underground electric

[rodney_morgan]

Hello all,

I am planning on running underground electric to my garage. First off, let me tell you how it is configured now. There is 10/3 romex running along the side of the house and then suspended until it reaches the garage. This romex is run out of a 30 amp double breaker. There is no breaker in the garage just a master power switch where the branch circuits run out of. I would like to run an underground feeder to the garage so I can get rid of this eyesore. My ground is very rocky so I will only dig a trench about 12' deep. I understand that this would require a conduit. My main question is can I run regular romex through the conduit or do I need to buy UF/B 10/3 since overtime I assume the conduit will fill with water. What other wiring options do I have? Single strand like what is run to my well? Also should I install a GFCI breaker for the underground feeder? What size conduit should I use? Any answers would be appreciated. I am not concerned about following code but do want the finished work to be as safe and reliable as possible.

Thanks, Rod M.

[Joe]

Far and away your best bet is local building codes and your power company. An example, in our locale underground service up to 100 A takes 1 1/4" conduit at a burial depth of 2'. In rocky ground conduit is a common sense requirement. Our power company will pull Type UF separate wires through the conduit, Al for service entrance. In your case you'll want Cu Type UF and a small service panel with main breaker in the garage. Use GFCI's where needed in the branch circuits. Nothing wrong with using good techniques and foloowing codes. It beats standing in the ashes of your dwelling and arguing with an insurance adjuster about what happened. HTH

Joe

[RBM]

You do want to use either UF cable or THWN conductors in the pipe. Romex would not meet NEC for underground, even in a conduit. Personally I'd sleeve

10/3 UF in a 1" conduit. You will want a double pole 30 amp breaker in the main building and a small panel in the garage. You can install a six circuit panel without a main breaker, or a larger panel, with a main breaker. You will have to drive ground rods at the garage and run a grounding conductor from them to the garage panel. I would not use a GFCI at the house, as there is no need to gfci protect the underground line, but any outlets at the garage will have to be gfci protected

[Tim Smith]

Why would you not be concerned about following code?

[rodney_morgan]

Thanks all for the advice. I have a couple follow up questions regarding some answers. If I run THWN conductors through the conduit, once the conduit terminates on the inside of the garage wall is there a proper way to run them. At this point I believe I will run either type of cable but am hoping to avoid installing a subpanel in the garage unless this is entirely unsafe and unwise. The garage has been wired this way for the past 25 years with no problems. Currently all I use it for is several various power tools (no two would be running at the same time) and two sets of fluoro lights. It is hardly big enough to house a car, perhaps I got a little overzealous referring to it as a garage when it is really a large shed. Secondly, I believe 10/3 UF to be closer to $3.00 a foot and the THWN to be about .42 x4 a foot. What are the advantages to either method? Third, is 1" conduit really the way to go as I think it would be a lot of empty space? In response to Tim Smith's question, I understand that code is meant to keep human and property damages to a minimum, however I just thought there may be other options for doing it right while perhaps violating code and saving a few $. I did not mean to come across as a renegade homeowner.

Rod M.

[RBM]

If you run larger than two 20 amp circuits, you are required to have a panel and ground rods. You also don't install 15 or 20 amp outlets on 30 amp wire or fused at 30 amps. If you don't have a need for 30 amps, connect it to a

20 amp breaker at the house, then you won't need a panel in the garage. Your trench is not deep enough to meet code, so for added protection, I suggested UF cable sleeved in conduit. If you do this, you only need a bushing at the house and garage ends of the conduit and the UF can come right out of it into the structure. If you run conductors in conduit, you'll have to terminate in a box at either end, where you can transition to some type of cable

[Tim Smith]

There can be several problems with violating code. Some are:

(1) If you ever do anything that requires a building permit and an inspection of the completed work, the city/county/whatever may require you to correct the code violation. That is quite often much more expensive than doing it up to code in the first place.

(2) For at least some kinds of code violations, licensed electricians will refuse to work on the system unless it is brought up to code. So, if a few years down the road, you want something done that is beyond your DIY skill level, you may end up paying an electrician to bring the system up to code--almost certainly much more expensive than if you did it yourself now.

(3) You may run into insurance problems.

(4) If you ever want to sell, the buyer's inspector might spot the code violation and tell the buyer. This may scare the buyer off. If it doesn't, the buyer may realize that #1 or #2 or #3 may apply to them in the future, and either insist that you bring it up to code, or want a discount on the price.

It's just a really good idea to follow code where feasible.

[J.A. Michel]

Rod, I understand the dislike of spending large sums of $$$, but you really need to consider doing this right and per code. I'd recommend running a 60 or even 100A feeder out in 1-1/4 conduit, THHN conductors, sub-panel in the garage, ground rods, GFCI's all done per code. The book "Wiring Simplified" is an excellent resource. Get it. Read it.

I have a 100A sub in my garage. The only difference between mine and yours is I did not need to bury conduit or run accessory ground rods - because my garage is attached. 100A is probably overkill, but it sure is nice to have.

[Edwin Pawlowski]

Can be had fro much less. $1.69 here

I have this type of wire direct buried. It is in conduit where it comes up from the ground. I'm not sure of codes at present though.

[Tom Horne, Electrician]

RBM wrote:

If the trench is not at least 18 inches deep to the top of the conduit then you do have to use a GFCI breaker to protect the feeder or branch circuit. The only code compliant alternative is to pour two inches of concrete over the conduit.

[RBM]

The GFCI protection only applies to circuits fused at 20 amps or less, which is a good reason not to use a 30 amp circuit, that he apparently doesn't need anyway

[rodney_morgan]

After reading all the posts. I have decided on running UF 10/3 from a

30 amp GFI breaker through 1" conduit covering a length of 70 feet buried approximately 12" deep (there is really no good way to dig a deeper trench as I live on the side of a mountain with very rocky ground). Once inside the garage I will install a subpanel where I will have three circuits; indoor outlets, indoor lights and outdoor lights. My last remaining questions are

1. What is the proper subpanel to buy for this setup?
2. I am still not entirely sure why direct burial cable is encouraged over the individual wires (THHN I believe) when the cost is more?
3. Are there any concerns with the setup as described?

Thanks, Rod M.

[dpb]

On May 6, 4:42 pm, rodney [e-mail] wrote: ...

You're burying it aren't you? And it isn't "encouraged", it's _REQUIRED_.

A non-U rated cable or wire insulation is not designed for direct burial and the insulation will not stand up for the long haul.

[rodney_morgan]

dpb, what I am referring to is the type of wiring that runs a well pump (THHN or THWN I believe it is called). Perhaps my house is different as well as most others I have seen around here but if you look in my basement or under the cap of my well shaft there are individual wires not one cable.

[RBM]

You can run four individual #10 THWN or similar conductors in a continuous PVC. NEC requires it to be minimum 18 inches deep, (with exceptions). You say you're only going down 12 inches. My opinion is that a direct burial cable sleeved in PVC, under those circumstances, affords the most protection

[dpb]

It's not clear the multiple individual wire will be any cheaper than the cable in small quantity, but if you're running conduit it may be more convenient. For underground it would definitely be considered a wet environment and THHN is only rated for dry so at a minimum it would have to have the "W".

I'm not positive whether it meets NEC for burial even in conduit--was always told it was considered the same as direct burial and couldn't find a direct reference for absolute confirmation.

[dpb]

I agree w/ your recommendation and in fact thought it was required -- that conduit underground was considered the same as direct burial rather than wet environment. But, I'm pretty sure on thinking about it that it's lore I've inherited, so might, in fact not be Code. As noted in other response, couldn't find it in a quick hunt...

[gfretwell]

BTW this is a compliant method that a lot of people ignore. If you are digging in southern Maryland bank run gravel all you really have to do is mix that stuff with some portland and pour it back in the hole when you can't dig anymore.

[gfretwell]

Well wire, in the well casing is another breed of cat.

[gfretwell]

You would have a hard time finding THHN that wasn't dual rated THWN. Just remember that is still THWN when derating. It is THWN (75c) whenever it is used in a wet location. As long as you use 240.4(D) rules (the good old 14ga=15a, 12ga=20a) it won't come up.