i'm comfortable replacing problematic equipment.
otherwise, i will leave it be, and the person can get
someone else to do what they want done. i won't
charge for showing up, and finding out the customer
isn't a customer after all.
they are someone else's customer.
yeah, you can replace breakers with home desperate
etl approved breakers, or.... you can replace the panel,
or.... you can walk away. three options.
~New signature under construction.~
~~~~Please excuse the mess.~~~~
- Not enough I²T (current² & time)
There's a difference between a bolted fault and waving a pigtail around. An arc will form, which will have a higher impedance than intimate metal-to-metal contact. A magnetic field will form, which will tend to open the "connection" between the end of the pigtail and the ground. The contact point may be contaminated with paint, rust or other debris. The connection between the white wire and the box may be marginal. (remember, current must return to its source, not necessarily to the "ground")
- Too much current
In the past, breakers were designed to interrupt lesser fault currents, often 5 kA. If the neighborhood distribution has been upgraded, there might be more fault current available than the breaker was ever expected to handle and the contacts might weld closed before the mechanism has a chance to act. (especially if the contact resistance is higher than expected, or the mechanism is slower than expected, due to contamination or weak spring tension)
To be clear: I do NOT advocate repeating this experiment, let alone conducting a "better" experiment with a bolted fault.
Though usually I just suggest the homeowner do their own research, lest they feel I'm just trying to sell them a service change. But the nbcbayarea report was excellent.
One other issue for the OP: the act of flipping on an FPE breaker can pull them away from the busbar. This is especially problematic with the FPE thin breakers, where only two small fingers are pushed into a busbar hole. If the panel cover isn't tight against the breaker, you can pull it lose just by turning it on. For most other breakers, turning on the breaker pushes the contacts onto the busbar. Often these panels (in California) are on the same garage wall as the garage entrance from the home. I've seen numerous instances of circuits going on and off from the door being shut.
My advice: Replace the panel or refuse to work on it.
Last edited by electricguy61; 01-26-17 at 01:57 PM.
Electricians do it until it Hertz!
That the size of the Kaboom Decreases the futher away from the panel ......... a long lenght of wire will Choke the amount of current (Kaboom capability)
I most current that I have seen on a 12 ga wire was approx 90amps( inrush of two motors starrting at the same time), It held for approx 2 mins before tripping a cold G.E. 20 amp snap-in.
When ever I see 60+ amps on a 20 amp breaker, I will go look for a locked up motor/rotor, or, it is a Dead short wire that has "welded" itself to ground
I was working with another sparky whom shorted out a wire while we working, and without looking I bet him lunch that it was a square D QO panel judging just from the "Little amount of Spark" ( more of a 'click' than a' kapow") from the fault.... Boy that cheesburger tasted good.
I'm curious what evidence people can point to regarding the UBI breakers. Good, better, or not better all?
Typical instantaneous trip setting is 10X the breaker rating, but there is no universal rule, I've seen some resi breakers that are as low as 4X. So on a 20A breaker that is between 80A and 200A current before it trips. Even then, there is a fairly wide tolerance band for the trip times plus there is the actual clearing time, the time it takes for the contacts to open far enough to stop the current from flowing. But to your point, yes, the trip curve is SUPPOSED to be lower than the damage curve of the conductors it's meant to protect, but that's thermally. Once you are acting in the instantaneous range, all bets are off. So yes, I too have had some large conductors vaporize on me AS the breaker was tripping on instantaneous. It's not fun...
Many people are shocked when they discover I am not a good electrician...
For the commonly used 10k and 22k devices the AIC rating has nothing to do with the 'tripping' of the device.
I don't think there has been any significant advances in miniature molded case breakers in more than 50 years. I doubt they are as inherently unsafe as many anecdotal tales make them out to be.
Just because you can, doesn't mean you should.
The only thing it has to do with tripping is that it must be able to trip under that current without blowing up or failing closed. It must be able to safely interrupt (the I in AIC) that current.