Electrical Forum - Support MC Cable

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Subject - Support MC Cable
David Hyatt	When jumping between lights in a lay in ceiling, Do you have to support MC. The code says every six foot and 12 inches from termination, but not real clear. If the lights are less than six foot apart. Also how is the best way to support them ( with tie wires from structural ceiling?
Ryan_J	No, in my opinion you don't have to support them. The 2005 NEC has new text in 330.30(A) to make this a more easily understood allowance. Perhaps when I get home tonight I'll post it (don't have the 05 here at work).
lctrc789	As long as we have done daisy chaining on lights we have not supported them unless they are over 6 ft anyway, We may use a tie wrap to help them from sagging but otherwise we have always gotten by without. I have seen a lot of different ways this is done tie wraps, batwings, and even tie wires lol.
SteveMc	Just don't support to the ceiling grid wires.
David Hyatt	Yea, thats what I was told from a fellow electrician.
Ryan_J	The ceiling gris wire issue can be found in the IBC, section 1621.2.5. It indeed is a violation of the building code to use the grid guy's wires. Should you decide to support, however, the wires you install must connect to the deck above and the grid below, 300.11
lctrc789	If we are doing a real large job we shoot in our own tie wires with a colored end, just for electrical wiring. We never attach to the existing tie wires for ceiling grid.
SteveMc	Good point Ryan, most electricians don't bother to attach to the grid.
iwire	I will admit we do not attach to the grid as required by 300.11, it is just not done around here. There is only one city that we work in that enforces this, in that city we will do it.
shocky	the grid wires you install must also be identified for the purpose(tagged,spray painted etc.)
Ryan_J	Only if it is fire rated. quote: (A) Secured in Place. Raceways, cable assemblies, boxes, cabinets, and fittings shall be securely fastened in place. Support wires that do not provide secure support shall not be permitted as the sole support. Support wires and associated fittings that provide secure support and that are installed in addition to the ceiling grid support wires shall be permitted as the sole support. Where independent support wires are used, they shall be secured at both ends. Cables and raceways shall not be supported by ceiling grids. (1) Fire-Rated Assemblies. Wiring located within the cavity of a fire-rated floor–ceiling or roof–ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided. Where independent support wires are used, they shall be distinguishable by color, tagging, or other effective means from those that are part of the fire-rated design.
ravengotu	Well in California code, which exceedes the NEC, is the City building codes...remember that the NEC is a general guide..and anything that makes it safer for all is what the inspector calls...we have to hang a support wire that will allow a caddy onto the mc 12 in from termination and every 5 foot we use another or the support that attaches to the light fixtures for sismeic......hope it helps but you can ask any inspector what there requirements are when they do rough insp
David Hyatt	Ryan, what about the exception list at the end of 300.11(2) where if install in accordance with ceiling manufactures instructions?
David Hyatt	I was just reading and noticed that the MC has to be secured but the lay-in light does not? Whats up with that. The light can be secured only to the grid.
iwire	quote: Originally posted by ravengotu remember that the NEC is a general guide..and anything that makes it safer for all is what the inspector calls The NEC if adopted into law is not a guide, it is the law. Is a 55 MPH speed limit sign a guide? Can the police pull you over and 'call for' you to go 50 MPH because it is 'safer for all'? Inspectors can only force compliance with adopted rules, which may be more or less than the NEC requirements. Inspectors can always ask for more, than it is up to you if you want to keep them happy. Many times the inspectors have good suggestions that are easy to comply with anyway.
RS377	quote: Originally posted by iwire quote: Originally posted by ravengotu remember that the NEC is a general guide..and anything that makes it safer for all is what the inspector calls The NEC if adopted into law is not a guide, it is the law. Is a 55 MPH speed limit sign a guide? Can the police pull you over and 'call for' you to go 50 MPH because it is 'safer for all'? Inspectors can only force compliance with adopted rules, which may be more or less than the NEC requirements. Inspectors can always ask for more, than it is up to you if you want to keep them happy. Many times the inspectors have good suggestions that are easy to comply with anyway. Actually they can and do, all of the time. Its called travelling too fast for conditions. And there are enough judgement calls in the vehicle code to make me sick.....
iwire	quote: Originally posted by RS377 Actually they can and do, all of the time. Its called travelling too fast for conditions. Agreed but again there is a law on the books that the cop writes the number down of. The cop does not get to make a law. I do agree the cops do get to make a judgment call on what laws to enforce.
SteveMc	quote: Originally posted by David Hyatt I was just reading and noticed that the MC has to be secured but the lay-in light does not? Whats up with that. The light can be secured only to the grid. Not where I live. It's not NEC, but all lay in fixtures must be supported separately from the ceiling grid. One of you building code gurus help me with a code reference.
RS377	In the bay area, we have to tie each lay in off at opposing corners with ceiling wires. In addition to that, we must use the clips provided on the fixture to secure it to the grid, and then screw the ficture to the grid itself. Some people say you have to screw the corners you didn't tie, off, while others say that each corner needs a screw. Without a doubt, our fixtures could supposrt the weight of the entire celing if need be.
Ryan_J	The requirement to secure the light to the grid is a building code issue. In the IBC, it is found in 1621.2.5, which references the CISCA 3-4. In the 2003 IBC, it is 1621 which references the ASCE 7. Both referenced standards require it.
Dave Nix	quote: 410.16 Means of Support.(C) Suspended Ceilings. Framing members of suspended ceiling systems used to support luminaires (fixtures) shall be securely fastened to each other and shall be securely attached to the building structure at appropriate intervals. Luminaires (fixtures) shall be securely fastened to the ceiling framing member by mechanical means such as bolts, screws, or rivets. Listed clips identified for use with the type of ceiling framing member(s) and luminaire(s) [fixture(s)] shall also be permitted. Ryan and Bob, You are saying this doesn't apply? According to this, if you fasten your fixtures to the grid, and the inspector thinks that the amount of support wires are adequate for the grid and the fixture, you are good to go! This of course doesn't take into account the earth quake stuff.
Ryan_J	Thanks Dave, I completley forgot about that section :D
Dave Nix	You are welcome Ryan!
Russell120	Just to make things even more fun. I recall that another issue affecting ceiling grid support is whether it is a UL listed assembly or not. Often the ceiling grid is an integral part of the fire rating of the structure (but not always). In which case you would need to follow the instructions of the UL listing. UL puts out books of these listings. If you have ever has to box the top and sides of around lay-in fixtures with additional tile material that is because of the UL assembly that the architect decided to use. If you ever bid a job, and miss the fact that the lights have to be boxed, you can take a real bath.
Ryan_J	Russell: I have only seen fire rated grid a few times ever. Here in siesmic design category D2, you can't use it because they don't make a rated 2 inch permiter angle. Using rated grid is a nightmare all the way around.
iwire	quote: Originally posted by Dave Nix quote: 410.16 Means of Support.(C) Suspended Ceilings. Framing members of suspended ceiling systems used to support luminaires (fixtures) shall be securely fastened to each other and shall be securely attached to the building structure at appropriate intervals. Luminaires (fixtures) shall be securely fastened to the ceiling framing member by mechanical means such as bolts, screws, or rivets. Listed clips identified for use with the type of ceiling framing member(s) and luminaire(s) [fixture(s)] shall also be permitted. Ryan and Bob, You are saying this doesn't apply? I do not recall saying that but as a matter of fact for us here in MA it has been amended. From the MEC quote: 410.16(C). Add a second paragraph as follows: In addition to, or in lieu of, the mechanical fastening means, electric luminaires (fixtures) containing ballasts, other than simple fluorescent reactance ballasts, shall be supported directly to the building structure by wire, chain, or threaded rod of sufficient strength to carry the luminaire (fixture). Fluorescent luminaires (fixtures) shall be supported at each end of a diagonal axis of the luminaire (fixture). Bob
veganfan	quote: Originally posted by Ryan_J The ceiling gris wire issue can be found in the IBC, section 1621.2.5. It indeed is a violation of the building code to use the grid guy's wires. Should you decide to support, however, the wires you install must connect to the deck above and the grid below, 300.11 What is IBC? Is it paart of NFPA or costruction code?
Ryan_J	IBC would be the International Building Code, adopted by about 40 states in the USA
luckyshadow	In my part of the world we are required to support our wires between lay in lights. We are to secure to our own wires dropped from the deck and attached to clips on the grid. We use a caddy made clip that is designed to give thus not directly affecting the ceiling. I have even had inspectors inforce the color issue. Our ceiling wires needed to be marked/tagged . I painted them a very bright pink. Another issue I come accross is tie wraps and where and how they can be used. They can hold things down but not up.
Ryan_J	The ceiling wires need only be identified if part of a rated assembly, as per 300.11
Russell120	Ryan Re: Boxing out lights That earthquake thing might do the trick! Some parts of North Carolina are in earth quake territory. Since most of the architects that I have worked with don't seem to really understand life safety issues- maybe I can throw that at them and make them come up with a different scheme. At least it will make them nervous. Boxing out (or tenting) of lights occurs on maybe 5% of the projects. Just infrequently enough to forget to look for it.