NEC 101 Terminology: What is an "Overcurrent" and "Overload?"

[jtedesco1]

[Paul W. Abernathy]

Overload.

Operation of equipment in excess of normal,
full-load rating, or of a conductor in excess of rated ampacity
that, when it persists for a sufficient length of time,
would cause damage or dangerous overheating. A fault,
such as a short circuit or ground fault, is not an overload.

Thanks JOE.....you explained my QOD very well.........

[jtedesco1]

Overloads can lead to an Overcurrent condition!

[jtedesco1]

[Paul W. Abernathy]

Very good point.....hopefully the OCPD will step in and do it's job at the prevent additional damage.

Important to know that the OCPD is their to protect that conductor from the conditions joe is speaking about.

[Greg Fretwell]

In the motor articles they make it easier to understand. They call it overload vs short circuit protection. Overload is what it sounds like. The motor is overloaded and drawing more than the design full load amps. There is generally a protective device in the starter or the motor itself that will open the circuit when this happens. On the other hand if you have a wiring fault where there is an effective short, the fault current will be many times the design current of the circuit and the branch circuit O/C device will operate before any further damage is done.
The only flaw in this scenario is an arcing fault where it will still not generate enough heat to trip the O/D cevice but a great amount of heat is generated at the fault site. Hence the AFCI.

The other likely type of overload is the user inflicted wound, too many things plugged into a circuit. 240.4(D) is supposed to deal with that on 14, 12 and 10 guage circuits. The ones most likely to have receptacles on them.

[Greg Fretwell]

I have always believed fuses were safer than breakers. They always fail "open".
A breaker can fail closed and never open. (can you say FPE?)

[Ted Allen]

Joe T.

I respect your knowledge, but why are you posting code on a HI forum?

The simple fact is that HI's do not report code(in the report) period!!!

Joe, I have your books and I have a great respect for you, but this is a HI forum and most folks have no clue what you are talking about.
My point is you should limit your comments to things that an average HI would see in there daily life.

[Greg Fretwell]

Todd I think the value in understanding the difference between overload and short circuit (overcurrent) protection is when you try to make sense out of the sticker on the side of an air conditioner condenser. If you understand that distinction you can see why you might have 12 guage copper, protected by a 30a or larger breaker and still be safe and legal. The breaker is only providing short circuit protection, while overload protection is integral with the equipment.