I believe that fuses are far superior for protection against an overcurrent condition. Some types of circuit breakers fail and we have been made aware that they have a history that may not be the safest protection.
Any current in excess of the rated current of equipment or the ampacity of a conductor.
It may result from overload, short circuit, or ground fault.
FPN: A current in excess of rating may be accommodated by certain equipment and conductors for a given set of conditions. Therefore the rules for overcurrent protection are specific for particular situations.
I agree with Joe. I never saw a fuse that did not blow on overcurrent or short/fault. If we all moved back to fuses, they could be designed so only the correct rating of fuse is installed for the conductor being protected. Toward the end there of the use of fuses that was being done with those screw in devices (I don't remember what they were called )that reduced the size of the socket so that only the correct sized fuse could be installed.
#37941 - 05/12/0412:33 PMRe: I believe that fuses are far superior than circuit breakers!
- a circuit breaker that fails to trip, vs. - an uninformed homeowner who replaces a blown 15 amp fuse with a 20 or 30 amp fuse "because it was all I had and it got the lights back on"?
If you're referring to a circuit breaker that fails to trip into the point of meltdown.. I think I'd rather have the 30A fuses... while I certainly understand 30A fuses on 14 or 12awg wire for general applications is a hazard.. At least theres some limit.. in a dead short situation, a 30A fuse would blow, whereas a frozen breaker, so to speak, wouldn't.. Besides, homeowners are getting pretty handy at changing breakers out over here when they think they're "too small"
-Randy PS...Gene,... You referrig to the type "S" adapters?
#37942 - 05/12/0412:41 PMRe: I believe that fuses are far superior than circuit breakers!
rlrct: To prevent the misapplication of plug-type fuses often used in older style residential fuse panels, NFPA 73 - Inspection Code for Existing Dwellings, in 2.3.5 - "where evidence of overfusing of or tampering with Edison-based-type fuses exists, Type S nontamperable adapters and fuses shall be installed". Thus, provided the fuse panel was properly inspected, this misapplication can be avoided.
I think Mean Gene's comment really gets to the heart of the issue, that is that a fuse can provide reliable overcurrent protection over the life of the system. A circuit breaker can do this as well provided it is properly maintained and tested (and replaced when needed) in accordance with manufacturer's instructions, NFPA 70B and NEMA AB4. However, many installations do not do so much as simply "exercising" the circuit breakers periodically. Because the circuit breaker is a mechanical device this and other maintenance/testing procedures are periodically needed to assure proper operation and protection. Thus, often the only time we know a circuit breaker needs maintenance or replacement is after the problem occurred.
With respect to Ron's comment, single phasing is not a fuse/breaker issue because neither device will protect against all single phasing conditions - it is really only an issue for multi-phase motor loads and with that, the only thing that will protect against all conditions is a single-phase relay (with come with most new electronic overload relays). With regard to replacement of fuses. If the fuse opened due to a short-circuit, you have much bigger problems than simply replacing the fuse (you need to fix the short-ciruit first). Because fuses require replacement (and cannot be reset), that may actually be a benefit (and avoid a potential OSHA violation). In addition, if this is referring to mains and feeders in a system, it most likely was a short-circuit so automatic resetting should be avoided until verified to be an overload or fixing of the short-circuit. Thus, often resettability is only beneficial in branch circuits because most overcurrent conditions here are overloads.
#37944 - 05/12/0401:34 PMRe: I believe that fuses are far superior than circuit breakers!
I agree that the ‘S’ type fuses would effectively eliminate over-fused circuits.
One advantage of CB’s is the flexibility in constructing a breaker panel. Would you have a “snap-in” fuse holder similar to a CB such that circuits could be added by installing the appropriate fuse-holder in a panel’s empty slot? I suppose that if there were no such thing as a “half-size fuse holder”, that would tend to limit panel overcrowding.
With fuses as the primary OCP, how would you handle GFCI and/or Arc Fault protection?
While single-phasing may be a motor-related problem, what about 2-pole common trip OCP for 240vac appliances (ex. dryer)?
#37946 - 05/12/0401:55 PMRe: I believe that fuses are far superior than circuit breakers!