There rae a few terms you’re going to come across out in the field which get thrown around mistakingly because many people don’t know the difference. Conduit, tubing, piping, and raceways. Here’s the breakdown:
Conduit and tubing are types of raceways. The term “raceway” is something that you will come to know as a catchall term for anything manufactured to run conductors through. Some examples of raceways our gutters, auxiliary gutters, tubing, conduit, cable tray, and enclosures. All of these things are made by companies with the express purpose of running and housing conductors from one point to another. Most of the time you’re going to see conduit and tubing between an electrical panel and a piece of equipment.
The only one of these terms that’s actually in the National Electrical Code is “Raceway.” A raceway in the 2017 NEC is defined as:
“An enclosed channel designed expressly for holding wires, cables, or busbars, with additional functions as permitted in this Code.”
Raceway is an overarching classification meaning, essentially, “anything you can run wires through.” The term raceway does allow for other things to be inside of it as well, like busbars, terminal blocks, whereas the term conduit simply refers to conductors.
Conduit and Tubing
Technically there is a difference between conduit and tubing, both are most often referred to as conduits by electricians out in the field. For example, EMT, electrical metallic tubing, is actually a type of tubing however most electricians out in the field simply refer to it as a conduit, rather than tubing. For the purposes of electrical work it’s not important to know the differences but if you’re curious “tube” and “pipe” are for moving liquid and/or gases under pressure. The main difference between the two is how they are sized. Pipe is sized according to it’s inside diameter while tube is sized according to its outside diameter. In the case of EMT (electrical metallic tubing) the wall of the tubing is so thin that there’s really not much of a difference between its inner diameter and outer diameter. However, PVC pipe and PVC conduit may have several different outside diameters, but share a common inside diameter.
Pipe is never used when talking about electrical, because the express purpose of pipe is for passing gasses and liquids through, under pressure. Think “pipeline.” This is also why white PVC used in plumbing is called PVC pipe, and the gray stuff in the electrical aisle is called PVC conduit. Conduit is not tested to hold gas or liquid under pressure, it is intended to pass conductors through. Another thing to note about specifications is that “pipe” is always rigid while conduit and tubing may be either rigid or flexible.