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What are the differences between PVC, riser and plenum rated cables?

What are the differences between PVC, riser and plenum rated cables?

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PVC, or PolyVinylChloride, refers to the coating of the cable jacket. If you have riser or plenum rated cables, they are slower to burn and produce less smoke than PVC and are rated to be installed in plenum areas (any area with return air). Riser cable is the minimum required cable for a riser application (floor to floor). There is also a newer kind of cable called limited combustible cable. In some jurisdictions the AHJ (authority having jurisdiction) supports the sprinkler standard which states that if you don't have LCC (limited combustible cable) then you have to install sprinklers under the raised floor and in the ceiling plenums. If you use PVC cable, you MUST install it in conduit if it is in plenum areas. There are three standards governing what type of cable you must use (I am assuming you are in the US… if not, the standards are a bit different. If you aren't in the US, let me know where you are and I will help you with the standards). The standards in the US include National Electrical Code, (NFPA 70), NFPA 90A (Standard for Air Conditioning and Ventilation equipment) and NFPA 13, which governs the use of sprinklers. In the last two, sprinklers are not required if you use LCC cable. In 90A, combustible cables such as CMP, CMR are allowed as an exception but LCC is required. The problem was that for years, we did not have LCC cable. Whatever you chose, you will want to talk to your inspector to determine if you will need additional sprinklers if you use plenum rated cable rather than LCC or if you will need conduit.

This was first published in February 2005

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