new 200 amp service

codnuggetsMay 20, 2010

I am installing a new 200 amp service and would appreciate some input. I'll be installing a combo meter/main panel outside. From the main, I intend to install breakers for the nearby A/C unit, outdoor outlets, future garage circuits, and a soon-to-be-installed netmeeting solar generation system. A subpanel (haven't decided on amperage) will be fed from the main about 20 feet away in the basement (same building). The rest of the house will be fed from the subpanel. My questions:

1. Any glaring issues with this plan?

2. How many amps for the subpanel? I know this depends on load, but is there a practical limit, i.e. is a 200amp sub just too big no matter what? I had tossed around the idea of buying a 200 amp main to use for the subpanel, and using the included main breaker as the feeder from the main. Can I do this or are the breakers not compatible that way.

3. Should I install a 'main' breaker in the subpanel for ease of shutting down the whole panel at the panel or is that overkill? Big breakers are expensive. Clearly I can go outside and flip the breaker if necessary, and really how often does one need to do that?

4. I'm planning on using 4/0 4/0 2/0 aluminum for the service drop. Can I run the same wire from the main to the subpanel? Obviously I will need a ground, which I think should be #4awg copper. Does the cable and ground need to be in conduit, or can I just run the ground along side the cable?

5. I will ground the meter/main with grounding rods connected to meter/main with unbroken #4awg copper. I can not ground to the water system because the entry point is not metal. Do I need additional grounding?

Thanks for the feedback.


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Ron Natalie

If this is the only "subpanel" off the main, it pretty much as to be 200A. Frankly, to get enough positions for modern houses, you probably also need to go with a larger panel.

Whether you want a main lugs only panel or a main breaker is purely a matter of convenience vs. cost you'll have to work out.

You need to get cable with all four conductors or you need to put all four as separate conductors in conduit.

If the water piping in side the house is metal it needs to be bonded even though the water pipe coming in isn't and can't be used as part of the grounding electrode.

    Bookmark   May 20, 2010 at 7:53PM
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Use a meter main with feed thru lugs and a 200A main lug panel for the sub.

    Bookmark   May 20, 2010 at 8:25PM
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Thanks for the info. I stopped by the electrical aisle at Home Depot while picking up some other supplies, and they happened to have a mock up of the exact system I'm planning. I'm all set now, except for 2 questions:

1. Nearly all of my water piping in the house has been converted to PEX. There are some remaining bits of galvanized pipe scattered throughout the basement. Should I run a #4awg copper wire to one of these pieces of pipe?

2. I will use 4/0 4/0 4/0 2/0 Al cable to feed the subpanel. It will need to go down from the meter/main panel about 3 feet then enter the side of the house through the rim joist. Should the exterior run be enclosed in condit for protection? If so, since the interior portion will not be in conduit, do I just need a cable clamp or something where the cable exits the conduit?

Thanks again.

    Bookmark   May 21, 2010 at 12:04AM
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Ron Natalie

Well, you will have to determine if it is subject to possible damage, against the side of the house and up away from the ground, you're probably safe.

You also need to be mindful that if it's exposed to sunlight it needs to be rated for that and if the area is damp/wet that you honor that rating as well. However, given the size of the cable involved, you're most likely talking a SE cable of some sort which will usually meet those requirements.

Actually the metal water pipe bonding has to be #2 cu (or 1/0 al) in this case (since you have 4/0 service conductors). However, if this metal in the system is "isolated" in an overall non-metal plumbing system, you don't have to bond these pieces. I guess I'd have to know just how much metal piping you have down there.

    Bookmark   May 21, 2010 at 7:25AM
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I'm pretty sure the cable I priced is rated for sun/weather exposure. My neighbor just put a new service in so I'll see what he did. I'd call the inspector, but staff cuts have made them very busy and mostly unavailable.

There is very little metal pipe. The only significant section is a run from the basement ceiling to the 2nd floor bathroom and the branch plumbing in the bath. I'd guess thats about 25 feet or so. Maybe that's enough, although I intend to swap that out with PEX in the near future. Other than that, there are just a few small pieces near the kitchen sink and hose bibbs.

You say #2 cu for the water pipe bonding. Does I need #2 cu for the main grounding too or is #4 large enough?


    Bookmark   May 21, 2010 at 11:49AM
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