Why every answer must include numbers
by w_tom - 9/3/12 1:41 PM
In Reply to: So Murphy? by R. Proffitt
> "A transistor protected by a fast-acting fuse will protect the fuse by blowing first."
Incorrect due to so many numbers. Some numbers are obvious even to layman.
For example, if three miles of sky cannot stop a surge, then why would millimeters inside a fuse stop it? Obviously, it won't. Demonstated is a common problem with surge protection. Many recommend by ignoring obvious facts and numbers. Also explains why advertising so easily manipulates so many.
2) What happens when a fuse blows during a surge? Voltage increases as necessary so that the current continues to flow (a first semester engineering concept called current source). All fuses have a number for that voltage (ie 250 volts). How does a 250 volt fuse stop a surge that, to do damage, must be thousands of volts? Obviously, a fuse does not do protection.
3) Another number: a surge is done in microseconds. Fuses take anywhere from milliseconds to hours to trip. A number obtained from fuse datasheets. Maybe 300 consecutive surges would pass through a fuse before it even thought about blowing. Even a millisecond fuse would not stop the typically destrutive (microseconds) surge.
Any protector device that claims to stop or absorb destructive surges is (and should be obvious to every layman) best called a scam.
A fuse, circuit breaker, or GFCI is for 'human safety'. It blows after damage has occured. So that a resulting house fire cannot occur. It blows only for 'human safety'.
GFCI or surge strip would protect by stopping or absorbing a surge. If so, then the number that says so is posted. Numbers say otherwise. Many who make recommendations avoid and do not post numbers.
How does anyone resolve conflcting statements? One based in reality includes perspective - the numbers. The most damning number: if three miles of sky cannot stop or absorb it, then how will 2 centimeter parts (or fuses) stop it? Protecting appliances for well over 100 years has never been about stopping or blocking a surge. Protection has always been found in a fundamental (and numerical) question: where do hundreds of thousands of joules harmlessly dissiapte?
Those numbers also say why safety (equipment) ground is irrelevant to the OP's request.
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