ARGOLDMAN(at)aol.com
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 Posted: Thu Jun 16, 2016 10:42 am Post subject: Review request for RV-9 Electrical System (G3X, ... |
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Or you can use a polyfuse. This will remain open until the fault is cured.
Of course when there is a fault, it behooves one to register it so that the problem can be corrected.
With the temporary overload, when the offending device is removed, in a very short while, the circuit is once again whole. These are used extensively on car windows since when they reach their physical limit the amperage draw goes up and the circuit breaks (when the window stops at its travel end, it is usually a signal to get your hand off of the switch. If you don't, instead of the wiring burning up, the poly fuse opens. Release the switch the polyfuse will again reconnect and if desired you can put the window up or down as you wish.
The polyfuse is available in various amperages and cost less than $1 usually.
The polyfuse is a thermally actuated device usually buried where the sun don't shine with no indication of circuit breakage (although you can devise a circuit that tells you). AlthoughI know many EABers who use them exclusively, I still use breakers for critical circuits (although probably overkill). I believe polyfuse is a trademark owned by littlefuse or some such company.
Rich
In a message dated 6/16/2016 11:28:06 A.M. Pacific Daylight Time, wgreenley(at)gmail.com writes:
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One place on my Cessna I have found a breaker VERY useful is the 12v power port (aka Cigarette lighter). Sometimes items with too big a draw get plugged in and blow the breaker, remove item, reset, and can still use other items in flight.
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Wednesday, June 15, 2016 4:11 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: Re: Review request for RV-9 Electrical System (G3X, GTN, etc)
At 02:14 PM 6/14/2016, you wrote:
--> AeroElectric-List message posted by: "gfb" <fly(at)bappos.com (fly(at)bappos.com)>
OK, I think I see your point on not needing breakers and going with fuses but I'm not 100% there yet. For my personal sense of comfort I'd like to have items on the endurance bus on breakers. Does this seem like a reasonable compromise?
Compromise for what? If a breaker ever opens it means
something is broke . . . and that something threatens
to set a wire on fire. You want to give it a second
chance?
What items in your airplane are high priority equipment
for comfortable termination of flight? From that list
of items, how many of them can fail in ways that do not
open a breaker? I can tell you that the vast majority
of equipment failures never open a breaker . . . if that
item is so necessary/useful that you're worried about
being able to reclose a breaker, then you'd better have
a plan-b . . . a back up for when the system decides
to take a vacation.
It allows me to load-shed even further by pulling breakers if needed and uses much fewer breakers and panel space. Thoughts?
Load shed? What's the e-bus for? The LAST thing
you should be doing in flight is running any kind
of mental gymnastics calculated to reduce risks
of dealing with some kind of failure. ALL such
things are done at THIS phase of your design
and fabrication. Should a necessary item go T.U.
then you go to plan-b. If the item is not necessary,
then there is no plan-B.
The idea behind the e-bus is to do a two-switch
load shed that either (1) does not overtax an
SD-8 or (2) produces a KNOWN endurance value
running battery only based on periodic capacity
checks of your battery.
Messing with any breaker or fuse in flight is a
demonstration of poor planning that should have
been managed during THIS phase of your project's
development. Put the fuse blocks out of sight and
out of mind. Deal with system difficulties as a
pilot with a plan . . . not an in-flight diagnostician
and maintenance technician.
Bob . . .
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