More on fuses.

["Laurence W. Coen" <lwcoen@freewwweb.com>]

Some questions were raised as a result of my last posting.  The devices I am talking about are best described as resettable fuses.  Fuses are generally rated at maximum allowable current.  Circuit breakers are rated at trip current.  In addition, circuit breakers are rated for hold time at rated current.  This is usually given as a range of time (6-30 sec.).  A 9 amp. resettable fuse is the equivalent of a 10 amp. circuit breaker.  Equivalent NOT the same.  The reason for giving the hold time as a range is because circuit breakers are affected by ambient temperatures as are resettable fuses.

Jim Glindemann brings up a good point about "trip free" breakers.  If you look up circuit breakers in the DigiKey catalog it doesn't tell if they are "trip free" or not.  Know what you're getting!  I had a friend tell me a tale about how he got a malfunctioning landing gear down by holding in a circuit breaker.  There are a lot of older aircraft around that still have these breakers installed.  If your wondering if what he did was a good idea or not, ask yourself the question, "Would I rather land gear up or have an in-flight fire?".

The reason for circuit breakers is to protect the wiring.  When they wired your house, they had no way of knowing what loads you would plug in where.  What they did know was that 15 amp. breakers go with #14 wire and 20 amp. breakers go with #12 wire.  The wire size behind your panel determines the maximum breaker rating for that circuit.  There are reasons to use a smaller breaker but never bigger.  As an example, say you have a 10 amp. breaker and wiring going to a trim motor that takes 1 amp running current.  The trim switch sticks and the trim motor stalls against the stop. Its stalled current is 8 amps.  Not enough to trip the breaker or hurt the wire but plenty to set the motor on fire. A 5 amp breaker would far more appropriate.

If you're not happy with the green LEDs at night, don't use them or add a dimmer.

Finally, if you don't know how to figure out what size wire or breakers to use, get professional help (Martin Hadley leaps to mind).

Larry Coen

"A fool learns from his mistakes.  The wise man learns from the mistakes of others".