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| Subject - EMT Code Question | |
| RS377 |
Today a coworker told me that you have to have a junction box for every 100ft of EMT. I think the guy's full of it, as he cannot tell me where in the code book it is. He actually told me "its not in 384 like you would think", which is rich because 384 is Auxillary gutters in the 1999 NEC, which is what we are tested on for certification. So, I checked general wiring methods, pull and junction boxes, and of course EMT. Nothing. So, come Monday, I'm going to lay down cash on the fact that he won't be able to find such a code. If I'm making a mistake, hopefully some of you old guys will be able to stop me before I have to eat crow and pay up. |
| JimmyDee | Before I look, I will say, that was the old rule of thumb because, the fishtapes were 100' long. I know we have pulled feeders a lot longer than that so I'm going to agree with you. If it is in there, it is well hidden. I see nothing in the NEC that would say every 100'. Jim |
| iwire | You can run as far as you think you can get the snake in. As Jimmy has pointed out many times feeders run great lengths between pull points. With EMT the farthest I have gone in one run is about 600' - 700' with only 180 degrees of bends in the run. That was a 3" EMT and to fish it we pushed two 200' x 1/4" snakes in from each end. One snake is sent in with an open hook, the other snake is sent in with a bunch of string folded over and tied to it. Once the snakes pass each other in the middle you pull one back and the open hook catches the string. Easy  Really it works pretty well, and once the snakes are together we pull in a 1/4" rope so that we can pull in a 1" rope to make the pull with. Underground with PVC we run longer than that but you can vacuum a pull string in PVC. EMT fittings leak to much to vac a string in them.  Bob |
| lctrc789 | This was an old rule of thumb thing, and I can remember back in the early 80 s this was a saying that was commonly used, every 100 ft install a Jbox for ease of pull. I haven't seen anywhere in the code that says you have to, and really don't think you will ever find anything. We use a lot of EMT and we use compression fittings and you can use a vacuum if you get them tight enough. I think if you bet on this they will have to pay up, but we would like our fair share LOL Think of this way a lot of companies, use Brown , Orange , Yellow, for 277/480 a rule of thumb not a code. |
| lctrc789 | RS377, Here are some code articles you can refer to for your question, on the EMT, I don't think you will find anything that your co worker is referring to though. Article 300-15 Boxes Conduit bodies or fittings where required. Article 348 E M T Article 370 Outlet, device, pull and junction boxes, conduit bodies and fittings. Good luck |
| veganfan | I have peronaly pulled 485 ft with 235 degree of bends. It was a little rough, but worked fine. I had to blow a mouse due to I did not have tape that long, but I felt good that I was able to do so without jbox. |
| shocky | one the reasons i was told to put a jbox every 100ft was that on long pulls the weight of the wire could stretch the insulation causing a possible short in the conduit,same reason for putting a box before 360 degrees of bends in pipe. |
| RS377 | quote: Having more than 360 degrees in a pipe doesn't stretch the insulation, it creates friction on the inside of each bend possibley causing damage to the insulation. Besides, you can't stretch the insulation without stretching the conductors themselves. Also, what does #10 wire weigh anyways? A hair over thirty one pounds per thousand feet, and I'm sure #10 could hold thirty pounds without any damage being caused to the wires. Just my thoughts about that. I spent a few weeks with a small, backwards company that didn't use fish tapes. All conduits, including flex (not sealtite) had string pulled in with a vacuum, and then we were told to pull with the string. It was about a week after that I was let go, being told that I didn't fit in. Go figure...... |
| iwire | There is another thing to consider other than friction on the corners, it is the sidewall pressure. When using puller that can pull with 8000 lbs all day long you do need to be careful. The insulation can actually be crushed against the side of the raceway at a corner. One way to get around this is to use large radius sweeps, this spreads the force over a larger area of insulation. There are calculations to figure all this out, although I would not bother if it was 10 AWG as RS377 mentioned.  Follow the link for a free Raceway Pulling Tension Calculator http://www.electrician.com/electa1/ductwirepull.html |
| Scott Vickrey | I just returned from helping to wire a mall in California. They where pulling 277 volt circuit home-runs into the electrical rooms where I was working. They were having hell because they where pulling 500' and longer runs with sometimes much more than 360 degrees of bends in the runs. I know this is wrong and so did the people supervising the pulls. To top that off the people pulling the wire had no previous wire pulling experience and where horsing the wire in without regard for the poor man feeding the wire. I watched them use benders in the pull rope where 3 people would then throw all their weight into the pull. This job took the cake as the worst supervised job I have worked on before. The foreman on the job put down electricians nonstop from the very minute I got there. You can imagine the effect this had on me.  He had cultivated a stench of superiority among his crew leaders that was just intolerable to listen to even indirectly. This company proudly boasted that they had fired over 70 electricians on this 1 year job! I decided not to return to this job after the thanksgiving holiday and was happy to leave. I sometimes smile inside remembering those laborers hanging from that pull rope. Do you think they are going to have trouble when energizing those circuits? Really, how hard would it have been to add a pull box to these home-runs? This is what happens when you confuse activity with progress. I won't tell you the name of the company but I will say it rhymes with BKB. I could go on as this is only the tip of the iceburg but this is not the place.
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| JimmyDee | Welcome back Scott. Not to wish them any bad luck, I hope they have rubbed through the insulation on some of those home runs. Try pulling them out when they have shorted out and melted the insulation. I have never ceased being amazed that jerks like you worked for ever make a dime on a job. When running a job, I found productivity always increases when the workers are treated with dignity. Now that I have reconsidered it, I hope they do have a lot of bad luck. Jim |
| iwire | quote: Well said!  That has always worked for me. Treat others as you expect to be treated and most of the time they will work their tail off for you. |
| veganfan | We have had wire pulls at my work that have used man lifts and fork fruck to pull the wire. Also seen four inch emt elbow brake and be ripped off of box. It is very common to see all thread that is used for support start off strait and end up shape like a "U". Great wiring practices? |
| Russell120 | The 100 foot rule is nonsense. But it is nonsense I have heard before. Maybe it is an old NEC rule that was deleted (like having to strap your pipe within 3’ of every fitting deleted in 93). Pulling small amounts of wire through straight runs of pipe over 200’ of pipe is not particularly difficult: not nearly as difficult as lots of wire in a 50’ run with six 90’s. I was on a job a few years back that used similar wire pulling methods to the mall job noted above (although the field super was nicer). They had really big strong guys just yanking on the wires to get them into the pipe. When they would flip switches to the 277 lighting, sheets of flame up to 5’ long would shoot out of the pipe. They would keep flipping until the flames would quite shooting. At which point they would proudly announce that they had “cleared” the fault. I wonder if the writers of the NFPA 70E (Safe work practices) really know what they are up against? |
| RS377 | quote: holy moly, I've been installing suports within three feet of every fitting for years! I never realized that the code says "tubing terminations". This is one of the great things, I think, about learning more about the code. I know that right now, everything I do is up to code, but there have been plenty of times where I've done more work than I had to because I didn't fully understand it. Thank you Russell |
| luckyshadow | I hear this from my apprentices every now and again. I pull out a hundred dollar bill and tell them if they can show me in the code book where it states a box every 100' they can have the hundred. I still have that hundred. It's right there with the ground on recepts must be up
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| JimmyDee | Luckyshadow, I would like to welcome you to the Electrical Knowledge site. Its one thing for an apprentice to get these wrong ideas but when an inspector, pushing his weight around, enforcing these non rules is when it gets fun. ( BTW, the ground is mounted down on a receptacle.) Jim |