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Reducing Circuit Breaker Count

PilotjohnS

Well Known Member
It seems the Garmin G3X system has a lot of fuses/ circuit breakers for the various boxes.
How do I combine the fuses / circuit breakers together to reduce the number in the system?
 
Remember the fuses/breakers protect the wires, not the electronics. So if you have 10 boxes that each draw 5 amps, you could put in one 60 amp breaker and use fat wires (maybe awg 9 gauge?) to everything. But do you really want that? That’s a lot of fat, heavy wires. And if one of those 10 boxes or their wires fails to ground, the breaker will trip and all ten boxes will go off. Not usually desired.
OTOH, if you have a lot of low current, non-essential boxes (maybe an intercom, an FM radio, a dome light, a cell phone charger, each of which draws 1/2 amp) go ahead and put them on a single 5 amp breaker, as long as all the wires are rated for 5 amps or more.
 
I used a 12 position fuse/ground block behind the panel and a hand full of CBs for things I wanted more control over (AP, Flaps, etc.). Saved a lot of space and $$.
 
Good idea

I used a 12 position fuse/ground block behind the panel and a hand full of CBs for things I wanted more control over (AP, Flaps, etc.). Saved a lot of space and $$.

This is a good idea. I could put things on fuses that I dont plan to reset in flight. Let me think about this. Thanks for the suggestion
 
The vpx will replace them all...

What are people's experiences with vertical power and similar devices?

Replacing all the circuit breakers with a single point of failure seems like a design flaw to me, but maybe I'm missing something. The ability to pull a circuit breaker when something goes wrong is an idea that goes back to George Westinghouse. Replacing all your breakers with something that depends on software and microchips seems like we are introducing another point of failure, and one that will catastrophically affect everything in the plane.

Don't get me wrong - I love the idea of elegant solutions. Aveo wingtips will replace a bunch of individual lights on my plane. G3x and G5 will replace six packs, vacuum tubes, and standby instruments. But replacing the ultimate safety device in the event of a short, electrical fire, or other emergency with a black box that kills every circuit in the plane when it fails seems wrong to me.

What am I missing?
 
I used an 8-place auto fuse block for LEMO power, 12V adapter, USB jack, etc. It is a good solution and works great. I'll put more of my avionics on same next time.
 
I believe it is much better to protect each LRU with a circuit breaker or fuse, rather than tying several of them together, so that you only lose a single LRU in the event of an electrical supply problem (short, open circuit, etc.).

One additional advantage to circuit breakers vs. fuses is the ability to open the circuit easily. So for example, if you are trying to reduce electrical load to extend battery time in the event of an alternator failure, you can pull the breakers on non-flight essential equipment (second display, second radio, audio panel, transponder, etc.) to reduce system draw. Most of the G3X devices do NOT have on/off switches, so the only way to shut them off is to remove power to them. It is also useful in testing and trouble shooting while on the ground to be able to easily cut power to individual devices.

So it's not just about being able to reset breakers while in-flight.

Regards,
 
OTOH, if you have a lot of low current, non-essential boxes (maybe an intercom, an FM radio, a dome light, a cell phone charger, each of which draws 1/2 amp) go ahead and put them on a single 5 amp breaker, as long as all the wires are rated for 5 amps or more.

...assuming the total draw for all of them on at once will be less than 5 amps...
 
If the fuse blows, how do you know which wire or load caused it?
Troubleshooting intermittent problems can be very frustrating.
Make it easier by having one fuse for each load.
 
A question for the more seasoned pilots

I have read on this forum :
* Why would you reset a breaker in the air ? It is telling you something is not good and it did its job. Go land if you can't do without that function and troubleshoot.
* Fuses are to protect the wire, so something is probably really wrong if you blow a properly sized fuse..

B&C advise a 5A breaker for the ALT Field because transients (not faults) can blow a properly sized fuse.

I added a breaker for the electric flaps, anticipating some binding or peak transients that may not be flight terminating.

I am sure the more seasoned pilots on here can add some value for your decisions.
 
I have to chuckle

It is not possible to create a perfect system; if you drill down far enough, you will ALWAYS find a failure mode.

It is about risk mitigation, which is different for everyone.

You want to use 35 circuit breakers? Do it.

You want to use a $5, made in China fuse block? Go for it.

You want to use an expensive vpx? Your choice.

There is NO perfect system and there is NO one size fits all solution...
 
I had a breaker trip, I reset it, and it never tripped again for about 250 hours now, under the same conditions.

Just a data point. Nothing more.
 
updates

So i am making the following updates based on all this wonderful feed back (thank you all).
1) things that are not important for continued flight, like cabin lights, USB power, defrost fans, etc are going on fuses.
2) I am adding an extra fuse to allow me to power up the panel, with an external power supply,without closing the battery contactor (master switch); mainly for data loading and software updates.
3) Most of the things that have switches, I am putting on fuses
4) I am using breakers for things that I want to reset in flight and try again, like the alt field , fuel pump and flaps.
5) I am using breakers for things i want to turn off in flight if they fail, like trim power, each G3X box, etc.
6) added separate fuses for left and right landing lights: what is the chance both will blow at night, on a near minimum approach, 5 minutes before the tower closes, and I have to go pee?

7)I did not move the ELT up because I think i need to change batteries every year, but I might still.
8) added three spare fuses spots and three spare circuit breaker holes so the panel will never look "done".
 
A couple of minor thoughts on your updates:

2) Any quality external regulated power supply will have built-in over current protection, so you may not need this fuse, unless you have a long wire running to the power supply that is left in place and you want to protect that wire in case of a fault.

8) You can find plastic hole plugs for the empty future breaker holes. You can either paint them to match the panel, or use black plugs. That's what I did for the future breaker spaces on my panel and they keep the panel looking finished (no open holes).

Cheers
 
What are people's experiences with vertical power and similar devices?

Replacing all the circuit breakers with a single point of failure seems like a design flaw to me, but maybe I'm missing something. The ability to pull a circuit breaker when something goes wrong is an idea that goes back to George Westinghouse. Replacing all your breakers with something that depends on software and microchips seems like we are introducing another point of failure, and one that will catastrophically affect everything in the plane.

Don't get me wrong - I love the idea of elegant solutions. Aveo wingtips will replace a bunch of individual lights on my plane. G3x and G5 will replace six packs, vacuum tubes, and standby instruments. But replacing the ultimate safety device in the event of a short, electrical fire, or other emergency with a black box that kills every circuit in the plane when it fails seems wrong to me.

What am I missing?

I'm not on a campaign to malign VPower, but just my opinion:

I'm well past this decision in my plane, as it was built with Klixon pull-able breakers. But as a "senior" and electrical engineer, I wouldn't have it any other way. Ability to pull individual circuits easily, electro-mechanically, and reset as well (not hunting around in menus and screens). While the Vertical Power approach seems to be so popular in the RV world, the idea of having software and silicon (that often enough would just as soon head back to the beach) involved in my power paths turns me off (pardon the pun). And a friend with an RV-10 across the hanger from me is often enough on the phone with the VP guys with some kind of problem. I'll take breakers (and fuses in selected circuits, as mentioned) any day.
 
Since this was something I was going to ask in my own thread I will ask here since its on topic. I was going to using something like the VPX in my build vs the traditional setup but then I saw the cost. The VPX kind of compares the cost of items it replaces but that doesnt add up to the 2100$ and 1500$ cost of the VPX Pro/VPX power system. My question is this, when you remove the fact it replaces some items and the time spent wiring does is this a worth while product?
 
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Since this was something I was going to ask in my own thread I will ask here since its on topic. I was going to using something like the VPX in my build vs the traditional setup but then I saw the cost. The VPX kind of compares the cost of items it replaces but that doesnt add up to the 2100$ and 1500$ cost of the VPX Pro/VPX power system. My question is this, when you remove the fact it replaces some items and the time spent wiring does is this a worth while product?

Let's try this bit of math: Say you have 30 breakers. They are $36 at Aircraft Spruce, so that's $1080. And if you go the way Dan Horton suggested, it's much less yet. And what do you replace with a VPX in wiring? It seems to me you still have to run power wires from each load to somewhere - either the VPX or you breakers/fuses. The only extra with the fuses/breakers is busing the input power to them. And no hooking up a PC and "programing", no software to eventually reveal it's residue of bugs. Yes, if you add/reconfigure loads at some point, it may be more work with breakers or fuses, but I have also heard of folks running out of VPX outputs or outputs of the appropriate current capability too.
 
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Just me

Since this was something I was going to ask in my own thread I will ask here since its on topic. I was going to using something like the VPX in my build vs the traditional setup but then I saw the cost. The VPX kind of compares the cost of items it replaces but that doesnt add up to the 2100$ and 1500$ cost of the VPX Pro/VPX power system. My question is this, when you remove the fact it replaces some items and the time spent wiring does is this a worth while product?

I dont plan on using the VPX. I prefer to just run wires, and I can better understand wires and lines on a schematic.

I bought a 12 position fuse block from West Marine and think this is going to work out great. In addition to the fuse bus bar, it also has a grounding bus bar. Really SWEET.
 
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fuses

One thing to keep in mind about fuses:

FAR 91.205 (c) (6) requires that a set of spare fuses, or three of each size fuse, be carried, accessible to the pilot in flight.

Presumably the fuse holder must also be accessible to the pilot in flight - it doesn't make much sense to be able to reach the spare fuses but not be able to install one.

91.205 (c) applies to VFR-Night operations by powered aircraft with Standard Airworthiness Certificate.

In the experimental world, you might think this does not apply, and it does not apply to VFR daytime operations. However, at least my E-AB Operating Limitations do say that for VFR-Night operations, my aircraft must comply with FAR 91.205 (c).

I have to confess that I am not sure I would be able to access my fuse holders in flight. I think I can touch the one that has the fuses for the nav lights, strobe lights and landing light, but I don't think I could look at it and determine which fuse to replace. It would take quite a bit of contortion.

Just something to think about.
 
FAR 91.205 (c) (6) requires that a set of spare fuses, or three of each size fuse, be carried, accessible to the pilot in flight

Just something to think about.

Ok, I thought about it. Done.

I can reach all of them, but I'm not changing any of them in flight, in particular at night. If it blew, it blew for a reason.
 
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Ok, I thought about it. Done.

I can reach all of them, but I'm not changing any of them in flight, in particular at night. If it blew, it blew for a reason.

I agree. Especially something like lights. Not going to experience a mysterious transient and continue to function if a new fuse was installed.
 
Just me

So for me, the essential things are on circuit breakers accessible in flight. The fuses are non essential that allow continued flight with that component lost, such as autopilot, cabin lights, taxi lights, etc. I dont plan on changing fuses in flight either.
 
Go with Dan's suggestion!

The method of using a breaker/switch to control a sub panel (fuse block) is an excellent way to go. I have had a trouble free installation on my RV-10 for the last 10 years.

A 10 amp breaker/switch on my panel labeled Avionics, turns on a sub panel to which avionics of your choice are connected via blade fuses. The fuses are not accessible in flight and as has been said, if one of those blows, it will stay that way until I get on the ground. (None has ever blown in 700 hours of flying.)

If I need to unload electrical draw for whatever reason, I can either turn the individual equipment off or simply turn "avionics" off.

Simply put, you can install several breaker/ switches on the panel and install the blade fuse box anywhere for convenient electrical hook ups.

Modern electronics and sensors often need only 1 amp wire/fuse capacity but there are many of them and your valuable panel space need not be cluttered with these breakers or fuses.
 
Just me

So after this wonderful discussion, i am planning my circuit breakers to be:
PFD
MFD
Comm 1
Comm 2
Nav (VOR) (GNX 375)
Transponder/GPS (GNX 375)
G5 (back up attitude)
Audio Panel
Gad 29 dig converter (required for transponder)
GMU 11 (Magnetometer)
GAD 27 (Airframe data interface)
GEA 24 (Engine Data Interface)
GSU 25 (AHRS)
XM rcvr (gotta have music or there is no reason to fly; happy wife, happy life)
Alternator Field
Bus (Voltage sense for alternator)
Hobbs / low volt warning ( may be removed if panel layout looks funky)
Flaps
fuel pump
Pitot heat
Trim
Spare 1
Spare 2

Fuses will be:
Landing light left
Landing light right
Taxi lights
Strobe
Nav Lights
Panel lights
AP power
Defrost fans
Gad 27 keep alive power (only needed for engine start)
USB power
Test power input
Option 1 (CO detector??)

Fusible links will be
Bat current sense 1 (Engine side of firewall)
Bat current sense 2 (Engine side of firewall)
cabin lights (Engine side of firewall)
Starter (Engine side of firewall)

ANL fuses will be
Alternator
Main bus feed thru firewall

the reason for the shunt to be configured to measure battery charge and discharge is because I want to know if alternator is putting out enough power to supply load. I am using a pad mounted alternator as primary.

Thanks to all who have contributed to this discussion.
I reserve the right to change my mind over and over and over.
 
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This is not how I would do it.
Maybe you misunderstood?

Your lights need to be switchable and you might as well use a braker/switch on the panel so you can turn them on and off when you need them.
Flaps and fuel pump need a breaker and a switch on the panel as well.
Alternator Field too, 5 amp breaker switch.

(10 amp) breaker switch on the panel labeled avionics:
to energize a fuse block behind the panel
fuse:Comm 1
fuse: Comm 2
fuse: Nav (VOR) (GNX 375)
fuse: Transponder/GPS (GNX 375)
fuse: G5 (back up attitude)
Gad 29 dig converter (required for transponder)
fuse: audio panel ect.

( 10 amp) breaker/ switch labeled Instruments
to energize another fuse block behind the panel
fuse : your PFD etc.
you'll need a number of fuses to hook up all the items that light up and make
your PFD and MFD work, most drawing less than an amp.

10 amp breaker only for the items you want to come on as soon as you turn the master on. This can be one or two breakers, pullable if you choose and can be labeled simply Instrument1, Instrument2 etc. :

GMU 11 (Magnetometer)
GAD 27 (Airframe data interface)
GEA 24 (Engine Data Interface)
GSU 25 (AHRS)
XM rcvr (gotta have music or there is no reason to fly; happy wife, happy life)
Alternator Field
Bus (Voltage sense for alternator)
Hobbs / lo

Maybe someone with avionics and panel expertise will draw up a schematic for you.
How you arrange it is up to you, hope that helps
 
More thoughts on VP

Someone asked about VP on another forum about a week ago. Here was my response. Thought I would add it to this discussion..

Power Distribution in a little airplane is a pretty straight-forward proposition. We have a small number of circuits and we are sitting right in front of the panel. Remotely-operated electronic-circuit breakers are great in an airliner, but overkill for our little airplanes. The VP systems are a lot of complexity to do a simple task.

I realize that the VP systems do a little more than distribute power, but not enough to justify the cost. Here are my concerns.

VP systems are:
1. a complex solution to a simple problem
2. expensive
3. not serviceable by you
4. if it fails it could ground your airplane (all your eggs in one basket)

I know a couple of people who have VP hardware who are "tweakers". They really enjoy configuring things and continually making adjustments (tweaking), simply for the fun of it. If that's your game, then maybe VP is for you. VP offers a lot of choices & freedom to pre-program behaviors and inter-connect things.

When it comes to Power Distribution in my airplane, I want the simplest, most robust, closest-to-the-metal system I can get, especially since I plan to fly IFR. Good old circuit breakers get the job done with a price tag with one less zero. There are plenty of systems/gizmos in experimental aircraft to "tweak" but getting power to the panel should not be one of them.
 
Well

That is the great thing about experimental aviation; we can, and do, build what we want...and everybody has a different opinion of how to do it...
 
It seems the Garmin G3X system has a lot of fuses/ circuit breakers for the various boxes.
How do I combine the fuses / circuit breakers together to reduce the number in the system?

I use Dynon Avionics so my setup maybe different than your Garmin equipment. I only have two electrical circuits to cover the entire avionics equipment. I have one primary EFIS circuit dedicated to the primary EFIS + ADHARS + EMS. The second avionic circuit covers the rest of the avionics including radio, transponders, ADSB, and a smaller EFIS. The primary EFIS circuit uses about 1.3 - 1.6 amps. The second avionics uses slightly less current. The other electrical circuits are dedicated to servos, flaps, lighting, etc, but I consider them to be separate from the avionics. Because of the makeup of the Dynon EFIS, the ADHARS and EMS are powered up the moment the EFIS is powered so I can monitor the engine while starting. The rest of the avionics can be powered on after the engine is running.
 
I spent many hours studying this subject, I read Bob Nucknolls book and I'm firmly in the "Why would you ever reset a protection device that operated as intended" camp, and I'd certainly never do it in flight without checking things out first. The only exception being alternator fields, as someone else pointed out above. I have the two alt field CBs that I can reach in the cockpit, but everything else is on a fuse accessed from the forward baggage area. My forward and aft baggage lights share a single fuse, but otherwise every circuit has its own fuse, and I have eight expansion slots between the two busses.
 

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For those going the automotive blade fuse route, it's not a huge additional cost to use fuses with built-in LED failure indicators. These aid in quickly locating the blown fuse - look for the one that's lit up and replace it. This speed in troubleshooting is particularly useful in our small aircraft where we might have to "assume the position" in order to access and change a fuse.

One other important point for consideration. When installing automotive blade-style fuse blocks it's always a good idea to also install a device nearby which holds the fuse replacement tool. Sometimes those blade fuses can be devilishly difficult to remove from their holder; the proper tool makes it much easier.
 
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