Fault
Fault
(OP)
What can you experts say this fault was cuased by? please see attched picture
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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RE: Fault
Overpacked conduit, sharp edges on cable, maybe some over heating caused by dense packed wires, or maybe over current.
The insulation seems a little rough, so they maybe a little old style.
Slag on the base of the conduit, could be arcing, or leftover from welding.
Seems to be clean around the conduit, was it swept, or natural blown?
Open weep holes, likely nothing, but not positive.
Gee looks like age and abuse.
RE: Fault
That's one possibility...
edit: changes cable 'shield' to cable 'sheath'
RE: Fault
RE: Fault
Agree with comments about the general state of the installation too - something was going to go wrong, it was just a case of which fault happened first.
RE: Fault
We had the same conclusion, overpacked conduit, so it was just a metter of time after construction for the failure to happen and the fire that destroyed many small market stores. We found other cables still intact but damaged by sharp edges of other conduits, so it was just a matter of time...
On reconstruction we will change many design details and will supervise the construction as the codes state. Thanks for your observations!
http://albanesmolina.wix.com/home
RE: Fault
http://albanesmolina.wix.com/home
RE: Fault
RE: Fault
At least there was no dead rodents, oily rags, standing water, snakes or the skins of, burnt foam fill, insects, or a nest in the mix.
And it is possible that old molded case breakers can fail, or operate out of normal test values (Who has ever tested these).
RE: Fault
http://albanesmolina.wix.com/home
RE: Fault
RE: Fault
How?? That whole bundle should've been able to burn inside the panel/conduit without resorting to a burned down structure. Are we missing more input?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Fault
The maximum size breaker allowed for #14 AWG wire is 15 Amps.
For 25 or more conductors the ampacity is 60%
A 20 amp breaker would protect a wire rated at 20/.6 = 33.3 Amps.
That would be a #10 AWG at 75 C. The ampacity of a #14 wire at 75 C will be 12 Amps.
For 43 or more conductors the ampacity is 50%
A 20 amp breaker would protect a wire rated at 20/.5 = 40 Amps.
That would be a #8 AWG at 75 C.
For 25 or more conductors the ampacity of #14 AWG is 12 Amps
For 43 or more conductors the ampacity of #14 AWG is 10 Amps
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Fault
@waross we are using NFPA 70 too, and the derating factor is considered now in the new design that it was not done before. Thank you
http://albanesmolina.wix.com/home
RE: Fault
.... So, this kind of breakers don´t detect arc faults and that´s why they didn´t protect this installation? The new change in the CODE requires AFCI to be installed in most 15 and 20 A circuits:
http://ecmweb.com/nec/2017-national-electrical-cod...
http://albanesmolina.wix.com/home
RE: Fault