MEP – Construction Yeti

It seems that many electrical apprentices learn this lesson the hard way. They get started running their first EMT conduit masterpiece and end up with about 6 or 7 90-degree bends. It looks awesome until they try to pull a fish tape through and can't get past the first 4 bends. That's when they quickly realize that there is a reason for the NEC guideline of maximum bends in a single run. National Electrical Code or NEC limits the total number of bends in one continuous run to 360 degrees or four 90 degree bends. It specifically states, "There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes." The obvious follow up question to this is, "How many degrees in the direction of a conduit run does a quarter angle bend provide?" A quarter bend to the NEC is what the rest of us call a 90 degree bend or simply a "90". In layman's terms this simply says what ever combination of bends (90's, 45's, 30's, etc), the total cannot exceed 360 degrees between pull points. Where in the NEC is Allowable Conduit Bends found? This guidance is found 11 times in the NEC in regards to each type of conduit. It can easily be found as the .26 section is titled, "Bends - Number in One Run" of each conduit type's article in Chapter 3. Purpose of Maximum Allowable Bends There's a good reason for the old phrase I've heard more than one electrician say. "You pipe it, you pull it." I was walking through a job recently and just happened to witness what looked like an electrical apprentice really struggling to get his fish tape through an EMT run. It caught my eye so I just hung around to see what was going on. After watching him struggle for a bit I went in to investigate and his conduit run had 630 degrees of bends (6 - 90's and a 2 - 45's). He was able to push it through the first 4 - 90 bends but almost ironically he couldn't get the tape through the 5th. As you can imagine every bend the the conduit makes it creates another friction point on the wire during the pull making it more and more difficult to pull as it crosses additional bends. The purpose behind the limit of bends is to solve problems like this and to ensure the conductors can be pulled through the raceway without damaging the insulation on the wires. You pipe it, you pull it.-Some Old Gray Hair Electrician What is a conduit pull point? A conduit pull point is essentially any device with a removable cover that allows access to the wires inside the conduit. Generally called "pull boxes" these devices create intermediate spots in conduit runs where you can pull the wire from. There are a few different types of manufactured pull points and they are typically made of a similar material as the conduit such as sheet metal or plastic. There are a few different varieties of conduit pull points such as conduit bodies, gang boxes, underground handhole enclosures. Pull Point: Angle Conduit Body Pull Point: Double Gang box or Quad box Pull Point: Underground Handhole enclosure Do box offsets count in the total? A box offset is the back to back small degree bends in opposite directions to offset the conduit to line up to an electrical box. The rule of thumb is no, box offsets do not count in the total offset count granted the offset is less than the diameter of the conduit. In this case there is still a straight path through the conduit where the wires can be pulled without adding friction. For instance is you have a 1" conduit then if the offset bends are less than 1" there is still a straight path through. This means you will still be able to see through the conduit at the bend. Example of a box offset that is the bend is less then diameter of the conduit. If however your offset is has to be greater than the diameter of the conduit, then the bends need to be added to the total count. This is typically an addition of 20 degrees (two 10 degrees bends). Example of a box offset that is greater than the diameter of the conduit and should be counted in the total run count. Do long sweeps count in the total? The NEC code book does not differentiate in bend radius's nor make exceptions to the total allowable bends for long sweeps. So as a rule of thumb, a long sweep is still a bend and adds friction to the conductors when pulling and therefore should still be counted as a bend when adding up the total. Where to get NEC book? Not going to lie, it took me a bit of googling before I finally realized that the NEC is actually published by NFPA (National Fire Protection Association) and is actually titled NFPA 70 "National Electrical Code." Adopted in all 50 states, NFPA 70, National Electrical Code (NEC) is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards.-NFPA Website NFPA does allow free access to book online if you register on the website for a free membership but their viewer is clunky and such a pain to navigate. It appears that with the 2020 version they took away the pdf purchase option so you can only get a 1 year Subscription Service for about $1400. I would recommend spending a fraction of that and getting spiral bound print version. I've also found you can save dollars if you buy a used copy. Check current prices for new and used here on Amazon. Screenshot of the NEC web viewer on the NFPA website. You have to manually click next on page and there is no search, copy or print function. How to bend conduit? A great video and resource I have found if you are looking to learn the basics of Conduit Bending can be found here. For a field guide tool box Quick-Card check out this 4-page water resistant guide to provides the essential electrical conduit bending information used in architectural plans and engineering drawings. Get it on Amazon in just a day or two for less than the price of lunch.