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Newbie Service Panel Question
On 19 Nov 2003, wrote:
Simplistic Hypothetical: ------------------------------------------
Circuit Breaker #1 on the service panel is a 20amp 120v circuit.
It's wired to *four* wall circuits [recepticles].
Each recepticle is now a 120v 20a outlet.
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Confusion point:
The book states that a full load for a 120v 20amp circuit is:
120v x 20a = 2400 watts x 80% (safe capacity) = 1900 watts
Does that mean each one of those recepticles can have up to a 1900
watt load on them *simultaneously* without tripping the breaker, or
that *collectively* at any given time their load in summary shouldn't
exceed the safe capacity of 1900 watts total?
Collectively. They are sometimes call "convenience outlets", and
the thinking is that you will never use them all at one time, or
even if you do, they will all be low load devices. You could
load up all 4 of those receptacles (8 spots) with things like
stereo systems, lamps, cordless phone bases, chargers for your
cell phone, etc, etc and never come anywhere near drawing 1900W.
But change those things to toaster ovens, coffee makers, hair
dryers, etc, and you get to your next question...
The reason I ask is this... the book also says that microwaves and
large appliances should have a "dedicated circuit." Do they simply
mean a dedicated wall outlet, or a dedicated circuit *breaker* --
meaning no other outlet is wired to that circuit breaker but the one
the appliance is plugged into...??
Exactly. One breaker, one outlet.
Because the way I read it, is I need a separate *circuit breaker* for
my washer/dryer outlet... one for my 1700watt treadmill (which can
also run a TV and lights in the garage, but then reaches the 1900watt
safe mark)... one for my garbage disposal and one for my microwave...
Actually, your usage will determine this. Your Treadmill/lights/
TV example is a good one. If you don't have a dedicated outlet
for those heavy drawing devices, you need to play the "I-can't-
run-this-thing-while-my-treadmill-is-running" game, effectively
creating a dedicated outlet, even though there are other duplex
receptacles on the same circit. People have been doing this since
we've had indoor electrical service, and as long as you do it in
a -SAFE- manner, it's OK. "SAFE" being not sticvking pennies in
the fusebox, propping a breaker handle in a closed position with
a chunk of wood, etc. That kind of stuff burns your house down,
the trial and error "learning" of your circuit limits gets you a
workout running to the breaker box.
Was that confusing enough??? 
Not a bit. You knew how to voice your questions, that's better
than half of the (cough)dim bulbs who show up here!
--
Baisez-les s'ils ne peuvent pas prendre une plaisanterie
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Tom Pendergast e-mail is for sissies, say it on line
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