REFLECTOR: Bus, Battery & Back Order

[Terrence Miles]

Al,
Thanks for the rundown.  I am going to print that one and have a closer 
look.  On voltage warning settings the Bob Nuckols answer (p 7-21) is 12.5 
for low and 15.5 for high.
Terry

>From: "Al Gietzen" <ALVentures at cox.net>
>Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
>Subject: RE: REFLECTOR: Bus, Battery & Back Order
>Date: Fri, 17 Jun 2005 23:25:37 -0700
>
>Subject: RE: REFLECTOR: Bus, Battery & Back Order
>
>
>
>Al,
>
>Thanks for the panel pic.  Can I ask you if you have a hot batt bus as well
>
>as an essential bus and a main bus?  Could you tell me your decisions on
>
>what went to hot and ess bus'es?  In the event of alternator failure will
>
>you be doing manual depowering (at the unit) anywhere?  I get the theory
>
>fine.  Seems for me the devil is in the details.
>
>
>
>Yes; I have a "hot" bus (what I like to call the "Critical" bus).  It is
>connected to both batteries, but isolated with 60A Schottky diodes so if 
>one
>or the other batteries goes down (bad short somewhere), the other still
>provides power.  The "Critical" bus drives fuel injection (two separate
>sets, primary and secondary), Electronic ignitions (two separate sets,
>leading and trailing) fuel pump 2, backup ECU, and backup EFIS (PFD and
>AHRS).
>
>
>
>The "Essentials" bus drives: ECU, fuel pump 1, EFIS PFD & AHRS, Alt field,
>SL-30 NAV/COM, Transponder, Engine monitor, Landing gear, Pitot heat, and
>landing light.
>
>
>
>The "Distribution" is connected via a 30A breaker/switch, and it drives
>position lights/strobes, vent and heater blowers, moving map display,
>interior lights, stereo/CD player, Auto pilot, Com 2, and misc, sensors
>(fuel level, low level indicators for coolant, oil, etc.)
>
>
>
>The Ess and Dist buses are downstream from the battery contactors powered 
>by
>both batteries.  I will normally have Batt 2 as a backup and the contactor
>off except for cold start, or alt failiure.  Batt 2 is charged via a
>Schottky diode when it is off.  I have two Odyssey batteries and plan to
>change one out every 2 years.
>
>
>
>Different folks I'm sure would make some different choices.  The idea here
>is that loss of alternator, or some mysterious heavy draw, one would first
>hit the distribution bus switch to shutoff nonessential loads; then 
>consider
>what items of the Ess bus can or need to go.  In the event of serious
>shortout of the main power distribution, I can turn off both battery
>contactors and the fan keeps turning.  This situation would most likely
>require a windmilling prop for restart.
>
>
>
>Where ever I went after redundany, I tried to keep the wiring separated.
>The critical bus is in front of the canard bulkhead, the other two behind
>the panel.  The main ground path is a copper pipe through the L side duct,
>with ground buses before and aft the firewall, behind the panel and up 
>front
>near the batteries.  Most of the power leads run inside the pipe.
>
>
>
>If you have time, I'd be happy to hear you explain that panel layout.  
>Looks
>
>
>real nice.
>
>
>
>Thanks.  I'll try to get something about panel layout on my website, and
>then refer you there.
>
>
>
>Best,
>
>
>
>Al
>
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