 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
nuckolls.bob(at)aeroelect
Guest
|
 Posted: Wed Oct 11, 2017 7:10 am Post subject: Dual Power Inputs, Dual Buss Electrical System |
 |
|
At 08:37 AM 10/11/2017, you wrote:
| Quote: | I’m redoing my panel in my aircraft which I built 15 years ago with a Z-14 electrical system. I’m installing a Garmin G3X panel and all the associated boxes. Most of them have the capability to wire for 2 separate power sources. With dual buss with crossfeed, I’m wondering if there is any significant benefit to having two CBs and two power feeds. I can think of a couple failure modes, but they seem remote. There is also a configuration using a backup battery on the second power feed, maybe that’s a better choice. Thanks in advance for the feedback.
|
With two batteries, two alternators and crossfeed,
there is no value in exploiting the redundancy
features you cited. Z14 has all that stuff built
in.
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
 |
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Thu Oct 12, 2017 10:46 am Post subject: Dual Power Inputs, Dual Buss Electrical System |
|
|
I have a Z-14 and agree. There are even some potential disadvantages.
I originally connected my (3) GRT EFISs to one bus and not incidentally, the engine starter circuit to the other bus. That configuration combined with an inadequate light weight starter originally supplied with the 6 cylinder IO-540 on the RV-10, meant that cross fed starts would sometimes reboot the GRTs. And starting with just 1 battery was marginal in cold weather. Given that I had no on/off switch for the GRTs, this was inconvenient given the boot time required. And it turned out that early versions of the GRT code did not like to have their boot sequence interrupted though that problem was fixed in later releases of the code.
Ideally as Bob has explained, one wants to start with the batteries cross-fed to keep stress on the batteries to a minimum. Then to do normal flight operations with 2 separate buses which makes any failure identification easier and would keep any damaging component isolated.
The other capability I wanted from my Z-14 was to be able to run my panel for an extended period of time on occasion without concern for having enough juice for a subsequent engine start. this is where the main disadvantage might lie. The GRTs are capable of connecting to up to 3 power supplies. At one point I used 2 of those inputs to connect them to both buses. That was a mistake because I found that my ability to run the panel for an extended period was diminished. That created several problematic scenarios that I just shouldn't have had to deal with.
In other words, the Z-14 gave me a lot of flexibility as long as I connect individual components to one bus or the other. It allows one to identify and isolate problem components and flexibly manage one's batteries if desired. If you crossfeed individual components at the component, you give some of that capability away with little if anything gained.
Post Script: Replacing the starter eliminated all problems with cross fed and single battery starts. Returning to a single power supply on a single bus for each GRT gave me back the battery management flexibility.
Bill "I love my Z-14" Watson
Bill mentions a starter replacement . . . what
kind of starter was removed and what was
the replacement?
This trace I captured of my 87 GMC pickup
was no doubt produced by inrush from a wound-
field starter. Here we see that the bus
falls to 8v for a few hundred microseconds.
[img]cid:.0[/img]
Figure 1.
I suspect that my younger cars may have PM starter
motors. I'll look into that.
We had some discussions at B&C many years ago about
the market shift of permanent magnet starter motors.
We elected not to join the parade . . . primarily
because the wound field motor had lower inrush
currents and offered better cold weather cranking
efficiency when the battery was being degraded
by the cold weather.
[img]cid:.1[/img]
Figure 8.
At the risk of being redundant, I'm repeating an assertion
that was offered some years ago when engine cranking inrush
reboots first raised their heads . . . I think it was back
in the days of Blue Mountain market roll out.
At that time, I posted the image above excerpted from
Mil-STD-704/DO-160 assertions suggesting that suppliers to
the industry should expect power perturbations over the
constellation of conditions illustrated.
Since that time, a number of processor based products have been
introduced to the market that re-boot when the bus falls
into normal/expected regions during engine start. While
the condition doesn't damage the appliance, it does
interrupt normal operations until the thing stands back
up. Intuitively, I believe it's possible to design this
characteristic out of most such products . . . but until
and unless the marketplace makes their desires known to
suppliers, nothing will change.
In the mean time, consumers of such products are obliged
to make fundamental changes to power system architectures
to accommodate an appliance that might well have been
designed for airplane friendly operations in the first
place. It wouldn't be out of line for Listers who
own such products to put the manufacturers on notice
that they've stubbed their toe.
Fee free to reference my writings. I'm also willing
to talk with any party interested in upgrading their
product. Give 'em my phone number too if you like.
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
| Description: |
|
| Filesize: |
78.1 KB |
| Viewed: |
1425 Time(s) |
|
| Description: |
|
| Filesize: |
107.48 KB |
| Viewed: |
1425 Time(s) |
|
|
|
| Back to top |
|
|
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Fri Oct 13, 2017 10:32 am Post subject: Dual Power Inputs, Dual Buss Electrical System |
|
|
At 12:36 PM 10/13/2017, you wrote:
| Quote: | On 10/12/2017 2:46 PM, Robert L. Nuckolls, III wrote:
| Quote: |
Post Script: Replacing the starter eliminated all problems with cross fed and single battery starts. Returning to a single power supply on a single bus for each GRT gave me back the battery management flexibility.
Bill "I love my Z-14" Watson
Bill mentions a starter replacement . . . what
kind of starter was removed and what was
the replacement?
|
The starter that was removed was the Sky-Tec 149-12LS Flyweight Starter.
I replaced it with the Sky-Tec 149NL.
The LS came as the standard configuration of the Lycoming IO-540 for the RV10 one could order through Vans back around 2009. People in the RV10 community quickly determined this was not a good combination. Even with 2 fully charged 680s, the starter would not consistently turn through the first compression stroke when cold - one had to learn to 'bounce it' through the first compression stroke. This was SOP on cold days but it never actually failed to start the engine. And it routinely caused my (3) unswitched EFISs to reboot if I had both buses crossfed, even if it did pull through the first compression stroke.
Lycoming and Sky-Tech came to the same conclusion at the time and specifically recommended that the LS is not a good starter for this application. For a period of time both companies were taking exchanges of the the LS for the NL at no charge. (Sky Tec now offers an XLT model as an updated replacement for the LS. Some RV10 builders used the HT model but reported similar problems.)
When I replaced it with the NL, it was immediately apparent that the NL turned slower but with much greater 'authority'. Even starting on one battery, switched so that it ran on the same bus as the (3) EFISs, the EFISs didn't reboot. Starts are now a no-brainer.
|
thanks for the data dump!
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
