2nd panel running off of primary electrical panel


I want to connect a second electrical panel in my house. I am going to run it from a 40 amp breaker in my main panel. The second panel I bought has a 100 amp main breaker in it. Is it code to keep that breaker in there? I assume it is redundant and would only act as a switch if I wanted to do some servicing in the 2nd panel.
Thx Gary
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change: i think the 40a supply must match a 40a wire,and the subpanel must have not 100a but a 40a breaker. but first see: http://www.selfhelpandmore.com/homewiringusa/2002/accessory/detgarage/index.htm
http://www.faqs.org/faqs/electrical-wiring/part1 /
Gary wrote:

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Why? As long as the wire will carry _at_least_ 40A, the 40A breaker provides all the overcurrent protection needed. What would be wrong with leaving the 100A breaker in the subpanel?
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Doug Miller (alphageek at milmac dot com)
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wrote:

Sure. Any overcurrent would trip the 40A breaker feeding the subpanel.
You *do* plan on running a 4-wire feeder cable to the subpanel, don't you? (Black, red, white, and bare wires) Also make sure that (a) the subpanel has two separate bus bars for neutral and ground, (b) they are not connected to each other, (c) the neutral bus is NOT connected to the chassis of the subpanel, and (d) you connect the white feeder wire to the neutral bus, and the bare wire to the ground bus.

Correct.
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Yup thanks I'm going to use one gauge up from what the amperage is rated for. I am also going to isolate the neutral from the ground in the subpanel. I just don't want to look like an idiot for the inspector. Code here says I do not even need a main breaker in the sub because I have a feeder breaker in the main. I thought I might as well put the sub with the 100A breaker in because it comes with a ton of assorted breakers including an arcfault breaker for only $19 more than a smaller 60A subpanel that comes with 4 regular breakers. Go figure.
Gary :-)
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You bought a main panel instead of a subpanel. That was a small mistake since you are paying for a breaker you won't be using (but won't do any harm either) and will have to buy a separate neutral bus.
Take it back and buy the right thing if you can. If not, you can use it, but don't forget the neutral bus. I just bought a real nice GE subpanel from Lowes for $30 with 4 breakers thrown in. I wish my main panel was as nice. But I see you are up North...
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wrote:

Actually, it already has a neutral bus. If he has to buy anything, it will be a grounding bus -- and it probably already has one of those too.
If he had bought a subpanel, he'd certainly have to buy a separate bus, and might have wound up spending *more* money.

Phooey. There's nothing wrong with what he has now.

Grounding bus.
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Doug Miller (alphageek at milmac dot com)
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I just bought a subpanel with two buses. The main panels had one bus. But, I am sure you are right everwhere but the Lowes I was in. Eventhough it doesn't make sense.
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wrote:

Here's an example, described as a "Main Breaker Load Center", i.e. a main panel:
http://contractorservices.homedepot.com/StoreProducts/ProductInfo. aspx?cid1951&pid{777006-021b-4a01-91bb-63b93a569c5d
You might need to click on "Enlarge" to see it... but there are definitely two buses there.
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Doug Miller (alphageek at milmac dot com)
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On 12/18/06 10:05 am Toller wrote:

My 200A Cutler-Hammer CH panel came with two buses installed and a removable link between them: bond the two buses together if it's a main panel, but remove the link if it's a subpanel.
Perce
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I was just at Menard's an hour ago -- every main panel on display had two bus bars installed, and every subpanel had one.
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