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

SCBO1

SCBO1

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

pc1
 
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?

.
 
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.
 
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.
 
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
 
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
 
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
 
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
Click to expand...
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
 
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.
 
Dennis,

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

pc1
 
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.
Click to expand...
See Note 2 in Chapter Nine for the information you are seeking
 
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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