Today's Message Index:
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1. 05:39 AM - Re: Re: Z-12 contactor failure (Robert L. Nuckolls, III)
2. 08:15 AM - SD-8 Alternator Feed 30A Inline Fuse Location (Airdog77)
3. 08:25 AM - Re: SD-8 Alternator Feed 30A Inline Fuse Location (Charlie England)
4. 08:25 AM - Re: SD-8 Alternator Feed 30A Inline Fuse Location (user9253)
5. 08:37 AM - Re: SD-8 Alternator Feed 30A Inline Fuse Location (Airdog77)
6. 10:14 AM - Re: Re: Z-12 contactor failure (Robert L. Nuckolls, III)
7. 10:24 AM - Re: Re: Z-12 contactor failure (Robert L. Nuckolls, III)
8. 07:57 PM - Re: Bulb replacement for my Sandel 3308 EHSI (blues750)
Message 1
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Subject: | Re: Z-12 contactor failure |
Agree the certified electrical system is much weaker and I found
first hand that master switches are not well maintained, but I will
attempt to bring this back around to the intent of my original post...
Not trying to reinvent anything. This will most likely remain a
philosophical discussion for me as Z-12 is already quite robust as
compared to the certified planes I fly in that E-bus devices will
still be available on battery + internal battery backups, etc.
I have found very little information specific to protecting for
master contactor failure.
Because it's so rare . . . and, with the carefully
contrived architecture and preventative maintenance,
it's failure does not represent a hazard to comfortable
termination of flight.
So is the philosophy for Z-12 that it is not worth worrying about
since E-bus will still operate?
The whole airplane will probably operate. Z-12 is simply
an illustration of how the secondary, engine driven alternator
was incorporated into TC aircraft. It was simply added to
the distribution system as a second source with the ability
to support plenty of electro-whizzies on the panel.
I can accept this, I just am confused when I see Z-13/8 that connects
the alternator on the battery side. Can anyone explain the reason for
the difference?
Sure. Z13/8 is a three layer electrical system.
(1) Battery only. E-bus powered appliances, no contactor loads
Endurance implications: "Plan C" loads tailored to
known battery capacity such that battery-only endurance
goals are met.
(2) Battery + 8. E-bus powered appliances, contactor load
optional depending on "Plan B" loads. Loads tailored
to hold battery in reserve for descent and approach
to landing. Electrical endurance essentially unlimited.
Descent and approach to landing loads can depend on
known battery capacity to supplement the 8A engine
driven power source.
(3) Battery + Main Alternator. Normal "Plan A" ops. No
limits on electrical loads.
The three-layer system is practical only on OBAM aircraft
. . . the 337 or STC to convert a TC aircraft would be
prohibitive and would not materially reduce risk.
Bob . . .
Message 2
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Subject: | SD-8 Alternator Feed 30A Inline Fuse Location |
Bob,
In your response on the Z13 Battery Bus Protection question in a very recent post,
you reminded us that
> Recall that circuit protection is for WIRES . . . and that the protective device
is installed as close as practical to the SOURCE of energy that puts the wire
at risk.
A friend of mine asked me a question on my Z-13/8 configuration that stumped me,
so I thought I'd ask you.
In keeping in line with your statement above, in Z-13/8 why is the inline 30A fuse
for the SD-8 wire connection from the battery contactor to the SD-8's S704-1
relay placed within 6 inches or less from the battery contactor, when the SD-8
is the source of energy?
Wade
--------
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479470#479470
Message 3
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Subject: | Re: SD-8 Alternator Feed 30A Inline Fuse Location |
On 4/21/2018 10:14 AM, Airdog77 wrote:
>
> Bob,
>
> In your response on the Z13 Battery Bus Protection question in a very recent
post, you reminded us that
>> Recall that circuit protection is for WIRES . . . and that the protective device
is installed as close as practical to the SOURCE of energy that puts the
wire at risk.
> A friend of mine asked me a question on my Z-13/8 configuration that stumped
me, so I thought I'd ask you.
>
> In keeping in line with your statement above, in Z-13/8 why is the inline 30A
fuse for the SD-8 wire connection from the battery contactor to the SD-8's S704-1
relay placed within 6 inches or less from the battery contactor, when the
SD-8 is the source of energy?
>
> Wade
>
I'm not Bob, but an alternator wire should be big enough to handle
everything an alternator can throw at it, meaning the alternator can't
damage it. But... The battery *can* damage it, so the protection is at
the potential source of the damage.
That help?
---
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Message 4
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Subject: | Re: SD-8 Alternator Feed 30A Inline Fuse Location |
There are two sources of energy, the battery and SD-8. The SD-8 is self current
limiting. It can put out perhaps 10 amps at most. Its output does not need
to be fused. The battery can put out hundreds of amps and possibly do lots of
damage. Placing the fuse near the battery will minimize the danger.
--------
Joe Gores
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Message 5
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Subject: | Re: SD-8 Alternator Feed 30A Inline Fuse Location |
Makes all the sense in the world.... now that you guys explained it!!
Crystal clear. Always good to learn something new!
Thanks Joe & Charlie!
Cheers,
Wade
--------
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479473#479473
Message 6
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Subject: | Re: Z-12 contactor failure |
>
>This makes perfect sense to me. Now look at Z-12 - the primary and
>backup alternators are both connected the same way - to the main
>bus. If you turn off the master both alternators are isolated from
>the battery. This means battery only operation unless the
>alternators remain stable without battery. Why do it this way? The
>only difference I see is the backup alternator is the larger 20A vs 8A.
>
>To ask another way. Why not connect the larger 20A backup
>alternator in the same way as Z-13/8 ( with relay and switch )? Is
>this not advisable due to the higher current being switched or some
>other reason?
The e-bus was conceived one evening about 1988 in
conversation with a LongEz builder in California.
This fellow did a lot of long distance travel over
mountains. I don't recall if his airplane had a
starter . . . don't think it did because I do
recall that he was fitted with a pretty light
battery in the nose.
The design goal being pondered was how to create
a battery-only endurance greater than his fuel
endurance . . . which was rather long.
At that time, his electrical endurance loads were
as I recall, about 3 amps. A battery contactor draws
about 0.8A after warm up . . . enough snort to run
a couple of useful electro-whizzies yet this energy
was tossed off as heat. His SD-8 would support normal
flight loads including contactor.
Emacs!
His endurance loads must have been a bit less than
3A because I recall we decided that a new 18a.h.
battery would carry his anticipated loads for 6
hours, hence his 4-hour design goal would be
satisfied to 75% of new capacity whereupon
the battery gets replaced.
So the e-bus was conceived as a method for setting
up a fixed, predictable battery-only endurance load
with a simple re-positioning of two switches.
Lots of Ez aircraft had only SD8 alternators on
the drive pad, no other alternator and no starter.
The B&C line of light weight starters and alternators
encouraged the Ez crowd on to the next evolutionary
step.
Added weight on the extreme rear of the a/c drove
a need for ballast in the nose . . . ballast
that was best achieved with a larger battery as
opposed to bags of lead shot! The 24 a.h. battery
was the next step up.
The SD-8 could be left in place on the drive pad for a
weight penalty of about 4 pounds. Hence, Z13/8 germinated
from the evolving goals of Long-Ez owners in the 1990
time frame.
At one time, I did have a Z13/20 architecture which
was discussed here on List and I think a few installations
were made. I was never happy with it as it offered
no particular advantages over Z12 and was un=necessarily
complex. There was no pressing need to eliminate contactor
loads on the much larger S/B alternator so it was
removed from the 'Connection after a few years.
Bob . . .
Message 7
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Subject: | Re: Z-12 contactor failure |
> His endurance loads must have been a bit less than
> 3A because I recall we decided that a new 18a.h.
> battery would carry his anticipated loads for 6
> hours, hence his 4-hour design goal would be
> satisfied to 75% of new capacity whereupon
> the battery gets replaced.
Hmmmm . . . my recollection of details may be
a bit fuzzy after 30 years, 4 hours is 66%
of new . . . anyhow, this illustrates the
thought processes for design decisions.
Bob . . .
Message 8
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Subject: | Re: Bulb replacement for my Sandel 3308 EHSI |
Thanks Bob, my main concern was inadvertently trashing the
Sandel somehow. If that is a non-factor I'm game to see what the LED presentation
would be like. Will indeed report back when I've got some field test info!
Dave
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