Why can I not assemble conduit around cable, but must pull it after assembly?

Far more opportunity to damage the wire insulation - either by mechanical damage from the exposed ends of the conduit/fittings being slid along the wires (metal or PVC), or from cement/primer if PVC.

An assembled conduit (or duct) will have all the various ends joined (and de-burred to remove any internal sharp edges, if properly assembled.) wires or cables slide along and don't get torn up.

In addition, there's increased opportunity for damage from the wires being draped around the workspace unprotected while you have them laid out but the conduit is not assembled.

Guaranteed Reusability

If you run the wire as you are putting together the conduit, there is a possibility, unless you are truly careful about all the details, that you could end up in a situation where your initial set of wires are perfectly fine, but that pulling them out to replace them - or more likely pulling in new wires (out is "easy") will run into unexpected problems. If you assemble everything first then the first time you pull wires through you will find and fix any problems. Plus you will be more careful (especially if you don't do this kind of thing every day) to play by the rules so that you will be able to pull that first set of wires without a problem.

Remember, conduit serves three different functions:

• Physical protection
• Grounding (for metal conduit)
• Ease of use - i.e., add or replace wires as needed

The first two, which obviously are the "safety" issues, will be the same whether you do conduit-then-wire or conduit-with-wire. But for the 3rd, it can make a big difference.

Well, it's never a good idea to "divining rod" the intent of the NFPA. Because jackasses mainly are looking for one reason that they can rationalize around, so they can fabricate a reason why the Code doesn't apply to them. Really, they just don't want to follow Code, but they are not honest enough to call themselves outlaws.

So, it is a stupid game. In every rule I have researched, there are usually a variety of "whys" which overlap to provide safety.

But I'll give you one.

It stops you from building "unpullable" conduit!

Building the conduit first, as Code requires, keeps you honest. If you build it unpullable, you won't be able to pull it! :)

We had one person on here, we finally convinced them that a route between boxes would be best done as THHN and conduit. But they had to follow a zigzag on the building wall, and when they showed us a picture, they did not use a sweep in the inside corner -- they just put the exact same common "pulling elbow" they had used on the outside corner! The cover plate was facing the wall. (they make a special corner pulling elbow with a side door, by the way).

It was completely obvious that a) the person had assembled the conduit around the THHN wires, and b) they were completely oblivious that you would do it any other way. What a pain in the butt to do that, only to be told it's wrong.

Oh yeah,

It's much, much harder to do it that way

It really gives you the worst of both worlds. You have the "coils of cable splayed all over the place all day" like you do with a direct cable installation. And then you also have the "fidgeting with conduit" part too, except the conduit is much, much harder to do, because every piece must be slid down all the wires.

I do a ton of conduit work, and SMH... that's nuts. What a royal mess. Making it 5 times harder than it has to be.

Building empty conduit makes the job easier.

• The pipe goes up easily, obviously.
• Your work area is a space about 10 feet long - no bigger than the next stick. That means for instance you don't need to clear belongings out of the entire route, just the immediate <10' work area.
• Take a break anytime you want. Tidy up, and come back to it after lunch or next month. I have a conduit run somebody installed ten years ago but didn't finish the last 20 feet, it's not in anyone's way.
• It's all an erector set, which is particularly important to novices, who aren't going to get it right first time. You can disassemble and reassemble any way you like, with no loss of material except maybe some tubing. You can seek feedback off forums, and if something needs changing (like that pulling elbow pushed against the wall), you just change that little bit. It all un-bolts. (or if it's PVC just don't glue it yet).

There's no throne. Threading pipe over wires doesn't buy you anything.

Honestly, after you build the conduit, actually pulling the wires is a "victory lap". It's the easiest part of the job. I can't grasp why someone would want to make the job so much harder by trying to assemble conduit around wire. It's like doing direct cable, but with 10 times more mess.

Do people really think conduit work must surely be harder merely because it is different than what they're already familiar with?