There's no reason you can't have a main breaker in a sub panel. All you need do is whatever provision the manufacturer provides for separating the grounds and neutrals (removing screws/straps, adding ground bars, etc...).

Further, if this garage/apartment is DETACHED you may actually NEED the disconnect at this panel.

ok. Thanks. So I have been doing more digging around. We have a 3 wire feed to the house. I have found some information that states that a panel in a remote location is to be treated as a new service. Would I be good to keep the grounds/neutrals as is and ground it with a rod?

You're mixing terms. The service is the thing that comes in from the power company. The thing running from your main panel in the house to the garage is a FEEDER. I'm assuming that's what we're talking about.

Yes you will need a disconnect out there (typically a main breaker).

Since you're talking about a subpanel out there I'll assume you have more than one circuit in the garage/apartment. Yes you'll need a grounding electrode system (typically two rods) at the garage. Not only would it be GOOD it is ABSOLUTELY required to keep the grounds and neutrals separate. You must also run FOUR wires (2 hots, neutral and ground) in that feeder to the garage.

Note that your feeder must be approved for underground (either a direct burial cable like USE by itself or wet-rated individual conductors like THWN in conduit). Note that depending on the cable or conduit used and whether you are going under the driveway affects the DEPTH that you have to place the feeder.

This post was edited by ronnatalie on Tue, Dec 16, 14 at 15:28

Without knowing where you live (US, Canada, or elsewhere,,,)

Without knowing under which electrical code your jurisdiction enforces...

Then NO ONE here can help you!

ALL of your questions need to be addressed within your adopted electrical code and jurisdiction.

You BEST approach is to simply call your municipal code office and heed their direction.

You will NOT get the correct answer to your questions here!

The poster's profile says he's in the US. The NEC pretty much as been adopted in all states. Even in places where it hasn't been adopted statewide, most of the local jurisdictions base their codes on it.

I don't know of many code officers that will answer a lot of questions from people trying to figure out electrical work. In fact, mine will not answer (and frankly, they have no clue about any of the specific codes). An inspector might be more forthcoming and arguably more knowledgable but you won't get him until late.

My answers apply to the National Electrical Code and are correct for versions from at least 2002 on. The only qualification is that there is an exception permitting only three wires to be run between the buildings in some circumstances, but that is gone in the last few versions. Even when it existed, you couldn't use it if you had other metallic connections (piping, cable tv, phone, etc...) between the two buildings, which is why I didn't mention it.

I am from Pennsylvania. The wire I have run is URD 4/0 4/0 2/0 that I have run in plastic conduit. What size ground wire would I need to run to make this work?

Pennsylvania seems to be using the 2008 NEC right how.

However, you've screwed up badly. First, that URD cable if it doesn't have a ground wire in it is not legal. (It likely doesn't, it's intended as SERVICE ENTRANCE cable). You must run a ground (as previously stated) and your choices are either to run a cable that has one OR to run individual conductors.

Even if you could legally just pull an additional ground, you'd find it near impossible to do so in a conduit with a cable stuck in it already.

The size of the cable required depends on what the load in the building being fed is. The size of the breaker in the feeding (main) panel is determined by what wire you used. The size of the ground is determined by the breaker used.

I think you may be over your head on this one.

This post was edited by ronnatalie on Fri, Dec 19, 14 at 16:39

Even though the original poster says he is from Pennsylvania...

And even though ronnatalie correctly asserts that the adopted "State" electrical code in Pennsylvania is the 2008 NEC...

It is NOT correct to assume that the 2008 NEC is enforced everywhere and in all municipal jurisdictions in Pennsylvania.

It is not.

Many municipal jurisdictions in Pennsylvania, especially the larger ones, have local amendments to the 2008 NEC which may completely over-ride it....or have their own more strict electrical codes than the 2008 NEC which do not even refer to it.

Which is why I stated and still submit:

"ALL of your questions need to be addressed within your adopted electrical code and jurisdiction.

You BEST approach is to simply call your municipal code office and heed their direction.

You will NOT get the correct answer to your questions here!"
-----------

And FWIW, I am a Pennsylvania certified residential/ commercial electrical inspector and plans examiner.

And if some wish to continue their debate by way of ignorance on this topic, they, too, will ALSO quickly find themselves "in over their own heads on this one!" :)
-------------

So call your local code enforce office and get local and PROPER direction!

You won't find it in this forum.

Tell me where it is in Pennsylanias Mr. Alleged Code inspector where they have a local modification which allows you to run a grounding conductor in a different cable or raceway from the rest of the circuit?

Tell me which local jurisdiction allows you, in new construction, to not run a equipment grounding conductor to a fed structure? In ours the code office knows little more than to rubber stamp the plans. It's not until the electrical inspector comes out do you find someone who knows how to spell code.

Tell me which local jurisidiction has some differing view of ampacity of conductors that's different from what the NEC has been using for the past 30 YEARS.

You've done nothing to other than be insulting to indicate any WRONG answers presented in this forum.

Perhaps in your obscure alledged jurisdiction, the code office will answer these questions, but in every one I am familiar with, they expect you to know.

According to the Commonwealth Department of Labor and Industry 90% of the municipalities have adopted the standard state code (which means NEC 2008).

This post was edited by ronnatalie on Fri, Dec 19, 14 at 22:00

Some people like to get on a DIY forum and browbeat people that have come to ask for help. They claim to be experts and might well be, but refuse to be helpful in any way. Bullies get gratification by beating up on others. Some things never change. I have always been grateful for helpful folks on boards like this.

Thanks to those who were willing to give me tangible guidance. I have learned that I only know enough about electric to get me in trouble. With that being said, I am still interested in learning more. I have been thinking about the advice and have spent some time looking at my disconnect. The wires come directly from my 400 amp service and there are two 4/0 conductors and a 2/0 neutral that appears to be bonded on the same bus as the ground wire that connects to the grounding rods. Since this comes directly from the service, does that have any implications as to whether there should be a 3 or 4 wire feed that goes to my house? When I had this installed, it was done with future plans of adding the 200 amp service at the house. Thanks and sorry if I'm wasting your time with questions that should be left to my code officer.

What do you mean it comes "directly from the service?"

If it comes from your the service at your house, it is a feeder and needs to be connected with four wires (both ground and neutral). If it came directly from the power company, that would be a service.

sorry. It branches from my meter. Think I have my terms switched around.

So since the 200 amp disconnect comes from the power company and is a service, do i still need 4 wires from the disconnect to my house?

Eh? Unless the service disconnect is at the structure being fed, it's a feeder and you need four wires.

Gotcha. Thanks for all the help ronnatalie!