Z-101
 

I'm a fan of Z-101 because endurance is fuel range (battery capacity is not a factor) and alternator capacity is over 30A with master contactor open (Bob also has an 8A version of Z-101). This is especially important with EFI+I current requirements. I spoke about Z-101 recently on VAF here. If interested, my files are linked in my signature. Full disclosure... Bob Nuckols calls Z-101 Preliminary at this time.

I learned a great deal recently on the AeroElectric List. There are some frustrations with fragmented threads which may be why I didn't have complete success using the search function on the site or Google. After subscribing several months ago I learned a lot in addition to what I have read in Bob's book over the years and recently when Z-101 came out I adopted it for my EFI+I equipped RV-6A (not flying yet). Beware, no love for ECBs on AEL.

I'm following Bob's and FAR 23.1361 advice to keep power distribution wires that don't have a remote switch (relay or contactor) close to the source (battery) fused at 7.5A or less. This has implications in maintenance, smoke in the cockpit, and crash scenarios. Attaching the backup alternator B lead to the battery without a relay violates this... one can either justify this that with vacuum pad alternators the alternator is close to the battery or one can add a B lead relay adjacent the battery. Automotive service manuals say first thing, disconnect the battery minus cable.

When I say battery bus I mean the fuse block; fuse block and bus are synonyms in this case.

The B&C aux alternator controller was designed for TC aircraft and has a light that illuminates if the voltage drops due to primary alternator failure causing the aux alternator to come alive. But modern EMS systems will tell us the voltage has dropped. I found my Bob quote:

"If the bus voltage drops below the AUX controller set point, the AUX alternator wakes up and a SPECIAL
circuity within the controller senses this and illuminates an ALTERNATOR LOADED light. The stand-by versions of the alternator controller are not recommended for simple dual alternator installations where the auto-switch feature is not necessary . . . this was a 'bell-n-whistle' aimed primarily at the
STC market for TC aircraft that were receiving the pad driven, aux alternators.

... Bob"

The 5x20awg wires from the firewall ground bus to the avionics ground bus are described in Chapter 18 of Aeroelectric Connection. Note 23 in the appendix, which is called out on the dwg adjacent the avionics ground bus, points to Chapter 18. In Bobspeak the (instrument) panel ground bus is the forest of tabs on the aft side of the firewall and the avionics ground bus is on the IP subpanel.

In a smoke in the cockpit situation the progressive switch for the main bus and alternator makes sense because to de-power the main bus you need to de-power the main alternator. If the aux alternator is on the main bus and switched on I image it would come alive in time to keep itself powered but don't quote me on that but it doesn't matter because your gonna want it off because you want the main bus cold. Keep in mind Z-101 puts the aux alternator on the battery.

With Z-101 I plan to keep the aux alternator on in flight; if the main alt fails I will get an EMS message; if I open the master contactor I won't have to remember to turn the aux alternator on. If using the Ford aux regulator I'm not sure what's wrong with keeping it on but I believe there are low-cost adjustable automotive regulators. I plan on a B&C "primary" regulator set at 13.8V for the aux alternator because I'm not being as frugal as Bob and I like the OV protection.

Yes the aux alternator will come alive with Z-12 or Z-101 if it is switched on after the main alternator fails because the battery is there to energize the field; I the case of Z-12 the master contactor is still closed so the main bus sees the battery; in the case of Z-101 the the aux alternator field is connected to the battery bus so it will come alive even with the battery contactor open.

Keep in mind the AeroElectric Connection book is not updated as often as the drawings at http://www.aeroelectric.com/PPS/Adob...itecture_Pdfs/

Changes I made to Z-101:

• Renamed clearance delivery bus to avionics bus and fed it from opposite ends from battery bus and main bus versus using a single post on the bus.
• Put com 1 on the engine bus with the idea if you kill both the main and avionics busses, you?ll still have a radio.
• Added electronic fuel injection and ignition components.
• Added Crowbar Test buttons to main and battery regulators for annual.
• Used B&C LR3C regulator for battery alternator versus generic Ford.
• Alternator B leads: Used MIDI current limiters versus fuselinks.
• Aux alternator switch is progressive.
• I show an optional aux bus B lead relay.
• Battery contactor is a low coil current version.
• Diodes are schottky.

Even Bob doesn't follow that advice. Z101 attaches the backup alternator's 10 AWG B-lead to the battery, using a 14AWG fusible link for circuit protection.



It is electrically the same as this:



Note that Z101 uses the generic Ford regulator, not the nice B&C with OV protection. The sense terminal is simply jumpered to the field terminal (S to A), so sense and field see the same voltage, taken from the battery bus. Mike's earlier drawings incorporated a B&C regulator, and took sense (and a light) from the main bus while taking field from the battery bus. That won't work with the main contactor open. So, move the sense/light source to the battery bus, same as the field. While there, arrange the ANL so it provides circuit protection for both the alternator B-lead and the battery bus feed through the firewall. It's the same as Z101, but allows the use of the fancy regulator.

Previous post...


Slightly different subject...the addition of circuit protection between the contactor and the main bus. There's none in Z101. The argument seems to be that it's protected by the presence of the master contactor...just open the contactor if that supply wire or the main bus is shorted to ground.

Yep, old school, and it works...but it goes against human nature. When the spit hits the fan, I submit that most GA pilots go all deer-in-the-headlights, and hesitate to open the master. It's a natural aversion to turning off important things in flight. With circuit protection, a shorted bus is shut down automatically, no pilot participation required...and with this system it doesn't shortchange anything to do so. The avionics remain live, the ignitions still ignite, etc.

BTW, for purposes of diagramming at this level, I don't care if I draw in an ANL, a MIDI, a fusible link, or a paper clip, as long as the final choice is reliable in normal use, and burns open at the right amps when things go abnormal.

Thanks for the great response John.

Thanks for the clarification on the battery bus...got it.

So it looks like Bob doesn't think the B&C standby regulator is necessary on a non TC aircraft.
You mentioned using the LR3C as a back up regulator and adjusting the set point a little lower so it will bring on the AUX ALT automatically. Is there a reason not to use the B&C SB1B standby regulator? Same price...

Just a technical point (excuse my ignorance). If voltage indication to the EMS is all we need (I'm OK with that). How does that voltage info get to the EMS? (I'm sure this is a head slapper)

I went back and re-read chapter 18 about the avionics ground bus being a female D-sub connector. This info didn't sink in on the first read but it's brilliant! I've already pencilled this in.


Thanks again for helping me get through this steep learning curve.

Great thoughts on the ANL to protect the main and battery buses. How would one size them? Now that I know what an ANL is :rolleyes:, I've spent some time looking at ANL holders at B&C.

Thanks for all the help

The LR3C:

• Flashes a light, if you install the light, if the voltage falls to "typically between 12.5 and 13 volts".
• The light would not illuminate if the standby alternator was online because the voltage would not fall that far.
• Has provision for a battery temperature sensor that is not used if the battery is in the engine or passenger compartment.
• Has provision for a crowbar OV test button.

The SB1B:

• Illuminates a light, if you install the light, if the bus voltage falls and the standby alternator comes alive.
• The light flashes above 20A if you install the optional hall effect current sensor but you may not want this to happen since the smaller "20A" B&C alternator puts out a little over 30A at cruise RPM.

Now that I think of it, it seems nice to have the SB1B with its "Standy Alt On" panel light feature since we don't need the battery temperature sensor feature of the LR3C.

P.S. The installation manuals say not to use an LED for the light but if you want to you can do this.

P.P.S. Bob Nuckolls says the standby alternator should be set higher than the 13.0V B&C mentions in the install manual. Bob suggests 13.5 V.

Any EMS would have a voltmeter input. I'm using Dynon Skyview; it has two voltmeters. In the Skyview installation manual the key words to search for are:

• "Voltmeter Inputs" where it tells you what pins to connect to.
• "Manual EMS Sensor Settings", then the example happens to be a voltmeter.

The usual. Max expected current plus some, protecting a wire which will carry a little more.

Made a sloppy error on the previous drawing. This one corrected. Eliminates the fusible link in the primary alternator B lead, at the start contactor in Z101. Which is not to say I have something against fusible links. I don't; they are compact and reliable, and particularly useful in small wires as an inline fuse. For larger amps, I'd rather have the ANL or similar, and the post mounting base is real handy for large junction terminations.



Primary power block diagram. It's a simple system really. Make a short-and-open list for the numbered wiring, check for critical failure modes.

Z-12 is at rev N dated 05/03/2020
 

I'm still a fan of Z-101 but FYI Z-12 was revised to rev N on 05/03/2020. Find it here.

Compared to rev M:

• Clearance delivery bus is remotely switched and fed by a fuselink versus a 7.5A fuse.
• Dual alternator B lead shunts are replaced with a single hall effect sensor.
• Main alternator ANL is replaced with a fusible link.
• No CBs on the main bus.
• Mag and EI are not shown.

Battery bus and clearance delivery bus are optional, that's why they are in color.
You can delete the hall effect sensor for the aux alternator regulator.
Well, you can do anything you want!
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Simplify-Simplify And Standardize
 

This has been a real learning experience coming up with an electrical architecture for my -7.

Here are some of the things that have driven me to this current design.

1. It dawned on me - I have a 6ah back-up battery for the important stuff
   
2. I don't like the expense, weight and complexity of the AUX ALT
   
3. I like the idea of a clearance delivery bus.
   
4. I respect the idea...but I like an avionics bus :D
   
5. I rediscovered the adage - build it for you ;)

So, here's my latest attempt: DWG F103

PS: I forgot the ANL to the battery bus but it will be there.

What is the function of the 10amp breaker feeding the avionics bus? This places a breaker in series with the the avionics load breakers risking a single fault on the avionics buss taking down the entire buss. If you are worried about a unprotected wire run (which you have many), consider bumping this 10amp breaker to 20 or 25. That way you have some confidence the downstream breakers will pop first on a fault.

The battery bus should be ?the last line of defense? while flying. For example external power depended ignitions and such. Strobes and boost pumps do not meet that criteria. For pMags and standard fuel systems (carb or fuel injected) there is no need for a battery bus.

Now consider two avionics busses - this provides for your clearance deliver objective and well as capability to isolate a fault and still have half of your panel (as in Comm1 + EFIS 1, Comm 2 + EFIS 2). Power these busses from the output of the master relay, not from the main buss. I note your TCW backup battery. You could use that to power one of the avionics busses for your clearance deliver function. It would also be a good way to verify it really works before you have a hard need when flying.

The #6 wire feeding your main buss is way too big for those loads. Save some weight.
Carl