On 12/13/2013 9:44 AM, Let's get it right! wrote:

Which raises an interesting fact. Most homes and office buildings I've
inspected have 20 ampere circuit breakers providing branch circuit
protection to wall outlets, switch, listed cord and direct connected
equipment. If the listed cord connected equipment utilizes a NEMA 5-15
plug, it's not protected, and because it cannot be applied to such branch
circuit protection and still be considered "PROTECTED".

Your theory is that every device plugged into a circuit with a 20A
breaker must have wiring that can handle 20A in case the device
malfunctions and draws the full 20A.

It's an interesting theory though you're wrong of course. The breaker
protects the internal building wiring, not each individual cord or
device plugged into that wiring, each of which draws less than the total
available current.

The cord or device needs its own protection. For example, at my
daughter's dorm the rule is that power strips must have their own
circuit breakers. She complied with this, but most cheap power strips
don't have circuit breakers and the university never checks up on this.

If an unprotected device with wire that was rated for 15A had a short
that caused a high current through the wiring then the 20A circuit
breaker would still trip long before the wire caught fire.