Apprentice path · Stage 13: Conductors and markings · Lesson 43

Read the jacket marking

What is printed on the jacket tells you what the cable is. What it looks like tells you nothing.

Why this matters on the job

Cables that are rated for completely different environments can look identical on the reel. The marking is the only thing that separates them, and it is right there on the jacket.

How to think about it

  1. Read the markings -- they identify the conductor or cable type.
  2. Check that it is suitable for the environment and temperature where it is going.
  3. Use the listed specifications, not appearance.

Worked through

Two black jackets side by side, same diameter, same feel. One is suitable for the location you are installing in and one is not, and the difference is a line of small print. Reading it takes a few seconds. Getting it wrong is discovered by the installation failing in service, which is much later and much more expensive.

Check yourself: A cable looks just like one you have used in a wet location before. Is it suitable for a wet location?

Answer: No. A similar-looking jacket does not prove a cable is suitable for a wet location.

Suitability comes from the listed specification for that cable, which is what the marking identifies. Appearance is not a specification, and two cables can look the same and be rated for different environments.

Watch out for: Going by the reel it came off or the colour of the jacket. The marking is on the cable itself for exactly this reason -- so the answer travels with the cable rather than with whoever remembers where it came from.
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Written from the owner's poster for this lesson. Nothing added beyond what the poster states.

Written for Texas apprentices as free study material. The Texas apprentice licence is an application, not an exam (Occupations Code 1305.161), and nothing here counts as apprenticeship hours or continuing-education credit. VoltMark is not affiliated with, endorsed by, or sponsored by NFPA, PSI, TDLR, or any state or local licensing authority. Always follow your employer's safety programme and your supervising electrician.