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wgreenley
Joined: 09 Jan 2010
Posts: 100
Location: Dowagiac, MI
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 Posted: Sat Dec 10, 2016 9:10 pm Post subject: Z-12 questions |
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Building an RV-10 and working on wiring following Z-12 with 60 amp main alternator from B & C, and 30A backup alternator also from B&C. Planning on using the mythical 6-cyl P-Mags, but in the meantime will be setting up shower of sparks as I have that on hand. A couple of questions regarding switches. As I look at the endurance bus, I am trying to figure out what is an appropriate switch to use, I am looking at putting the GTN 650, a G3X display, flap motor, fuel pump, and landing lights on the endurance bus. While the 650 can be a large draw, that is only while transmitting, similar with the fuel pump and flap motor. Lights would only be for a few minutes on landing. But in total these could be a large draw for short periods of time, what is an appropriate switch to use for the endurance bus, typical toggle switches I see are rated at no more that 15 – 20 amps. I really don’t want to use one of the pull switches.
A similar question for an avionics bus, while I know this is not needed to protect the avionics, I have been advised it is a good idea so that there is minimal battery drain while starting the plane, after start you flip the avionics master to turn on the majority of the avionics. Some items like one display, and the engine sensors would be powered on with the main battery switch. It seems like this switch could be asked to handle a lot of amps, with radio, transponder, etc. What are your thoughts on an avionics bus for this reason, and also what is an appropriate switch to use?
Bill Greenley
Build an RV-10 in SW Michigan
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donvansanten(at)gmail.com
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| Posted: Sat Dec 10, 2016 10:45 pm Post subject: Z-12 questions |
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William,
The EBus should be switched with a relay. The avionics switch is not a good idea as it introduces a single point of failure. I believe that you might be misunderstanding the EBus concept. It is designed to power only essential items such as in an electric ac one efis one com and maybe the pmags. The idea is that you can easily reduce the electrical load such that the available fuel is the only determining factor as to when you will need to land. Switching the master off reduces the load to the point that your standby alternator can power the remaining load till you arrive at your destination. You could then switch the master back on and hve your entire panel for the landing. Fuel pump and flaps are not required for cruise flight although they do draw any current when switched off, so they are not against the EBus concept. Hope this helps. I have an RV7 with Z12-8 from day one and it works perfectly as designed. My standby alternator is the B%C SD8.
On Sat, Dec 10, 2016 at 9:09 PM, William Greenley <wgreenley(at)gmail.com (wgreenley(at)gmail.com)> wrote:
| Quote: |
Building an RV-10 and working on wiring following Z-12 with 60 amp main alternator from B & C, and 30A backup alternator also from B&C. Planning on using the mythical 6-cyl P-Mags, but in the meantime will be setting up shower of sparks as I have that on hand. A couple of questions regarding switches. As I look at the endurance bus, I am trying to figure out what is an appropriate switch to use, I am looking at putting the GTN 650, a G3X display, flap motor, fuel pump, and landing lights on the endurance bus. While the 650 can be a large draw, that is only while transmitting, similar with the fuel pump and flap motor. Lights would only be for a few minutes on landing. But in total these could be a large draw for short periods of time, what is an appropriate switch to use for the endurance bus, typical toggle switches I see are rated at no more that 15 – 20 amps. I really don’t want to use one of the pull switches.
A similar question for an avionics bus, while I know this is not needed to protect the avionics, I have been advised it is a good idea so that there is minimal battery drain while starting the plane, after start you flip the avionics master to turn on the majority of the avionics. Some items like one display, and the engine sensors would be powered on with the main battery switch. It seems like this switch could be asked to handle a lot of amps, with radio, transponder, etc. What are your thoughts on an avionics bus for this reason, and also what is an appropriate switch to use?
Bill Greenley
Build an RV-10 in SW Michigan
|
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wgreenley
Joined: 09 Jan 2010
Posts: 100
Location: Dowagiac, MI
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| Posted: Sun Dec 11, 2016 6:03 am Post subject: Z-12 questions |
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My thinking on the ebus was that the radio has a very small draw when not in use, and the flaps, landing light and fuel pump have zero draw. Having them on the ebus would allow their use for landing in case of master contactor or switch failure, if not for that failure mode, the need for the ebus would be if both alternators fail. Wonder which is more likely.
On Sun, Dec 11, 2016 at 1:33 AM, don van santen <donvansanten(at)gmail.com (donvansanten(at)gmail.com)> wrote:
| Quote: | William,
The EBus should be switched with a relay. The avionics switch is not a good idea as it introduces a single point of failure. I believe that you might be misunderstanding the EBus concept. It is designed to power only essential items such as in an electric ac one efis one com and maybe the pmags. The idea is that you can easily reduce the electrical load such that the available fuel is the only determining factor as to when you will need to land. Switching the master off reduces the load to the point that your standby alternator can power the remaining load till you arrive at your destination. You could then switch the master back on and hve your entire panel for the landing. Fuel pump and flaps are not required for cruise flight although they do draw any current when switched off, so they are not against the EBus concept. Hope this helps. I have an RV7 with Z12-8 from day one and it works perfectly as designed. My standby alternator is the B%C SD8.
On Sat, Dec 10, 2016 at 9:09 PM, William Greenley <wgreenley(at)gmail.com (wgreenley(at)gmail.com)> wrote:
| Quote: |
Building an RV-10 and working on wiring following Z-12 with 60 amp main alternator from B & C, and 30A backup alternator also from B&C. Planning on using the mythical 6-cyl P-Mags, but in the meantime will be setting up shower of sparks as I have that on hand. A couple of questions regarding switches. As I look at the endurance bus, I am trying to figure out what is an appropriate switch to use, I am looking at putting the GTN 650, a G3X display, flap motor, fuel pump, and landing lights on the endurance bus. While the 650 can be a large draw, that is only while transmitting, similar with the fuel pump and flap motor. Lights would only be for a few minutes on landing. But in total these could be a large draw for short periods of time, what is an appropriate switch to use for the endurance bus, typical toggle switches I see are rated at no more that 15 – 20 amps. I really don’t want to use one of the pull switches.
A similar question for an avionics bus, while I know this is not needed to protect the avionics, I have been advised it is a good idea so that there is minimal battery drain while starting the plane, after start you flip the avionics master to turn on the majority of the avionics. Some items like one display, and the engine sensors would be powered on with the main battery switch. It seems like this switch could be asked to handle a lot of amps, with radio, transponder, etc. What are your thoughts on an avionics bus for this reason, and also what is an appropriate switch to use?
Bill Greenley
Build an RV-10 in SW Michigan
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Sun Dec 11, 2016 10:37 am Post subject: Re: Z-12 questions |
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Minimizing battery drain during engine cranking is not a valid reason to have an avionics switch. Avionics use very little current compared to the starter motor. A better way to improve starter performance is to use larger wire size. An avionics master switch is an unnecessary failure point.
Use an automotive relay located near the battery to power the E-bus. A small panel mounted switch can control the relay. Relays have the advantage of remote control and larger current carrying capacity. Search for relay part number 1432793-1. It is rated for 40 amps, costs less than $5, and has a built-in diode for arc suppression. The diode arrow should point towards positive or else it will self destruct.
Here is a link to a circuit that you might consider:
https://drive.google.com/file/d/0B7ZTG2VpCuDRSVNVa3JwUmFuMzQ/view?usp=sharing
The E-Bus will not draw power from the main battery during engine cranking. The small brownout battery will prevent E-Bus voltage sagging during engine start. Thus avionics will not reboot.
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nuckolls.bob(at)aeroelect
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| Posted: Sun Dec 11, 2016 10:55 am Post subject: Z-12 questions |
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At 07:54 AM 12/11/2016, you wrote:
| Quote: | | My thinking on the ebus was that the radio has a very small draw when not in use, and the flaps, landing light and fuel pump have zero draw. Having them on the ebus would allow their use for landing in case of master contactor or switch failure, if not for that failure mode, the need for the ebus would be if both alternators fail. Wonder which is more likely. |
Your throwing a lot of rocks into the electro-gearworks . . .
First, the E-bus is an ENDURANCE bus originally intended
to offer a simple, plan-B approach to MINIMIZING loads
on limited energy resources for the en route phase of
flight.
The idea was that should the ONLY engine driven power source
become unavailable, then it's entirely possible and
practical to plan for continued, comfortable flight to
airport of intended destination (or a similarly
friendly one where repair resources are available).
In other words, inoculate your system against the
'dark-n-stormy-night' syndrome.
As originally proposed, the E-bus would let flyers
continue with RUNNING LOADS as small as a few amps
with a goal of reaching friendly concrete.
Over the years, the E-bus has been badly mutated
into a collection of band-aids that go to addressing
very unlikely if none existent worries. Worries easily
address by consulting gray-beards here on the List
and deciding just what devices are must useful for
meeting the ENDURANCE mode design goals.
Z-12 was the next evolutionary step for replacing
a pieces-of-(at)#$# generator on Bonanzas with an
alternator having about 4-5x the output and 100x the
service life. . .
It was never being suggested as the elegant solution
for a clean piece of paper design. I'm not suggesting
that it's not going to perform as intended . . . in
fact, it's a perfectly satisfactory alternative to
the legacy architecture typical of a few hundred
thousand spam cans (the vast majority of which will
not be center stage in a dark-n-stormy-night story).
[img]cid:.0[/img]
If you're well down the road with Z-12 then I would
recommend ditching e-bus, and anything resembling an avionics
bus. With a robust second alternator, you will not
be energy deprived for the en route phase of flight.
Just reduce loads till the alternator loaded light
stops flashing. This holds ALL of the battery's
contained energy in reserve for descent and approach
to landing . . . turn on anything else you want to
have (short of the air conditioner).
[img]cid:.1[/img]
Loosing ONE properly selected, installed and maintained
alternator is very unlikely. Loosing BOTH alternators
is on a par with being hit by an incoming meteor.
if Z-12 is good for hundreds of Beech, Piper and Mooney
airplanes obsessed over by hoards of folk paid good
salaries to WORRY about everything . . . then it's
golden in your projct.
Bob . . .
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