Oversizing a breaker would not be safe in the same term as oversizing a fuse would not be safe.
If a conductor is 14 AWG and is designed to be protected by a 15A OCPD…in order to ensure the wire does not overheat…putting larger breaker on it would reduce the likelyhood the breaker would trip before the conductor exceeds it rating.
Now where you see smaller conductors on larger breakers under the exception of the NEC is for allowance of start up conditions and so on and demands someone having that KNOWELDGE of why it is done…but in general in normal branch circuits oversizing a breaker is the same as oversizing a fuse…the OCPD is there to protect the conductor itself…and in turn the house…
Over Protected is not a good term…UnderSized Breaker or improperly sized breaker is the better term in the case of the example I posted above.
Should read "Breaker is oversized for conductors being protected and be corrected by a qualified electrician. Failure to do so may result in a fire if the circuit is overloaded.
We see it often in the Service Disconnects. Wire is 15 AWG with a 20 amp disconnect (breaker). I’ve been told by electricians this is not critical for this application. What is the truth? Their response is the Service disconnect is little more than an On/Off switch.
Depends on why you are using that term and if someone insists on using an improper term to get through life.
Lets talk about a general branch circuit…if I place a 30A breaker on a 14 AWG conductor ( not using the exceptions here )…then the conductor has a rating of 15A as defined by the NEC…now if the load upon that breaker exceeds the 15A rating ( for simplicity sake ) it will heat up and eventually trip the breaker…now at the rating of a 30A breaker…chances are it will far exceed its relative rating where as a normal 15A breaker would have tripped…saving a potential ground fault condition and so on possibly.
Your question is because of a use of an improper term…
NOw I would agree with your view…could it be considered over protected by putting lets say a 15A breaker on a 30A circuit with 10 AWG conductors…sure…but being over protected would imply it will still function and in the case of the standard rating of the breaker which in this case is 30A it will shut down in a condition where it should not…so I guess you could say it is over protected…if it helps ya sleep at night…I prefer to in this example call it Improperly Sized to the conductors being served.
I say that “over protected”, “over protection”, “excessive overcurrent protection” are phrases that are being used incorrectly to describe a breaker that is too big.
Nick the terms-Excessive overcurrent protection and Over protected are used incorrectly when describing the situation you posted. It’s that simple and anyone using those terms doesn’t get it!
Jeff, you are correct in your use of the word overfused. I think the term is the source of the misuse of the terms above. Some inspectors (not wanting to imply that a CB panel has fuses) are calling big breakers on small wires “over protected.” This is backwards IMHO.
Sorry Jeff…I dont like references that come from inspection generated companies or providers…I prefer to use Electricians Verbiage for the condition…lol…
So does anyone disagree with me when I say that “excessive overcurrent protection” should not be used to describe a breaker that is too big? It shouldn’t be used because the term describes a breaker that is too small and excessively protecting (will trip when a load the circuit can handle is drawn).