power to garage

I'm gutting my existing detached garage(no electric) There are two rooms for this garage. First room will have 9 over head lights and will be running at least one power tool ( table saw, saber saw, drill, etc) 2nd room will have nine over head lights, nothing else.

I believe my electric box has been updated in 1990 but none of the wiring. On my breaker box there are 12 spaces the 6 on the left are rated 15, 20, 20, 15, 15, 20 and the ones on right are double switches rated at 40, 30, and 30. I don't use any of the breakers on the right side.I know the 40 amp was for an electric dryer and one of the 30 amps was for an electric range.

The garage is detached and the wiring has to go from the attic to the garage, what are my options?

 

Personally I like underground if you can do it, but if you have to go overhead you can. Te 40 was the range and you could use that if you wanted to. Use wire rated for a bit bigger though in case you ever need a bit more,, minimum of number 6, 4 is even better. A little depends on how far away it is. You are going o need 4 wire for this application. Here is a site that shows several options. Look and come back for some fine tuning.
http://www.homewiringandmore.com/homewiringusa/2002/accessory/detgarage/detgarage.html

 

So what I think I'm looking at is taking the 240v 40 Amp breaker and run that to the garage, and then split that into 2 20 amp breakers. Am I getting warmer?

 

As long as "split that into 2 20 amp breakers" means you are installing a subpanel. That implies three insulated conductors plus a grounding wire run between the buildings, plus two grounding rods at your garage.

If you use a 40-amp double pole breaker in your main panel, you can use 8-gauge wire. You may want heavier wire if the garage is very far away (you didn't take sberry's hint that you tell us how far that is). With a 40-amp breaker at the main, you can install a lot more than just two 20-amp breakers in your garage if you want.

 

I honestly don't know if I'll ever need more than a 20 amp circuit, but I like to go overboard but if going overboard means drowning I will rethink what I will be using this garage for. On that note can I simply make a 30 amp 240 volt into a 20 amp 120 volt at my main breaker and run it from there.

 

the garage is no more than 20 feet away

 

Actually you could replace that 30 with a 20 a 240 breaker and get twice the power out there with one 4 wire cable. That would be the best option as close as it is. You would use a 20 A double pole switch as a disconnect in the garage and you wouldnt need panel or ground wire and all that stuff. That would give the power of 2 20A circuits. I believe it showed that circuit on home wiring garage site that I recomended. You can also use a single circuit which would be the very simplest, but it severly limits power for power tools and lights. Look at the circuit on that site again, then check back. A 40 A sub fed actually can provide 4 fully loaded 20A circuits as John stated.

 

So the double pole switch will turn the 240v 20a into 2 120v 20a circuits and act as the disconnect. Thanx for the help so far

 

It wont really turn it into 120, but it will act as the disconnect for the building. The way the wires are connected splits it into 2 circuits. Maybe someone has a drawing of the circuit on the net you can get. You need a number 12/3 with ground uf wire for this. Underground would be best. You could use 10/3 too if you wanted, it is more common in the store, its a bit more difficult to work with at the garage, but you are still limited to a 20 a breaker. In fact if it was mine I would, it allows for a little upgrade if it ever was needed and helps motor starting a little.

 

shoot me now! please! It would be easier-

 

dont panic yet. Look down that home wiring site, it shows all the details of this job. Maybe you can find a friend to help that has some knowledge. First things first. Can you trench to the garage?

 

all right - we are going to run 240 20 amp to garage to the double pole switch and from the switch we are going to share the neutral so that we will have 120v on two circuits. Let me know if I'm on the right track. Going to go do some more homework on sharing neutrals. Thanx again

 

Yes, you are on the right track now. This is the most power with the simplest circuit.

 

We are making some progress - Okay do I want to even out the current as much as I can between the 2 circuits say I know I'm going to have a clock on always and a light on always should these be wired say red-neutral and black neutral, or should I be more concerned with maybe alternating every other recepticle and everyother light switch. I hope this makes sense, I am drawing a mediocre schematic tonight.

 

That is a difficult question. I might be tempted to put all the lighting and any other steady loads, and a couple misc recepts on one circuit and ones I will use power tools on anther.

 

so basically I just want to keep each circuit under 20 amps correct, I don't really need to be concerned with trying to even out the consumption on each circuit. Thanx again

 

Correct. If they were known constant loads you could attempt a better balance. Youre so close and the loads are light that it wont make much difference. I like lighting on one leg and motor loads on the other, it just keeps the dimming to a minimum when you turn on a tool and leaves all the available power on that line for the tool. Then you can ground fault that circuit too without nuisance tripping the lights.

 

So I'm going to have 2 hots a neutral and a ground coming to the double pole switch - the two hots get connected to the switch the neutral will be pigtailed into 2 outgoing neutrals. One hot and 1 neutral go to one circuit the other hot and other ground go to the other circuit. Does the ground wire get pigtailed there into 2 grounds one to each circuit? Do I need a ground rod?

 

Yesm the grounds get pigtailed together and thats one of the benefits to using that system is that a ground rod isnt needed. When you add a panel you need one. Remember, 20A double pole switch and I think I would mount that in a 4x4 box and you would have room to work.

 

sberry27 I'm looking at this Black and Decker book and I'm wondering if I have to run 12/3 througout the circuit and pigtailing out the wazoo or if I can split it into 2 12/2's at the double pole switch and run say red, neutral, ground to outlets and the other black, neutral, ground to lights and known loads. Another question is do I need metal boxes or can I use the plastic ones. Thanx again I hope these questions made sense

 

You shouldnt really need any 3 wire once you are on the load side of the switch. (unless you want recept and switch or multiple switches in same box) Only wire with black and white in it. On these branch circuits you cannot share a neutral. They each need there own. Use 2 wire with ground. Run around and catch the lights with one circuit and do another for recepts. Well,, with only 2 circuits in the building I guess you could share the neutral,, my mistake, but if it was ever converted to a sub panel the feeders would need to be connected properly and made sure they didnt get fed from same leg. I am not so sure its a good idea even though it would work. Its late, its too much strain for me, ha

 

You could complicate this having to use gfci. I think I would run 2 distinct circuits so that you could cover all recepts with one unit.

 

If you get a chance could you take a look at my cheezy drawing and tell me if this is what I want to be doing thanx

 

Yes, that looks excellent. You should gfci first outlet.

 

Did I just turn two lights on?

 

Yes you did.

P.S.What software are you using for your graphics?

 

old printmaster 7.0

 

I know your sick of me by now, but I have updated my schematic- it is not the entire circuit but that would take for ever to draw with the program I'm using.

Questions are 1. Do I want to use junction boxes where I made all of my splices or should I get deep boxes that will hold them and if so could you recommend what size 2. Can you double check the gfci wiring and the outlet that follows. 3. What type of outdoor rated wire do I need- it is 12/3 but it will be in the elements- Do I go to Home Depot and just get 12/3 outdoor wire?

 

(1) You can do it either way. I'd use the largest single-gang boxes you can find and make all splices in the same boxes as the switches, receptacles, and lights. You can get 22.5 cubic inch single-gang plastic boxes at Home Depot. Most areas allow plastic boxes in garages, but some require metal boxes. The largest single-gang metal box isn't as big.

(2) The GFCI wiring is correct.

(3) The easiest outdoor wire to use is UF cable. It can be direct buried. Home Depot carries it. Since your wire isn't GFCI protected until it gets to the garage, you will need to bury it at least 24" deep. If you used a double-pole 240/120 GFCI breaker in your main panel, then you could bury it 12 inches deep and skip the GFCI receptacle in the garage.

 

Hi john, and thanx for replying - the wiring is overhead coming from a 20 amp double breaker - I know you guys like the clean (and probably safety) look, but I have to go overhead - If I am allowed, what wire is suitable for this?

 

You need messenger wire. Home Depot doesn't sell it or any other overhead wire. You'll need to go to an electrical supply house. There are a lot of requirements about how high it has to be based on what it passes over. If at all possible, bury it instead.

 

I can go underground, but have a couple questions on that. 1. The run will be longer maybe 100 ft- 150 ft I will upgrade the 12-3 to 10-3 is this correct? 2. Is there a minimum height that the wire needs to be exiting the home - I live on a slab and may have to exit the home 2 ft above the ground 3. When I exit the home can I use Pvc piping to run the wire 12 inches (if gfci protected breaker) into the ground and then up on the garage side 4. Can I throw a telephone wire, cable wire in the same trench? thanx again alll