Fuses versus Breakers

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In article , Eric Greenwell
writes
ContestID67 wrote:
I have some fuses in my glider. One is on the main battery itself.
The other fuses are in the instrument panel and are for individual
devices (radio, computer, vario).

I got it in my head that I should replace the panel fuses with
breakers. There are several advantages, like being able to reset the
breaker in flight and being able to "pull" the breaker.

I have been told that all new breakers must be able to be manually
pulled (tripped) in case of emergency. Older breakers could be reset
but not pulled. Obviously fuses can be pulled also but I have an image
of my fumbling the loose glass fuse in the cockpit which isn't a pretty
picture.

Looking at a particular brand of breaker, the Texas Instrument Klixon
7277 line (http://www.ti.com/snc/products/controls/acb-7277.htm) from
Aircraft Spruce, I found that at low current draws you can loose a volt
or more from your primary.

1/2A 2.00 Vdc drop my vario
3/4A 1.45 Vdc drop
1A 1.10 Vdc drop my computer
2A 0.70 Vdc drop
3A 0.33 Vdc drop my radio
4A 0.30 Vdc drop
5A 0.25 Vdc drop

This is not good. It got me thinking that a glass fuse isn't too bad
after all especially considering a fuse is $1 each and the breaker is
$25 each.

In 5000 hours of flying gliders, I've only had to replace a fuse once in
flight (fuse actually went bad), and disconnect only one fuse (gear
warning going off at the wrong time). I think electrical problems where
a breaker would be handy are so rare, I like to keep it simple: I have a
master switch to disconnect the battery if there is smoke, and then just
fuses on the usual things. I carry a fuse of each type in a little
baggie in the pocket so I can replace fuse if I need to.

That may be so Eric, but breakers stop the incorrect value fuse being
used if it is the only one available.

One option worth considering is the use of Self Resetting Fuses. These
electronic devices work like breakers but reset themselves when the load
is removed.

Tim Newport-Peace

"Indecision is the Key to Flexibility."