I'm installing a garage on the side of my house furthest from the electrical box. I don't want to trench the entire distance (60 ft), so I am planning on running conduit along the exterior of my home to the wall nearest the garage. From there I would dig my trench to run to the garage (~ 10 ft), and transition from an above ground to a below ground installation. I'm planning on a 60 Amp circuit to power the garage. EMT can be placed underground according to 358.10.A.1. If I read correctly it only needs to be buried 6 inches, where I need to go 18 with PVC. Am I understanding this correctly or off base in my analysis? What would be the recommended choice in this instance.

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    Rigid can go 6 inches deep. EMT requires same as PVC though I would expect it to rust quickly. Rigid is expensive, though that may not be such a big deal for you given the short run. – Harper - Reinstate Monica Jan 7 '18 at 18:31
  • If I ran PVC along the house, can I connect it to Rigid prior to the in-ground installation? – FlyFish Jan 7 '18 at 18:53
  • sure. Definitely at a junction box or conduit body, which I recommend you have as often as feasible for easy pulling. – Harper - Reinstate Monica Jan 7 '18 at 20:03
  • Thanks for the response. After I posted this, I thought I just might go with Sched 80 and dig 18 inches to save a few bucks. I guess time will tell. – FlyFish Jan 7 '18 at 20:16
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    If you install PVC above grade, make sure you use at least one thermal expansion coupling, and use PVC clamps that screw down on both sides of the clamp and do not hold the pipe tightly, so that the clamps won't bind and the pipe can move. If you don't, you will end up with warped or broken conduit when the weather (temperature) changes. – Craig Jan 7 '18 at 20:26

If you do use EMT outside or in ground you will need to use compression couplings listed for wet/ damp locations, it will need to be secured every 10' and within 3' of the boxes. EMT would require 18" burial depth. Knowing you are going from 1 end of the home down then back up you will have more than 360 degrees of bends so conduit bodies or boxes will be needed to provide pull points. I will usually use conduit bodies to go around corners makes a tight turn with a LB then further away I will use another to make the turn to go in the ground LR or LL with 90 deg sweeps in the bottom of the trench at both ends and a LB or box to enter the building (box being a exterior disconnect). I think you might find schedule 80 PVC a bit cheaper and easier to work with than 1" or greater EMT.

  • I've abandoned the thought of using EMT for all of the reasons everyone has mentioned. – FlyFish Jan 8 '18 at 19:00

There are a few things you need to consider before running a long feeder and it seems you have at least given it some thought about method and materials.

First you say:

I am planning on running conduit along the exterior of my home to the wall nearest the garage.

The word "to" bothers me. Shouldn't it be "on". In other words you can't just run conduit on the ground. Conduit has to meet code requirements on securing conduit to something that doesn't move. So it needs to be strapped onto something so it doesn't move freely. There are different strapping requirements for each type of conduit and these can be found in individual articles in Chapter 3 of the NEC.

Also NEC code only allows 360 degrees of bends before adding a pull box this can be a variety of different types of boxes, condulets, etc. You will find you will need to follow these rules when you are trying to pull conductors as a 90 requires around 10 time more resistance than a straight pull.

You can bury EMT but most contractors I know won't do it. Depending on the PH of your soil could cause the conduit to erode, sometime in less than a year. PVC is you best bet. Also most good contractors will always bury conduit at least 18" in the ground if possible. The reasoning being that anyone accidentally cutting a 60A underground circuit is not an experience anyone enjoys.

Good luck on your project and stay safe.

  • I am planning on attaching the conduit along my house sides until it reaches the wall closest to the garage. At each corner of the house I will have a pull box. There will be 90 degree heading to the underground PVC, a 90 degree at the horizontal underground transition and another where I transition up along the garage. I'll have another pull box to feed into the garage. I plan on burying the conduit 18 inches. I'm still debating whether to use Schedule 80 or go down to 40. – FlyFish Jan 8 '18 at 18:59

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