romex in emt

[Dogger]

I will be doing a short run of two 10 guage Romex NM-B AWG cables through about 30 inches of EMT to connect the disconnect boxes to a popout chute for an AC installation.

It looks like 2005 NEC clarifies that you can run cable through EMT.

My question is about the allowable percentage fill specified in Table 1, Chapter 9. Is this table available online?

I did find a Belden Conduit Capacity Chart, but I'm not sure if it is the same as the one in the 2005 NEC.

The larger width diameter of the 10 guage cables is just shy of 1/2 inch, so I used 1/2 inch as the size estimate. If I am following Belden's calculations correctly, it looks like I should be able to run both #10 cables in the 3/4 inch EMT.

1. square the OD of each cable and add the results (.5 x .5 = .25, .25. + .25 = .50)

2. Two cables are limited to 31% conduit fill. Multiply the total by 1.134 for two cables. .50 x 1.134 = .5067

3. From the Actual Area on the chart, select a conduit size with area equal to or greater than the total area.

The Belden chart shows that the Actual Area of 3/4 inch conduit is .53, which indiates that I can run two #10 Romex cables through the 3/4 inch EMT.

Am I doing this correctly? Is this the same calculation as Table 1 in Chapter 9?

 

[1793]

This is my take...

This is my take...

#10 NM-B measured at 1/2" or.5
Find area (R*R)*3.14(Pi)

.5 / 2 = .25

.25 * .25= .0625

.0625 * 3.14 = .19625 area

2 * .19625 = .3925 two #10 NM cables

Chapter 9 Table 4:

EMT @ 31% would need to be 1-1/4" @ .464

I don't think I missed anything but it is still early.

 

[Dogger]

I found the online version of 2005 NEC.

Thanks for the detailed math. :grin:

1-1/4 seems like overkill. This is about a 30 inch run and is used to protect exposed Romex.

Just below table 1 it says, "(2) Table 1 applies only to complete conduit or tubing systems and is not intended to apply to sections of conduit or tubing used to protect exposed wiring from physical damage."

Table 1 (5) also says, "For conductors not included in chapter 9, such as multiconductor cables, the actual dimensions shall be used."

If I take the actual physical dimensions of the #10 Romex, which are .4687 x .25 (measured with calipers).

.4687 x .25 = .1172

.1172 x 2 = .2344

1 inch EMT with 31% fill = .268. It looks like I could use 1 inch EMT.

The wording in Table 1 (2) makes an exception for conduit used to protect exposed wiring, but I couldn't find guidelines for protecting exposed wiring. Does this mean that the capacity rules are tossed out? The cables easily slip into 3/4" EMT, but I want to make sure it is done right the first time.

Are there any 2005 NEC rules for short runs that are used to protect exposed wiring?