I wonder if that is not the reason why for most applications 12 & 14 AWG must be on 20 & 15 amp breakers even though the conductors are rated 25 & 20 amps @ 60 C? 
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Bob Badger wrote:
I wonder if that is not the reason why for most applications 12 & 14 AWG must be on 20 & 15 amp breakers even though the conductors are rated 25 & 20 amps @ 60 C? 
You just might be right there ... plus the actual capacity of those 12 & 14 AWG wires with the usual THHN insulation (90C) are 30 and 25 amps. I understand applying the lower 60C values for cable assemblies like romex is conservative used to keep the outer sheathing cooler.
Plus I also understand that fuses have a lower failure rate in general, especially after some time where a breaker may not have been periodically operated as required maintenance.
So I would rather have a fuse protecting me in the event of a short circuit instead of a breaker ... unless you are going to do some welding, then having those FPE breakers can come in handy ...
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
Robert many engineers in this area agree with you, many of the jobs we do specify fuses for feeders, breakers for branch circuits.
Breakers have come along way though an fully electronic breaker (will not be seen in dwelling units for some time to come) can do what a fuse can do and more.
They can be set up with whatever trip characteristics you want and provide ground fault protection, not 5 ma trip but more likely 1/4 of the over current device trip setting.
The best part of these is you can retrieve data on the reason it tripped, that said there is a lot to fail, fuses only fail open. 
So for supervised installations I too like fuses, for a typical home I must agree with Jerry that the benefits of fuses are outweighed by the over fusing that is all to prevalent.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Bob Badger wrote:
So for supervised installations I too like fuses, for a typical home I must agree with Jerry that the benefits of fuses are outweighed by the over fusing that is all to prevalent.
I actually agree with you guys there about panels with breakers being more desirable from a tamper-resistant point of view ... never underestimate Harry Homeowners ability to "fix" a problem.
I just tend to think fused panels have gotten a bad rap due to the very common overfused circuits, and because the standard edison base fuse sockets easily accept an oversized fuse. But, I think Type-S fuses/adapters have gone a long way in improving the safety of these panels. I just cant figure out why insurance companies don't require that.
If Harry Homeowner puts a penny or aluminum foil in a socket to "fix" a problem, I really think he has crossed that "stupidity line in the sand" and should be on his own.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
