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Requesting Review: modern electrical diagram

humptybump

Well Known Member
I am designing a panel and have a sense for what I want the end result to be.
With that said, there are a few "I think" areas of my design and anytime I say "I think" it really means, "get help"!

Below is my high level plan for power. There are [at least] three questions I would like assistance with (each question has a matching label on the diagram):


Q#1 - Is the Battery + Alternator circuit really this basic ?

Q#2 - Should the button switches on the stick (being used for the flaps) be protected by their own breaker ?

Q#3 - Do the two electrical buses need their own 'main' breakers and if so, how are they sized ?


Also, if you see real errors and places that are not safe, please point those out as well.

I very much appreciate the help !


click for larger image

Updated Diagram to 1.1:

click for larger image
 
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Where is the Voltage Regulator for the Alternator? You also should have circuit protection between the alternator and battery.

A1. Yes after you add a voltage regulator and OVP to the alternator.
A2. Each circuit (not switch) requires its own circuit protection. (Fuse or CB)
Tie the switch into the same CB.
A3. IF all the wire from the 60 Amp fuse is sized for 60 amps all the way to the next fuse or circuit breaker, then no. IF you go to a smaller gauge wire anywhere after the 60 Amp Fuse before you go to another circuit protector, then you need circuit protection sized for the smaller gauge wire.
 
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I assume you are using a PP alternator with internal regulator.
You don't show the stater wiring. It cannot go thru that 60 amp CB.
Many people protect the alternator with a 60 A CB but protect the battery separately, with a very heavy duty fuse, and run it directly to the bus(es), so if the 60A CB fails at least you have battery power available. Or some don't protect the battery wiring at all except to hope the master relay drops in and out without welding the contacts in case of a direct short.
I would move the 5A flaps CB to protect the up/down switch wiring, too.
You don't show the wiring labeled "landing plus taxi" and "taxi" but taken at face value you will need diodes for isolation to achieve the desired result (e.g., if these wires are connected as labeled then turning on taxi, the power will run backwards thru the wires and turn on the landing light too).
I'm not sure why you have two buses but only one power source, except that if one of those switches fail, you still have half the avionics?
 
Do modern alternators have the voltage regulator buit-in / integrated ?

Best aircraft practice is to have a separate voltage regulator and Over Voltage Protection.

Internal voltage regulator is fine on a car or ground vehicle but not on MY airplane.
 
Great questions and comments. Here is some of what I was thinking.

I assume you are using a PP alternator with internal regulator.
Yes.

I would move the 5A flaps CB to protect the up/down switch wiring, too.
The grip is a Ray Allen and the documentation says they are only good for 1A. If they were 5A I could do without the relay. So I'm guess I should have a 1A CB between the buss and tho grip switches ?

You don't show the wiring labeled "landing plus taxi" and "taxi" but taken at face value you will need diodes for isolation to achieve the desired result.
The switch is a DPDT ON-ON-ON. I stole the wiring from the B and C website. Their drawing of the switch is much better than my symbol and it will do what I suggested. But, you're point is well taken and I will test it on the bench for sanity.

not sure why you have two buses
My theory is the two buses will allow me to quickly dump all non essential usage with a single switch. Down the road, I am likely to add a second battery with diode isolation. But that is just complicating my current learning curve too much.
 
Thanks Gary, I think I see a new problem in my plan ...

if you go to a smaller gauge wire anywhere after the 60 Amp Fuse before you go to another circuit protector, then you need circuit protection sized for the smaller gauge wire.

The switches I planned to use (700-1-2 ON-OFF) are from B and C. Based on a paper by Bob Nuckolls (posted on the B and C website), these switches are conservatively rated at 15A and some at 20A.

Update: reviews of others' implementations suggests the Bus switches need to be relays to handle the current, unless there is a 60A switch out there that does not look (or cost) huge.
 
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The Aeroelectric diagrams show the alternator output (B terminal) on the same side of the master contactor as the battery. Is there a reason you put it on the opposite side here?

Better question: Is there a reason NOT to do it as depicted by Humpty (assuming the 5A field breaker is pullable)?
 
The Aeroelectric diagrams show the alternator output (B terminal) on the same side of the master contactor as the battery. Is there a reason you put it on the opposite side here?

I hope someone will answer your second question as I have not seen the Aeroelectronics diagram your mentioned.

I stole the battery+alternator portion of my diagram from Bob Ellis. (G-JBTR) and Paul Dye.


The 5A CB is pullable.
 
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There is nothing wrong with an alternator like the PP units with internal regulation and OV protection.

Many many many of em out there and working fine for years and years....

Yes there are documented failures...Show me an alternator setup without em!
 
On the subject of internal VR andOVP, I'm going to have to plead Switzerland.

If we set aside the VR and OVP, how do I get the two buses correct ? Is thecright design to use the switches to drive relays? Is relays, can someone point me to a source ?

Guys, I'm really greatful for everything so far! Really !
 
Breaker sizes?

Looks good. Just a couple suggestions:

Consider breaker switches for Comm or an avionics switch so you can energize engine monitor and MFD at engine start but w/o avionics.

A breaker switch on the fuel pump would also make your panel simpler.

I don't know which radios you are using but my Icom transmits at over 8 amps which requires a 10A breaker and you only have 5A on each

Your MFD has only a 2A draw?? (My Dynon has 5A breaker...but does also power an integrated GPS)

Recommend increasing the 12V auxillary to 10A to cover all portable devices you might want to plug in. Most auto auxillary plugs are rated at least 120W.

And need breaker between B+ on Alt and wherever you tie into bus or battery (as others have mentioned).

Great drawing compared to my "back of the napkin"
 
I don't know which radios you are using but my Icom transmits at over 8 amps which requires a 10A breaker and you only have 5A on each
The radio is the MGL V10 - a solid state radio and only calls for 5A

Your MFD has only a 2A draw?? (My Dynon has 5A breaker...but does also power an integrated GPS)
The EFIS is the MGL Xtreme. The MFD is "future". I was guessing. I can increase that to a 5A.

Recommend increasing the 12V auxillary to 10A to cover all portable devices you might want to plug in. Most auto auxillary plugs are rated at least 120W.
The circuit is for a pair of cigarette lighter plugs. I only plug things like an iPhone or other portable devices. However, if I plugged in a Gerber, you are right. I'll rework that circuit.

And need breaker between B+ on Alt and wherever you tie into bus or battery (as others have mentioned).
This error was pointed out above so a CB is an easy fix. However, the down stream buses are an even bigger error so the placement and sizing of these breakers (and possible relays) are my next challenge. Ugh.

Great drawing compared to my "back of the napkin"
I'm using the free software, ExpressPCB. It's pretty good. It would be even better if those of us here on VAF using it were to band together and share our component libraries. You don't need too many components and we all are using most of the same components.
 
Looks good. Just a couple suggestions:

Your MFD has only a 2A draw?? (My Dynon has 5A breaker...but does also power an integrated GPS)"

The Xtreme only requires a 1 amp slow blow fuse. And it also powers an internal GPS............:D
 
I want to thank everyone who has contributed to my "education" on electrical systems. I was not the fastest learner in the class, but I think I'll pass the final exam :)

The process reminds me of something from my high school senior physics class. The teacher was Commander Jack Wibby. 
A few weeks prior, we had finished the module of pendulum motion. I had aced the exam. We had moved onto ballistics. One day, I arrived to class a few minutes early and the pendulum apparatus was still installed on the front lab table. I started playing with it. Somewhere along they way, Mr Wibby walks and and watches me. I start the pendulum in motion. I drop on a second weight and observe the rate. I reduce the line to half length and I observe the rate. I remove the weight I added early. Then it happens - I say out loud, "oh cool, now I get it!" Mr Wibby just shakes his head.​

I'm not a wrote learner. I need to get my hands and head right into the middle of a problem. I appreciate the patience you have shown in answer some pretty basic questions. In a couple days, I'll have it written up and will post it back here. in the meantime, all I can say is, "cool, now I get it!"
 
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