Security technicians will take many paths as they evolve in this industry. Since most installations in the security industry only involve low-voltage wiring, the skill we are going to talk about this month typically eludes technicians’ grasp.
Due to the National Electrical Code’s (NEC) low-voltage requirements, cable can be run in almost any location, with the exception of some fire restrictions such as plenum areas. However, if a low-voltage technician is going to better him/herself by tackling larger integration projects and becoming involved in new commercial construction, they will need to acquire the skill — or what some say is an art — of bending and installing conduit.
Bend There, Done That
The first time I ran into installing conduit was many years ago, and in this case, it was a requirement of the job. It was a control room and the specifications read, “All wiring must be in metal conduit.” This meant not just the high voltage cabling, but also all wiring, including my low-voltage wiring. At that time I was installing an access control system with a room full of power supplies used for door strikes, access and other alarm panels.
Being a small dealer, I did not have the luxury of someone showing me how to properly bend conduit. Frankly, at first, the rookie in me told me I need not be that concerned. After all, I had observed others doing it. Just bending the pipe should not be all that hard. My lesson was to come shortly.
I probably used three to four times the amount of conduit I needed on that first job and took twice as long. I was a young, small contractor forced to eat my mistakes, learn from them and move on. Through the years I became good enough to get the job done, but most of the time when I had to bend conduit I still did most of it by the seat of my pants, so to speak.
Bending Rules
OK, so now you know what not to do. Let’s take a look at some ways to learn the proper way to bend and install some of the most popular types of metal conduit: EMT (electrical metallic tubing), otherwise called thinwall.
First, why would someone who installs low-voltage cabling even need to install metal conduit? There may be a variety of reasons, such as providing good protection from damaged cabling; an easy path to fish cable through a building; electrical protection from EMI (electromagnetic interference); fire resistance; extra physical protection from quick attacks; or in my case, the building specs or code requires it.
According to Franck Benedetti, president of Phoenix-based Top Hat Video, “The primary goal of an installer is to make a bend that fits the first time.” Benedetti has a good series of training videos that show technicians how to properly bend conduit. He also has a manual that complements the video and is free for download at www.hatvideo.com. Some of his tips are included throughout this article.
EMT typically comes in a variety of sizes such as 1⁄2 inch, 3⁄4 inch and 1 inch. Make sure you have a bender for the exact size you are bending. Some try to cut corners on equipment and use a larger bender on smaller conduit. Doing this increases the likelihood of kinking the tubing or flattening the bend. Another tip is to apply steady pressure when using a hand bender.
According to NEC, how many bends can you have between junction boxes? Not more than a total of 360°. This is to make it easier when pulling cable. Another goal of bending conduit properly is making your life easier, especially if you are also the one doing the wire pulling.
Bending to Your Will
Make sure you have two other important tools to go with your hand benders. The first is a torpedo level with a magnetic base. You already have one of these for mounting control boxes level, right? Place it on the side of the conduit to make sure you have the correct right-angle bend. The next will be a protractor with a magnetic base as this will help to check bending angles more accurately.
As you get more expert in your bending skills you may also want to get a copy of trigonometry tables for calculating more complex bends. One handy source many techs carry is Ugley’s Electrical Reference pocket book.
One of the handiest bends to make is called an offset, which is when one conduit has to make a slight bend in elevation to get over another conduit or obstacle, or into a junction box. One of the most helpful bends to make to ease wire pulling is a 30° offset. However, with a little practice and calculation, try making a 20° or even in some cases a 10° offset as it will make your wire pulling even easier.
Up Around the Bends
In addition to the offset, there are several other types of conduit bends you should master. Some of these I am sure you are familiar with, however there are some you may want to add to your bending repertoire.
90° bend — This is the most common and easily done on the floor. Make sure to use the magnetic torpedo level on the bend to see if it is 90°. Use the back of the bender handle to correct any over bend. Typically, you would account for a 5-inch deduction in length on 1⁄2-inch conduit, 6 inches on 3⁄4 inch, 8 inches on 1 inch and 11 inches on 11⁄4 inch. When measuring, use a Sharpie, or a pencil or tape to avoid showing marks.
Back-to-back 90° bends — A little tip on this is to use the handle as a straight edge to see if the bends line up. Use the “star” mark on the bender for reference.
Three-point saddle bend — Used to jump over obstructions less than 6 inches. Bends such as these include the art of making an “air bend”.
Four-point saddle bend — Used to get over larger obstructions. Tip: Make sure all bending marks are made BEFORE you start bending.
Shepard’s bend — A combination of 90° and small offset for going into a junction box in a tight space.
