Question on adding 220V and 110V circuits to garage

I want to add two 220V and some 110V outlets to my garage. The wall where I want to add them is far from my breaker panel (at least 70 feet) but is close to my meter. There is even a box with a removable panel on the inside wall right behind the main service box that provides access, from the inside the garage, to the house's main 400A breaker in tne meter box.
I would like to install a breaker box with two 30A 220V and two 20A 110V circuits and connect right to the main service box (after the main 400A breaker of course). This would save me from running a long run from the distribution breaker panel, where I don't have enough room anyway.
I have done a fair amount of home wiring and am pretty handy with this, but I have never worked on mains side of a distrubution or breaker panel. I don't want to mess this up, so I have some questions. When I look at the main 400A breaker and the buss bars coming from the meter, I don't see a neutral line.
There are two large hot wires that pass through a 400A ganged breaker in the main box, and a green ground that looks like it only goes to earth. My questions:
1) Is it OK to connect my new panel right to the 400A breaker in the main box?
2) How would I wire the 110V circuits? I know that each hot end of the 220V feed (through an appropriate breaker in my sub panel) will be a 110V hot, but where are the 110V neutrals? Do I simply run two wires back to the green in the main service box and call one "neutral" and the other "earth"?
3) Is it typically OK code-wise to split up the output from the main breaker right in the service box? I doubt they make wire nuts that big and I don't think it's OK to "double up" wires on a breaker, so if it is OK, how is done? Do they sell monster terminal strips?
To diffuse all the safety related replies I'm likely to get, let me say that I'm incredibly careful around wiring. If this seems too much for me, I will certainly hire an electrician. But if the answers are not too intimidating, I'd rather do it myself - not to save money, but because 1) I have found that I am more careful and do better work than the trades people I've been able to hire, and 2) Where I live, you can't get people to show up for small jobs. It will take a least a month to get this done by an electrician and I'd like to start welding now.
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http://www.selfhelpandmore.com/homewiringusa/2002/maindwelling/attgarage/index.htm
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In order to do this safely, you need to cut the seal and pull the meter. In my area, you need a licensed electrician to do that.

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In northern calif, my MAIN has the meter on the left side of the box, and then a distribution panel arrangement on the right side. I can install all the breakers I need in the right side of the box without disturbing the left. It is ideal to connect to the main entry point with your sub-panel feed if you can do it.
(By the way, when the house was re-wired 4 years ago, the electrician simply clipped seal on the meter, changed the entire box/panel all out, and then put the broken seal back in place like it was never touched. Never called PG&E at all. PG&E simply 'sealed' it again next time they noticed it was opened. Perhaps because it was obviously a new contruction/major remodel? Hummm.....)

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Without seeing your current service installation it is impossible to give you specific answers. Generally speaking it may be possible to tap off of the line side of the 400a breaker with a smaller feed that goes directly to another main breaker sized to the tap. The lugs on the 400a breaker would need to be rated for multiple conductors or you may be able to change the lugs. You can contact the breaker manufacturer or a distributor for that info or it might be on a label somewhere. That second main breaker would need to be located near the 400a main. The second main can now feed a subpanel wherever you want.
I am not sure what is going on with your neutral conductor, but you would need to bring that and a grounding conductor of appropriate sizes to the second smaller main breaker and continue them on to your subpanel. It is unlikely that your existing neutral conductor is separated from the hot wires.
Since you have a 400 amp service there should be some current transformers somewhere. If you have been looking in the CT box, then it is quite possible that there is no neutral in there and I don't think that it is possible to make splices in there.
This is not the kind of installation that I would suggest that could be done by a homeowner. To do it right you may need to disconnect your service and redo several components. A trough may need to be installed to split the feed into two main breakers. You can try contacting your power company and have a rep come out and give you his input.
Is it possible to put in some thin or twin circuit breakers in your existing main panel to give you the space that you need for a two pole circuit breaker to feed a subpanel in the garage? Read the cover or label inside of the panel for information on how many thin circuit breakers are allowed.
John Grabowski http://www.mrelectrician.tv
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Since your main is by the meter you are just installing another sub panel from there. You house is a sub too. The first question is do you have empty breaker slots in that 400a main panel?
If so put in a breaker and run the appropriate FOUR wire feeder to the garage. Install a panel there with the extra ground bar. Don't bond the neutral to the can. Grounds go to the supplimerntal bar, neutrals go to the isolated neutral bar. If you have less than 6 breakers in the garage you don't need another "main" in that panel (the one in your 400a will suffice) You DO need a ground rod in the garagem, connecterd to the "ground" bar. It is really more complicated than this but this is the basic process
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Thanks for the repies. I too am in Nor Cal and can get to the wiring I need without pulling the meter. But there is no room in the main panel for more than the main breaker. This is going to sound dumb, but I am not sure about having 400A service. What I see in the box are two 200A breakers (or a big ganged breaker). There are a total of 4 fat wires coming out of separate screw lugs on these breakers. The wires are connected TOGETHER in pairs after the breaker. Each pair then connects to a fat wire that goes on 70 feet to my breaker panel. The paralling of wires after the main breaker made me think that I had two 200A breakers in parallel for 400A, but maybe I am misinterpreting what I see. The house was rewired around 1988 and is about 3400 sq ft. Would 400A be unusual?
It may be easier to make the 70 foot run and power a subpanel from the the breaker panel back in house. It turns out I do have room in the panel. It was full of breakers, but at least 3 are unused. This leads to another question. I'd like to use the 2.5" conduit that holds the main feed from the entrance, to carry a 100A line that I run back to a garage sub-panel, but I am told that this is not allowed (i.e. that conduit can carry ONLY the entrance lines). Does that seem correct? If so then I have to run another conduit, which will be a pain. or......
The guy who told me that the 2.5" conduit could only hold the main feed suggested I put a another big subpanel in the garage and run the main feed straight to that. This would take about 2 feet of new wire. This new panel (with a new 200A or 400A breaker) then feeds the rest of the house on the old main feed wires (I can pull these over to the new sub-panel) and also houses breakers for my new garage outlets. Does this sound reasonable?
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lens wrote:

I presume that it is an attached garage so installing a feed through panel of appropriate size is one way to deal with your problem. Your informant is incorrect about the conduit being limited to just the feeder conductors. If they were service conductors he would be correct but service conductors are never allowed to run very far into a building. Since the feeder to your houses panel has Over Current Protection in the form of the main breaker in the meter mains assembly on the outside of your garage you can use that conduit for branch circuits as long as you do not exceed the permitted wire fill for that conduit.
Can you tell me the size of the wires in that feeder and the type of conduit that was installed for the 2&1/2 inch raceway to your main panel. The size and type of wire is printed on the insulation every two feet for it's entire length. If your main breaker is labeled 200 amperes then that is all it will carry. Some listed breaker assemblies are actually two common trip, double pole, 100 ampere, circuit breakers assembled in parallel using a handle tie. If the breaker handles are not labeled 400 amps then you do not have a four hundred ampere service.
You could use a smaller panel in your garage and simply tap it's supply off of the existing feeder conductors. You would have to install a new conduit run from the back of the meter mains assembly were your main breaker is located to the new panel. Presuming that the service is in fact 200 amperes, a one hundred ampere panel could be located up to twenty five wire feet away from the tap point to its main breaker as long as the conductors are in conduit. A sixty ampere or smaller panel would have to be within ten wire feet of the tap point under the same conditions. You would need experienced help to install the taps themselves as it would involve the installation of split bolts or patent taps to the existing conductors inside the wiring compartment of the meter mains assembly in order to connect the tap conductors to the existing feeder conductors. There are Insulating Displacing Taps (IDTs) that you can install without knowing how to strip the insulation off of the feeder conductors without damaging them but those IDTs are expensive. Alternatively you could consult the manufacturer of the meter mains assembly and install multi barreled terminal lugs on the load side of your main breaker. This would permit the connection of two sets of conductors to the main breakers output. The limitation on the length of the tap conductors would still apply unless you sized them to carry the ampacity of the main breaker. You would have to check the size of the terminal lugs in your new panel to be sure it could take wire that large and the use of that size of wire would be more expensive and wasteful of valuable metals.
One word of caution. If your existing feeder is 2/0 Cu or 4/0 Al for a two hundred ampere feeder then a particularly picky inspector could require you to replace it with the next larger size if you install a second feeder to a new panel. Those sizes are only permitted for 200 amps when they are THE main feeder to a dwelling unit. Once you install a second feeder to serve the same dwelling neither one is THE main feeder and both would have to be sized by the ampacity table for regular conductors rather than from the table for single phase three wire dwelling services. -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison
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Tom - Thanks so much for the detailed reply. If I haven't worn you out, here are more details and pictures.
Re: "Can you tell me the size of the wires in that feeder and the type of conduit that was installed for the 2&1/2 inch raceway to your main panel."
The wires say THHN 4/0 AWG and measure 0.61" diameter with the insulation. They are copper. I had the old aluminum upgraded about 3 years ago. All I can read off the conduit is "AHF 42040635". Does this help? Even if I could only run 50A or 60A sub
back through that conduit, I would settle for that, since it is simpler than what's discussed below.
Re: "Some listed breaker assemblies are actually two common trip, double pole, 100 ampere, circuit breakers assembled in parallel using a handle tie. If the breaker handles are not labeled 400 amps then you do not have a four hundred ampere service."
I took a picture of the main breaker:
http://home.pacbell.net/shermfam/main_breaker_close-up.jpg
The breaker has four sections and reads 200A twice. The red and black pairs on the load side are paralleled, so I assumed 400A, but I think I may be wrong. The fine print on the breaker label also shows it's outputs paralleled. Do I have 200A service?
Re: "Presuming that the service is in fact 200 amperes, a one hundred ampere panel could be located up to twenty five wire feet away from the tap point to its main breaker as long as the conductors are in conduit."
My subpanel would be less than 4 feet away on the other side of the wall. The open box (open for pic only) in this pic is just opposite the main breaker. The main feed to the house comes straight thru the wall into this box and then goes out the top.
http://home.pacbell.net/shermfam/inside_gar_crop.jpg
Re: "Alternatively you could consult the manufacturer of the meter mains assembly and install multi barreled terminal lugs on the load side of your main breaker."
Something like this was already done: The 4 wires leaving the main breaker in the photo are paralleled down to two with lugs that look like what you describe. I may not have another space availalble in them however. I can't tell because they are wrapped with tape.
New questions: If I tapped the main feed for a new panel, you are saying I could not run this feed through the same hole where the main feed comes through to the house? It is an 8 inch long conduit through the wall into the big box in the inside_gar_crop picture. I could poke my tap through the same hole and mount the sub-panel to the right of that box. The total run would be less than 4 feet so I don't care about wastefully oversized wire. Would I still have to poke a new hole in the wall and run a new pipe? Or could I connect IDTs to main feed wires, but do it in the box on the INSIDE of the house (shown in inside_gar_crop)?
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