1/2 EMT vs 3/4 for branch circuits...
- Thread starter Mule
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No different except more likely to have that many ccts heading in the same direction for any distance in commercial (Mcmansion excluded). IMO by the time you install 9 wires & sort through the colors & the grand plan you could have run 2-3 homeruns in 1/2". I see whole houses w/o 1 stick of 3/4".
mkgrady
Senior Member
- Location
- Massachusetts
I run a lot of emt where support is limited. Like several feet down from the ceiling across the middle of a mechanical room. I hang unistrut from 3/8 inch rod. I can often run 1/2 inch emt on these racks but I use 3/4 inch because it is more rigid. If I use 1/2 inch it wobbles around more than I like
So if you needed to run 9 wires, you'd rather run two or thee 1/2"s? I'd fire someone who did that on a consistent basis.
As for colors, the Code doesn't restrict you to any specific scheme (Bk/Rd/Bl for 120/208/240 and Br/Or/Yl for 277/480). There's no reason not to use every color you need to keep the circuits seperated. If you DO want to limit yourself to a set color scheme, just wrap each set with tape.
Or are you saying you can run pipe faster than I can wrap 2" of tape around 3 wires?
You'd better watch it, he's got a bigger sparky number than you !!!!! Sorry, Im falling out of my chair laughing !! couldnt resist....forgive me...!!!
Ok Im sorry,:smile: Ive probably offended 480sparky
Come on 480Sparky, give me some air !!
cadpoint
Senior Member
- Location
- Durham, NC
- Occupation
- Electrician - but not by NC Law.
When did more than Three Current Carrying Conductors not be required derating?
Table 310.15(B)(2)(a) covers that well enough.
Your numbers above refer to Annex C Table C.1, which is: (based on Table 1, chapter 9)
It all boils down to all for a max. fill ratio to 40% of the EMT size used.
No where does it say that you can go beyond a 40% in respect to the numbers stated about, based on anything from the OP. I'm considering all this branch circuits.
You can run a bigger conduit to increase the number of circuits, in this instance but it's not correct to say that derating starts after the maximum amount of the circuits is met using Annex C Table C.1, again
see Table 310.15(B)(2)(a)
tryinghard
Senior Member
- Location
- California
I install per application some ?? some ??, I don?t standardize this. I can probably count the times I?ve added circuits in an existing conduit, I usually add the conduit as needed. If you do add circuits to a conduit don?t forget to adjust ampere capacity.
They are derated. But you derate using the ampacity of T310.16. Circuits using 14, 12 and 10 can be derated up to 9 conductors and still not be below the maximum OCPD specified in 240.4(D).
In other words, nine #12 THHNs have an ampacity of 21 amps (30*0.7). So you still can use a 20a breaker.
Thousands & thousands of homes in EMT in this area. No NM, No 3/4" EMT.
totaly Nieve on my part, I did not realize that there were homes being wired in EMT. My post question was aimed at commercial ......
We have some older larger homes in our town that were wired in emt, but I always thought it was just the boom days of folks having alot of money from oil..
peter d
Senior Member
- Location
- New England
More than likely Sparky555 is from Chicago or a surrounding area, which require dwellings and presumably all commercial buildings to be wired in EMT.
cadpoint
Senior Member
- Location
- Durham, NC
- Occupation
- Electrician - but not by NC Law.
I understand your statement, I don't think you gave my statement a correct thought.
My point was that Sparky5555 seems to imply that its ok to keep adding
circuits to a max.d out conduit. If I didn't say that I meant to!
You yourself said you'd fire one for filling up a conduit!
I've never thought of Annex C, T C.1 as pre-derated anything, I do beleive Annex C, T C.1 only shows the maximum number of CCC's based on some sum of the Cmil's or AWG, of any wire size to be under the 40% fill ratio per the conduit that might be used.(see note 1, in Chapter 9 Tables 70-671.
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- Location
- Massachusetts
Now there is a major waste of time.
(I know, it is required)
You must know that 99.9% of us will never wire an entire home with EMT.
From a fire code stand point, I figure that as the density of homes and people tightens up closer and closer, it comes to the point that the risk of loosing several homes from one fire makes them require conduit installations over romex....
To each their own, but I for one could not live like sardines, but Im spoiled by my surroundings
To each their own, but I for one could not live like sardines, but Im spoiled by my surroundings
- Location
- Massachusetts
They run the EMT in wood framed homes, I don't see the benefit. :smile:
peter d
Senior Member
- Location
- New England
The only benefit that I can see is being able to add more circuits down the road. But that can easily be done with ENT/"smurf tube" faster and cheaper than EMT.
- Location
- Massachusetts
I was replying about the fire prevention angle. :smile:
peter d
Senior Member
- Location
- New England
A little touchy today Bob, cause I was replying to whatever I darned well pleased to!
I reserve the right to derail this thread. But yes, I see no benefit to requiring EMT in a dwelling for ostensible fire prevention reasons.
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