Too Many Circuits? Need some input

WingsOnWheels · #1 11-25-2011, 01:02 AM

I have been working on my electrical system for a while and feel that I I may be making things more complicated than they need to be. So far I have quite a few separate protected circuits and am wondering if some of these should be combined. Looking at the panel layout of other builders I have yet to see so many breakers/fuses.

Here is my current list:

Main Bus:
Position Lights
Anti Colision Lights
Taxi Light
Landing Light
Alternator Field
Starter Contactor
Avionics Master / E-Buss Primary
Flaps
Pitot Heat
CD/DVD Player
Instrument Lights
Flood Lights
Aux Power Outlet
Autopilot Servos
Pitch Trim - On Stick
Defrost Fan
Primer Valve
Boost Pump
Main Spare 1 (Unused)
Main Spare 2 (Unused)

Avionics / E-Buss
Glareshield Lights
Audio Panel
Comm 1
Transponder
EFIS
GPS 1 (Portable / Dock)
GPS 2 / Comm2 (Panel) - Unused for now
Avionics Cooling Fan
Headset Power
Avionics Spare 1 (Unused)

Battery Bus
Hobbs
Battery Contactor
E-Buss Alternate Feed
DVD Player Memory

In case you lost count by now, that is 34 circuits including 3 spares. Also note that the Main/E-Bus split isn't 100% decided yet. I am planning a combined avionics / E-Bus with the expectation of manual load shedding as required. I'll happily take input on the main v. E-Bus breakout also, but that is not the main concern in this post.

Thanks,

Toobuilder · #2 11-25-2011, 08:02 AM

There's a few areas that could be eliminated (primer solenoid) or combined (some lighting), but it does not look too out of control to me.

rleffler · #3 11-25-2011, 08:11 AM

Quote:

Originally Posted by WingsOnWheels

I have been working on my electrical system for a while and feel that I I may be making things more complicated than they need to be. So far I have quite a few separate protected circuits and am wondering if some of these should be combined. Looking at the panel layout of other builders I have yet to see so many breakers/fuses.

While I admit, you've got me by a few circuits, the number of circuits doesn't bother me. The decision is whether or not you want that level of control and isolation or a less expensive implementation by using fewer breakers. There is no right answer, only the one the is best for your mission and comfort.

I've implemented a Vertical Power solution, which I would recommend taking a look at, it will make your life easier answering these types of questions. But my point of mentioning this isn't to convince you to go down the VP route. Take a look at their installation guides on either the VP-X Pro or the VP-200. They do a very good job of walking you through these issues that you are struggling with. After reading them, I think you'll be better prepared to answer your own concerns yourself.

I would recommend taking a look at what you MUST have when you have an electrical issue, not necessarily what your would LIKE to have. It will make the design easier. Also, many don't have an E-Buss and a Battery bus.

SmilingJack · #4 11-25-2011, 08:28 AM

I have 1 C/B in my airplane - its a 60 amp breaker for the alternator. The rest are protected and controlled by my VP.

bruceh · #5 11-25-2011, 11:23 AM

You could easily eliminate the CD/DVD player and just get an iPad/iPod and plug that into the AUX power jack. You sure have lots of lights! Flood, taxi and landing could be simplified. Glareshield and instrument lights could be combined (flashlight as a backup?)

+1 for the VP-X. I'm using the Sport model (simple VFR) and this makes some things much simpler (flaps, trim). If nothing else download the installation manual and play around with their online planner. Lots of great information there.

WilburD2 · #6 11-25-2011, 12:02 PM

Colin, no offense but it looks like you're planning on being able to watch inflight movies while flying night IFR in the dead of winter.. Is that your plan?
Also, shouldn't the starter contactor be on the BATT bus? Main bus is useless if the engine won't start.
I also agree with Bruceh. Except I would combine floods and glareshields and re-label that one emergency or backup lights.
Are you planning a glass cockpit or a mixture? If a glass one, why would you need instrument lights? If you're going with backup gages, they too can go on the same circuit as the backup lights. Just my opinion of course

"[i]The more they overthink the plumbing, the easier it is to stop up the drain[i]"
Capt. Montgomery Scott
ST-III TSFS

Ironflight · #7 11-25-2011, 03:05 PM

If it were me, I'd combine much of the interior and exterior lighting on a fewer number of circuits - likewise your fans. None of those should be flight critical. All those exterior lights might have potential for combination as well. Think in terms of what is CRITICAL to your continued flight, and don't put critical backups on the same circuit, and you'll be fine.

Paul

Bevan · #8 11-25-2011, 04:14 PM

Individual power and ground wires to each device is a circuit. If that circuit has it's own fuse or breaker, it is isolated from the others and is truly independant in terms of power distribution. Because you can pack many circuits into a small space (with the use of a fuse block and forrest of grounds), individual fuses for each device makes the wiring simpler to follow. Troubleshooting and modifications in the future may be easier too. There may be a bit more wire (weight, but not much) but I think it is worth it on these small "one-off" machines.

I have even a few more circuits than you have there.

Bevan

WingsOnWheels · #9 11-25-2011, 09:20 PM

Thanks everyone for your input, it has been very helpful.

To address a some of the comments:

Bob: I did consider a VPX system, but can't justify the price tag for me. A great looking system though. I will take a look at the system planner they created.

Michael: To eliminate the extra circuit for the Primer, did you combine this with the fuel pump (would make sense since the pump has to be on for the primer). Great idea, thanks.

Bruce: I have a space on the pilot side of my panel for a portable GPS or tablet. The DVD player is strictly for my wife (not a real happy flyer) and is all the way to the right on the panel. The DVD has a pop-out screen so it uses very little panel space when the screen is retracted. You are right, and I will combine some of the interior lights, no need for three circuits.

Bill: I guess it depends on the movie..haha, just joking. To clarify, the battery buss is on the batter side of the contactor so it is always hot. The main buss is energized when the battery contactor is closed. So you can't crank the engine until the Master is turned on. As far as I know this is standard practice...I could be wrong though.

Paul: You bring up some good points. Since I have made the E-Buss an Avionics buss I was having a hard time deciding what goes where. I intended the avionics fan to be unswitched and come on when the Av buss was powered (hence the separate circuit from the defrost). That brings me to another point; does anyone have a defrost fan? does it work?
For the lights, the taxi and landing are on the opposite wing tips and I am concerned about those long wire runs and high current draw. I'll have to recheck my numbers and see if they can be combined. Interior lights can and will be combined.

Bevan: This is the same thinking I went in with. When I started to lay out where all the circuit protection devices were going to fit I becan to realize that I need some large fuseblocks or a sea of circuit breaker. I need to cut down a bit to save some space.

Ironflight · #10 11-25-2011, 09:42 PM

One thing to consider with unswitched loads (like the avionics fan) that are non-critical is to simply use a fuse - inline, or a small block for those items. If it truly never needs to be switched off when the bus is on, then the circuit protection is "pure" protection, and a fuse is fine. Certainly saves the space of a breaker.

Paul