Running electrical wire through PVC pipe

[bud--]

Well ain't that interesting. IMHO it conflicts with 322.22 for PVC conduit (and xxx.22 for most other raceways): "Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9"

============= The 2002 NEC change proposal (for xxx.22) came from the code writing panel and says very little about why the change was made. The explanation is the change "clarifies that cables, where permitted elsewhere in the code, are allowed to be used in a raceway." The language was later changed to "where such use is not prohibited".

============= From the NFPA/IAEI code changes book: Using raceways as isolated protective sleeves for cables was accepted in the past.

It appears that the proposal may be for raceways that are connected to the electrical system on one end. There are 2 examples shown.

One example is a box with a receptacle that has a conduit out the top and has a Romex run through the conduit into the box. The top of the conduit has a conversion fitting with a Romex connector. [It is common practice to use essentially the same arrangement, without the Romex connector, to protect exposed Romex.]

The other example is for one or more Romex runs into a panel through a conduit as allowed in 312.5-C. ===============

Seems like the application, as written, would be Table 1, Note 2 applies in general but 322.22 applies specifically to all uses of PVC conduit. But most raceways have an xxx.22 section, so I don't know what Note 2 applies to. Not likely that is what was intended.

If Table 1, Note 2 applies to all raceways that protect from physical damage that leaves isolated raceways, as used in this thread, covered by xxx.22 (which may or may not have been the intent).

This is unreasonable ambiguity. I guess the answer is ask the inspector.

[gfretwell]

You do not usually need to support cables in a conduit, certainly not every 4 1/2 feet. There are rules about vertical runs but for copper

18ga thru 8 ga it is a vertical run over 100' that needs supplemental support. Table 300.19(A)

Electricians usually use different colors of tape to identify cables and conductors.

[Wayne Whitney]

No, that is the point, if you use the gray electrical conduit, you don't have to support the NM cable every 4 1/2 feet inside the conduit.

Cheers, Wayne

[Wayne Whitney]

In the NEC 2008, Chapter 9 Table 1 gives the conduit fill allowances. Note 2 says "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." So it doesn't apply to sleeves.

Note 4 says "(4) Where conduit or tubing nipples having a maximum length not to exceed 600 mm (24 in.) are installed between boxes, cabinets, and similar enclosures, the nipples shall be permitted to be filled to 60 percent of their total cross-sectional area, . . ." So this is relaxing the Table 1 requirements for certain parts of a conduit system, it does not apply to sleeves.

Yes, it is completely illogical to say "this installation would be compliant if that piece of PVC pipe weren't there, but now that it is, it is in violation".

Good idea.

Cheers, Wayne

[hibb]

Great. I think I am good to go now.

Thanks, David

[hibb]

Thanks again to everyone for helping me work through these problems.

David

[Wayne Whitney]

I would say that Note 2 is part of Table 1, Chapter 9, so that the

322.22 reference includes Note 2. I don't see the ambiguity.

Cheers, Wayne

[Wayne Whitney]

Oops, that should be 352.22 for PVC conduit.

Wayne

[bud--]

That works.

For the "sleeve", it is not intended to protect from physical damage, so fill restrictions apply via 322.22 to Chapter 9, Table 1. Heat is as much a problem as full wiring systems.

Also wire ampacity derating applies, as you wrote long ago.

[Wayne Whitney]

Well we are still reading "Note 2" differently. The first half of the sentence already exempts all sleeves. The second half of the sentence elaborates and gives a specific example but doesn't in any way limit the first half. The upshot is that all sleeves are exempt.

Right, and that is handled by the derating requirements when bundling, not by conduit fill. Conduit fill is for protection of conductors from damage during installation.

Cheers, Wayne

[bud--]

I do read it different. IMHO Note 2 is taken as a whole and not split into 2 sections. If the first half is independently applied, the second half is not necessary.

Some of the other notes (5 and 9) are specifically for cable, which would not likely be used in "complete conduit ... systems".

I figured out temperature was the wrong limitation right after I hit Send.

As you said, the point of Table 1 is to prevent damage to wiring at installation. By your reading of Note 2, there is no limitation on the number of cables that can be fished into a sleeve, and no protection from installing too many cables. The limit that would protect a "complete system" would not apply to a sleeve.

[Wayne Whitney]

I see the second half of the sentence as only an elaboration and explicit identification of the most common case of the first half. It is like saying "Crash test regulations apply only to vehicles with 4 or more wheels and are not intended to apply to motorcycles." That sentence means to me that crash test regulations do not apply to vehicles with 3 wheels.

That's correct, but I don't see any problem with that. Cables have an overall jacket that will help protect the conductor insulation from damage. And a sleeve is likely to be a shorter run which would require less pulling force than many "complete system" installations.

Cheers, Wayne

[dpb]

bud-- wrote: ...

The Note does not supersede nor provide relief from the general workmanship clause to cover flagrant abuse of the privileges granted therein.