Honeywell TotalPlant LCN System Installation page 40

STEP 3 Local Control Network (LCN) cables are grounded in two different schemes.
• Systems with the 12.5 KHz system clock are self-grounding, by way of the cable
shield, when the cable is connected to the BNC receptacle on the CS/R paddle
board in the clock source node.
• In systems with the 5 MHz bit digital system clock (a segment with only K2LCN
boards in the modules), the coax ground connection is made once for each cable
(A and B) by a wire from the KLCNA or KLCNB board to chassis ground. This
wiring is to be done in one module for each cable, preferably in the Module
designated as clock source modules.
In a segment that has had the processor board (EMPU, HMPU or HPK2)
replaced with K2LCN boards, the CS/R board must be retained but placed in an
empty slot in a module (the CS/R PWA is now used for grounding only).
If the system includes Hiway Gateway (HG) module(s) and a Hiway Traffic
Director (HTD), the Data Hiway cable shield grounding rules specified in the Data
Hiway Subsystem Site Planning manual must be followed. An overview of HG
preferred-access cabling is presented in Figure A-5.
If the system does not include the HTD, the Data Hiway cable shield is grounded
at the primary HG as follows: connect an AWG #14 wire from terminals 11 and
13 on terminal TB1 of the primary HG, DHI I/O board to the HG service post at
the bottom of the cabinet or station. See Figure 4-4. The HG service post must
be connected to Master Reference Ground (MRG) through AWG #4 wire.
The LCN cable connectors, like the Data Hiway cable connectors, must not be allowed to
touch the cabinet frame. All LCN cable connectors that enter or exit the cabinet or station
must be covered with heat-shrink tubing insulation.
Note that all LCN cable runs must be terminated the same way as the Data Hiway cables.
The 75-ohm terminators are interchangeable; however, the T-adapters are not.
For LCN cable, use BNC T-adapter P/N 51190728-105 (Kings No. KC-99-52 or Amphenol 31-
208-1051). For Data Hiway cable, use BNC T-adapter P/N 30732055-001.
In an all K2LCN segment of an LCN coax system, a ground must be provided for the coax
shield by placing a wire between the grounding screw of the KLCN CA/KLCN CB boards
and the logic ground terminal on the back of a Dual Node module. This should only be
done at one point on each cable in a coax segment. Ground Cable A and Cable B in
different modules.
Verify the integrity of the system ground wiring after the system power has been connected
(see Section 7). Any grounding problems must be identified and immediately corrected to
eliminate the possibility of any of the following conditions:
• Shock hazard to personnel
• System operating problems
• Damage to equipment
LCN System Installation
NOTE
4-4
4.2
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