Rodent Proof CablingBy Brian Rhodes, Published Oct 18, 2012, 12:00am EDT
The biggest risk to your surveillance systems can be from the smallest threats. Cabling that connects and powers cameras is quite vulnerable, but often nothing is done to protect it from being damaged by insects and rodents. In this note, we examine the problem of rodent damaged cables, the options for combatting the issue, and how much those options cost.
Rodent damage occurs when animals or insects attack cable jacketing and wire cores. Even when damage is limited to "superficial" jacket damage, the underlying cable is left susceptible to shorts, breaks, and interference. Every major classification of cable used in video surveillance: Coax, UTP, and Optical Fiber is vulnerable to being damaged by pests, invariably in hard-to-access locations.
Pests and rodents destroy cable jackets for a variety of reasons:
Chewing Impulse: Because rodent's teeth grow continuously over their lifetime, the animals frequently chew to keep incisor length in check. Especially given the hardness and density of cabling compared to natural materials, wire bundles are a frequent target of attack.
Attracted to Material: Often, insects find a food source in the insulating materials or in the gel conductive layers. In the absence of better food sources, pests may find sustenance from cabling. In addition to being food, the odor, texture, and color of cabling can attract pests.
Warmth/Electromagnetism: Several types of rodents are attracted to the warmth of conductors inside cable jackets, or are sensitive to the EMI of the cabling. This affinity is the source of significant cable damage.
The image below depicts multiple examples of cabling damage:
The problem is compounded because damage and breakage occurs at hard-to-reach locations - not only in cable segments buried in ceilings and walls, but often in runs buried in the earth or under concrete. As a result, cable repairs are expensive and often result in abandonment of damaged lines and re-running entire segments.
There are a few cabling products that market 'rodent resistance', including:
- Kevlar Jacketing: the fabric in bullet-proof vests and tank armor makes an impermeable, direct bury type cable cover than cannot be penetrated by rodent teeth or claws. Kevlar is chemically inert and will not attract insects.
- Braided Metal Jacketing: An alternative to Kevlar, woven metallic sleeving can be installed around standard cabling.
- Chemically Treated Jacketing: specialty cabling products are available with 'anti-rodent' additives [link no longer available] cast into the jacketing plastic during manufacture.
- Anti-Pest Plastic Coating: Cabling can be field dipped before installation into rubber-like coatings formulated to hide odors and insulate heat transmission.
- Chemically treated Pull Compound: Some integrators have described success in keeping rodents at bay by adding repelling fragrances to cable installation 'pull compound' [link no longer available]. This allows standard cabling to be used, but field installed to be 'rodent resistant'.
Other successful, albeit costly, methods of preventing problems include running cabling in hard conduit pipe or 'EMT' tubing, and in sealed raceways. In the next section, we examine the general cost of each solution.
As a general rule, those most effective anti-rodent protections are those that add metallic barriers to cabling, ie conduit and EMT. However, this method is also the most costly in both additional materials and installation labor. Chemical additives are less expensive, but the potency (effectiveness) will wear off over time.
- Conduit: 3/4" tubing costs an average of $0.40 - $0.55 per foot. For an average run of 150 feet, conduit adds ~$60 - $75.
- Specialty Jackets: Whether factory applied or field installed sheathing, specialty jackets using cost an additional $0.25 - $0.35 per foot. For the average camera run, using specialty jackets add ~ $35 - $55.
- Chemical Coatings: While varied in form, dipping cables in chemicals or coating jackets with fragrances adds between $0.02 - $0.10 per foot. For the average run, chemical coatings add ~ $3 - $15.
For a typical system of 16 - 24 cameras, taking 'rodent proofing' measures can add $500 - $1500 in cost, but that expense can save thousands of dollars over the operation life of a system in prevented downtime, troubleshooting, and repair materials and labor.
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