# of NM cable in 1/2" EMT?


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Old 03-07-09, 10:01 PM
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# of NM cable in 1/2" EMT?

Can I run 2 14/2 cables in 1/2" EMT? this is in an unfinished area where I am using NM for the lights. I have it stapled to sides of joists, but where it runs down along concrete to the switch box, It will be in EMT. I supposed if needed I could have it go to the lights first and then I would only have a switch loop of 1 14/2 going in conduit.
 
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Old 03-08-09, 07:46 AM
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The answer is somewhere between 1 and 0. In general you shouldn't run NM in conduit. It can be used as short lengths for protection. In that case 1 cable would be max. I'm not quiet sure what you are doing, Ceiling joists? Floor joists? Inside, outside? where exactly is it.
 
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Old 03-08-09, 09:42 AM
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this is in a unfinished room with concrete walls and concrete floor that is below my new dining room. It will be used for storage. My furnace is located here. So I need the protection on the concrete wall to come down from the floor joists above to the switch. One of the books I have(either Wiring Simplified or Wiring a House-for pros by pros) states that this is how usually done-NM along the joists and pull it into conduit for the down runs along concrete walls.

Since NM has THHN (or is it THWN?) wires, could I just strip the outer jacket off of the NM right after it is clamped to the NM-EMT coupler?
 
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Old 03-08-09, 10:12 AM
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Since NM has THHN (or is it THWN?) wires, could I just strip the outer jacket off of the NM right after it is clamped to the NM-EMT coupler?
NM has wires that look like THHN but they are not rated as THHN so no you can not strip it. Now that I know what you are doing your plan sounds fine. It comes under the heading of using short lengths of conduit for protection of NM.
 
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Old 03-08-09, 01:09 PM
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thanks. glad to know it is OK. I thought I read somewhere that the wire in NM was rated THHN?--

just found it in Wiring a House-says it "is SIMILAR to THHN; it even has the same clear protective sheath over the insulated conductor....NMB is rated at 90deg."

Wiring Simplified says a little differently--"nonmetallic-sheathed cable-this is a very common type of cable containing two or three type THHN or THHW wires. Many people call it "Romex"..."

So one says it is and one says it is similar??
 
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Old 03-08-09, 03:23 PM
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I don't work at a wire company, but here is my thought. Since the conductors inside NM cable are not marked, you therefore can't be sure, as an inspector, what they are. Very likely, the NM cable manufacturer is really pressed for cost, and the ability to NOT have to the mark the internal conductors saves $. I'll take a wild guess that the manufacturer pulls unmarked THHN and then runs it into NM/UF.
 
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Old 03-08-09, 03:40 PM
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I thought I read somewhere that the wire in NM was rated THHN?
They are THHN, but they are not rated THHN.

When Ray said that your plan sounds "fine", he means (I think) that it is "fine" to use 1/2" EMT for short lengths of one 14/2.
 
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Old 03-08-09, 04:08 PM
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Originally Posted by John Nelson View Post
They are THHN, but they are not rated THHN.

When Ray said that your plan sounds "fine", he means (I think) that it is "fine" to use 1/2" EMT for short lengths of one 14/2.
Yes, that is what I meant. John could he run two in 3/4 inch? I think he originally wanted to run two in one place.
 
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Old 03-08-09, 04:09 PM
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little confused, it IS THHN but it is not RATED THHN? what exactly does that mean and what are implications? If it IS THHN, how can it not be rated since isn't the rating part of requirement for being THHN?

so really my question--can I use two 14/2 and the answer is no, only one 14/2? Is that correct John? If so, I will just have to reroute wire to fixture first and then do switch loop. no big deal. If I have more than one fixture, can just run them to the main fixture and connect them white to white and black to black with the wires from that fixture (in parallel) and then connect the "one" combined black and "one" combined white as normal for switch loop?
 
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Old 03-08-09, 04:17 PM
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Originally Posted by hammerash View Post
little confused, it IS THHN but it is not RATED THHN? what exactly does that mean and what are implications?
Wire that is rated to be THHN is marked as such.
Therefore, unmarked wire is not rated to be anything, since, it is effectively uninspectable in the field.
 
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Old 03-08-09, 06:06 PM
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It means that you cannot strip the wires out of the jacket and use them for anything. It's a bad idea even if you could because it's a lot of work and you risk damaging the wire and you can easily buy THHN at the store.

Another alternative that only requires one cable in the EMT is to put a junction box in the joist cavity above each outlet or switch.
 
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Old 03-08-09, 06:24 PM
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Originally Posted by hammerash View Post
lso really my question--can I use two 14/2 and the answer is no, only one 14/2?
My understanding is that using conduit to protect NM cable, you can squeeze as many in there as you can fit. You don't have to worry about derating until you have 9 current carrying conductors (4 NM cables).

If it's just a straight EMT run, you should be able to fit two 14/2 cables without a problem. If there are any bends, you likely won't be able to get them through. You'll have to run them both at the same time and keep them straight for them to fit.

If you don't want to cram them in (which I still say you can do), you could use two separate 1/2" EMT conduits down the wall to two separate knockouts in the box.

Good luck!
 
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Old 03-09-09, 11:01 AM
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Ok so I have another issue with the conduit. If I run it straight up wall, I end up running right into the bottom of a joist. So I either put the NM-EMT connector up as high as I can-which will be just below the bottom of joist, or If that won't work (meaning that inspector won't pass that) then I guess I have to find a 1" offset to get around the joist to get up into the bay? Big Box only had offset for connecting to EMT to box, none for connecting two EMT together. How should I handle this?
 
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Old 03-10-09, 05:50 AM
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conduit bender. Or, cut it a bit short; if you can't reach the NM, then most would consider it sufficiently protected, when indoors.
 
 

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