1
3
SFT GRD
None
4
REF
F3
5
SFT GRD
None
6
HRD GRD
None
To check the TBC fuses, remove the single screw that holds the board in
place. Pull the board out far enough to enable you to probe the
non-component side of the board. Using an ohmmeter, measure for
continuity across each fuse by first placing one probe on the exposed
portion of the fuse (Figure 32). Place the second probe on the
non-component side of the board, onto the fuse pad with a trace leading
to the ribbon connector.
For example, to test fuse F1, place the probes on the exposed portion of
F1 and to the F1 pad on the non-component side whose trace goes to the
connector. If you measure an open circuit, the fuse is blown.
54
Network Communications—N2 Communications Bus
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. Both channels must have the
same gain or volts per division setting.
3. With no signal applied, adjust each channel’s vertical position at the
same graticule on the screen (i.e., center screen).
4. Select the Channel A minus B function. If your scope does not have
this function, select the Add function (Channel A Added to B then
Invert Channel B),
5. Select the 0.5 mS horizontal range.
Network Communications—N2 Communications Bus
55
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.
Note: At the dead time between messages, you can measure the bias
voltage. In this figure, it is 0.5 VDC.
Factors that can cause improper signal levels are:
56
•
N2 Bus wires are not polarized correctly (i.e., wires are reversed).
•
N2 cable runs are too long.
•
24 AWG wire has breaks in it.
•
An ASC has malfunctioned.
•
N2 Bus is improperly terminated (e.g., EOL jumpers configured
improperly).
•
N2 Bus contains too many devices, loading down the bus.
•
N2 Bus wiring has T or Y connections installed.
•
Check all wiring and devices to pinpoint the problem. Replace parts if
necessary.
Network Communications—N2 Communications Bus
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. Tech
Fiber Modem Power
Supply
Model 2121 Power
Supply Battery Charger
(110 VAC to 12 VDC) or
Model 2122 (220 VAC to
12 VDC)
S.I. Tech
9-pin Male Connector
Kit
Plug: Amp Type
No. 747904-2
Cable Clamp: Amp Type
No. 207467-1
Amp Corporation
CompuAdd 39661
CompuAdd
(for N2 Fiber
Application)
Interface Cable,
9-to 25-pin (AT Pigtail
serial, 2 feet,
DB9F-DB25M)
Notes:
The 2110 modem comes standard with ST-style connectors. However,
SMA-style connectors are available as options. You will need to coordinate
the fiber terminations with the type of connector ordered. Check with the fiber
installer or the customer for the type of fiber connector used.
A rack-mount version of the 2110 modem is available. For more
information, contact S.I. Tech.
A cable assembly (Model 7110) for the 2110 modem is available from
S.I. Tech.
For engineering assistance with single mode fiber, fiber cable, and extended
distance modems, contact:
S.I. Tech
P.O. Box 609
Geneva, IL 60134
(630) 761-3640
FAX (630) 761-3644
Network Communications—N2 Communications Bus
57
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.
Table 10: Metasys Order Numbers
58
Component
Order Number
NCU Communication Terminal
Board (new model)
EN-TBC821-0
NCU Communication Terminal
Board (old model)
EN-TBC801-0
N2 Submodule
NU-N2B101-0
Network Communications—N2 Communications Bus
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.