100 Amp panel service, but total is more?

Question

I've what I think are 2 very basic questions.

My main electric service panel reads "100Amp" service. But when I add up the break current of all the existing circuit breakers, it sums to about 280. I suspect that's because no one will be using the max of each breaker at the same time. But how does one determine this max number of breakers you can have in a panel ?

If possible, reference to a code chapter or section would also be appreciated.

Some breakers in the panel are 15Amp while others are 20. Whereas I can understand one may want to protect a specific piece of equipment (i.e. furnace, water pump, etc.) with a specific amperage, there doesn't seem to be any reason to me to protecting the kitchen vs. the bedroom with a different cutoff amperage. Unless for some reason, the wire size servicing one area was smaller. Any opinions?

Thanks.

RBM · Accepted Answer

You are correct on both counts. The NEC doesn't permit any panel to have more than 42 circuits. 100 amp panels generally have up to 20 circuits. Some circuits are required to be higher than 15 amp to feed heavier appliances that will be plugged into their outlets, like outlets in bathrooms and kitchens

Tony Hwang · Answer

Hi,That means your panel has max capacity of 100Amp. The branch circuit breakers allow max load of stated Amperage each. Do you think all thosebranch circuits will carry max load simutaneously ever? Very unlikely. If you want to know what's going on, you can buy a cheap clamp on type current probe and look,see what is typical total current draw on your panel. If it's very close to 100 Amp all the time, I'd consider upgrading. You can invest less than 80.00 or so for a handy digital multi meter which can measure AC, DC volt, current, Ohmic resistance, temperature etc. Very useful tool for home DIY type handy man.

gfretwell · Answer

They are fixin' to change that. When your AHJ adopts the 2008 thatrule will go away.

Toller · Answer

You realize that is 100a @ 240v. Your 280 is probably only 140. But yes, if you use your dryer at the same time as your oven, range, and water heater you will probably have a problem.

Breaker size is tied to wire size. Kitchens generally use more current than bedrooms, so bedrooms use #14 and kitchens #2 typically. If your bedroom has the same cable as your kitchen, they will both have 20a breakers.

Big_Jake · Answer

That should read "kitchens #12 typically"JK

Tekkie® · Answer

posted for all of us...Man o man did a heck of a lot research did ya?   NOT  you putz

100 Amp panel service, but total is more?

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