National Electrical Installation Standards

Standards as High as Your Own

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Monday, October 8, 2018

Question:

Re: CQD answer published Wednesday, September 14, 2018 -Suspended Ceiling Luminaires 1

Charlie, In regards to the question from Sep 13, 2018 about supports for light fixtures in a suspended ceiling grid. I offer the following standard found in most AIA specifications for acoustical tile ceilings and grids. That standard is ASTM C636. It is also part of most manufacturer’s guidance that the grid needs to be installed according to this standard.

The meat of the standard with regards to this question says: “supports on main tees should be at 4 foot intervals and Fixtures shall not be supported from main runners or cross runners if the weight of the fixture causes the total dead load to exceed the deflection capability of the ceiling suspension system. In such cases, the fixture load shall be supported by supplemental hangers within 6 in. [150 mm] of each corner, or the fixture shall be separately supported. “So, whomever inspects the ceiling grid should call out the problem to the ceiling installer. If the fixture exceeds the dead load rating, the ceiling installer should add the supplemental wires, unless the specifications call for the fixture to be supported independently of the grid (most often in seismic areas) when the electrical contractor should be providing the fixture supports. The ceiling grid installer has a reflected ceiling plan showing the location of the lights in it.  He should be able to bid accordingly.

In our specifications (we are not in a seismic area), we call out that the ceiling installer shall provide the wires at the corners regardless of the dead load rating. We coordinate with the architects to make sure they have the wording in their specifications.

Thank you, Alex

A

Answer:

Hey Alex thanks for your comment and the additional information. It is important to coordinate installations with other trades to comply with all of the rules. See tomorrows answer for more details about luminaires in suspended ceilings.

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ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

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