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  #51  
Old 04-22-2018, 12:49 PM
Walt's Avatar
Walt Walt is offline
 
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Quote:
Originally Posted by rv7charlie View Post
That might well be true for your a/c and your mission. It works fine for my day VFR -4, too. But you can't apply Walt's 'at all' philosophy to every a/c and mission, and as a 'pro', he should know better than to make a statement like that.

IFR and electrically dependent panel?

Electrically dependent engine?

One alternator or two? If two, can the backup alt carry the full electrical load?

If you know anything at all about Bob Nuckolls, you know his decades of experience in the certified world, and his desire to make available more useful (and when possible, simpler) electrical system designs than have been available to those locked in the certified world. If one simple system would suit everybody, I'm very confident we wouldn't have the Aeroelectric Connection book; it would be a one-page diagram.

Charlie
Seems like we seldom agree Charlie, but thats ok.

However you seem to be saying a complex system is required for IFR, but in another thead today talking about req'd IFR equip. you said:
"Put at least the minimum required gear for IFR (plus what you need for your comfort zone) in the plane, log it, rewrite the weight/balance if needed, get the IFR transponder sign-off, and go fly."

So which is it?

And I think Nuckolls is a great guy with tons of knowledge, but his "Ess buss" design is quite old and the intent I believe was to be able to load shed easily in the event of an alt failure and fly to an airport.

I merely suggest that things have changed and with a current glass panel with their associated backup batteries and Pmags (OP equipment) the EBuss is really kinda dated IMO.

Heck I've flown plenty of practice IFR approaches with just my Ipad and a G5 (neither of which require external power), its really pretty easy. As long as the engine keeps running I'm good.

We don't have to have an electrical system designed for the space shuttle to stay alive, and we shouldn't have to take an electrical systems training course to get in and fly an RV.

PS: None of this applies to an electrically dependant engine, thats a different ball game and not what the OP was planning for.

PSS: almost all the backup alt's will carry the load from a full glass panel, my own panel G3X, 650 etc. with everything running draws less than 10 amps.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 04-22-2018 at 01:01 PM.
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  #52  
Old 04-22-2018, 01:37 PM
Mich48041 Mich48041 is offline
 
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Bob N recently posted his reason for having an E-bus.
http://forums.matronics.com/viewtopic.php?t=16769582
Quote:
The e-bus was conceived as a method for setting
up a fixed, predictable battery-only endurance load
with a simple re-positioning of two switches.
The idea is to reduce pilot workload immediately after an alternator failure.
All the pilot has to do is to turn on the E-Bus and shut off the master switch.
Shutting off the battery contactor shuts off all loads on the main power bus
and also saves energy that the battery contactor coil is no longer using. The
E-Bus also provides a backup current path is case the master switch or
battery contactor fail. If a Schottky diode is used, it will not get as hot or
drop as much voltage. The voltage drop doesn't matter as long as the
alternator is working. Electrical loads will work just fine on 13.5 volts
instead of 14.2 volts. When the E-Bus switch is turned on, current no longer
flows through the diode.
Let's consider reasons for not having an E-Bus. Simplicity. If it is not
installed, it can not fail. And the electrical system is simpler for a pilot to
operate. If the alternator fails, there is no hurry to immediately shut off
unneeded electrical loads. Modern avionics and lights do not use as much
power as they used to. When the pilot is not busy, he can shut off unneeded
items one at a time to conserve the battery. What about master switch
failure or battery contactor failure? Those failures are rare and are more
likely to occur on the ground than in the air. Below is an E-Bus circuit that
eliminates the diode and separate bus and etc. It provides an alternate
current path in case the master switch or battery contactor fails. E-Bus
switch must be off in order to start engine. That prevents starter current'
from flowing through small relay.
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  #53  
Old 04-22-2018, 01:55 PM
rv7charlie rv7charlie is offline
 
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As you said, that quote was from another thread. Just so you don't twist my words, readers should look at that thread and see that the question asked was about whether existing oplims wording needed to be changed when going from VFR to IFR. That quote was addressing regulations; not design/operation.

Your words:
This is a great exercise, but personally I question the need for an "E Buss" at all these days
Then in response to me, you hedge, saying that an electrically dependent engine is a different ball game (which was exactly my point), and that with a backup alternator (which not everyone has) you don't have to worry about load shedding.

Sure, you can wire everything on one bus, and start flipping switches and/or pulling CBs or fuses when you need to shed loads to get down to backup alt capacity (or down to remaining battery capacity, if there's no backup alt). And in a given a/c, no action might be required. But that isn't a universal truth.

The whole point of the E bus is a low-work-load method to configure the plane to deal with a failure of the primary alt. We read all the time about distractions being our enemy when flying. I just saw the mention (again) of the L-1011 that flew into the ground in FL while the flight crew fiddled with a landing light that wouldn't come on. Where's the problem with a one-step action to deal with primary alt failure, if the a/c needs to shed load to stay within electrical capacity for the rest of the flight?

I don't doubt that you can fly practice approaches with your ipad & G5, but a lot of people have come to grief with more backup resources available after electrical and/or vac failures while in real IMC.
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  #54  
Old 04-22-2018, 02:51 PM
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Walt Walt is offline
 
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Quote:
Originally Posted by rv7charlie View Post
This is a great exercise, but personally I question the need for an "E Buss" at all these days
Then in response to me, you hedge, saying that an electrically dependent engine is a different ball game (which was exactly my point), and that with a backup alternator (which not everyone has) you don't have to worry about load shedding.

Sure, you can wire everything on one bus, and start flipping switches and/or pulling CBs or fuses when you need to shed loads to get down to backup alt capacity (or down to remaining battery capacity, if there's no backup alt). And in a given a/c, no action might be required. But that isn't a universal truth.

The whole point of the E bus is a low-work-load method to configure the plane to deal with a failure of the primary alt. We read all the time about distractions being our enemy when flying. I just saw the mention (again) of the L-1011 that flew into the ground in FL while the flight crew fiddled with a landing light that wouldn't come on. Where's the problem with a one-step action to deal with primary alt failure, if the a/c needs to shed load to stay within electrical capacity for the rest of the flight?

I don't doubt that you can fly practice approaches with your ipad & G5, but a lot of people have come to grief with more backup resources available after electrical and/or vac failures while in real IMC.
Well we were reviewing the OP diagram, which in not an electically dependant engine so thats not what we were talking about.

The OP's "EBuss" is really just an avionics buss (with some other items on it) with an alternate feed as he has put all his avionics on that bus, most of which is not really "essential" anyway, and we've added some additional failure points.

So we've really complicated things just so we don't have to turn off "non essential" items with a switch if we loose the alternator. I think common sense, even for the most non-electrical oriented pilot is if you loose the alt and have a low voltage situation you should probably turn off the extras like seat heaters, lights and such. Turning off a few switches seems "simpler" and is basic SOP than knowing what the effect may be when you turn off the master and flip on the Ess buss (which you likely haven't ever used in flight before).

I honestly have lots of customers with purchased RV's that have 'complex' electrical systems (dual busses/E busses, etc) and most have no clue what any of it does or how it works.

Lots of RV's change hands these days and some day we will all have to move on, I want the guy who owns my airplane to be able to get in and go without a bunch of non-standard procedures.

My aircraft SOP:
1)Electrical fire, flip off the master and aux battery switchs and land.The standby G5 will continue to operate with its build in battery to provide primary flt instruments.

2)Lose the alt, just flip on the backup and land when it's convenient (or not as the b/u will easily carry everything except the pitot heat and all the lights).

3)Backup alt inop, no problem, the PFD/MFD/GPS, engine instruments and com 2 will run off the backup battery for over an hour.

See ya on the ground.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 04-22-2018 at 05:39 PM.
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  #55  
Old 04-22-2018, 03:19 PM
rv7charlie rv7charlie is offline
 
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Again, my comment was about your 'at all' statement (which, when you snipped my comment, now looks as if *I* said it...).

Oh, well....
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  #56  
Old 04-22-2018, 04:51 PM
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Walt Walt is offline
 
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My comment below, and I stand by it.

"This is a great exercise, but personally I question the need for an "E Buss" at all these days."
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #57  
Old 04-23-2018, 06:35 AM
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Nihon_Ni Nihon_Ni is offline
 
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Gents,

I really appreciate the continued dialogue. I took down the link to my latest version last week because I thought I had gotten so far off track that I was afraid others would use it as a reference, and I thought it would be better to hold onto it for a while.

I'm still not sure about my design, but I'm going to post the latest version again. Afterall, this is a forum for builders to exchange ideas, good or bad, and this version of the design is key to continued dialogue in this thread.

https://www.dropbox.com/s/uvk4vy9nxn...13%29.pdf?dl=0

I'll also repost my load analysis, although I've been challenged on its accuracy without the benefit of a hint to find whatever errors may lie within, so future builders should carefully consider my math before copying this chart.

https://www.dropbox.com/s/dweoi3rghg...0Plan.pdf?dl=0

Thanks,
Rob
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RV-8 N884RA under construction

Last edited by Nihon_Ni : 04-24-2018 at 06:16 AM.
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  #58  
Old 04-23-2018, 11:19 AM
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Nihon_Ni Nihon_Ni is offline
 
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George,

Thanks for the time you took to offer this feedback. It's really helpful to me!

Quote:
Originally Posted by 444TX View Post
Nice diagram and load charts.

I have been watching your system design progress and most of the problems I had seen have been addressed. I have a few ideas, not that they must be followed.

1. SD-8 alternator. You might call B&C. The regulator needs good cooling to achieve maximum available output. Under the cowling may be too hot for the best results.
Thanks, I'll ask about that.

Quote:
2. The main alternator current limiter is too small. Most alternators easily put out more than advertised current. Recommend 70 amp.
I'll defer comment on this one -- Joe has a response below and I have no experience with it, so I need more study to figure it out.

Quote:
3.The Auxiliary Alternator warning light will always be on with the switch turned off. Unless you plan to leave on, the solution would be a double throw switch that would also turn off the light circuit when not being used. A warning light on all the time would be a nuisance.
I'll have to go back to Bob's notes on this light. I may be missing the details off the top of my head, but I think the design goal is for that relay to always be closed, but I could be wrong. I understood this light to function in two capacities -- it would come on if the crowbar removed power from the relay, and it would also be on if the switch was off with power applied, serving as a reminder to turn the switch on for normal operations. It also serves the dual purpose of an idiot light if I leave the master on after flight (which I've NEVER done ).

Quote:
4. The 20 gauge essential buss jumper is too small for a continuous 15 amp load of more than 2 seconds. I would recommend a 14 or 16 gauge jumper with no protection. Same for the 22 gauge main buss jumper. Protection is unnecessary, especially if a very short run.
The topic of fusible links between my buses has caused me tremendous angst in the past week. I frankly don't know what to do. The distance between E-Bus 1 and E-Bus 2 is about 18", same for Main Bus 1 and MB2. E-Bus 2.

Main Bus 2 will draw 3A continuous and 4.5A max, E-Bus 2 will draw 2.9A continuous, 8.2A typical max, and 16.7 theoretical max (everything on at once, which is unlikely). I used the typical max to size the wires, so that gives me a figure of 24 AWG for M-Bus 2 and for 20 AWG E-Bus 2 for 18" wire runs. Since I don't plan to use wire smaller than 22AWG, I up-sized the MB2 feed to 22 AWG as the fuselink, and stepped up the rest of the wire 4 sizes to 18 AWG. On the EB2 feed I used 20 AWG fuselink and 16 AWG feed wire. If this is all wrong I'm certainly willing to scrap it and go with something else. If I removed the fuselink, wouldn't I just have the wires sized at 22 and 18 respectively? I'm really confused about this part of the design.

Quote:
5. The 30 amp inline fuse for the E-buss alternate feed relay is just adequate for full load. Would put a 40 amp with the wire size used or would recommend a 40 amp current limiter. (same thing different package)
This is another area I'm having trouble understanding. Bob recommends 30A fuse, the manufacturer specs a 10A fuse. I can't figure out what the electron flow would be across that fuse. Would it get 60A from the main alternator when the battery contactor is closed? It seems to me that unless there was somewhere for those electrons to go (i.e. a short in the SD-8 or relay), they wouldn't flow towards the SD-8. But again, I'm an electro-novice, so I don't know what I don't know.

Quote:
6. The main alternator and auxiliary field breakers should be easily accessible and identifiable by feel.
Roger that.

Quote:
7. Recommend all Honeywell TL quality and/or type switches. The Carlin can give problems, especially on inductive loads. Fast-on are nice, but a quality switch is more important.
I'll take a look at those. I really haven't given a ton of thought to switches yet, other than load ratings and function.

Quote:
8. Have no provision to power up the avionics prior to engine start. Would be nice for IFR. Set up radios, check ATIS, insert flight plan, call for clearance, etc.. A small/medium Lithium could be used.
Couldn't I just turn on the E-Bus Alt Feed switch, which should power the Endurance Bus directly from the battery?

Quote:
9. I would not use a Lithium for the main battery, especially IFR all electric plane. Time will tell. (I'm sure to start a fire storm for that suggestion)
Thanks -- a few people offered me the same advice and I'm still thinking about it. I was firmly opposed to lithium batteries until Vans came out with it as standard equipment in the RV-12IS; that made me reconsider it as a viable option. I still have some research and thinking to do before I commit to a battery.

Quote:
10. Would recommend a Honeywell double throw switch for the avionics switch. (extra contact area). Why the diode, unnecessary voltage drop and can control current with the avionics switch. Breaker switches can be problematic. Does the avionics switch circuit between the busses need protection? You could put a 14 gauge fuse link on each end, but I would not bother.
Can you explain how a double throw switch provides extra contact area? Is it a DPDT that has both switches wired together, or something else I'm not considering?

E-Bus 1 & 2 draw a typical max of 21.9A and a theoretical max of 29.6A. Given those figures, I thought I needed a switch rated for 30A but had trouble finding one. The CB switch is rated for 35A, so that's how I landed on it. The distance between MB1 and EB1 is a matter of inches; if it includes a trip to the switch it will be on the order of two feet total. I'm not sure if that requires circuit protection or not. I initially had a relay there to solve the amperage rating issue, but I tried to get fancy with it in an early design which just complicated the issue, so I opted for a CB switch in the name of simplicity. However, I'm not sure I achieved that goal. I've been flying several different Beech products lately, and they have extensive use of CB switches, so that has certainly biased me toward a CB switch, but I don't have any experience maintaining one. Perhaps putting the relay back in (in a less fancy way) is the better solution? That would reduce the power wires to a few inches, and remove the need for circuit protection. I think...

I don't see a Honeywell switch rated for more than 20A, but again I'm not sure I've done my calculation correctly. Do you have a part number for the switch you recommend?

Quote:
11. Would run the strobes through a breaker rather than a fuse. Have seen multiple strobe fuses melted. This is documented, but not fully explained.
The fuse to CB comparison is another item that I don't have a firm grasp on. I know not all fuses are the same, as in some are slow blow, and others are not. I'm installing Pulsar LED strobe lights, and the install instructions recommend three conductor 20 AWG shielded wire to power supply, and "Budget 5A per strobe light input." Since I have three strobe lights, I've budgeted 15A, but according to table 11-3 in AC 41.13, 16 AWG wire should be used for 15A CB or 10A Fuse. I have a note to pose this question to AeroLEDs, but it's still something I need to learn.

Quote:
12. You have fuses for the GTN650. There is no way to reboot the radio. This is done with the breakers. Suggest easily accessible, small breaker panel with the necessary breakers.
Why would I need to reboot the GTN650? Is there a function that requires it, or is it a trouble shooting step of some sort?

Quote:
You have the diagrams, now for the install. Be sure and use high quality connectors. Be careful of chafing areas and protect well. With the large number of connections a Daniels crimper, used red/blue crimper, tefzel strippers would be worth the investment, but not necessary with verification of proper results. Get the proper solder sleeves. Work on perfecting your techniques. Follow techniques in the manuals. The install is only as good as the harness and connection quality.

Looks like you are on the right path. Hope I am helping and not being too critical.

George Meketa
RV8, 16 years
Thanks George -- I really appreciate your feedback!
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  #59  
Old 04-23-2018, 12:10 PM
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Nihon_Ni Nihon_Ni is offline
 
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Joe, I feel like I'm going to have to paint your name on the side of the plane as a contributing builder will all the time you've spent helping me understand electricity!

Quote:
Originally Posted by Mich48041 View Post
1. Yes, heat is an enemy of electronics.
2. A 60 amp ANL current limiter will conduct 70+ amp indefinitely without blowing. Read Bob Nuckolls' post:
http://forums.matronics.com/viewtopic.php?t=16762449
Thanks for that info. Am I right to think that if I try a 60A current limiter and it blows, that I could replace it with a larger one later on without having to modify the wire size or other components of my system?

I also found this post on AEC about current limiters:
Quote:
There are some noteworthy characteristics of the ANL series devices. Note that they will carry nearly 2X their rated current indefinitely. This makes them behave more like the fusible links we've described elsewhere on this website. So, if you wish to size an ANL current limiter more in line with the output rating of your alternator, you could do so without regard to the "headroom" we suggested for the use of JJS fuses. The long time constant and overload capability of ANL current limiters are not subject to the nuisance tripping we encountered occasionally with the much faster fuses in this application.
http://www.aeroelectric.com/articles/anl/anlvsjjs.html
This leads me to believe a 60A CL will work for my system. Would you agree with that assessment?

Quote:
3. Using a double pole switch is a good idea. One half of it can disable the aux alternator warning lamp.
I need to go back to the reference on this one to make sure I understand what I intended this light to do for me.

Quote:
4. The E-Bus jumper is 16 AWG. The #20 is a fuselink. It will conduct more than 50 amps before it melts. See this chart:
http://www.litz-wire.com/New%20PDFs/..._R2.011609.pdf
The main bus jumper is 18 AWG (not labled). The 22 AWG fuselink will melt if current exceeds 40 amps.
Thank you very much for this reference! I've been advised for and against fuselinks, but I know very little about them so I'm having trouble making an educated decision about them. This chart helps me understand the capability of the link.

So what happens in the event a fuselink blows? As I understand the intent of it, it's the weakest part of that wire run, so if the wire were to short or otherwise have an overload, the smaller gauge wire in the fuselink will melt. Will the silicone covered fiberglass sleeve contain the melted fuselink? I presume that once the link melts, power is broken so it's a momentary condition, not a steady state condition (like a fuse blowing inside a protected case). Is that correct?

Quote:
5.
6.
7. Yes, switches that use rivets as conductors (through plastic) are prone to fail.
8. There is a TCW 3 AH battery to prevent brownout during engine cranking.
That's correct. In my reply to George I said I could use the main battery, but I could also use the backup battery, and one of it's purposes in my system is to prevent brownout.

Quote:
9. Lots of aircraft use a Lithium battery including Van's new version of the RV-12 But who knows? I plan to keep my Odyssey PC680.
More thinking required...

Quote:
10. The diode is necessary to block starter current if the builder or future pilot inadvertently leaves the E-Bus switches turned on. The diode will also block reverse main bus current if the battery contactor fails or if the pilot turns on the E-Bus before turning on the master switch.
11.
12.
Thanks for the scenario descriptions. I "shouldn't" need the diode if the switches are always thrown in the correct order, but I think it's worth installing as a fail safe device.
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  #60  
Old 04-23-2018, 12:41 PM
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Nihon_Ni Nihon_Ni is offline
 
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Quote:
Originally Posted by 444TX View Post
I will attempt to explain

2. When designing an electrical system one normally uses manufacturer supplied specs to provide the necessary data required to make informed choices. In choosing the current limiter size there are multiple selection factors, with current value being only one. For temperature the standard fuse re-rating is -25% for temperatures over 25C. That means that your 60 amp fuse would now be de-rated to 45 amps under the hot cowling. We have a 4 gauge B-lead cable that is capable of handling more than 80 amps (125 amp free air)(333 amps wire melting point from Joe's supplied chart) under the worst conditions being protected by a 60 amp current limiter. I stand by recommending a higher than 60 amp current limiter (80 is what is available). Not that the 60 will not work, maybe. I will disagree with Bob K. on this one. Do what you want.
George, thanks for that additional explanation. I see how temperature has an effect on the function of a current limiter. I had another builder recommend a 70A CB in lieu of the planned current limiter -- perhaps temperature effect was part of that recommendation?

Quote:
4. The small gauged fuse link buss jumpers are without doubt too small for the application. At times there are reasons to design a circuit with high voltage drop, minimum wire size and tight overload protection, but this is not the place. The max E-bus amp load is 15 amps. A 16 gauge wire is rated at 12.5 amps (free air) and a 20 gauge at 7.5 (free air). The buses are powered by an unprotected 10 gauge cable. The #1 and #2 E-buses are likely next to one another requiring a short jumper that has no realistic chance of a short. I will up my recommendation to a 14 gauge or larger jumper. Same for the main bus jumper.
E-Bus 1 has a typical max draw of 13.7 -- it's a fuse block located on the forward side of the avionics bay/aft bulkhead of the RV-8's forward baggage area. E-Bus 2 has a typical max draw of 8.2, and it's CBs located on the right side of the instrument panel, so the distance between them is about 18 inches. I sized the feed wire to EB1 to handle the total load, and sized the EB2 jumper to handle just the EB2 load, which I determined to be 20AWG (10A for 5 ft or less according to this chart):



As we discussed fusible links up thread, I ended up using 20 AWG as the link size and upsized the rest of the jumper wire to 16 AWG. If I decided the wire didn't need circuit protection, wouldn't it just be sized at 20 AWG "naked"? Are you recommending that the fuselink be upsized to 18 AWG, and the jumper wire upped to 14 AWG, or am I missing your point?

I guess I should have asked first, what rating do I use to size wires: continuous, typical max, or theoretical max (everything on at once, which is unlikely)?

Quote:
8. I still highly recommended an E-bus battery to power up the avionics, including the radio. The brown out battery does not provide this function. I assume, with this panel, the plan is to fly IFR. With all the items requiring boot up and set up time this is a feature that is closer to being required than just nice to have. My 8 (IFR) has a E-bus battery (lithium) that is the first thing turned on every flight when entering the plane.
Yes, I'm planning an IFR capability. My current backup battery configuration will not power up the GTN650. I am considering a two battery system, with a second battery that's larger than the current backup battery I have planned. What is the lithium battery you use on your E-Bus?

Quote:
10. The diode is a band-aid for a design flaw. Why would you want to drop voltage to the E-bus under all normal conditions. The switch wiring flow could easily be designed in a way to have the diode isolate the E-bus only when using the Alternate E-bus switch. If left alone at least monitor main bus voltage with the EFIS and not just E-bus voltage.
I've pulled out the POH for every airplane I've flown for the last 6 months and done a detailed review of its electrical system. The G-36 has a similar diode, and I understand the voltage drop you're referencing based on how the Bonanza functions. This is a good point that I hadn't thought about. I'll have to consider this one some more. Last time I tried to get smarty on the switchology I designed a circular logic flaw, so I'll give this one some more thought.

Quote:
These changes are not that difficult.

I will work on suggestions for Rob's "How Do I Get Electrical Experience" thread. Design is the hard part, now just need to work on techniques.

George
Thanks George! I really appreciate your input.
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