410.10(F) Luminaires Installed in or Under Roof Decking.

It’s obvious that this high-bay luminaire is NOT installed at least 1.5 inches below the roof decking but it was code compliant when first installed based on the 2005 NEC. There are still other problems. Can you identify anything that was code compliant in 2005 but would be a code violation now?
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It’s obvious that this high-bay luminaire is NOT installed at least 1.5 inches below the roof decking but it was code compliant when first installed based on the 2005 NEC. There are still other problems. Can you identify anything that was code compliant in 2005 but would be a code violation now?

Code Change Summary: A new code section now requires luminaires installed under roof decking to be a certain distance from the roofing.

Everyone has seen it; while looking up at the ceiling inside the hardware store it is clearly evident that the roofer forgot how to measure and decided to fasten down the roofing with 6-inch roof deck screws (see image).

The 2014 NEC® has a solution for that. New section 410.10(F) requires all luminaires installed under metal-corrugated roof decking to maintain a distance of at least 1.5 inches between the luminaire and the lowest part of the metal roofing. This should work for a while until the roofer catches on and starts buying 8-inch roofing screws.

Below is a preview of the NEC®.  See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

2014 Code Language:

410.10(F) Luminaires Installed in or Under Roof Decking. Luminaires installed in exposed or concealed locations under metal-corrugated sheet roof decking shall be installed and supported so there is not less than 38 mm (1 ½ in.) measured from the lowest surface of the roof decking to the top of the luminaire.

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410.10(F) Luminaires Installed in or Under Roof Decking.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is required when installing luminaires under a corrugated metal roof deck?

A: The luminaires must be installed at least 1 inch below the lowest part of the corrugated metal.
B: The luminaires must be installed at least 1.5 inches below the lowest part of the corrugated metal.
C: The luminaires must be installed at least 2.5 inches below the lowest part of the corrugated metal.
D: There must be at least 1.5 inches below the highest part of the corrugated metal and the bottom of the luminaire.
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