Message-ID: <c=US%a=_%p=CDI_Corporation%l=CDIM-PTS-MAI-981119190041Z-10875@cdim-pts-mail.ports-va.marine.cdicorp.com>
From: "Rumburg, William" <wrumburg@cdicorp.com>
To: "'rchesley@soca.com'" <rchesley@soca.com>, "'lancair.list@olsusa.com'"
	 <lancair.list@olsusa.com>
Subject: RE: Circuit Breakers
Date: Thu, 19 Nov 1998 14:00:41 -0500
Mime-Version: 1.0

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Bob and others -

  OK, I'll jump in to say to I installed a "hybrid" circuit breaker / 
fuse
arrangement, which I feel is a well conceived overall design.
   First, circuit breakers are there only to protect the system from 
being
taken down by a fault. They trip quickly on 300 - 600% overcurrent,
more slowly on less current, with a long-term minimum trip at 120%.
Their current rating is chosen appropriate to their load. They might 
do so,
but are not intended to offer protection to the load.
   Fuses do offer some incremental protection over circuit breakers, 
but
that is of real use only for your electronics and gyros (i.e. it's 
possible
that your faulted electronic device or gyro might be tripped off and 
thereby
protected from serious damage by the somewhat faster response of a 
fuse).
   I installed (miniature) circuit breakers on the right side of my 
panel in a
conventional manner for all the devices usually protected by circuit 
breakers
(fuel pumps, pitot heat, strobe power supply, panel lights, flaps, 
etc., etc.)
I made a separate "Flight Instruments" and "Avionics" bus by routing 
power
 Through 20 amp switches labeled as such. Their output is then wired 
directly
to a string of appropriately sized fuses on the bottom left panel for 
individual
electronics and gyros.
  I feel this is a well-conceived design.

                                            Bill Rumburg
                                            N403WR  (Sonic Boom)