Circuit breakers and fuses behave quite differently. For that reason I
always use fuses on the basis they don't blow without reason so shouldn't
need replacing in flight and when something is wrong they blow far quicker
and near their specified value giving the protection you think you have.
Conversely circuit breakers release very slowly and at much higher values
than might be expected. (Fuses are also light and cheap - can't believe cars
would have fuses if circuit breakers were better).
Jerry
Jerry@ban-bi.com or LTS@avnet.co.uk
www.Ban-bi.com or www.avnet.co.uk/touchdown
----- Original Message -----
From: "William Mills" <combined.merchants@virgin.net>
Subject: Crowbar installation
> All,
>
> In case anyone else is contemplating fitting the Club Mod to fit a crowbar
device to protect A/C avionics from high volts alternator failure
(run-a-way), fitting a 5A fast blow fuse in stead of a circuit breaker does
not work. I fitted one because I thought it would do the same job, but I
was mistaken. It must have blown quite early in the first flight owing to a
"voltage spike" so the alternator circuit was isolated and the voltage
dropped back to 12v. I reduced the electrical load and continued the
flight, but when I subsequently investigated the problem I saw that the
22,000uf capacitor had blown leaving fluid and soot everywhere.
Fortunately, it appears that the capacitor had protected the alternator and
regulator from a more expensive repair, so I was lucky. I have now fitted a
delayed action 5A fuse which seems to be OK until I next remove the panel,
when I shall fit the 5A circuit breaker, as specified in the mod.
>
> Regards,
>
> William
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