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E-Bus Fuse - Advisable?

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user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Sat Dec 10, 2016 7:57 am Post subject: E-Bus Fuse - Advisable?

There has been a recent discussion on VansAirforce questioning whether or not the E-Bus should be fused.

http://www.vansairforce.com/community/showthread.php?t=144607

In that thread, I stated that if two fuses or breakers are connected in series, a hard short circuit can blow both simultaneously, even if one of them is much larger than the other.  Someone questioned whether that is actually true.

What do you think?

  In Z-11, both the E-Bus feeder and the Nav/Com are protected by 7 amp fuses.  If there is a hard short in the Nav/Com circuit, which of the two fuses in series will blow?

  Perhaps the E-Bus feeder fuse should be replaced by a relay located near the source (battery).  The same logic used for main power bus can be applied to the E-Bus.  Good workmanship, double insulation, the ability to shut off the power at its source, and the need for reliable electrical power, are all factors that suggest that an E-Bus fuse might not be required.

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_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Sat Dec 10, 2016 9:11 am Post subject: E-Bus Fuse - Advisable?

On Sat, Dec 10, 2016 at 9:57 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 There has been a recent discussion on VansAirforce questioning whether or not the E-Bus should be fused.

 http://www.vansairforce.com/community/showthread.php?t=144607

 In that thread, I stated that if two fuses or breakers are connected in series, a hard short circuit can blow both simultaneously, even if one of them is much larger than the other.  Someone questioned whether that is actually true.

 What do you think?

   In Z-11, both the E-Bus feeder and the Nav/Com are protected by 7 amp fuses.  If there is a hard short in the Nav/Com circuit, which of the two fuses in series will blow?

   Perhaps the E-Bus feeder fuse should be replaced by a relay located near the source (battery).  The same logic used for main power bus can be applied to the E-Bus.  Good workmanship, double insulation, the ability to shut off the power at its source, and the need for reliable electrical power, are all factors that suggest that an E-Bus fuse might not be required.

 

 --------

 Joe Gores

 



	
Hi Joe,

I posted to that thread, as well. My 'must have' stuff (electrically dependent engine, etc) is on a bus powered from the battery terminal through a fusible link & hi current switch, with an alternate switched path off the 'main' bus, which is controlled via the regular master contactor. As I mentioned on VAF, I never noticed that fuse feeding the endurance bus in the drawing. I'd have to agree that two 7A fuses in series could result in either blowing. In that exact setup, it seems more likely that the bus supply fuse would go 1st, since there are additional loads besides the radio on the bus feeder fuse.

Charlie

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 10, 2016 8:04 pm Post subject: E-Bus Fuse - Advisable?

At 11:09 AM 12/10/2016, you wrote:



 

  	  Quote: 	
		  On Sat, Dec 10, 2016 at 9:57 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

   --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>



  There has been a recent discussion on VansAirforce questioning whether or not the E-Bus should be fused. 	
 

   <snip>  I've read it . . . and there are several pieces

   of spaghetti getting wrapped around unrelated axles.

   I'm updating Z-11 and working on the supporting narrative.

   Watch this space . . .



   In the mean time, please encourage participants

   in the VAF forum to bring the discussion to the

   AeroElectric-List.  Wayyyyy back when, there was a

   time that I tried to play electro-whizzy hop-scotch

   across a half dozen forums and it became totally

   unwieldy.



   If a Z-figure is being discussed, please bring the

   conversation here where analysis and resolution can

   be archived on the AEC-List and appropriate changes

   made to Z-figures and supporting documentation.



   Thanks!



 

 

   Bob . . .

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