I've what I think are 2 very basic questions.
1. 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
2. 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?
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
That means your panel has max capacity of 100Amp. The branch circuit
breakers allow max load of stated Amperage each. Do you think all those
branch 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.
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.
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