On Mon, 9 Jan 2017 08:01:56 -0800 (PST), trader_4
wrote:

An 80% rated breaker may trip if it's subjected to greater than 80%
current, but it will take a long time. It depends on the temp environment
the breaker is in, how much above 80% the current is, and how long
it continues at that level. If it's a typical kitchen and the toaster
pushes it to 90% for 5 mins while making toast, it's not likely to trip
unless the breaker is already in a hot environment.

There are rules about acceptable loads on a breaker but if you look at
the curve data on a breaker you will see that it should hold 100% of
the rating pretty much forever at 40c. There will be some variance due
to manufacturing tolerance but it ranges from ~.95% to 1.25%
There is an example of a trip curve graph here.
http://static.schneider-electric.us/docs/Circuit%20Protection/Molded%20Case%20Circuit%20Breakers/0100-400%20A%20Frame%20FA-LA/FA-FC-FH/0600DB0105.pdf



Technically, you can put them on the same circuit, you just can't run
them all at the same time if they will exceed the breaker limit. If you
have a refrigerator on it, that's already running and contributes to amp
usage. Therefore, whatever else you add to that circuit combined with
the fridge needs to be less amps than the breaker limit.

It is recommended to put large appliances on it's own circuit, such as
stove/range, refrigerator, washer, dryer and even a microwave.

Not only recommended, it's code in most cases. An exception would be
the refrigerator, which isn't a large load at all and can be on a
shared circuit, though it may not be a good idea for obvious reasons.
Most new ones are under 100W continuous.

The code only addresses fixed in place equipment. For example, that
would include a microwave built into a range hood or bolted to a
cabinet but not one sitting on the counter.