I wanted to write this article quickly to help those who wanted to remove the jacket from NMD90 wire.
To keep things simple, there is no actual “residential wire” or “commercial wire”.. it all comes down to the application at hand, and what the electrical code determines (which changes all the time, and varies in each country, state/province, or even city to city!).
But some things don’t change that much, and if they do, it’s to IMPROVE SAFETY.. and it’s VERY important you understand how to select wire properly.
What We Cover in this Article:
- Why Different Wire Types Exist
- Must Know Wire Selection Knowledge
- Residential Wire Must Knows
- Commercial Wire Must Knows
Why Different Wire Types Exist
When it comes to the construction world, it’s EXTREMLY important to understand about “Galvanic Reaction Between Dissimilar Metals”. In addition, it’s important to know that not all materials are created equal.. some can take the UV rays of the sun, some materials can be buried underground, and some materials CANNOT.
When we are talking about wires, it’s VERY important to understand the code rules regarding the outer jacket (sheathing), as this is what its environment is going to hit first!
I’m not going to cover the in-depth stuff, but some general basics for you to be a WISE electrician about wire types are:
- Fire Rating (FT1 produces toxic fumes.. FT6 is smoke and fire rated!)
- Mechanical Damage.. (NMD90 is not rated for mechanical damage.. AC90 or BX is [armored cable])
- UV Rated (the Sun Rays + Heat)
- Direct Burial (If you dig a ditch, and place a wire in it!)
- Conduit Rated (If you’re allowed to use the wire in a pipe!)
- Extreme Hazard Areas (Gas Stations, Special Mills / Factories, etc.)
In addition to the certain types of wires, there are often special connectors or pipes or cables that must be used. This is why it is so important to understand the dangers, and the different pieces of the puzzle that allow for a proper connection the whole way!
In the extreme hazard areas, this could literally mean EXPLOSION if there’s an arc from the wires!
Galvanic Reaction Between Dissimilar Metals
I want to quickly discuss this if you’re not aware of this.
In my early apprentice years, I was told to put electrical tape on my armored wire when it was going to touch a plumber’s copper pipe.. I was confused, I didn’t understand why.
But when two dissimilar metals touch (armored cable is aluminum, and the pipe was copper), a corrosive reaction takes place over time, and the metal’s reaction can cause some serious damage!
You can read this article I found on Galvanic Reaction .. it was actually super interesting.. it says current flows between the two metals!!!
Must Know Wire Selection Knowledge
A quick summary before we continue..
When you select a wire, you must first figure out its environment, as that will dictate what type of wire you’re allowed to run, and in what areas.
For example, if you want to run normal NMD90 wire in an air return plenum, that is a big no-no, and against code. Why? Because when NMD90 burns, its fumes are toxic! This is a return path for the building’s HVAC (air flow and quality).. which would SPREAD those toxic fumes!
Here’s an article I found about HVAC plenums for you to learn!
To further clarify what to know about fire rating, NMD90 is FT1 fire rated. (Which gives off very toxic fumes when burned). So you have to be aware WHERE your wire is pulled, because if it’s going to go in that plenum air way, then it HAS to be FT6 rated (this number keeps changing.. it was FT4 when I was an electrician.. so make sure to check your jobsite’s specs!).
And guess what? This also goes for extra-low-voltage wire, too, like your telephone, cat5, and fiber-optic wires! They have to be rated to be run in special areas!
Now you know! Be careful out there!
So with that said, here’s some “common electrical knowledge” for residential vs commercial wires.
Residential Wire Must Knows!
In short you may hear “residential wire” called NMD90, Loomex, or Romex.
(Loomex and Romex are just brand names.. NMD90 is what the code states it as!).
The reason YOU CANNOT use NMD90 wire in many commercial situations is because of mechanical damage or fire-rating! (Those are the two most common things to be aware of when you are selecting a wire as an electrician!)
The main reason electricians use NMD90 is because it’s AFFORDABLE (compared to Armored Cable). If your environment allows it (wood studs), then you’ll typically be using NMD90, which has very little mechanical damage prevention.
Commercial Wire Must Knows!
There isn’t too much to know about commercial wire in terms of mechanical damage or fire rating, as it’s built to be overkill on purpose for the reason of being able to take the heat (literally!)
This “commercial wire” can come in various forms, but typically we think of it as armored cable.. (AC90 or BX).
Typically our main feed wires or feeders are armored cable. (Sometimes they can be NMD #2 for feeders in a condo, again to save money, but most often you will see armored cable!)
But, the reason you DO NOT want to use commercial wiring (armored cable) is because it’s EXPENSIVE!
So that’s why your company will try to pull NMD90 (residential wire) simply because of cost. If you are in metal studs, you’ll most often use this armored cable as NMD90 is easily skinned or sliced!
(Make sure to wear earplugs if in a commercial setting and pulling armored cable.. you only have one set of ears! 😎)
Conclusion.. Now You Know Wire Types!
Well, not really, because even after years of school, you’ll ALWAYS be having to look in the code book to determine what kind of wire you’re allowed to pull in what situation.
And the SAFEST way is to look at the electrical engineer’s specs.
I hope this helps..