# Needing help calculating how many ROMEX wires are allowed in EMT conduit



## Pcinspector1

How many peices of ROMEX can you stuff in a piece of 3/4" EMT and still be code compliance?

pc1


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## BSSTG

What size the romex?

BS


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## steveray

How long is the EMT?


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## Pcinspector1

Three pcs. 14/2w/g less than 10' EMT.


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## steveray

If you exceed 3 CCC you need to start derating......


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## globe trekker

Pcinspector1,

You will need to know the size (sq. inches) of the Romex cable assembly planned for

installation. Table 4 in the 2008 NEC, Ch. 9 gives the per centage of volume in a

3/4" EMT that cannot be exceeded (0.213 sq. inches) for over 2 conductors.

Do you know the area of your planned Romex cable assembly?

.


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## gfretwell

The area of 2 wire Romex also has to be calculated with the widest dimension as the diameter.

My bet, 2 per 3/4. The ironic thing is 3 wire Romex computes lower since it is round.

I will track down some 14-2 and measure it.


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## Pcinspector1

Thanks globe,

To answer your question, NO.

I can do the calcs. for single wire (i.e. THHN) but the romex is difficult to measure. It looks tight and thats what alarmed me and why I'm checking. It not a long run.

I also came up with the 0.213 Max. Fill for the 3/4" EMT as you have posted.


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## Pcinspector1

gfretwell, thanks

IMO two per 3/4" would be better.

pc1


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## codeworks

why not just pull thhwn or thwn and not hassle with this? just curious as to why the romex in conduit


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## gfretwell

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

             one wire 53%    2 wires 31%   3 or more 40%

1/2"EMT   104 mm2            61mm2            78mm2

3/4"EMT   102                  106                  137

1"EMT       295                 172                  222


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## gfretwell

My guess is physical protection above FF.


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## gfretwell

See if this is easier to read

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%..... 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


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## Pcinspector1

codeworks,

Field inspection with three romex in 3/4" EMT in basement for switches next to foundation, protection to the top of the wall as gfretwell pointed out, above FF.

gfretwell,

So theres no table for ROMEX type wiring which accounts for the jacket, you have to know the wire manufacture? Is southwire only in metric?

pc1


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## raider1

Pcinspector1 said:
			
		

> codeworks,Field inspection with three romex in 3/4" EMT in basement for switches next to foundation, protection to the top of the wall as gfretwell pointed out, above FF.
> 
> gfretwell,
> 
> So theres no table for ROMEX type wiring which accounts for the jacket, you have to know the wire manufacture? Is southwire only in metric?
> 
> pc1


No there are no NEC tables that provide the area of NM cable. Each manufacture may have a different thickness of outer sheath etc. You need to get the information from the manufacture.

Chris


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## Pcinspector1

Thanks, Chris! Have'nt heard from you for awhile.

pc1


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## gfretwell

That was a direct measurement with a caliper across the widest part of each.

Evidently Southwire is what is most popular here because that is all I had on hand in my stack.

I do have some old TW style NM here (installed years ago) but I am not sure that was worth listing.

I can give you the "inch" too but it was easier to do the calculation in metric.


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## Dennis

Is this a sleeve or is it a complete raceway?


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## gfretwell

There was an error in my post 3/4" 1 wire is 182, not 102


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## Pcinspector1

Dennis,

Not a complete raceway back to the panel, open EMT where it enters the basement rim from the gargage.

pc1


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## globe trekker

Pcinspector1,

Here is a link to Southwire's web site & the NM cable assembly. It gives the dimensions of various

copper assemblies. The dimensions are in mils though!

*http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet6*

Hope this helps!

.


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## jwelectric

Pcinspector1 said:
			
		

> codeworks,Field inspection with three romex in 3/4" EMT in basement for switches next to foundation, protection to the top of the wall as gfretwell pointed out, above FF.


 See Note 2 in Chapter Nine for the information you are seeking


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## Dennis

Mike has gone where I was getting at.  If the raceway is not complete then the fill does not matter however de-rating would apply.  Since there are only 6 ccc then the derating would not affect the ampacity with 90C wire.


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