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  #11  
Old 01-30-2022, 08:36 AM
Walt's Avatar
Walt Walt is offline
 
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IMO an ‘EBUS’ is a waste of time and adds unnecessary failure points. Just load shed if you lose the alternator. I installed the gigavac contactor years ago, much better than stock and draws almost nothing. KISS always good.
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  #12  
Old 01-30-2022, 10:21 PM
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skylor skylor is offline
 
Join Date: Aug 2009
Location: Southern California
Posts: 1,046
Default Failure Mod?

Quote:
Originally Posted by Walt View Post
IMO an ‘EBUS’ is a waste of time and adds unnecessary failure points. Just load shed if you lose the alternator. I installed the gigavac contactor years ago, much better than stock and draws almost nothing. KISS always good.
If you follow the simple layout of the Aeroelectric Z-11, it’s hard for me to understand what “unnecessary failure points” could possibly be added by the Endurance Bus. It’s about as simple as it gets while using well proven components.

The idea behind the EBUS is to allow a quick and easy changeover to essential equipment by flipping just two switches without any thought or decision making by the pilot in middle of an electrical emergency, thus allowing him to continue doing the most important part of flying - aviating. The second function of the EBUS is to prevent the master contactor circuit and the main bus feed from becoming a single point of failure for essential avionics and instruments.

One mistake that I’ve seen many make is to put more than just truly essential equipment on the EBUS. This not only defeats the purpose of having it, but it also potentially overloads the isolation rectifier, which can then become a failure point.

Skylor

Last edited by skylor : 01-30-2022 at 11:32 PM.
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  #13  
Old 01-31-2022, 06:33 PM
h&jeuropa h&jeuropa is offline
 
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Location: Kalamazoo, MI
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I see there have been no responses that answer your question directly. Here’s my take.

You plan to have one buss (called Main/E Bus) that powers everything and a separate Batt bus. You have a main alternator and a SD8 backup alternator.

From your sketch, ignoring the diode for now, normal operation has the main alternator feeding the Main/E Bus and the battery and the Bat Bus.
In case the alternator fails, the battery contactor is switched off and you switch on the E Bus Alt Feed switch. You state you wish to remove the Essential Bus (I’m imagining your sketch as if it is a piece of wire – see attachment). So the E Bus Alt Feed would connect to the Main/E-Bus and you would shed loads individually as needed.

The diode is not needed. Its purpose in Fig 17-4 is to isolate the Essential Bus. When power is applied to the Essential Bus, the diode ensures just the Essential Bus is powered by preventing current flow to the Main/E-Bus.

Hope this helps.

Jim Butcher
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  #14  
Old 01-31-2022, 09:58 PM
jpowell13 jpowell13 is offline
 
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Default Diode

Good to know the diode is unnecessary Jim, and it makes sense. In case of an alternator failure, the process would be to turn on power from the battery buss, then turn off the main or battery contactor switch. (The power to the avionics stays at 12v even when both switches are on.) Then, turn off unnecessary lights and avionics and land.

Something I do look forward to having in the system are positive and negative battery busses.... not just for bypassing the battery contactor, but for an easy way to connect a battery charger or jump starter without having to remove the battery cover. I also like having my cigarette lighter power plugs on when rhe main switch is off (with in-lines fuses) so I can be booting up my ifly gps and picking up ATIS on the handheld before startup. The busses will make that easier.

Last edited by jpowell13 : 01-31-2022 at 10:23 PM.
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  #15  
Old 02-01-2022, 08:39 AM
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johnbright johnbright is offline
 
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Re post #1:
  • If the alternator is externally-regulated as shown, main alternator output voltage will rise by the diode voltage drop.
  • Bob Nuckolls would limit the endurance bus feed diode to 7-1/2 A unless a relay is used. Ref FAR 23.1361 Master Switch Arrangement. Bob allows a 7-1/2 A fuse vs a 5A breaker because fuses are faster I2T.
Re post #3:
  • The diode has no function re overvoltage.
  • Your master contactor probably has a 15 Ohm coil, 0.96A at 14.4V.
  • If a relay were used in the aux feed to the endurance bus, A 20A automotive relay has a 144 Ohm coil and a 40A one has a 90 Ohm coil.
Re post #13: If you leave the diode out the endurance bus fuse will blow under the scenario master off/endurance bus on/starter engaged. Of course you don't plan on doing it but it's a baited trap.

Z templates are at http://www.aeroelectric.com/PPS/Adob...tecture_Pdfs/:
  • Figure 17-4 of the Aeroelectric Connection is shown in greater detail in the Z13 template.
  • Z13-8T shows the endurance bus fed with a 15A fuses and relay. The fuses could be larger if desired.
  • Z13-8 E-Bus Feeders shows endurance bus fed with 7-1/2A fuse and switch.
  • Z101 is Bob Nuckolls' latest. No fuses are shown to the bus now called clearance delivery/brownout/aux and the asterisks indicate the relay, bus, and diode are close to the battery such that a short to ground is considered impossible. Z101 incorporates a high-capacity aux alternator such as B&C 410 or 462.
As mentioned in post #10, you could choose an aux alternator larger than the SD-8, attached is a summary of aux alternator advertised outputs on a Lycoming engine.
.
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Z101 as a template, links

Last edited by johnbright : 05-06-2022 at 04:05 PM.
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  #16  
Old 02-02-2022, 08:00 AM
jpowell13 jpowell13 is offline
 
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That's great information John. This is what I needed. Many thanks.

Regarding the 8a alternator, I once lost my alternator on a VFR flight due to a loose battery wire connector. I was surprised how well my 32 amp AGM battery kept the avionics going (over one hour). This convinced me that the smaller/lighter 8a backup alternator would be adequate in an alternator out situation, if I were to shed unnecessary power draws.

Last edited by jpowell13 : 02-02-2022 at 08:25 AM.
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  #17  
Old 02-18-2022, 04:39 PM
jpowell13 jpowell13 is offline
 
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Default What I did.

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Sorry for the orientation of the photos. I'm a little old for working under the panel, but managed to install positive and negative busses behind the rudder pedal support tubes. Used a 30amp in-line fuse and a 10 gauge wire to stsp switch in the panel. Works fine on the ground.

Already used the busses to connect a jump starter and get my engine started on a cold morning in TN. (My Pmags are great, but not as good at igniting the fire on a cold day as the old Bendix.)

My next step will be to update my old TWC backup battery with the Li Fi Phosphate version. John

Last edited by jpowell13 : 02-19-2022 at 10:26 AM.
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  #18  
Old 02-24-2022, 10:08 PM
jpowell13 jpowell13 is offline
 
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Default Next stage completed

TCW backup battery installed.
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