One of you clowns that went to college.....

Status
Not open for further replies.
mxslick said:
K, so who's been callin you names? Now they have to deal with me... :grin:
Click to expand...

Man you missed it, last night got ugly in the safety forum, thread is closed and grounds keeper willie threw away the key.
 
zog said:
Man you missed it, last night got ugly in the safety forum, thread is closed and grounds keeper willie threw away the key.
Click to expand...


Darn, I miss all the fun... :wink:

I think the bad economy is making everyone cranky. :)
 
I could be talking through my butt- as I often do but here it goes anyways-

Typically in a residential breaker set up your main breaker has a smaller current limiting ability then your branch circuits.
for example-
15A breaker - 22,000 A
100A breaker- 10,000 A
I think it's because it's more expensive to make larger breakers be able to handle larger fault currents.

So when a direct phase to phase short (this is is the only time I've ever seen a main blow first before a sub or branch breaker go) the typically the larger breakers, therefore the smaller current limiting ability, will trip first protecting itself from blowing up.
 
That is because there is resistance within the source itself.
Click to expand...

Is the source itself, anything/everything upstream?



I think the definition he is looking for is The Avalible Fault Current is the absolute highest level of current or amperage that can or will travel through a fault before it is cleared.
Click to expand...

Thanks! That was very clear. I am still trying to digest the way we determine that and how to make the leap to 10,000-20,000 amps.

Given the title of this thread I'm surprised that anyone even responded
Click to expand...

I've been around here a while now and most people probably have an understanding of my personality. I am a very casual kind of guy who doesn't treat most things in a very serious manner. Clown is a term of endearment :cool:

Well I did not go to collage so I know he was not talking to me
Click to expand...

You made me look.



I agree kind of an slap for going to college.
Click to expand...

All in fun. Internet communication is decades old. The first thig I learned is that context is more difficult to determine in written words. That's why these things :grin: help. I should have tried to put one in my title.



Some of us took it for what it was , an attempt at humor . Nothing more
Click to expand...
.

Attempt ? :mad:

Thanks for your replies.....replys.....responses. I appreciate all the help.
 
alfiesauce said:
I could be talking through my butt- as I often do but here it goes anyways-

Typically in a residential breaker set up your main breaker has a smaller current limiting ability then your branch circuits.
for example-
15A breaker - 22,000 A
100A breaker- 10,000 A
I think it's because it's more expensive to make larger breakers be able to handle larger fault currents.

So when a direct phase to phase short (this is is the only time I've ever seen a main blow first before a sub or branch breaker go) the typically the larger breakers, therefore the smaller current limiting ability, will trip first protecting itself from blowing up.
Click to expand...

It is not a current limiting capability, it is an interupting capability, the amount of current the breaker is capable of interupting (without exploding). That rating has nothing to do with when the breaker trips. The setting or T/c charteristics (fixed) of the breaker determine how long at what current the breaker trips.

You are right about one thing, higher AIC's= more $.
 
alfiesauce said:
I could be talking through my butt- as I often do but here it goes anyways-

Typically in a residential breaker set up your main breaker has a smaller current limiting ability then your branch circuits.
for example-
15A breaker - 22,000 A
100A breaker- 10,000 A
I think it's because it's more expensive to make larger breakers be able to handle larger fault currents.

So when a direct phase to phase short (this is is the only time I've ever seen a main blow first before a sub or branch breaker go) the typically the larger breakers, therefore the smaller current limiting ability, will trip first protecting itself from blowing up.
Click to expand...

Start in the beginning of this post and reread all post explaining why a 100 will trip before a 20, You are off base with your explanation.
 
zog said:
Man you missed it, last night got ugly in the safety forum, thread is closed and grounds keeper willie threw away the key.
Click to expand...

Sorry - did you want the beating to continue, or did you just want to make the rest of us suffer through it? :-?

220/221, I took it in the vein intended. A friend of mine frequently said that one person or another was working their way through Clown College; it never failed to get a laugh. :)
 
charlie b said:
I'll try, but a plumber probably wouldn't understand, because I am going to start with Ohm's Law. The current you get, in any circuit and in any circumstances, is the voltage supplied by the source divided by the resistance that that source must push current through. When you have a short circuit, it means that the resistance went down to nearly zero, due to a wire, a tool, or some other low-resistance item coming into contact with two hot wires (or a hot wire and the neutral, or some other combination).

But the "total resistance" seen by the source is not, quite, exactly zero. That is because there is resistance within the source itself. So when we talk about "available fault current," we pretend that the thing causing the short circuit has absolutely zero resistance, so that the only resistance in the overall circuit, the only resistance seen by the source, is the resistance of the source itself. Then when we divide the source voltage by that value of resistance, and when we get a high value of current, we will be very confident that the actual value of current that we would ever see during a real fault can never be higher than that value. It is the most that the source can give, because of the limitations of the source itself.

Does that work for you?
Click to expand...

Charlie,
That was beautiful! (Looking for a smiley that has a tear in his eye.)
 
mxslick said:
And higher AICs make for a more impressive explosion when things go wrong... :D
Click to expand...

No, higher SCA (short circuit amps) makes for a more impressive explosion. A correctly sized AIC (amps interrupting capacity) would result in proper operation and little excitement.
 
alfiesauce said:
. . . typically the larger breakers, therefore the smaller current limiting ability, will trip first protecting itself from blowing up.
Click to expand...
The values of 22,000 and 10,000 do not represent “current-limiting ability.” The breakers cannot, and will not, limit current to those numbers. The things that limit current are the voltage at the fault point and the total resistance of the circuit, as viewed from that fault point.

What those numbers represent are the highest values of current that the breakers can withstand, without themselves suffering a major failure. If you try to push more than 10,000 amps through a breaker that is rated for 10,000 amps, it is possible that the excessive heat generated by the current will cause the metal contacts to weld together. Forever thereafter, it will be impossible for that breaker to open. So the reason we take intentional steps to limit the fault current to below the breaker’s rating (or if you prefer to put it this way, we select breakers that have a rating at least as high as the available fault current) is to make sure the breakers will be able to open, and thus to terminate the event
 
realolman said:
Good grief.. what an awful thread title.

It should be: One of you clowns WHO went to college.;)
Click to expand...

Yes, but I think the target clowns are the engineers and we cant spell or do good grammars anyways.
 
zog said:
Yes, but I think the target clowns are the engineers and we cant spell or do good grammars anyways.
Click to expand...
Ain't it supposed to be, ". . . do good grammars nohows?" :-? :smile:
 
wow all I got out of college was..................:grin: .............

But I want a chance at this too..

lets say your well pump will produce 60 gallons a minute and a dead head pressure of 250lbs and the well pump is the source....your pressure relief valve is set for 100lbs and someone closes a valve to the relief valve..the motor seizes up at 250lbs and quites..that means your plumbing was correctly done but the safety point was in the wrong spot..so that means you need to redo the plumbing so the relief valve does it job correct without seizing up the source..

the transformer that feeds the equipment is the source..The breakers the relief valve..the fuses are the sources protection from exploding..so in essence you need to fix the coordination problem to save your fuses..which is a process I would have to think about to explain in plumbers terms..

so now did my plumbing experience do it for you..
 
Status
Not open for further replies.
Top