Guidance on my electrical system

I am having issues doing the full design of my electrical system. I keep thinking I have it right, and then go back to find something missing.

Books that I already have:
The AeroElectric Connection - Bob Nuckolls
Aircraft Wiring Guide - Marc Ausman
VP-X Wiring Guide

And I found myself in the situation that Vertical Power warns you against right off the start: Don't begin wiring until you have a complete schematic. So I am trying to do that now, even though my equipment is selected, panel cut (including switches and indicators).

What I don't have, is a finalized Schematic, and someone to sit down with and ask me questions to make sure it is ok, nothing missing, and nothing stupid. I can do that here once I get a schematic to post, but I need some guidance on a few points.

My equipment relative to this question are (will be) as follows:
VP-X Pro
Dual Dynon SkyView
Electronic Ignition and Fuel Injection, making it an electrically dependent airplane
B&C 60 and 20-30 amp Alternators with LR3C-14 voltage regulators
12v LEDs with internal resistors (i.e. give them 12v, and they light up)

I also have a schematic sketch that B&C sent me to wire a low voltage LED instead of a lamp to their LR3C-14 (that they said came from Nuckolls' book).

On my panel, I have:
Alt Switch(On/Off/On): Primary / Off / Backup (wired to VP-X switches 2 and 3)
LED lamp: Primary Alternator OV
LED lamp: Backup Alternator OV

The VP-X does automatic OV sensing, and will kill the field switch for any Alternator that is on, when it senses an OV condition. But this leaves the pilot to switch from Primary to Backup. It also prevents both alternators from being on at once. My switch does this as well.

The SkyView will echo a VP-X alert if it senses an OV condition, but I was hoping for an external lamp (or lamps) for this specific condition, near the Alternator switch.

I can repurpose the two LEDs (the labelling isn't finalized yet) that I have to be OV and Low Voltage lamps, but I can't think of any way to wire them to be either, and work with both Alternator/Regulators.

Does anyone here have any suggestions or directions to point me in?

A proper response exceeds, in my opinion, this media's ability to facilitate.

For example, you do not discuss power distribution beyond the two alternators. If using the traditional single battery and master solenoid, then most likely both alternators will be off line if the master solenoid fails, or for that matter if the battery ground wire falls off. At that point your panel is dark and if not using an electronic ignition like pMag (provides its own power) you lose your engine as well.

Lock down the power distribution and the rest is plug and play.

Happy to discuss off line if desired.

Carl

Carl - There will be a second battery for sure. My question for now (until I can post my schematic) is limited to just my options for Low Voltage alert and Overvoltage alert LEDs:

1) Is there a way to wire an OV LED that will tell me if an alternator OV condition has been tripped.

2) Is there a way to wire a low voltage lamp to both regulators without causing an issue.

3) In the below diagram, I think it assumes an LED with no internal resistor. My LEDs do have an internal resistor (16.4 ohms). It also looks like pin 5 is pulling to ground in a low voltage condition, but I think it does that a bit always, hence B&C's warning to not just use an LED instead of a lamp, as it will always turn on. Does anyone know what Pin 5 of the LR314 is actually doing electrically in both the normal state, and in the low voltage condition?

The SkyView will give you a low voltage alert in your headphones. The B&C regulator will trip the 5amp regulator breaker on over voltage. When you get the Dynon alert you need only look at the primary alternator regulator breaker being open to verify.

So - set the primary B&C alternator for normal voltage output (14.1vdc). Set the standby alternator for 13vdc. Set the Dynon low voltage alert at 13.5vdc. This way if the primary alternator fails (over voltage or whatever), you get the SkyView audible alert "Voltage", the standby alternator (that normally just rides along with no output) picks up the load, and the standby alternator lamp goes on to tell you something is not normal. You check buss voltage holding at 13vdc or so, and fly on. Fix the primary alternator problem when you land.

This is the easy part of the power distribution design. The more complicated part is designing in fault tolerance. Right now you have mitigated only one fault - failure of the primary alternator. Look for any common point or component that if it failed would leave you in a less than desirable position.

Carl

Carl - Great advice, and now we are getting really close. One question on what you wrote. How do I wire the standby alternator lamp?

If I can wire an indicator to know which alternator is actually running, rather than having to deduce it, then I will be happy there.

cdeerinck said:

How do I wire the standby alternator lamp?

If I can wire an indicator to know which alternator is actually running, rather than having to deduce it, then I will be happy there.

Click to expand...

The B&C standby alternator regulator (model SB1B, not LR3C-14 as you state) provides instructions on how to wire the lamp - and they even provide the lamp. Follow the instructions. Both the primary (model LR3C-14) and standby alternator regulators (model SB1B) provide the over voltage protection, not your VPX, and both provide a lamp to tell you what is going on. I guess the VPX can be considered a back up to the back up.

There is nothing to deduce. If you have the SkyView and both alternators set up as discussed you have direct indication and audible alarms on what is going on. In short, there is no practical reason to add LEDs like you state in your original post.

I have no clue as to what, if anything, the VPX will do for you. I'll leave that to the VPX experts as I am not one.

Carl

Carl - I appreciate the feedback, but unfortunately you are guiding me to design around the VPX, and the VPX is kind of central to this aspect on my plane.

I should point out that I agree that without a VPX, what you are describing is a very ideal setup.

The VPX is wired into both alternators, watches the VSense, and controls the field wires. It monitors their voltage, prevents both alternators from being on at once, and allows me to test the backup alternator without the primary having to fail.

I will send an email to Chad Jenson, and ask to see if there is a way to provide an external indication of having either a OV or Undervoltage external indicator. Probably not, given that they are built into the SkyView screen, so I am probably being redundant.

cdeerinck said:

The VPX is wired into both alternators, watches the VSense, and controls the field wires. It monitors their voltage, prevents both alternators from being on at once, and allows me to test the backup alternator without the primary having to fail.

Click to expand...

Like I said Chuck, I'm no VPX expert but my reading of what the VPX does and does not do leads me to think you are still going to use the both B&C regulators. The VPX does not replace that function. It might open the regulator breaker on over voltage but the regulator already has a crowbar overvoltage protection circuit in it. On "the VPX does not allow both alterators on the buss at the same time" - this make no sense. Setting the aux regulator at 13vdc does this for you - with no additional circuits and the aux alt picking up load if the primary one fails is automatic - no pilot action.

You are going to use both the primary and secondary B&C regulators as I discussed. Do not use the same regulator for both alternators. B&C has already figured this out. The VPX is a minor player on this aspect. The last thing you want is for the VPX to trip both regulators on overvoltage. Testing the aux alternator is as simple as opening the primary alternator regulator breaker.

Please let me know if I'm off base on how what the VPX does and does not do.

Good luck,
Carl

Carl Froehlich said:

Like I said Chuck, I'm no VPX expert but my reading of what the VPX does and does not do leads me to think you are still going to use the both B&C regulators. The VPX does not replace that function. It might open the regulator breaker on over voltage but the regulator already has a crowbar overvoltage protection circuit in it. On "the VPX does not allow both alterators on the buss at the same time" - this make no sense. Setting the aux regulator at 13vdc does this for you - with no additional circuits and the aux alt picking up load if the primary one fails is automatic - no pilot action.

You are going to use both the primary and secondary B&C regulators as I discussed. Do not use the same regulator for both alternators. B&C has already figured this out. The VPX is a minor player on this aspect. The last thing you want is for the VPX to trip both regulators on overvoltage. Testing the aux alternator is as simple as opening the primary alternator regulator breaker.

Please let me know if I'm off base on how what the VPX does and does not do.

Good luck,
Carl

Click to expand...

I can't speak to the reasons why, but the VPX manual states to use only the LR-3C regulators, even if you have two B&C alternators starting on page 26, there are pretty detailed instructions on how to install two B&C alternators.

I would give Chad a call for clarification.

Hi Chuck,

You have some great advice and direction here so far. As Bob mentioned, please feel free to give me a call if you have any specific VPX questions that we can't get answered easily over email or forum posts.

The VPX was designed to be simple, and the LR3C is a simple and reliable VR, so it the VPX was designed to use it. Others can be used, but not all have been officially tested with the VPX.