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Is there a requirement in the NEC that you may not use smaller than 3/4" EMT in a commercial building? I always thought that but can't find it in the code book..
NOTHING in the NEC "requiring" a minimum of 3/4" raceway unless your raceway fill calculation requires it. However, many project specifications do require a minimum of 3/4" raceway.
 

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Chief Flunky
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The 3/4" inch conduit only rule is urban legend or a specification. It is the companion rule to "you must install a pull box every 100 feet" rule. I think both are in Section 13.

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John
I wrote the spec for multiple foundries and mines. It is not urban legend. I wrote things into my specs like “must be designed to be pulled gently by a D8 dozer” for portable substations. I just had a Westrock paper mill require RMC or IMC in substations. Not even getting into insane ABS (maritime) stuff. Honestly not sure what you use 1/2” EMT for…it’s hard finding even fish tapes that will work in it.
 

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I wrote the spec for multiple foundries and mines. It is not urban legend. I wrote things into my specs like “must be designed to be pulled gently by a D8 dozer” for portable substations. I just had a Westrock paper mill require RMC or IMC in substations. Not even getting into insane ABS (maritime) stuff. Honestly not sure what you use 1/2” EMT for…it’s hard finding even fish tapes that will work in it.
...stick with the engineering portion, we got it 🙂
 

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This is silly. If you are running pipe from light to light it is much better to install 1/2" then 3/4. If you run down to a switch it is much better than 3/4". If you are running receptacle outlets then 3/4 " is better cause every body adds sooner or later.

What do engineer's really know about anything ? They should be more worried about cancer from the carpet in the office, and blindness from sitting under those LED lights they spec'd for the office remodel.
 

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Old thread that got bumped but what are some of you guys talking about!? Lol. 1/2" is used a lot in commercial and it's not hard to push multiple circuits of wire through. I can easily push five #12s through a 1/2" emt with multiple 90s no problem. Are you guy only using solid wire? With EMT stranded wire is a must! The flex of the stranded goes around the bends way easier.

And 1/2" bends a lot easier than 3/4", it's not the same.

I hate when the spec only 3/4" and I have to run a 3/4" down a wall for one receptacle with one circuit, what a waste. What, is the CEO in this corner office in downtown Chicago want to run a grow room in his office in the future and need an additional 5 dedicated circuits? Just ridiculous

The standard in office buildings around here is 3/4" or 1" home runs and 1/2" down the office walls. If there is a kitchen then one or two 3/4" to the first two boxes then branch out with 1/2" to get around all the plumbers pipe.
 

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This is silly. If you are running pipe from light to light it is much better to install 1/2" then 3/4. If you run down to a switch it is much better than 3/4". If you are running receptacle outlets then 3/4 " is better cause every body adds sooner or later.
Many industrial plants require 3/4” IMC or GRC. The problem with 1/2” anything is that if you even step on it, it is destroyed. At 1”+, even EMT is strong enough to withstand anything except fork truck drivers ... Honestly not sure what you use 1/2” EMT for…it’s hard finding even fish tapes that will work in it.
In industrial settings you often have conduit where someone might use it as a stepladder rung around the machinery, but that almost never happens in commercial. It's above a drop ceiling, along beams or bar joists, or strapped to a wall. But supported 8' - 10' apart, you need a really big conduit to work for stepladder duty for a 300 pound operator. It would be a better spec to say conduit can't span more than 1' unsupported unless strapped to a surface.

You can fit nine 12awg or six 10awg in half inch. I would guess that maybe 80% plus of the 3/4" EMT installed to spec in commercial buildings will never see more wires than that. Switch loops, lighting where the wiring is exposed, building controls, fire alarm, residential basements, lots of places 1/2" is more than enough.

Any fish tape will work most of the time, and a regular reliable steel fish tape with a spring leader will work almost every time. In fact I am pretty sure the floppy non-conductive ones, which often disappoint me, work better in smaller conduit - although the 90s are sharper, it pushes through better because the tighter conduit keeps the tape straighter. Likewise I think you might get away with pushing the wires through without using a fish tape more often with 1/2" than 3/4".

Half inch is less steel so it costs a little less and the bundles are lighter to carry around and half inch EMT is so easy to bend in the air. Half inch RMC is not much harder than 3/4" EMT to bend, and easy to thread too. You can fit more KOs on a small surface. The tighter bend radius will occasionally let you shoehorn it in places 3/4" wouldn't fit.

If you want to use half inch, the leftovers are too expensive to throw away, is it too much space and trouble to bother with? My inventory of leftover 1/2" EMT couplings and connectors (compression and set screw) and clips, hangers, and straps, bushings and doughnuts takes up a large milk crate. It's a different bender head but the same handle as 3/4". I don't keep that crate on the truck every day but I do keep the half inch bender head.
 

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Half the time you see 1/2” EMT above ceilings it’s separated from the coupling
Hence the reason to pull the EGC in EMT raceways. I know its not required, but I do it. 3/4" separates just as easy as 1/2"

What is this Fish Tape you speak of? I can't remember the last time I looked for mine. Just use a vacuum, string and a piece of plastic bag. Of course, I work where there is power mostly...;)
Short runs is not the time to pull out a vacuum or air compressor. In most cases you can just push the wires in. When I did high rise it was all pipe. 1/2" in the condos and 1.25" for panel feeders. We never used 3/4".
 

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If you run down to a switch it is much better than 3/4". If you are running receptacle outlets then 3/4 " is better cause every body adds sooner or later.
How many wires are you going to add to a conduit going to a switch? And even receptacles? If you add that many wires in the future, run your own freakin' conduit. I'm not in the habit of accommodating the next 1/2 dozen electricians that come along on my dime.
 

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How many wires are you going to add to a conduit going to a switch? And even receptacles? If you add that many wires in the future, run your own freakin' conduit. I'm not in the habit of accommodating the next 1/2 dozen electricians that come along on my dime.
read it carefully, I'm suggesting that 1/2" is better for switch loops. As for the 3/4" for receptacles, well, I keep getting requests for adding split ac systems in concrete condo's where the compressor is out on the lanai. And yes I have been able to pull two new #10 stranded for the unit thru the existing 3/4" run of buried in concrete emt thru 4 or 5 receptacle outlets to the lanai outlet which I convert to a j-box and then wire the compressor and new lanai outlet...
So I prefer you use 3/4". As for me? Not anymore , conduit is nuts nowadays. Well...... I did just win a bid to wire a basket ball/ volleyball gym , and it spec's 3/4 min on emt conduits so ................................................ all I need to do is convince the Engineer he needs to leave the country for a while and it will all turn out right for us both.....
 

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This thread is rediculous. Of course its legal. They make it, UL list it, give us code reference’s for it. So what’s the question?

On certain commercial new construction jobs, the prints sometimes say you cant install anything smaller than 3/4”, but outside of that, it’s free rein. Do it!
 
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