Question on cutting EMT

[Jim Spallin]

I'm installing lights in my shop and I'm using EMT for the first time. I've done a lot of searching and have found nothing that describes the details of how to install short inline sections of EMT. Here's an example. In a row I have:

fluorescent fixture------------box---------------------fluorescent fixture
18" 30"

where the measurements are edge of set screw connector to edge of set screw connector - the actual gap.

How long do I cut the EMT and how do I install it. I read that that the EMT needs to be inserted at least 1/2" but given that the depth of the connector is 7/8" I can't just cut it 1" long and slide it to the end of one connector, insert in the other and center it. Do I loosen the box or fixture and then tighten it after inserting the EMT? How much longer than the gap should the EMT be cut.

Figured I'd ask what is the "normal" way.

Thanks for your input.

Gidday,
Jim

[Murray Roblin]

Hi Jim,
Not an electrician, but have wired lights in my shop and a friend's as well.

First, easiest and most common way is to use flexible conduit. length can be approximate, conduit can be flexed to allow easy installation between two fixed junctions, and will easily tolerate misalignment. In a commercial setting, the fluorescent fixtures usually have whips attached (pigtailed conductors in flex conduit, or flexible metal cable). JB's are installed with emt leading to them (from power source, switch, ...). then fluorescent fixtures are installed (suspended by chain, laid into ceiling), and then the whips connected to the JB.

If using emt or other rigid, one would usually install conduit as lights/jb being installed, e.g. install JB, measure approximate distance and cut emt, install to jb end, hang light. However, this is finicky as mounting the lights while attached to conduit at one end is tough.

If at all possible, I'd get some flex conduit, appropriate fittings and do it that way. Make sure to install plastic bushings at the end of the conduit (inside the fitting) to protect the conductors from the conduit's sharp edges. (Also, I find it's easiest to get a square and clean edge on the flex conduit by cutting with a dremel and a cutoff wheel. There are flex cutters available, but they leave sharp edges, and hacksaws only work if the conduit is very well supported during the cut.)

[Ryan Myers]

Hi Jim I am an electrician. To install conduit you measure just like cutting lumber. Take a measurement between the two items your installing then maybe deduct no more than 1/8" unless your installing box offsets. A box offset is the distance the knockout hole is from the back of the box to the bottom of the hole. If you use conduit hangers or Minnie's you don't really need to worry about it. Only if your using one hole straps is it am issue. Then it requires bending the conduit.

I wouldn't use flex since it is really only intended for vibrating equipment or equipment that needs small movements. And bushings on conduit are only required for wire #6 and larger

[Murray Roblin]

Ryan,
Thanks for correcting me. Always good to have a pro weigh in on these issues. I guess my use of flex is more of a diy hack than I thought.

Murray

[Ryan Myers]

Muray-

No biggie. I appreciate a nice conduit job but that's because I've seen a big switch in the last 10 years on commercial jobs everyone uses MC cable which is 3/8 flex basically pre-wired. Hate this stuff but it is fast to install and it saves lots of labor. You have to use it wherever possible to stay competitive. But real craftsmanship like running conduit is almost extinct, many of our 150 electricians don't even know how to bend conduit. It is a bit of art form. I guess that is part of why I enjoy woodworking so much, if you cheat on the craftsmanship it shows. Electrical wiring buried in the wall most people could care less what it looks like. I am bit like Steve Jobs you could say, I think the inside of a wall should look as good as the outside.

[Brett Bobo]

Hi Jim,
As you're finding out, it can be very difficult installing EMT between hard points based on the overlap with the connectors. I found that it's best to work "downstream" piece by piece and even pre-install sections before mounting them.

Also, for manually cutting EMT, an adjustable tubing cutter works well, followed by a few turns of a reamer. Just avoid the pre-sized tubing cutters, e.g. Autocut, for copper as the pipe diameters are not the same.

[Rollie Meyers]

Hi Jim I am an electrician. To install conduit you measure just like cutting lumber. Take a measurement between the two items your installing then maybe deduct no more than 1/8" unless your installing box offsets. A box offset is the distance the knockout hole is from the back of the box to the bottom of the hole. If you use conduit hangers or Minnie's you don't really need to worry about it. Only if your using one hole straps is it am issue. Then it requires bending the conduit.

I wouldn't use flex since it is really only intended for vibrating equipment or equipment that needs small movements. And bushings on conduit are only required for wire #6 and larger

It's 4 AWG or larger see NEC art 300.4(G).

[Jim Spallin]

Hey guys, sorry for not saying "thanks" for the input. Did it all with EMT and used your advice. Very happy with the installation.