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Hi all
Is it permissible to use BX in a commercial building or must it be EMT conduit encased wires?
I’ve got a commercial building used as a shop and need to add new lighting. The wiring would be run at the ceiling along the girders. BX is a lot easier to run than EMT. Is BX OK?
Thanks in advance!
Zap
Replies
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Zap,
Hey, dude, bending pipe is FUN! Watchumean, you want to use BX? Well, if you really want to...
Use MC cable (it has an insulated equipment grounding conductor inside the armor), not BX.
Often, the armor of BX has corrodes away from the fitting, leaving a high-Z ground path to ground, or none at all. Also, the spiral armor isn't a great conductor even when new. MC cable doesn't use the armor as the ground path (though the armor is grounded).
In fact, in my city, you can't use BX. It's MC or pipe (flex, rigid, IMC, EMT) for commercial occupancies.
HAve fun...
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Greenfield yes; BX no.
Eric
*I was under the impression that there was no such thing as BX, that it was just trade lingo for MC.Unless you're running an unusual number of conductors, BX (or is that MC?) is alot easier than greenfield.
*There is a difference: Bx doesn't have a full-sized insulated grounding conductor. It is described in the NEC under AC cable. MC does have a full-sized insulated grounding conductor. It is discussed in the NEC as MC cable. Different applications and restrictions.Lee
*As one of the resident non-electricians at Breaktime, check me out here as I don't have a copy of the NEC handy:BX Originally a trade name from the original vendor of the stuff, refers to armored-clad cable (AC) that has a spiral steel galvanized cover over wires that are covered with kraft paper. Usable in dry locations only. Not codelegal in California and some other places. Commonly used in residential construction in the twenties and thirties,i.e. after tube and knob and before "ROMEX". ROMEX - Also a trade name. Commonly refers to non-metallic sheathed cable (NMC) - a (usually white) plastic coated two or three wire electrical cable, with or without ground wire, that is very commonly used in residential construction. Conducting wires are plastic wrapped while the grounding wire is generally bare (or paper covered).MC -Also a type of armor clad cable. TypeMC cable is manufactured with a green insulated groundingconductor which is used in combination with the metallic armor for the equipment ground. (From http://www.afcweb.com/faq.html and you will be quizzed on this..."One of the most important differences between these two cabletypes is the grounding means of the assembly. Type AC cable usesthe interior bond wire in combination with the exterior interlockedmetal armor as the equipment grounding means of the cable. TypeMC cable is manufactured with a green insulated groundingconductor, and this conductor, in combination with the metallic armor,comprises the equipment ground. ")(Note: Neither BX or ROMEX is to be used inside conduit - I assume that also applies to all AC and MC.)Greenfield - (I assume that this also was/is a trade name?) Used to refer to flexible metal conduit - for dry locations onlyLiquid tight - flexible metal conduit with a moisture resistant plastic covering Rigid Metal Conduit - Heavy wall steel tubing or pipe - not recommended for use with hand tubing benderPVC Conduit Thick walled plastic conduit (I think it comes in a couple of different formulations and in Schedule 40 and Schedule 80).EMT - Electrical metallic tubing - thin walled steel tubing that is fun stuff to work with with the proper benders- easily can be bent into all sorts of incorrect angles - however, bending over one's knee doesn't give the best results... (not for direct burial unless specially coated.)OK, I forget, what was the question? Oh yeah - EMT is great stuff to use - much more fun that BX. Besides, if you run EMT, you can change the color of your wires whenever you get tired of the old ones... (Let's see now, was I supposed to pose each of these in the form of a question?)
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CaseyR--
IS THAT YOUR FINAL ANSWER?
(Really, he's got it, I think he's got it...)
Except rigid (and IMC) are fun to bend too (3/4 inch or 1/2 at least). Bending 1" rigid can be done, get the two heaviest guys on the jobsite to help...
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Alright, I've always wondered where the "b" came from in NMC-B.
And I've put romex in emt pleanty of times where the emt was exposed but went into a box or up into the attic and I just wanted to switch to romex and passed inspections. They even make bushings and cable clamps for the end of EMT just to let you do this.
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The B comes from when the temperature tolerance of the insulation was raised from 60 deg C to 90 deg C. It distinguishes it from the lower temp cable. I think this happened sometime in the mid 80's.
Mike
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Ryan....Passing inspection has nothing in common with "up to NEC code."...
Next time strip the outer cover after entering the conduit....It's to do with heat as much of the code is to do with heat build up....But don't expect your utility to follow code as they are not required to....I just increased a service from 60 to 200 amps, had the utilities engineer out to look into hanging new wire...but nope...he said they would if it glowed to bright at night and kept the neighbors up or possibly if it melted off the poles...but not until then....
near the electron stream (or is it really holes migrating)...
aj
*AJ,How right you are !!! Or should I say, How similar are our utility companies....To meet code I had to wire my end of things with 3/4 inch copper cable running up the pole, and everything before that is heavy duty as well, (for 200 amp service.)Yet, when the P.U.D guy came out and hooked up my new 200 amp service, what did he run from the transformer at the street to my wires at the pole ??? 5/16 aluminum crap !!!! I am left wondering if this actualy makes my electric bill higher than it would be if it were run with the same cable I was forced to run...
*As I understand it, most of the wire that the utility companies run these days is aluminum.
*Luka - You could check for voltage drop under significant load (like an electric dryer, say) at the main lugs of your panel. Should be around 240V between hot legs. If so, then there isn't a problem.Lee
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Hi all
Is it permissible to use BX in a commercial building or must it be EMT conduit encased wires?
I've got a commercial building used as a shop and need to add new lighting. The wiring would be run at the ceiling along the girders. BX is a lot easier to run than EMT. Is BX OK?
Thanks in advance!
Zap