jumper
Bronze Member
What is the reasoning of why NM is allowed in drop ceilings in residential, but not commercial buildings? I am talking about commercial buildings where is it okay to use NM in walls because of the correct type of construction.
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Makes sense. I thought it would be something like that, but I never really knew..raider1 said:My understanding is that the big problem is with the toxic smoke that the PVC jacket of NM cable can produce.The amount of NM cable in drop ceilings of homes would be a lot less that then there would be in a commercial dropped ceiling.
Chris
Did know that. I admit that I was never taught the correct rules for where you can use NM in non residential apps. Basically, we used MC in anything that was not residential. I am trying to learn the construction tables.Paul Sweet said:The NEC used to allow NM above dropped ceilings.
Don't we have a four story limit in VA. I added my location to my profile, forgot to do it when I joined.A few years ago they eliminated the 3-story height restriction for using NM, and this was the trade-off.
Basement ceiling only not required to be concealed?I personally believe it is because in a commercial environment, it is subject to physical damage compared to a residential environment. The NEC states in other than dwelling units, NM must be concealed. There's no way around that, and a dropped ceiling is no exception.
Basement ceiling only not required to be concealed?Pcinspector1 said:McClary's Electric,I personally believe it is because in a commercial environment, it is subject to physical damage compared to a residential environment. The NEC states in other than dwelling units, NM must be concealed. There's no way around that, and a dropped ceiling is no exception.
Chris© In Unfinished Basements and Crawl Spaces. Where cable is run at angles with joists in unfinished basements and crawl spaces, it shall be permissible to secure cables not smaller than two 6 AWG or three 8 AWG conductors directly to the lower edges of the joists. Smaller cables shall be run either through bored holes in joists or on running boards. NM cable installed on the wall of an unfinished basement shall be permitted to be installed in a listed conduit or tubing or shall be protected in accordance with 300.4. Conduit or tubing shall be provided with a suitable insulating bushing or adapter at the point the cable enters the raceway. The NM cable sheath shall extend through the conduit or tubing and into the outlet or device box not less than 6 mm (¼ in.). The cable shall be secured within 300 mm (12 in.) of the point where the cable enters the conduit or tubing. Metal conduit, tubing, and metal outlet boxes shall be connected to an equipment grounding conductor.
Basement ceiling only not required to be concealed?Pcinspector1 said:McClary's Electric,I personally believe it is because in a commercial environment, it is subject to physical damage compared to a residential environment. The NEC states in other than dwelling units, NM must be concealed. There's no way around that, and a dropped ceiling is no exception.