The Same Cable Is Fine Inside the Conduit and Wrong Outside

Correct answer: C) The exposed metre is the finding: that conductor is not marked for sunlight resistance, so it is wrong where it leaves the conduit and acceptable where it does not

A conductor is not suitable or unsuitable on its own. It is suitable for a set of conditions, and it can meet them along one part of its route and fail them a metre later. Inside the conduit this conductor is protected from sunlight and from mechanical damage, and its wet-location and temperature ratings are the ones doing the work. The moment it leaves the conduit body it is in direct sun on a roof, and sunlight resistance becomes a condition it has to meet and does not.

That is why the answer is a metre of cable rather than the whole section. Re-pulling everything would treat the conductor type as the defect, when the defect is a conductor type in a place it does not belong. The fix is scoped to the exposure: either that span is protected, or it is replaced with a conductor marked for it.

The marking is the thing to read, not the type name. Some THWN-2 is dual-marked as sunlight resistant and some is not, and the two look identical on a reel. This conductor's legend settles it, and reading the legend takes a few seconds that no amount of reasoning about what THWN-2 usually is can replace.

The O&M point: the plan set is not wrong about the design, it is out of date about the site. Somebody repaired this run and the drawing was never touched, which is the normal fate of a repair done at eleven at night to get a site back online. The next person to read that conductor schedule will believe it. Recording what you found, and what the run actually is now, is as much of this job as the metre of cable, because the finding you do not write down has to be discovered again by whoever comes after you.

Why the other options are wrong

A) No finding — THWN-2 is rated for wet locations and 90 °C, which covers rooftop conditions

Both ratings quoted are real and neither is the one under question. Wet location and temperature cover water and heat; sunlight is a third condition with its own marking, and insulation that is not rated for it degrades under ultraviolet whatever its other numbers say. This is the answer that comes from checking the two properties that are easy to remember and stopping there.

B) The whole replaced section has to be re-pulled, because mixing conductor types within one run is not permitted

This scopes the repair to the conductor type rather than to the exposure, which makes it larger and more disruptive than the finding warrants. There is nothing inherently wrong with the conductor inside the conduit, and re-pulling a whole run to correct a metre of it is the kind of proposal that gets a genuine finding rejected on cost and then left unfixed.

D) The finding is a documentation one: the conductor installed is suitable, and what is missing is the as-built update

Half of this is right and it is the half that lets the defect stay. The as-built really is wrong and really should be corrected. But calling it documentation-only depends on the installed conductor being suitable, and for one metre of its route it is not. A finding that is written up as a paperwork item gets scheduled like a paperwork item.

References

• NABCEP OMAT JTA v.2026.5 — Domain 3, Task 1.D: "Conductor properties (e.g., temperature ratings, ampacity ratings, UV resistance, moisture resistance)". UV resistance is named alongside the other properties, which is the separation the question turns on.
• No ampacity table, code article or correction factor is quoted. The JTA names conductor properties as knowledge and does not test numeric thresholds, and the answer here depends on which property applies where rather than on any figure.