Treat Meter's Service Disconnect as Main Panel?

Any residential setup I've seen has three incomers, 2 live one neutral...The power company neutral is usually grounded at the pole....the main disconnect box usually has a neutral bus, and the box a separate ground rod tied to another bus with just ground wires....so the house has a separate grounding system and all the neutrals go back to the pole ground....now I've seen these tied together with the neutral and grounds tied together via jumper, or just a single neutral/ground bus, but I always considered those grandfathered in from precode installations...so it depends on the timeframe of installation and local codes, usually any major upgrades include bringing everything up to code, but minor repairs allow the original setup to remain, unless it's deemed unsafe in some manner....

The 1/0 wire is good for 120 amps at least, not undersized for the 100 amp load...the 200 amp main is obviously sized for future upgrade and should have different wire size feeding it....now if the wire feeding the 200 amp breaker is 1/0, then you have a problem....

Thanks for the replies!

Unfortunately it's still not clear to me whether the disconnect should be treated as a main panel and the house should be treated as a sub-panel (separate neutral/ground).

I did read in another forum somewhere that some power companies just use the 200A breaker next to the meter as their own disconnect (not sure why they can't just pull the meter), and consider it to be part of the 'line' side. This would suggest it was installed 'properly' according to them.

Regarding the 1/0 wire, yes I know it's plenty for 100A (and more), but imagine we shut off the house's main breaker and then shorted the 1/0 wires... they could burn before the 200A service disconnect would trip. Unlikely I know, but I'd never get away with a setup like that here.

There has to be a main disconnect at the meter for the fire department to shut off in an emergency....The 200 amp breaker is just a disconnect...it has to be installed like that because the meter is not mounted on the house....Everything from the can to the pole is the power company, everything from the can down is the homeowner.... What makes you think the 200 amp won't trip in a short situation?...are you thinking that that wire can only draw 100 amps?

Sorry - yes I understand the need for a disconnect - I'm really just trying to figure out whether it should be treated as the main panel or not.

But to answer "are you thinking that that wire can only draw 100 amps?"... No, and that's precisely the problem. Even very small wires can draw many amps until they burn... Imagine a scenario where there is a short, but just enough of one to draw 150 amps exactly. What would happen then is the wires would overheat but the 200 amp breaker wouldn't trip. Like I said, very unlikely, but it seems silly to even leave an opening for something like that to happen if it can easily be prevented by just installing the correct size breaker.

In any case it's irrelevant because the reason for my post is because my brother wants to upgrade the service by running 200A (4/0) to his shop, and then feeding the house 100A from the shop - I feel very confident about that part. It's where to bury the ground rods (at the meter's disconnect or at the shop) that I'm still not sure about.

So, I'm trying to figure out whether the disconnect should be treated as the main panel and the house as a sub-panel. If you happen to know the answer to that, I would very much appreciate it!

Thanks again for this answer. Today I actually contacted the utility and then when that didn't bear fruit, a local electrician who said, "Well the first disconnect should definitely be treated as the main panel and there should be four wires to the house, but you might get lucky and an inspector will let you get away with what you have."

So, it seems pretty clear to me. :-)

Well any job like that is going to have to be inspected, so you need a permit....the inspector will then tell you how he wants it done.....A detailed drawing and a trip to the city hall is required...when you make the permit application an inspector will be assigned, and he will approve or require changes to the plan....just stick to the code...

Yes, agreed. The house panel that currently functions as the main panel will need some work. Not only is neutral bonded to ground there, but as is often the case, the neutrals and grounds from each branch circuit are 'mixed' on the busses.

I would be more concerned about a continuous overload causing cable failure than a direct short circuit.

An Al 1/0 conductor will have a short circuit withstand current of around 4000 amps over a full 60 cycles.

A 200A breaker should open at way less than that and well before any insulation damage occurs.

F***ing outstanding answer! I wish I had more upvotes to give. Thank you very, very much!

I 100% agree with all of your recommendations. I just wasn't sure because apparently some POCOs install the disconnect at the meter base and run the lines to the home as the service entrance, making the service disconnect part of 'their' equipment. This may in fact have been the case 30 years ago when it was all installed, but I agree it should be fixed today.

Out of curiosity, do you know why there is a bare ground coming in to the meter/disconnect box from the transformer? The transformer is in a pedestal (not on a pole) if that matters.