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6.4 - Wiring Path & Cabling

Creation date: 10/26/2020 11:40 AM    Updated: 12/23/2020 12:38 PM   odn field services manual service manual excerpt
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Wiring Path & Cabling

(Section 6.4 in ODN Field Services Manual)


The purpose of running cables in conduit is to protect the wiring from environmental challenges. Aside from the basic corrosive forces of sun and rain, cables at un-attended sites may be subjected to deep snow cover, chewing rodents and tall weeds. There are also human challenges such as weed-whackers, foot traffic, truck traffic, etc. Try to use common sense regarding the conduit path, as all these facilities will be different. Generally, try to use the shortest, least obstructive, tidiest path possible. 

While not required, ODN strongly recommends VSAT cables be protected with rigid conduit, especially in tower site environments where falling debris and ice are likely. Check with customer on the requirement of conduit for your installation environment.

Some helpful tips when planning & installing conduit:

  1. If possible, situate the antenna construction so that the center pole lines up with the straightest path to the wiring destinations (without compromising satellite view).
  2. Run all cables (AC power, RF and ground) in separate conduits. AC power and RF should not share a conduit as per electrical protocol. Also, the 2AWG Ground wire is too large and inflexible to be pulled with another cable without risking cable damage.
  3. Choose a conduit path that least impairs regular foot traffic that can be anticipated. Consolidate multiple conduits so that wiring paths do not create multiple obstacles.
  4. Use as few degrees of turns as practical. Use no more than 360 degrees total in each conduit path. (No more than four 90-degree elbows) This will ensure that wires will pull with enough ease that they do not get damaged in the process.
  5. Use wide enough footings and enough anchor points so that the conduit is not easily moved or tipped. 
  6. Tighten all coupling seals and use weather heads wherever practical to prevent the conduit from filling with water.
  7. If any conduit path looks like it would need to be noticed and avoided by personnel entering and exiting the equipment shelter, mark the conduit with safety paint or reflective stickers.
Typically, several (approx. 6”) sections of Unistrut are used in the conduit installation. The Unistrut is either mounted to the shelter wall/foundation with fender washers and Tapcon screws or laid on the ground for anchor points. The conduit is then affixed to the Unistrut pieces with properly sized conduit clamps designed for Unistrut.

Alternatively, conduit can be buried depending on site environment. Ensure all local regulations are followed.

Examples & aspects of above-ground conduit installations at tower sites:

[Figure 6.4.1] Sometimes it is possible to mount conduits to the side of the building. This is preferable as it keeps the ground clear of obstacles. Note that the span in front of the shelter door in [Figure 6.4.2] is marked with reflective tape.

   
            [Figure 6.4.1]                                                            [Figure 6.4.2]

[Figure 6.4.3, Figure 6.4.4] When running across the ground, keep the conduits grouped and mounted to the same set of Unistrut props until it is necessary to diverge to different destinations. (nearest ground bus, outdoor GFI outlet & RF cable entry on shelter) This makes for less clutter on the ground and fewer areas for personnel to navigate over and around.

  
            [Figure 6.4.3]                                                            [Figure 6.4.4]

[Figure 6.4.5, Figure 6.4.6] Occasionally it is necessary to turn the ballast blocks in the tray 90 degrees to provide a straighter conduit route.

  
            [Figure 6.4.5]                                                            [Figure 6.4.6]

[Figure 6.4.7, Figure 6.4.8] Weather heads: Install weather heads on conduit ends for Heater AC power and RF conduits. Be sure to leave a drip loop. Try to make vertical runs of conduit at the antenna and equipment shelter tall enough to be at a height above seasonal snow and weeds. Ground cable usually does not fit thought the weather head well without exceeding bend radius requirements and since it is bare grounded wire in first place, moisture protection is not as critical. However, if not using a weather head for any reason, seal the conduit ends with silicon.

  
            [Figure 6.4.7]                                                            [Figure 6.4.8]

[Figure 6.4.9] Conduit end should deliver the cable to within 4 feet of the shelter cable ingress and be located where falling ice from the tower does not have an opportunity to damage the exposed cable. (Usually there is an ice bridge at the cable ingress)
[Figure 6.4.10] Cable ingress: Ideally, there will be accommodations for your RG6 cable in form of a weather sealed gland assembly that is empty and sized correctly. However often this will not be the case. Sometimes the dual RG6 cable must share an entrance with an existing RF cable. This requires disassembly of the gland, notching out enough space in the corner of the center rubber disk with a saw or knife, running the RG6 cable into the shelter, and then reassembling & sealing the gland with silicon. 
Caution must be exorcised to not damage the other RF cables!

  
            [Figure 6.4.9]                                                            [Figure 6.4.10]

[Figure 6.4.11, Figure 6.4.12] Optional De-icer (heater) unit power: This line should be running to the exterior GFI AC outlet and should always have a weather head and drip loop. To fish the AC cable through the conduit, the AC cable will need to be disconnected at the antenna end and then re-spliced. Often the 25’ AC cord that comes with heater unit is not long enough and must be replaced with longer cable, so keep a spare 50’ outdoor 14AWG extension cable in your supplies as well as butt splices.

  
            [Figure 6.4.11]                                                            [Figure 6.4.12]

[Figure 6.4.13, Figure 6.4.14] Markings: Remember that even if the tower location seems to be in the middle of nowhere, there are several other companies and people who need to visit the location periodically (at all hours and seasons) for electrical maintenance, fuel delivery, grounds keeping, etc. Wherever you believe there is a section of conduit that may be a tripping hazard or need to be noticed, mark it clearly with reflective tape or safety-colored spray paint!

  
            [Figure 6.4.13]                                                            [Figure 6.4.14]

Conduit tooling, supplies & labor considerations:
Do not underestimate the time and labor involved in conduit installation. Depending on the location, the time it costs to evaluate the path, install conduit, and run the cable is often about the same as building and pointing the 1.8M antenna. So, delegate the labor accordingly.

Minimal conduit installation tools:
  1.  1” Conduit bender –
  2.  Conduit scoring tool –
  3.  Frame Hacksaw –
  4.  Sawzall with metals bit –
  5.  Screwdriver set –
  6.  Adjustable spanning & plumbers wrenches –
  7.  Hammer drill with proper bit for Tapcon masonry screws –
  8.  Nut driver for Tapcon masonry screws
Conduit supplies:
  1.  1” conduit (100’ average per site) –
  2.  Watertight compression fittings (9 average per site) –
  3.  1-5/8” to 2” Unistrut channel (3’ average per site) –
  4.  Unistrut clamps (15 average per site) –
  5.  Weather heads (5 average per site) –
  6.  1” conduit section, 90-degree sweep (average 2 per site) –
  7.  Tapcon masonry screws (if needed) –
  8.  Fender washers for Unistrut (if needed)
  9.  16-14 AWG butt splices (if needed for heater)
  10.  50’ AC Extension cord (if needed for heater)
Weather proofing connections for long-term trouble-free operation:
An improperly sealed/installed connector can work great at the time of install but can typically cause failures within the next season. Outdoor RF connections must remain dry. Otherwise they will short out or corrode, making the system have severe TX/RX errors and render it unusable until the problem is repaired. Each of the 6 outdoor RG6 connections on a satellite system (4 at the ground block, 1 @ BUC & 1 @ LNB) is a potential point of failure. The following are prevention
measures technicians should use so that sites do not require a re-visit.

[Figure 6.4.15] Cable ingress: Ideally, there will be accommodations for your RG6 cable in form of a weather sealed gland assembly that is empty and sized correctly, but typically this is not the case. Often the dual RG6 cable must share an entrance with an existing RF cable. This requires disassembly of the gland, notching out enough space in the corner of the rubber disk with a saw or knife, running the RG6 cable into the shelter, and then reassembling & sealing the gland.
Use outdoor waterproof rated RG6 connectors! Not all RG6 connectors are rated for outdoor use, and not all “outdoor use” descriptions are accurate. Typically, on the outdoor RG6 connectors, you can see a small o-ring in its rear plastic section before it is compression crimped. Please be mindful in selecting the right type!

[Figure 6.4.16] Fill the connector with a water proofing compound before tightening down. Several products are available on the market that fill the negative space inside the connector and thus prevent water from entering. See: STUF Dielectric Waterproofing Grease, Super Lube Silicon Dielectric Grease.

  
            [Figure 6.4.15]                                                            [Figure 6.4.16]

[Figure 6.4.17] Tighten the connector threads with a small wrench, do not merely “finger tighten”. (But be careful not to over-torque!)

[Figure 6.4.18] Cover and wrap the entire connector with a rubber or mastic splicing tape. Do not use vinyl/plastic electrical tape as it will dry out and deteriorate in sunlight and is not truly watertight in the first place. Use wire ties to tie down the ends of the rubber tape to prevent un-wrapping.

  
            [Figure 6.4.17]                                                            [Figure 6.4.18]

Loop
[Figure 6.4.19] The “Drip Loop” is a concept that has been employed by wiring professionals since the earliest days of electrical installations. The basic idea is that gravity is the best deterrent for rainwater penetration. When a wire enters a wall of a building from outdoors, it should first loop downward near the opening before returning to the level of the egress. This causes any moisture to shed from the wire before it can get to the opening in the building.

[Figure 6.4.19]

The same principle can be applied to preventing water from entering outdoor electronics (BUC, LNB) and connectors on ground blocks.

[Figure 6.4.20] On side-connected BUC units, orient the BUC on the feedhorn so that the connector faces down, flushing the rainwater away from the connector instead of into it.

[Figure 6.4.21] On ground block assemblies, orient the ground block so that wires connecting to it loop down from it for at least a short span, so that water falling on the rest of the run will not follow into the connections.

  
            [Figure 6.4.20]                                                            [Figure 6.4.21]
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