What You Need to Know About Installing Cables Outdoors

Dan Dunar by Dan Dunar | 11.20.2013

Seeing Christmas tree displays and shelves full of colorful LEDs signals to me that here in Wisconsin, it’s about to get cold, dark, and snowy really soon. Meanwhile in Phoenix, my friend Jeff loves to remind me, “You don’t have to shovel sunshine!”

As a manufacturer of low voltage wire and cable, we must make sure that our cables can withstand the environments in which they are installed. While I’m shoveling snow, the exposed cable on the side of the house must resist moisture. While the sun is burning Jeff to a crisp, the cables outside of his house must resist damaging ultraviolet rays. Various ratings and listings exist to ensure environmental suitability for cables, but the practical meanings of these listings are not always well understood. Let’s explore some of the more common listings for outdoor cables and the test procedures that define them.

Honeywell Cable OutdoorsSunlight Resistant
Cables marked “SUNLIGHT RESISTANT” or “SUN RES” can be installed where exposed to sunlight and moisture such as splashing or misting.

Wet Location
Cables marked “WET LOCATION” are rated to withstand additional moisture. Often these cables contain water blocking tapes, powders, or gels to absorb water to keep it away from conductors. If buried, these cables must be installed in conduit.

CMX – Outdoor
A CMX listing designates a cable for one or two unit dwellings. The outdoor designation allows for short distance exposure to sunlight and moisture.

Direct Burial
Cables marked “DIRECT BURIAL” or “DIR BUR” are resistant to crushing and can be installed underground without conduit. Their rigid and virtually impervious jackets provide excellent water resistance.

Testing
Three of the criteria for cables installed outdoors include UV/Sunlight Resistance, Water Resistance, and Crushing Resistance.

 

Jacket Marking

Sunlight Resistance

Water Resistance

Crushing Resistance

SUNLIGHT RESISTANT

-or-

SUN RES

720 hour Weather-Ometer test

WET LOCATION

12 Week Insulation Resistance Test

CMX – OUTDOOR

300 hour Weather-Ometer test

DIRECT BURIAL

-or-

DIR BUR

Mechanical Water Test

1000 lb. crushing test

 

To understand the tests, we must define a few measurements.

Tensile Strength: The force required to pull a material to the point where it breaks.
Elongation: The increase in length of a material at the point of breaking.
Insulation Resistance: The electrical resistance of the insulation material that covers an electrical conductor.

Weather-Ometer Test
In this test, samples of cables are exposed to intense light at repeating 120 minute cycles of 102 minutes dryness followed by 18 minutes of water mist. For “SUNLIGHT RESISTANT” listing, this repeats for a total duration of 720 hours (30 days.) For CMX-Outdoor listed cables, this repeats for 300 hours (12.5 days.) At the end of the exposure, the samples are dried and measured for tensile strength and elongation. If the ratio of tensile strength to elongation has been preserved by at least 80% (85% for 300 hour test,) the cable passes.

Insulation Resistance Test
In this test, a 1,000ft. length of cable is submerged in water for 12 weeks. At several times along this period and at the conclusion, 50ft. sections of the cable are removed, dried, and tested for insulation resistance. If the resistance has not degraded by more than permitted by a specified formula, the cable passes.

Mechanical Water Test
Cable samples are weighed and then submerged for 168 hours (7 days) for the mechanical water test. After this period, the water on the samples is shaken off, and the samples are weighed. The samples are dried for 48 hours and weighed a third time. If the difference between the second measurement and the lower of the first or third measurement divided by the surface area of the submersed surface is less than 20 milligrams per square inch, the cable passes.

Crushing Test
For the crushing test, a cable laid over a metal rod is crushed with a flat metal plate with a force of 1000lbs. for 60 seconds. The cable is tested at three points along the sample. If the jacket or insulation material splits, tears, cracks, or ruptures in anyway, the cable fails.

Understanding the different ratings and listings for outdoor cables and the corresponding test procedures can help you determine the right cables for your next outdoor job. Whether your next install takes you to a dry and sunny desert or a wet, winter wonderland, you can feel confident knowing that Honeywell has a Cable for That!