Question regarding EMT for overhead wiring requirements in an open shop plan

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Gorf

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Seattle, Washington
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Cybersecurity Researcher
Greetings all, my first post here. I am working with a team building a small datacenter space for some very proprietary research and we have a space that is basically an open steel frame and wood commercial space. Insulated, but not drywalled. This is in Washington State and I'm very confused on some aspects of NEC and what the local state (and King County) are asking for running all the thhn cabling via EMT. My understanding is that there is a height requirement in spaces like this in which you can transition out of EMT and hook up to standard NM wire. But then one of our team mates brothers, ex-college roommate or something told us that in Washington state we had to run it fully in EMT. I'm not opposed to that but it definitely adds cost. And if code doesn't require it, then I'm kinda inclined not to do it. For reference the space height is 14' and there are cable trays hanging about 12" down from that. Although those trays are what I'm familiar with for CAT5/6 and Fibre cabling so I'm not sure we are supposed to run any NM cabling in them.

Thanks all!
 
I did a job that was commercial with wood framing. We used EMT in exposed ceilings but ran MC cable through the bored holes in framing. The transition from EMT to MC would be much cleaner than EMT to NM at least NEC wise.
Are you suggesting to have EMT run around the ceiling area but have exposed NM run a short distance to the wall and through to the devices in insulated wall? Or is the transition from EMT to NM happen in a wall mounted box?
I am pretty sure that exposed NM cable to not allowed anywhere at any height. 334.10 (3) says should be concealed with 15min fire rating. I guess one needs to see if that insulation can satisfy that 15 min fire rating. If not, then the NM is a no go.
Not familiar with King county local codes but I find it hard to think that they would allow that.
 
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