EMT electrical conduit -- how many NM wires?

[TomR]

I have a dedicated 15-amp circuit in an unfinished basement that runs to an
outlet on the wall for the sump pump. The wire/cable that goes to the
outlet is white 14/2 NM-B w/ground. From the ceiling down to the outlet it
is fed inside of metal EMT conduit. I assume that the metal conduit is
1/2-inch (the outside diameter of the conduit is about 3/4-inch).

I would like to add a pull string ceiling light above the sump pump for
better lighting while working on the sump pump and/or the HVAC which is next
to the sump pump.

What I am thinking of doing is getting power for the light from the outlet
and running new 14/2 NM-B w/ground from the existing outlet back up through
the same EMT metal conduit to the new ceiling light.

My main question is, is it okay to have two 14/2 NM-B w/ground cables inside
a 1/2-inch EMT metal conduit?

[recycl...@gmail.com]

You can’t have any NM cable inside a conduit.
It has to be single conductors.

[Nate Nagel]

I don't know the answer to that question as I'm used to seeing THHN
instead... I'm assuming the reason for using NM is that the EMT just
terminates at a bushing above the ceiling, and is only used for
protection of the cable?

Is the recep in a 1900 (4" square) box or a handy box? If a 1900 box I
would just get another stick of EMT and do it that way. (don't forget
the bushing where the EMT terminates, to prevent chafing the NM.) If it
is a handy box you probably don't have enough room in the box to legally
add more conductors anyway, and should consider replacing it with a 1900
box.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

[RBM]

If you run NM inside of metallic conduit, the metal should terminate in
you box using a proper fitting. At the other end of the conduit sleeve,
there should either be a choke or a bushing on the end of the conduit
and a staple into some framing near the end of the conduit. If you need
more cable entries in the box, use additional sleeves

[Doug Miller]

recycl...@gmail.com wrote in news:64bcf2b4-d88f-4d98-8daf-383a8784b898
@googlegroups.com:

>
> You can’t have any NM cable inside a conduit.
> It has to be single conductors.

Absolute nonsense. NM cable is permitted inside conduit in any location where NM is
permitted without conduit.

[Doug Miller]

"TomR" <To...@tomrljp5.lhd> wrote in news:krpmvc$hde$1...@dont-email.me:

> My main question is, is it okay to have two 14/2 NM-B w/ground cables inside
> a 1/2-inch EMT metal conduit?

Probably not physically possible anyway... but no, not as far as I know.

[TomR]

Thanks. That's how the conduit and wiring is set up now -- with the right
fittings clamps, etc.

> If you need more cable entries in the box, use additional sleeves.

Okay.

[TomR]

Thanks Doug, gfretwell, RBM, Nate, et al.

I have another option that I think will work. The existing 14/2 NM cable
runs along the side of a ceiling joist close to where I want to put the new
light. Most likely, I can just unstaple that cable and create enough slack
to place a junction box in the circuit there and run the light from that
junction box. Or, if that doesn't create enough slack, I could just use two
junction boxes.

But, before doing that, I thought that I would check to see if I could do my
original idea of having two NM cables in the one 1/2-inch metal conduit --
apparently not.

[tra...@optonline.net]

I ran two romex inside 1/2" liquidtight going to my furnace and it was
an easy fit. I would think you could do the same with metal.
think you'd get two inside metal as well.

[recycl...@gmail.com]

NEC Note 9 in the Chapter 9 tables says
"A multi conductor cable of two or more conductors shall be treated as a single conductor for calculating percentage fill area. For cables that have
elliptical cross section, the cross section area calculation shall be based on using the major diameter of the ellipse as a circle diameter".

[recycl...@gmail.com]

On Friday, July 12, 2013 1:58:08 PM UTC-7, gfre...@aol.com wrote:
> On Fri, 12 Jul 2013 13:15:41 -0700 (PDT), recycl...@gmail.com

> Wrong
>
>
>
> 334.15 Exposed Work.
>
> In exposed work, except as provided in 300.11(A), cable shall be
>
> installed as specified in 334.15(A) through (C).
>
>
>
> (B) Protection from Physical Damage. Cable shall be protected from
>
> physical damage where necessary by rigid metal conduit, intermediate
>
> metal conduit, electrical metallic tubing, Schedule 80 PVC conduit, or
>
> other approved means.

Even in that exception the conduit would have to be larger than ½” so as not to exceed the fill capacity.

[Doug Miller]

recycl...@gmail.com wrote in
news:168c113c-dc41-4949...@googlegroups.com:

How on earth did you manage to read that as prohibiting NM inside conduit?

[recycl...@gmail.com]

On Friday, July 12, 2013 5:20:47 PM UTC-7, Doug Miller wrote:
> recycl...@gmail.com wrote in
>
> news:168c113c-dc41-4949...@googlegroups.com:
>
>
>
> > On Friday, July 12, 2013 2:15:55 PM UTC-7, Doug Miller wrote:
>
> >> recycl...@gmail.com wrote in
>
> >> news:64bcf2b4-d88f-4d98-8daf-383a8784b898
>
> >> @googlegroups.com:
>
> >>
>
> >> > You can�t have any NM cable inside a conduit.
>
> >> > It has to be single conductors.
>
> >>
>
> >> Absolute nonsense. NM cable is permitted inside conduit in any
>
> >> location where NM is permitted without conduit.
>
> >
>
> > NEC Note 9 in the Chapter 9 tables says
>
> > "A multi conductor cable of two or more conductors shall be
>
> > treated as a single conductor for calculating percentage fill
>
> > area. For cables that have elliptical cross section, the cross
>
> > section area calculation shall be based on using the major
>
> > diameter of the ellipse as a circle diameter".
>
> >
>
> How on earth did you manage to read that as prohibiting NM inside conduit?

It exceeds 53% of the area for ½” conduit.

[Pete C.]

gfre...@aol.com wrote:

> You could get 2 in there if you aligned them perfectly and pulled them
> in together but it is still an over filled conduit.
> He also has another issue, the existing box is probably not big enough
> to terminate 2 cables.

Probably not applicable in this case, but you are allowed to ignore
conduit fill calculations for cases where the cables are passing through
a short length of conduit sleeve. What was it, 24" length max?

[Doug Miller]

recycl...@gmail.com wrote in news:509607f9-50bb-4b4c-9ad7-
c1c17a...@googlegroups.com:

All that proves is that _that_particular_combination_ can't be run in _that_particular_size_ of
conduit.

You made the blanket claim that "You can't have any NM cable inside a conduit" -- which is
complete and utter nonsense.

[Doug Miller]

"Pete C." <auxRe...@wpnet.us> wrote in news:51e0b891$0$51390$862e30e2
@ngroups.net:

> Probably not applicable in this case, but you are allowed to ignore
> conduit fill calculations for cases where the cables are passing through
> a short length of conduit sleeve. What was it, 24" length max?
>

It is 24" max, but you are *not* permitted to simply "ignore conduit fill calculations". Rather,

"where conduit or tubing nipples having a maximum length not to exceed 600 mm (24") are
installed between boxes, cabinets, or similar enclosures, the nipples shall be permitted to be
filled to 60 percent of their cross-sectional area ..." [2005 NEC, Chapter 9 Tables, Note 4]

[Unquestionably Confused]

On 7/12/2013 9:37 PM, Doug Miller wrote:
> recycl...@gmail.com wrote in news:509607f9-50bb-4b4c-9ad7-
> c1c17a...@googlegroups.com:
>
>> On Friday, July 12, 2013 5:20:47 PM UTC-7, Doug Miller wrote:
>>> recycl...@gmail.com wrote in
>>> news:168c113c-dc41-4949...@googlegroups.com:
>>>> On Friday, July 12, 2013 2:15:55 PM UTC-7, Doug Miller wrote:
>>>>> recycl...@gmail.com wrote in
>>>>> news:64bcf2b4-d88f-4d98-8daf-383a8784b898
>>>>> @googlegroups.com:
>
>>>>>> You can't have any NM cable inside a conduit.
>>>>>> It has to be single conductors.
>>>
>>>>> Absolute nonsense. NM cable is permitted inside conduit in any
>>>>> location where NM is permitted without conduit.
>>>
>>>> NEC Note 9 in the Chapter 9 tables says
>>>
>>>> "A multi conductor cable of two or more conductors shall be
>>>> treated as a single conductor for calculating percentage fill
>>>> area. For cables that have elliptical cross section, the cross
>>>> section area calculation shall be based on using the major
>>>> diameter of the ellipse as a circle diameter".
>>>
>>> How on earth did you manage to read that as prohibiting NM inside conduit ?
>

>> It exceeds 53% of the area for ½†conduit.

>
> All that proves is that _that_particular_combination_ can't be run in _that_particular_size_ of
> conduit.
>
> You made the blanket claim that "You can't have any NM cable inside a conduit" -- which is
> complete and utter nonsense.
>

And now that he's been shown to be wrong, he's back peddling, trying
desperately to look like he's still correct. Wait for it, we'll soon
see the be-all, end-all answer of "BECAUSE! That's why!" <g>

[tra...@optonline.net]

It was probably about 5 feet long. I don't remember having any
difficulty getting the two romex to go in either. And they
were not brand new, perfectly flat either. Both were re-use
of the existing.

[recycl...@gmail.com]

For that matter you can make an air conditioner that runs on water instead of Freon if you made the pipes about a foot in diameter. It would work but wouldn’t be practical.

[Randy333]

NO, NO, NO. Do not add two j-boxes. add one 4" sq box at top of EMT.
You will need to pull the wire back out of the outlet box anyway to
add on the box. Now cut and strip the old wire so you have 6" inside
the box, this wire is now too short to make it back down the the
oulet. Use 2 new runs of 14-2NM to go to the old box and to the new
box for your light.

Remove 333 to reply.
Randy

[Big Al]

On 7/12/2013 4:01 PM, TomR wrote:

> I have a dedicated 15-amp circuit in an unfinished basement that runs to an
> outlet on the wall for the sump pump. The wire/cable that goes to the
> outlet is white 14/2 NM-B w/ground. From the ceiling down to the outlet it
> is fed inside of metal EMT conduit. I assume that the metal conduit is
> 1/2-inch (the outside diameter of the conduit is about 3/4-inch).
>

Pull the existing romex out of the outlet box and conduit and route it to your new light fixture location.

Run a new piece of romex from your new light fixture to the old receptacle.

[The Daring Dufas]

On 7/12/2013 11:31 PM, gfre...@aol.com wrote:

> Not true at all for a single 14-2 NM.
> A single conductor or cable can fill 53% of a raceway but when you get
> to two, that drops to 31%
>
> Ok to make the math easier this is metric
> Using Southwire RX
>
> width...........area
> 14-2 9mm ...63.6 mm2
> 12-2 10mm..78.5 mm2
> 14-3 7mm....38.5 mm2
> 12-3 8mm....50.24 mm2
> 10-3 9mm....63.6 mm2
>
> From Table 4
> Trade size..one wire 53%...2 wires 31%....3 or more 40%
> 1/2"EMT....104 mm2 ...........61mm2............78mm2
> 3/4"EMT....102 mm2 ...........106mm2...........137mm2
> 1" EMT......295 mm2 ...........172mm2...........222 mm2
>
> Two 14-2 RX would need a 1" EMT to be legal.
>

1" PVC might be easier to handle and install but I don't know about the
capacity. It's been a while since I installed any and I often used
calipers to compare the inside of different types of conduit when
planning a job. Scrap pieces of conduit and wire come in handy when you
want to do a practical measure of what you're installing especially when
it's signal or network cables that may not appear in any tables. Any of
the phone system or computer network installations I've done have 3/4"
EMT run to every phone or network outlet inside any wall but the wires
are not carrying any significant power. It makes it easier to install
the wires, besides, I'm lazy. ^_^

TDD

[Jake29]

Well, duh. . . , I should have thought of that. Thanks. That's a good idea.

[Jake29]

Also a good idea! With the setup that I have there now, that's would be the
easiest thing for me to do. Thanks.

[TomR]

Jake29 wrote:
>
> Well, duh. . . , I should have thought of that. Thanks. That's a
> good idea.

Oops, "Jake29" = "TomR" (me, the OP).

I accidentally posted from a different account that has a different identity
associated with it.

[TomR]

Jake29 wrote:
>
> Also a good idea! With the setup that I have there now, that's would
> be the easiest thing for me to do. Thanks.

[Doug Miller]

recycl...@gmail.com wrote in news:70136510-9282-4908-bccb-3adbdce953d9
@googlegroups.com:

What in the world does that have to do with whether NM is permitted inside conduit or not?

Perhaps you should sober up before you post again.

[The Daring Dufas]

On 7/12/2013 3:01 PM, TomR wrote:
> I have a dedicated 15-amp circuit in an unfinished basement that runs to an
> outlet on the wall for the sump pump. The wire/cable that goes to the
> outlet is white 14/2 NM-B w/ground. From the ceiling down to the outlet it
> is fed inside of metal EMT conduit. I assume that the metal conduit is
> 1/2-inch (the outside diameter of the conduit is about 3/4-inch).
>

> I would like to add a pull string ceiling light above the sump pump for
> better lighting while working on the sump pump and/or the HVAC which is next
> to the sump pump.
>
> What I am thinking of doing is getting power for the light from the outlet
> and running new 14/2 NM-B w/ground from the existing outlet back up through
> the same EMT metal conduit to the new ceiling light.
>

> My main question is, is it okay to have two 14/2 NM-B w/ground cables inside
> a 1/2-inch EMT metal conduit?
>

If you're worried about protecting the wire and it's in a fairly dry
location, have you considered MC cable? It's a lot easier to install
than conduit and the wire is inside the metal cladding. You don't have
to buy a whole roll and you can probably get the length you need cut at
many hardware stores or even one of the Lowe's/Depot stores. You don't
have to buy a Roto-Split tool for a few connections but there are easy
to use one screw connectors having an integral insulated bushings used
to install the cable into the conduit boxes. ^_^

TDD

[John G]

On Friday, July 12, 2013 4:01:12 PM UTC-4, TomR wrote:
> I have a dedicated 15-amp circuit in an unfinished basement that runs to an
>
> outlet on the wall for the sump pump. The wire/cable that goes to the
>
> outlet is white 14/2 NM-B w/ground. From the ceiling down to the outlet it
>
> is fed inside of metal EMT conduit. I assume that the metal conduit is
>
> 1/2-inch (the outside diameter of the conduit is about 3/4-inch).
>
>
>
> I would like to add a pull string ceiling light above the sump pump for
>
> better lighting while working on the sump pump and/or the HVAC which is next
>
> to the sump pump.
>
>
>
> What I am thinking of doing is getting power for the light from the outlet
>
> and running new 14/2 NM-B w/ground from the existing outlet back up through
>
> the same EMT metal conduit to the new ceiling light.
>
>
>
> My main question is, is it okay to have two 14/2 NM-B w/ground cables inside
>
> a 1/2-inch EMT metal conduit?

*I would install a round box in the ceiling area and pull the existing Romex up from the sump pump outlet and bring it into the round box on the ceiling. Then run a new Romex down from the round box into the sump pump outlet box. Pig tail the pull chain light so that the load is not feeding though the pull chain socket.

There should be a connector at the top of the EMT to prevent pullout and to act as a bushing. In this case you need a 1/2" EMT to Romex changeover connector.

[Radon50315]

replying to TomR, Radon50315 wrote:
Why not use a lighting box and feed off the upstream end. Add new wire to make
up for lost length to the receptacle. I mean, that seems like the least
complicated solution. So what if it's a pull chain light. Light base wires
like a receptacle, receives power and doesn't interrupt downstream power if
pull chain light is on or off.

--
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