Wiring do's and don't

I want to direct wire my detached garage. I have run 10 ga wire. Can I now run 12 or 14 ga Romex and splice it to the 10 ga?

 

If local codes allow you to use 14(some don't) it must be protected by no larger than a 15 amp breaker.If you use 12,it can be protected by no larger than a 20 amp breaker.

 

My plan is to run 30 amps to my garage. I have run 10 ga under ground to the garage. I will receive my power from my house's breaker box. I plan to add one 30 amp breaker. Will I need some type of breaker box in my garage or can I just hook directly into the 10 ga wire? If I can do this can I use a 12 ga wire within the garage?

 

You have to use a 20 A breaker to hook directly to the number 12 wire. I would have used 10/3 with ground, a 3 conductor wire will give twice the power. Look down a few posts and see thread on detatched garage. There is no benifit to using a 30 in the house and a 20 in the garage. Its redundant, just use 20 in house for a single circuit.

 

Running ten awg, then attaching 12, or other sizes smaller then ten. Is not a problem. The problem is, and what most everyone is trying to say, Is 10awg can be protected with a 30 amp breaker. And smaller wire has to be protected with smaller breakers. Like 20/15 amp. Attaching smaller wire to the ten without protecting the smaller wire on a breaker that is compatible to the wire size will cause overheating If the smaller wire is would pull the 30amps. And you can not just say. OK, I will not allow it to pull 30amp, I just will not plug as much stuff in. You might not be the one using it. And if you would sell then someone else would be the one needing good insurance. Beside the point it is not allowed per the National Electrical Code.

 

So if I wire my garage with 10/2 ga on one 30 amp breaker I can still use 15 or 20 amp outlets? What I will be running will be a deep freeze on a regular basis. I want one additional outlet for random use of drill, skill saw.etc. One more outlet for a shop light, and one outside GFI outlet.

 

No. No devices or wires are allowed to be installed in a circuit they are not rated for. If you install 30amp breaker, then install "20/15 amp devices, See they problem !!!

 

again,, NO,, you cannot connect 12 or less to the 30 amp circuit. You need to get this 30 a circuit idea out of your head. Hook it to a 20 instead of a 30 and you can use 12 in the garage. You cannot connect any branch wiring to a circuit that has a breaker larger than the ampacity rating of the smallest wire in the circuit. If you use 14 wire you must use a 15 A breaker. Use a 20 in the house and you can connect 12 in the garage.

 

I want to thank you for being patient with me. I don't think sb27 understands my question. I am now looking to wire inside my garage with 10/3 wire( after looking I saw that this is what I had installed in ground all along.) Art, I think what you are saying is that if my breaker is 15 amp my outlet must also be 15 amp, 20 with 20 and so on. Question...what can happen if I wire with 10 ga to a 30 amp breaker and have 15 amp rated outlets?? I know that the 10 ga can handle the amps, wouldn't this make the outlet safer??

 

Phil,,, again,,, you have to forget this 30 a breaker here in this situation. You can use the 15 rated outlets on a 20 a circuit, but you cannot use them on a 30 A circuit. Did you use 10/3 with a ground wire or a 10/2 with ground? I would have a 10/3 wg wire and use a multi wire circuit so essentially you could have a circuit for the freezer and a couple lights and the other for tools and the outside outlet. One gfci can cover the inside and outside outlets. Garages require cfci except the freezer. You are getting confused, here for some reason we cant seem to straighten out. We are trying to protect the wire, not nessarily the devices. There is no real application you can use the 30 here to protect the wire and devices. Aurther related that clearly in an earlier post also. If you have 10/3 let us know and we can help get the needed power. Go to the detached garage post and read the posts and then follow the link. This may help. It is in here down a few threads.

 

Your way of thinking about this is just a little off. If you have 30 amp breaker and wire, Then install 15/20 amp devices, then what is stopping the devices from being loaded 30 amps. Everything must coincide from the outlets all the way back to the panel, or nothing is safe. Think of it like this. If you would run 2in water feed to the shower, then install a 1/4" inlet into the shower!

You have 30-amp circuit out there now. Is it 3 wire, or 2 wire? What I am thinking is install a 20 $ 4 circuit breaker box in the garage, then in it install 15 or 20 amp breakers. You then can install the outlets with respectable amperage devices, and wires.

 

Another possibility is to just replace the 30 amp breaker you currently have with a 20 amp breaker, leave the #10 wire just put it on the 20 amp breaker. Then you can run #12 wire and use your 15 or 20 amp rated devices.

 

Thats what we have been trying to say.

 

So ... let's say you put a 20-amp breaker in the house's panel and connect it to that 10/3. You sell the house. New buyer sees it and swaps out the 20a breaker with a 30. He doesn't know that the wire at the other end is 12 or even 14. He plugs some high-draw stuff into each of the several receps in the garage. The new breaker doesn't blow, but the 12 or 14 wires heat up & burn.

Also, how far is the run from the panel to the garage? Can that length of run actually handle a full 30-amp load at that distance?

I think I'd at least write a note explaining the situation in permanent marker inside the door of the panel box.

 

The run from my panel box to the garage is 50 ft. My main concern is that with my freezer running all the time, that I have enough power for the other things. I admit my thinking has been flawed. I guess I've been thinking that if more amps are availible then I can run more things. I wasn't thinking about a light drawing more amps than it can handle. I've done some reasearch but some of these qusetions are hard to find straight answers on when you don't have the basics. Thank you for some lessons on electricity 101.

 

Phil, do you have 10/2 or 10/3 to the garage? It makes a big difference on the available power.

 

My wire has one white,one black,and a bare copper. The only thing that I'm sure of anymore is that it's 10 ga.

 

You're going to have to settle for one 20-amp circuit in the garage. This will give you 2400 watts of power. I hope that's enough. Based on what you've listed, it probably is (depending on the size of your freezer, and assuming you don't also have a garage door opener).

If you do need more power, you will need to install a subpanel and run a new cable with at least 10/3 (black/red/white/bare). Grounding rods will also be required at your garage. If I went to this extra trouble of rerunning the cable and installing a subpanel, I'd run at least 8/3 instead of the 10/3.

Another option that could use your existing 10/2 (although quite unusual) would be to install a small 120-volt subpanel in the garage. You would still need grounding rods, but this would give you 3600 watts of power. Personally, I would not implement this solution for only 1200 more watts.

 

Not necessarily. He can use the 10/2 to supply 30A to the garage,
an use a two spot breaker panel with 2 15A breakers, one for the freezer, another for everything else.

 

I would consider what Gary suggested, didnt want to get anymore complicated than we were already, but I have seen that done with a 15 for freezer and lights and a 20 for the recepts. If I was doing it I might just start over with a 10/3 and use a multiwire circuit, with a switch for disconnect and that would leave the option of a small sub for the future. If I am going to install a sub in a garage I get to 60 a minimum and that always leaves the option of hooking a welding machine if it had to be done for some reason. We do lots of garages with number 2 al for the feeders with a 60 brkr on a 6 space main lug panel. Even fully loaded V drop is minimum and its cheap.

 

Phil, Something we all neglected to mention is that the wire you have buried must be UF and it will say it on the wire. It MUST be rated for outdoor. I meant to mention this a couple times but forgot it.

 

John, is this because of the distance versus wire size?

I plan to run a line to a shed this summer. It's also about 50 feet away. I only need a small utility light and convenience recep there, and 2400 watts is plenty. However, I want to make sure it's safe for the next owner.

How does one go about properly labelling a circuit breaker in a panel box to let future homeowners know that the 20amp CB attached to the 10 awg should not be swapped?

 

Hang an ID tag from the wire attaching to the breaker with a brief description of why not to change the breaker size.

 

Rick,

The comment about "live with one 20-amp circuit" had nothing to do with distance.

In my prior post, I gave Phil three options:

(1) Live with one 20-amp circuit.
(2) Run new /3 cable and install a 240/120-volt subpanel.
(3) Use the existing 10/2 cable to install a 120-volt subpanel.

The comment you quoted referred to option (1), and was made because he plans to put general-use receptacles and lighting in the garage, and general-use receptacles and lighting are limited to a maximum breaker size of 20 amps.

Note that I specifically did not include an option to keep the existing cable and run another cable out there for a second circuit. This is prohibited by the NEC.

I applaud your desire to make things safe for the next owner, and Art's labelling suggestion is a good one. However, anybody that changes a breaker size based solely on the size of the wire at the panel is a fool (not that there aren't a lot of those around).

But 50 feet is not far. You can easily use 12/2 for your line to the shed if all you need is 2400 watts.

 

Based on all of the excellent commentary, I am now inclined to change my wire. Since nothing has been connected all I would have to do is pull it thru my underground pipe (18 ft) and run the rest thru the crawl space under the house. ( I used UF wire and ran it thru PVC pipe.)
I'd like to hear different opinions on what type of setup would be safe, easy, and economical. Although I only plan on a few plugs at this time, I would like to leave open options for down the road use. Maybe even for 240 use later.
I have 200 amp service to the house and should have plenty for the garage.

 

How big of pipe did you use?

 

one inch

 

Legal you can put in a one inch will be number 4,, 3 number 4's and an 8 ground. Easier would be 3 6's and a 10 ground would be good too. (thwn wire) That with a 50A breaker would be good. With the 6's you could weld with a regular machine if you had to and keep a couple of lights on. You would have to pipe all the way to the panel. You could probably get a number 8 cable down there too without a problem. Both would require a sub panel and a ground rod. I use 6 space main lug panel for this setup. Its cheap and leaves some options. 4 circuits for 120 stuff and 2 spaces for a 240. Now, all that said you could use a simple multi wire circuit with a 10/3 wg that only requires a double pole switch as disconnecting means in the garage. You put this on a double pole 20 A breaker in the house gives overcurrent protection for the branch circuits. This is cheap doesnt require a ground rod and gives a circuit for your freezer and lights and a circuit for some recepts. It also allows an upgrade to a 30 amp feed at some time in the future with addition of a panel in the garage. Take a look at this site and look at the options. http://www.homewiringandmore.com/hom...detgarage.html This is a great site for all options for garages.

 

I'm leaning toward running a /3 wire cable with a 240/120 subpanel. Eariler, John had said that he would run a #8 wire. Why would I want the #8 vs the #10? Will either 8 or 10 require a ground with the subpanel?

 

A panel in a seperate building needs a ground rod. The reason John suggested an 8 is it will deliver substancially more power. The installation labor is the same and you get a quarter more power. You can use a 40 A breaker then.