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-   -   Measuring EMT conduit for bends (http://www.diychatroom.com/f18/measuring-emt-conduit-bends-17098/)

alvanos 02-14-2008 10:09 PM

Measuring EMT conduit for bends
 
Hi all, question to all the chicago-crew who use EMT conduit. I've read a good deal now on how to measure the distance, and the add/subtract take-ups and shrinkage, all that good stuff. But there is one small detail that escapes me in making the original wall-to-wall measurement. in this example, I have a stub running off the ceiling and down between two studs. The junction box is in the middle of the two studs, so I'm going to take the running end down and the 90 degree over to the receptacle box. So for my question ... when taking the "raw" measurement from the ceiling down to the receptacle, where on the receptacle's side punch-out do I measure? To the top, to the center, or to the bottom? Seems a small detail, but it can also set me off up to a 1/2" if I don't know the right place. Hope I explained my question with clarity, and thanks!!

InPhase277 02-14-2008 11:23 PM

Not sure exactly what you're asking. Are you trying to figure out where to measure to on the box knock-out? If you are measuring between boxes, remember that you are measuring to the BACK OF THE BEND on each 90. You measure from the left side of one KO to the right side of the other KO.

Be a little more specific if you can.

InPhase277

goose134 02-14-2008 11:27 PM

When measuring your 90's, you are measuring from your mark to the back of the 90. So, let's say your pipe is hanging out of the top plate by 12". Your center KO is 55" From the bottom of the top plate to the bottom of the center KO. Take 55" minus 12= 43". Now your 5" take up (for 1/2") and your mark should be at 38". Place the star mark 38" off the end and bend.

I would say that if the box is in the same stud bay as the stub, then maybe offset into the top?

220/221 02-15-2008 05:36 PM

Always measure to the back (far side) of your fittings/pipe.

BigJimmy 02-15-2008 09:30 PM

I'm not an electrician but I've run (and will continue to in my crack house remodel) a lot of pipe. Here are a couple of things that I've learned that I think are worth sharing:

1. When running pipe, I usually install the boxes first followed by the pipe. When measuring a straight piece that will 90 into a box, I often keep a couple of short pieces of pipe handy to help in measuring. In your instance, you will drop to the KO and 90 into it (as Goose said, your better bet may be an offset to allow you to enter the top of the box). If it was me, I'd select and break out the KO and install the box connector. Then, you can put a small piece of pipe in and use it as a guide to make your mark on the perpendicular pipe for making your 90. And as 220 said, your mark will coincide with the back of the bend (you can put the star on this point or measure 5" beyond for 1/2 emt and used the arrow).

2. Because I install the boxes first, I usually use 2-piece box connectors since this allows you to install the pipe between two fixed objects (in my cases boxes) without trouble.

3. I like making non-90 deg. bends in the air, i.e. with the bender handle on the floor. It gives me a better sense of control and puts the angle marks closer to your head. In addition, I feel that it makes it easier after the first bend (esp. in offsets and kicks) to sight the pipe in the bender shoe to avoid dogs and judge the co-linearity of the second bend (I don't necessarily trust the angle marks). BUT--when using the star (which always coincides with the back of a bend), make sure you have the shoe oriented correctly, i.e. with the take up hook away from you. In my earlier attempts, I goofed a lot this way.

4. To make box offsets, use the 10 deg. angle and measure 2" between bends. With my Ideal bender, I make a single mark at 3-1/8" from the end of a pipe. I've found that if you insert the end of a piece of emt flush with the mouth of the shoe, the arrow is pretty much at 1-1/8" (2" between bends). Just make sure that the orientation of bends is correct. I've made a lot of really impressive pretzels only to bend the final box offset opposite of what it should have been! Thank god for couplings! :laughing:

Good luck and feel free to PM me any time with questions. Perhaps I can help you avoid the bone yard that I've created through my trial and error(s)! As I said, I'm not an electrician, but I've done enough bending to at least know what the heck I'm doing!

TTFN,
Jimmy


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