Does anyone know if there is a web site that gives a clear, to the point, explanation of the numerous codes that regulate the support of lighting fixtures in suspended ceilings. I have read the posts on a number of forums and Googled the codes (IBC, ASCE 7, CISCA, ASTM C-636) but it just goes in a circle. One code will specify that you have to meet the requirements of another. Is there chart or table somewhere that spells out if you have this set of circumstances then you must do it this way?
I want to know under what circumstances and conditions independent support wires are requires. ASTM is a 'performance based" standard. IBC has different 'categories'. CISCA listed different 'zones'. Is their a concise, simplified explanation of these various codes as they apply to supporting fixtures in a suspended ceiling?
Re: lights in suspended ceiling#53763 07/07/0501:29 PM07/07/0501:29 PM
NEC 410.16 only requires that the fixtures be securely fastened to the ceiling grid. Local codes will dictate whether they need to be independently supported also, most do. This is usually by opposite corners sometimes by all four corners.
I wouldn't worry about that stuff you have been looking at, the local jurisdiction will tell you what they require.
Since most of the jobs we do are from prints and specs spelled out in the contract we are bound by them. Almost always the engineers spec the independant support. So we just got used to it, and unless the distance from the grid to the joists is more than about 5 feet it is not the end of the world. A bundle of commercial ceiling wire bought from a ceiling contractor is the cheapest way to go, as hardware stores get way more for the stuff, or many times the ceiling guys leave plenty for us and tell us to use it. It's always nice to know your troffers aren't going to be responsible for a chain reaction ceiling collapse.
Re: lights in suspended ceiling#53766 07/07/0510:19 PM07/07/0510:19 PM
Here it's not the jurisdiction of the elec. inspect. but the building inspector and they are required. They're referred to as seismic wires and no doubt a good idea. I saw footage of an earthquake from a security camera at a mall and it showed a bunch of troffers come crashing down and it wasn't that big of a quake. "nuff said" zero