My wiring diagram with VPX and EFII componets

[219PB]

A thread was started by Scott Balmos earlier to encourage members of this forum to review his electrical diagram for his aircraft. I am at the same point in my build and it inspired me to get my drawings done.

The aircraft will be using the EFII’s fuel injection and dual ignition systems integrated with the VPX system. The review of Scott’s diagram made me think differently of my original designed system. My diagram is at a point that I want to encourage others to review my diagrams and give me feedback.

I have elected to have an electrical dependent aircraft with dual fuel pumps, ignition systems and alternators. I have three busses; main through the VPX, Essential for the engine and a Battery Buss for an alternate power for mission critical components in the event of a VPX failure.

in the event of a software failure, I plan to carry a Stratus and iPad along with a portable radio for additional redundancy.

https://www.dropbox.com/s/huean6xr27...0Rev2.pdf?dl=0

This is my latest drawing

N219PB rev4

[gfb]

What did you use to design your diagram?

[219PB]

AutoCAD.

I converted it to a pdf so that anyone would be able to view. Did it view OK?

[rv7charlie]

1st thing I saw was the fuses on the alternators. Circuit protection on an alternator that's a lower current rating than the alternator's output ability is asking for nuisance trips (blown fuses). Maybe a low probability, but an undercharged battery or other unforeseen high demand situations can max out the demands on an alternator, driving it to full or even above full rated output. Best practice is to size wire for significantly higher current than alt's rating (most can do more than their rating), then fuse to protect the wire.

2nd, what type alternators? If internally regulated (don't see external regulators in drawing), and they aren't diode isolated, they will likely fight each other's regulating ability. Regulators are available that have setpoints far enough apart to avoid this; other options are available if using internally regulated alternators.

3rd, I know nothing about the EFI buss manager, but I see only one Power path feeding the essential buss/engine controller components. Is that correct? If so, it's a single point of failure on 'essential' stuff.

4th, overvoltage protection??

Do you have the Aeroelectric Connection book?

Charlie

[219PB]

Originally Posted by rv7charlie

1st thing I saw was the fuses on the alternators. Circuit protection on an alternator that's a lower current rating than the alternator's output ability is asking for nuisance trips (blown fuses). Maybe a low probability, but an undercharged battery or other unforeseen high demand situations can max out the demands on an alternator, driving it to full or even above full rated output. Best practice is to size wire for significantly higher current than alt's rating (most can do more than their rating), then fuse to protect the wire.

I am not sure which fuses that you are speaking of. I have a 60 amp shunt for the 60 amp alternator and a 30 amp shunt for the 30 amp alternator. I purchased both of them from B&C with the alternators at the same time. The 5 amp fuses are for the alternator field circuit.

2nd, what type alternators? If internally regulated (don't see external regulators in drawing), and they aren't diode isolated, they will likely fight each other's regulating ability. Regulators are available that have setpoints far enough apart to avoid this; other options are available if using internally regulated alternators.

They are both externally regulated alternators. For this schematic I did not include. I will continue to develop the drawing. They are not isolated. I am choosing to keep them manually activated. I could have purchased the regulators with different voltages so that I could have left both on but decided that I could manage. The reason for having two toggle switches instead of a SPDT is so that when the aircraft is shut down I can run my hand along all switches and they should be down. My plan is to cycle through the alternators curing startup to verify both are operating and run on the 60 amp alternator. If I get a low voltage alarm, 12.5 volts, I will look at the screen, take my time because there is no immediate threat that requires split second decisions, switch off the primary alternator and activate the 30 amp alternator.

3rd, I know nothing about the EFI buss manager, but I see only one Power path feeding the essential buss/engine controller components. Is that correct? If so, it's a single point of failure on 'essential' stuff.

The Bus Manager has a bypass switch internal to it that connects the essential bus to the battery lead coming in to the unit. That is the Emergency Bus switch on the side of the Bus Manager. A neat feature of the Bus Manager.

4th, overvoltage protection??

The external regulators from B&C have the overvoltage built in to them.

Do you have the Aeroelectric Connection book?

Yes, I have Bob's book. A lot of good information. I tried to incorporate his philosophies into my design but some of the new electronic hardware that is available now is not described in his books so you cannot go directly from the book.

Charlie

Thanks for your review. Please let me know if these responses adequately addresses your comments. They are most appreciated.

[DanH]

Perhaps it would be best if you would verbalize exactly why the system is arranged this way.

What do you wish to achieve, why did you select particular components, and why are they connected as they are?

[219PB]

Dan,

Here are planning thoughts on designing my electrical system. My aircraft?s mission is to fly primarily VFR. I do plan to expand my radius beyond the 300 miles that I normally kept with my Cessna 150. My 150 was IFR certified but I never got my ticket. I should have. With that said, I am not going to install the systems necessary for this aircraft to fly IFR until I know that I will be committed to taking the training. I will leave room in the panel for a certified WAAS GPS.

I decided to incorporate electronic fuel injection for ease of engine starting and operation (no mixture control). If I realize some fuel savings, so be it. My goal is not to squeeze every last horsepower out of the engine. The Lycoming 360 will make slightly over 180 hp. Electronic ignition is another good technology that I also want to embrace. I have had a few instances of Slick mag problems in the past. They were not dramatic events, just cost me money. Both of these technologies will make the engine easier to operate and run smoother in my opinion.

For my fuel injection and ignition systems I have decided to go with the EFII?s components. There are many different systems to choose from and there are plusses and minuses to all of them. With that said, my aircraft will be electrically dependent.

I am choosing the EFII?s Bus Manager for its capability to switch on the main and essential bus and switch the fuel pumps if the fuel rail pressure degrades. I believe that the electronic relays are more reliable that traditional master solenoids. The capability of the Bus Manager to switch the fuel pumps is a good capability as I would have to install additional components to perform this function. I do not want to have to have a pilot?s intervention necessary for this function. It needs to happen instantaneously. The system will give me an alarm stating that the switch has been made.

The Bus Manager has two internal busses. The essential bus is dedicated to run the engine components. It has an internal bypass switch in the event that its electronic relay fails. The main bus feeds all of the other components through the VPX system.

I have chosen the VPX system for its electronic circuit breakers and simplicity of installation. It also has many other features that integrate flap control, wig wag of the lights, etc.

In the event of a VPX failure I have identified components that I feel are necessary for flight. The Battery Bus Bar provides an alternate power source for these components. I am planning my panel so that these emergency backup switches and the switches necessary to start the aircraft are going to be in the upper left hand corner of the panel. The switches that are associated with the VPX will be along the bottom of the panel and will be used during flight operations.

I have elected to install a backup alternator in lieu of a backup battery. I know that I could do both but I have not heard of a battery failure in flight that caused an aircraft to go down. A battery failure typically will not allow the engine to start and that is a problem on the ground. An alternator failure in flight will give me a low voltage alarm, not an immediate emergency. I will be able to switch off the primary and activate the backup. I could put in an alarm that would sound if both field wires are on at the same time or install regulators with different voltage set points. My thought process at this time is to keep the alternator selection simple and manual.

Again, thanks for your review.

[rv7charlie]

The dropbox diagram shows 40A & 30A fuses on the two alternator outputs.

If you're using B&C alternators/regulators, you have the option to use their 'backup' regulator, which allows both alternators to be on line at the same time, ensuring that if one drops out, the other is already active (and you get notification if you lose one). That way, the alternator field controls can be simple circuit breakers that are left on all the time during normal operations, just like a car. Advantage: lower workload for crew. Personal preference, but I actually like the fact that I can ignore the electrical system in my car unless there's an actual problem. :-)

If I'm reading the diagram correctly, it looks like there's a lot of extra switching to supply alternate feeds to non-essential stuff like radios, landing lights, etc from two sources (VPX Sport or Battery Bus), but no truly independent alternate feed to the essential (engine) bus.

Again, I know nothing about the EFII Bus Manager...But I see only one power path from the alternators/battery through the bus manager to the engine DC power bus. Does the 'Emerg Pwr Ess Bus' switch actually tie the B+ from the manager power input directly to essential bus bar (meaning that it's a >20A switch), or is it a low current switch that controls a relay inside the manager? If the latter, then the bus manager is still a single point of failure. A workaround would be a high current switch that can tie the battery bus & essential bus together, giving an alternate DC path to the essential bus.

I'm setting up an electrically dependent engine, too, and I'm looking at ways to get the two alternator feeds into the engine bus on separate wires, so a single failure (wires & especially, crimped terminals can fail) won't take out the engine.

Hoping the above is helpful, and not just picking nits....

Charlie

[219PB]

Originally Posted by rv7charlie

The dropbox diagram shows 40A & 30A fuses on the two alternator outputs.

I must have uploaded an earlier version of my file. I corrected that to show 60A and 30A for the primary and backup. I will update the file tonight. My bad.

If you're using B&C alternators/regulators, you have the option to use their 'backup' regulator, which allows both alternators to be on line at the same time, ensuring that if one drops out, the other is already active (and you get notification if you lose one). That way, the alternator field controls can be simple circuit breakers that are left on all the time during normal operations, just like a car. Advantage: lower workload for crew. Personal preference, but I actually like the fact that I can ignore the electrical system in my car unless there's an actual problem. :-)

I spoke to B&C about this and you are correct, this would make it just like a car. My current understanding of that system is that it is totally automatic and I would not be able to cycle the alternators manually. My plan is to cycle each alternator right after starting the engine and verifying oil pressure. That way I will know at the start of each flight both alternators are functional.

If I'm reading the diagram correctly, it looks like there's a lot of extra switching to supply alternate feeds to non-essential stuff like radios, landing lights, etc from two sources (VPX Sport or Battery Bus), but no truly independent alternate feed to the essential (engine) bus.

Again, I know nothing about the EFII Bus Manager...But I see only one power path from the alternators/battery through the bus manager to the engine DC power bus. Does the 'Emerg Pwr Ess Bus' switch actually tie the B+ from the manager power input directly to essential bus bar (meaning that it's a >20A switch), or is it a low current switch that controls a relay inside the manager? If the latter, then the bus manager is still a single point of failure. A workaround would be a high current switch that can tie the battery bus & essential bus together, giving an alternate DC path to the essential bus.

The Emerg Pwr Bus switch is a >30A rated switch that carries the full load of the essential bus. It ties the batt 1 connection directly to essential bus connection on the Bus Manager. It basically bypasses the Bus Manager.

I'm setting up an electrically dependent engine, too, and I'm looking at ways to get the two alternator feeds into the engine bus on separate wires, so a single failure (wires & especially, crimped terminals can fail) won't take out the engine.

Hoping the above is helpful, and not just picking nits....

Charlie

You are not nit picking. It is the back and forth comments that enable clear communication.

[rv7charlie]

The low voltage monitors from B&C should let you know if either alternator is off line, but you could also still control the alternators manually with 'pull-able' field circuit breakers or better, CB switches.

If the bus manager dies, what's the alternate DC feed to the fuel pump(s)?