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I'm looking into buying a few rolls of bulk Cat6 cable to wire up a few cubicles to a test rack we have. One of the choices is PVC cable versus Plenum cable.

What is the difference? Will this make any difference with crimping or crosstalk/interference?

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There's no telecommunication difference (e.g. noise, crimping, termination), just the sheathing. The difference is an electrical code safety issue.

Regular network cable (i.e. non-plenum) is flammable, can catch fire, can spread fire, and emit toxic fumes when burning.

Plenum quality cable is required for use if you run your cable in air handling spaces (i.e. air ducts), or if you're running them between floors. Plenum cable is fire-resistant (it will melt, but not support combustion or carry a flame). It also emits less toxic fumes when it does burn.

If you look at some network cable, you can see which type it is:

  • CMP: Plenum rated cable (plenum means "air handling space")
  • CMR: Riser rated cable (riser means "between floors")
  • LSZH: Low smoke zero halogen rated cable
  • CM/CMG/CMx: General purpose cable
  • PVC: Unrated cable

CMP burning:

enter image description here

CMR burning:

enter image description here

Notes

  • CAT6 is still very precise about how the cables are terminated. Sloppy termination will reduce the capacity of the run. This is generally not the case with CAT5.

  • The linked wikipedia article, has good diagrams illustrating what is plenum space and what isn't. Generally, you should use plenum cable in a dropped ceiling unless you are certain that it is not air-handling space. If a duct in your drop ceiling is missing a section: your drop ceiling suddenly, inadvertently, becomes an air-handling space.

See also

  • @Ian - Good info .. hope you don't mind the edit to clarify. If you do, feel free to undo it! – tomjedrz Oct 30 '09 at 17:03
  • That's fine, tomjedrz. i just changed it SO IT WASN'T ALL IN BOLD BECAUSE THAT WAS A BIT MUCH. Don't you think? :P – Ian Boyd Oct 30 '09 at 17:06
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Put simply, PVC Cable is the most common type of cable used today and consists of a chemical compound called Poly Vinyl Chloride. If a fire occurs, burning PVC Cable can emit large quantities of dense black toxic smoke, and significant amounts of hydrochloric acid.

If you have a Plenum ceiling, having PVC cable in the ceiling during a fire would cause a concentration of these fumes to be spread throughout the building. Exposure to these fumes could then hinder the safe evacuation of persons in the vicinity and result in increased fatalities. Plenum Rated Cable has a special coating on the wire, which causes it to burn at a much higher temperature and emit fewer fumes than conventional PVC. As a result, the National Electric Code (NEC) requires that only plenum rated cables be installed in plenum air spaces.

Therefore, for fire safety and code compliance concerns, choose PLENUM rated cable. If fire safety is not any concern or local code requirement, choose PVC for ease of installation and lower cost.

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A PLENUM area is the air return for an air conditioning system. In most buildings, the PLENUM area above a drop ceiling is used as the source of air for the air conditioning systems. Wire and cable are usually installed in the same area, and if that wire burns during a fire, it would emit toxic fumes. The fumes could carry to the rest of the building through the air conditioner, and, as a result, the fumes could harm others.

PLENUM cables are manufactured and tested to ensure the cable will not be the fuel to a fire. There are many materials that meet Plenum specifications. The most common is Teflon TM by DuPont. The materials required to pass PLENUM fire test specifications usually cause a price increase over non-plenum-rated cables. Usually, PLENUM fire resistant rated cables are two-three times the cost of PVC versions.

PLENUM cable tends to be a little more difficult to install because it sometimes will “kink” more readily during installation, and, it is more difficult to “strip” than PVC cable.

PVC means polyvinyl chloride, and it is a common plastic cable insulation or jacket. Special additives can be added to PVC to make it flame-retardant to meet plenum specifications in some installations.

For fire safety and code compliance concerns, choose PLENUM rated cable. If fire safety is not any concern or local code requirement, choose PVC for ease of installation and lower cost.

protected by Community Jan 17 at 19:56

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