100 Amp Branch Feed in a commercial building

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  #1  
Old 04-22-11, 04:56 PM
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100 Amp Branch Feed in a commercial building

Hello to all.

I have been asked to run a 100 amp feed approximately 75 feet from a UPS battery backup system located on the second floor to a branch circuit panel that will feed some computers on the first floor. The entire feed run will be anchored to the steel beams above a drop ceiling except where it enters into the branch circuit panel. There are no concerns about physical damage and this is NOT a plenum type situation.

The building is a ten year old, two story office building with about 20 employees.

The problem with running this circuit is that it requires drilling a hole in concrete between floors to reach the UPS which is located on the second floor. Also, the location of this hole is in a very congested space on the first floor (Duct work, sprinkler pipes, etc.) that it is extremely difficult to get to.

Trying to run ANY type of rigid style conduit (EMT, non-metallic, etc.) is nearly impossible because of the congestion of the ceiling area where the cable will have to go between floors. I can get some sort of flex conduit fished through this area that will allow pulling the proper cable, but that too will be difficult.

I have been told that I have to use a metal sheathed type cable or conduit for the wiring because it is a commercial building. However, I can't find #2 wire already in a flexible metal sheath without using "Green field flexible conduit.

It was suggested by one supplier that I could use triplex within the Green Field conduit, but another said triplex is not permitted for use inside a building.

To add to the confusion, I have also read that in a two story building, NM cable CAN be used. So that raises the argument as to whether metallic type cable has to be used.

Lastly, do I even HAVE to even use conduit? Can I install a properly rated and jacketed Non Metallic type cable as long as it is protected from physical damage?

Thanks to all who respond, I appreciated your educated input.
 
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Old 04-22-11, 05:43 PM
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You're talking about an installation in a commercial building. I can't speak to where you reside - mostly because I don't know where it is - but most jurisdictions required licensed electrical contractors to perform any electrical work in commercial buildings.

Why?

How many MILLION $$ worth of liability insurance do you carry? How do you plan to pull a permit? What engineer/architect prepared the stamped installation drawings?

This isn't a project that should be undertaken by an inexperienced DIYer.
 
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Old 04-23-11, 07:17 AM
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There are prohibitions against non-metallic cables being used in ceiling spaces of commercial buildings.
 
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Old 04-23-11, 07:30 AM
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Nm is not permitted under drop ceilings in other than 1 and 2 family dwellings.

Tldoug, He seems to know what he is doing.
 
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Old 04-23-11, 11:14 AM
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Everybody else mentioned the legal aspects of your project so I will not beat a dead horse. I have never seen a commercial building that is too congested above the ceiling to run EMT, let alone one that is only 10 years old. IMO EMT and THHN wire would be the best wiring method for this job. Pipe does not need to be attached to the building structure, you can hang it off of threaded rod or ceiling wire (installed by you) and spring steel clips/mini's. Depending on the construction of the building you may have to get the floor scanned if it is a post tension building. Electrical suppliers will carry or can get MC cable the size you need but the cost would be off the chart!
 
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Old 04-25-11, 12:38 PM
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First I will say that it is inappropriate for your employer to ask you to do this job illegally. I would advise you to hire an electrician.

Originally Posted by jjdad2001 View Post
The problem with running this circuit is that it requires drilling a hole in concrete between floors to reach the UPS which is located on the second floor. Also, the location of this hole is in a very congested space on the first floor (Duct work, sprinkler pipes, etc.) that it is extremely difficult to get to.
I agree with Mr. Ironhand that you should not drill through this concrete slab without getting a structural approval. If you break a tension member in the slab you can seriously weaken the building. Precast concrete buildings only have certain spots you can punch through the slab safely. I would consider subbing that part out to a concrete cutting/drilling contractor; they can do a very nice core drill through the structure. The penetration through the floor and any other fire wall will need to be resealed in accordance with local fire code.

Trying to run ANY type of rigid style conduit (EMT, non-metallic, etc.) is nearly impossible
It shouldn't be a problem to find a route for EMT. It might look busy, but I bet there is a path.

I have been told that I have to use a metal sheathed type cable or conduit for the wiring because it is a commercial building.
Not necessarily because it's commercial, but because it's a steel and concrete structure. Anything NM is inappropriate here.

However, I can't find #2 wire already in a flexible metal sheath without using "Green field flexible conduit.
A supply house should be able to get MC in the right size no problem, but I personally would lean toward EMT and THHN.

It was suggested by one supplier that I could use triplex within the Green Field conduit, but another said triplex is not permitted for use inside a building.
Triplex would be wrong on a number of accounts.

I have also read that in a two story building, NM cable CAN be used.
In my experience that is only for wood framed buildings.
 
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