Conduit Question

**Verdeboy** · 09-21-2007, 10:04 PM

For minor residential jobs where you need to run some cable outside, is it customary to use EMT, IMC or Rigid? I want to buy a manual bender and conduit cutter, and if I'm only going to use EMT, It'll make the decision easier.

**Speedy Petey** · 09-22-2007, 03:33 AM

Originally Posted by Verdeboy

For minor residential jobs where you need to run some cable outside,

Define this. Do you mean conduit runs, or just short sleeves for protecting cable?

For outside runs I use PVC. In fact for most residential conduit work I use PVC.

hj · 09-22-2007, 07:46 AM

Here, if it is going to be above ground it must be schedule 80 PVC conduit.

**jwelectric** · 09-22-2007, 08:20 AM

Originally Posted by Verdeboy

For minor residential jobs where you need to run some cable outside, is it customary to use EMT, IMC or Rigid?

By the term “cable” I hope you are not talking about NM (romex) going in the raceway installed outside.

Originally Posted by Verdeboy

I want to buy a manual bender and conduit cutter, and if I'm only going to use EMT, It'll make the decision easier.

What do you mean by “cutter”?
A tubing cutter is very bad when cutting EMT as it leaves a sharp ring on the inside of the pipe and also reduces the size of the pipe as it indents the conduit.

**Verdeboy** · 09-22-2007, 10:35 AM

Schedule 80 PVC it will be. I'm finishing up a minor outdor run (above ground) where someone had used metal conduit. Since I was told he was a "real" electrician, I thought the metal was code. Obviously not.

BTW, If only PVC is used outdoors, why is metal conduit used in all the carports and up the sides of buildings in the apartment complexes I worked in?

Also, is there a simple way of bending the PVC? Like using a heat gun or sticking the end in my Jeep's tailpipe? Or do I need to buy a PVC bender?

As for the conduit cutter, JW, I was looking at the Greenlee, which is advertised as Burr-free and no sharp edges. They also say, you can cut it with the cable inside. Are they lying?

**Bob NH** · 09-22-2007, 10:53 AM

You can buy 90 and 45 elbows for PVC, or you can bend it with equipment, or you can use a heat gun if you have patience. I have bent up to 1" Schedule 40 with a heat gun. I have never had occasion to bend Schedule 80.

If you are careful you can get as good a bend with a heat gun as you will buy in the electrical supply. It is easiest if you can work the piece on a flat surface.

It is also a violation of the code to bend it with equipment that is not designed for the purpose.

**jwelectric** · 09-22-2007, 12:13 PM

Originally Posted by Verdeboy

, If only PVC is used outdoors,
As for the conduit cutter, JW,

Eric

When installing a raceway outside it is a matter of choice as to what is used. EMT, RMC or RNC either would be proper to install outside except EMT will not last long if in contact with earth.

There is no code requirement that all outside conduits be rigid nonmetallic conduit (RNC) or PVC as some would call it.

I will not allow the tubing cutter to be used on my jobs. This cutter will indent the pipe and leave a very sharp ring on the inside of the pipe that will damage the conductors as they are being pulled through the pipe. No matter how hard you try to remove this ring on EMT it is all but impossible to remove so no damage will occur.

As to cutting the pipe with the conductors installed, it would be a violation of the NEC and IRC.

300.18 Raceway Installations.
(A) Complete Runs. Raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors.

Again I do hope that with your repeated use of the word “cable” you are not planning on installing NM cable in this raceway on the outside.

**Verdeboy** · 09-22-2007, 01:27 PM

Originally Posted by jwelectric

Again I do hope that with your repeated use of the word “cable” you are not planning on installing NM cable in this raceway on the outside.

What is the approved cable for this? I've got UF-B and tray cable, but I can buy something else if needed.

The run is about 20 ft total, starting from an outlet box on an exterior wall of the shop, along the bottom of a stone wall, through the stone wall (~16" wide), up a post of the porch, and terminating in a junction box, which feeds various light switches for the porch, one other outlet, and an indoor/outdoor ceiling fan.

**Bob NH** · 09-22-2007, 02:18 PM

One of the places that tray cable may be installed is in a raceway, such as a conduit. Ampacity is determined per 310.15. You should be able to use the usual ampacities for up to 3 current carrying conductors in a conduit. If you have more than 3 conductors you may be able to use those numbers if the cable has a 75 or 90 C temperature rating and you do some calculations per 310.15(B).

Underground is considered a wet location so the cable must be rated for that if used in an underground conduit.

You would need to run the raceway for the full length of the run if you use TC.

Most people use THHN/THWN in conduit. You can usually pick up a 500 ft roll of #12 on the auction site for about $50 with shipping; #14 a little less. You need a roll of white or grey for the neutral, green for the ground, and any other color for the ungrounded (hot) conductors. You can use the same color for all of the hot conductors if you keep track of wires.

**Speedy Petey** · 09-22-2007, 04:17 PM

Originally Posted by jwelectric

I will not allow the tubing cutter to be used on my jobs. This cutter will indent the pipe and leave a very sharp ring on the inside of the pipe that will damage the conductors as they are being pulled through the pipe. No matter how hard you try to remove this ring on EMT it is all but impossible to remove so no damage will occur.

Actually Mike this cutter will not do as you say. Although I have not used one personally yet it does seem to live up to it's reputation.
It is made specifically for EMT. It is NO ordinary tubing cutter.

**jwelectric** · 09-22-2007, 05:23 PM

Originally Posted by Speedy Petey

Actually Mike this cutter will not do as you say. Although I have not used one personally yet it does seem to live up to it's reputation.
It is made specifically for EMT. It is NO ordinary tubing cutter.

Sorry bout dat, havn't heard of one yet.

**Verdeboy** · 09-22-2007, 07:29 PM

Here's an interesting thread from another forum on a related topic. After reading it, all I got was a headache, and I still don't know why you can't use Romex in conduit.

http://ths.gardenweb.com/forums/load...003331911.html

**jwelectric** · 09-22-2007, 08:11 PM

Originally Posted by Verdeboy

I still don't know why you can't use Romex in conduit.

Didn’t say that you couldn’t install NM cable in conduit but I did say you couldn’t install NM cable in this pipe,

Originally Posted by Verdeboy

For minor residential jobs where you need to run some cable outside, is it customary to use EMT, IMC or Rigid?

Originally Posted by NEC

334.12(B) (4) Where exposed or subject to excessive moisture or dampness

Even though the cable would be in a raceway the raceway would be in a wet location.

Originally Posted by NEC

Location, Wet. Installations under ground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather.

**Verdeboy** · 09-22-2007, 08:40 PM

Okay, I got it.

But can you explain why individual conductors (inside conduit) like THHN-THWN are safer in locations exposed to weather than Romex (inside conduit)?

I actually thought the reason why Romex wasn't used in conduit had more to do with difficulty pulling it through (90 degree bends, etc.) especially with the sheathing still attached.