Today's Message Index:
----------------------
1. 06:55 AM - Re: Question on Grounding (ronaldcox)
2. 08:14 AM - Splice wires (Dick Gurley)
3. 08:33 AM - Re: E-Bus Fuse Size (skywagon185guy)
4. 08:58 AM - Re: Splice wires (Robert L. Nuckolls, III)
5. 09:16 AM - Re: Re: E-Bus Fuse Size (Robert L. Nuckolls, III)
6. 10:19 AM - Re: E-Bus Fuse Size (user9253)
7. 10:51 AM - Re: Re: E-Bus Fuse Size (Robert L. Nuckolls, III)
8. 12:02 PM - Re: Splice wires (Dick Gurley)
9. 01:12 PM - Re: Re: E-Bus Fuse Size (skywagon185guy)
10. 03:49 PM - Dual Battery Dual Alternator Power Distribution System (lwesterlund)
11. 09:48 PM - Re: Splice wires (Art Zemon)
12. 11:02 PM - Re: Splice wires (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: Question on Grounding |
Rocketman1988 wrote:
> Sorry I asked...
And that is exactly why the rule is there.
We need the level of our discussion to be such that NO ONE is ever sorry they asked.
Every year or two someone shows up here and decides they need to kick over the
chairs and pee in all the corners. Fortunately, it usually works itself out amicably,
as I hope it has here.
No need to be sorry. Your question was not out of line. It's exactly what we're
all here for. The sharing of questions and ideas, and hopefully some answers.
Don't let this scare you away.
--------
Ron Cox
Glasair Super II F/T
Under Construction at C77 - Still just about to fly!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484240#484240
Message 2
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What is the proper technique for splicing two #14 wires to one #16 wire. Sorry
for the newbie question. Thank you
Sent from my iPhone
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Subject: | Re: E-Bus Fuse Size |
Joe,
. . . didn't you mean "parallel" instead of series. . . ??
On Wed, Oct 31, 2018 at 5:40 PM user9253 <fransew@gmail.com> wrote:
>
> A pilot recently experienced an instrument panel blackout at night. When
> he turned on the E-Bus switch, the panel briefly came back on, but soon
> went black again. Luckily the weather was good and he landed safely. You
> can read about it here.
> http://www.vansairforce.com/community/showthread.php?t=165520
> The E-Bus was protected by 15 amp fuses. Evidently the second and third
> owners of the aircraft connected more loads to the E-Ebus, eventually
> overloading it.
> If two fuses are connected in series, even if one is bigger, either one or
> both could blow in case of hard ground fault.
> Should the E-Bus have main fuses?
> If so, then how much larger should the main fuse be than a branch circuit
> fuse?
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=484131#484131
>
>
Message 4
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Subject: | Re: Splice wires |
At 10:09 AM 11/2/2018, you wrote:
>
>What is the proper technique for splicing two #14 wires to one #16
>wire. Sorry for the newbie question. Thank you
>
>Sent from my iPhone
Lots of ways work just fine. you can use a crimped
butt splice, although you'd have to use a yellow
splice and double up one of the wires.
You can do a soldered lap-joint covered
in heat shrink.
But I'm curious as to the mixture
of wire sizes. What power do these wires carry and
what is the circuit protection for those wires?
Bob . . .
Message 5
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Subject: | Re: E-Bus Fuse Size |
At 10:12 PM 11/1/2018, you wrote:
>
>What I meant by being in series are the input fuse to the E-bus and
>one of the E-Bus loads. My concern is what will happen in case a
>load circuit shorts to ground. For a fraction of a second, the
>current arcing across a fuse will exceed the fuse value. That high
>arcing current could be enough to blow an upstream fuse, even if
>that upstream fuse has a higher current rating. Ever notice that
>circuit breakers in a home service entrance panel are labeled "10K
>Amps" even though the breaker size is 15 or 20 amps? The reason is
>that when the circuit breaker trips with a dead short, the current
>arcing across the opening contacts is only limited by the power
>company's ability to provide it. Thus the circuit breaker is
>capable of withstanding very high arcing current up to 10K amps for
>a fraction of a second without blowing itself apart.
That's not a concern.
Consider the ac power distribution in your house.
A hand-held appliance may have some small protective
device inside it . . . then you move up the chain to
a breaker in your entry box. There may be a mains
breaker upstream in the same box. There are probably
fuses in the transformer behind your house. The
neighborhood distribution system has yet more upstream
fuses. From there on up the chain, fuses are generally
replaced with circuit breakers all the way back to
the power plant.
Any one of those protective devices can be faulted
without opening the upstream protection . . .
IN SPITE of whatever pre-heating may be present
due to other running loads sharing the same
feeder.
You can be sure that the I(squared)t fusing
constant for every device is much greater than
any downstream device, much less than any upstream
device.
The protection architecture behaves gracefully
irrespective of the system's source impedance . . .
which sets the maximum, instantaneous fault
current.
The thing that made our fuse choices more critical
was the fact some devices were fed by upstream
devices of the same class . . . i.e. plastic
automotive fuses. This is not inherently a bad
thing but it does take some careful design
combined with verification testing.
I slipped up in not evolving the protection
philosophy along with step with expanded design
goals for the e-bus. This placed the uninformed
builder at risk for the 'Dark E-bus Syndrome'.
Going foreward with Z36 should eliminate that
risk.
Bob . . .
Message 6
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Subject: | Re: E-Bus Fuse Size |
> Joe, . . . didn't you mean "parallel" instead of series. . . ??
No, I meant series. There is a fuse protecting the E-Bus and there are individual
loads on the E-Bus each protected by a fuse. The fuse for the whole E-bus
and a load fuse are in series. The fuse protecting the whole E-Bus needs to
be chosen so that a hard short to ground on an individual load does not blow both
the load fuse and the main E-Bus fuse. Bob has addressed this issue with
his proposed Z-36 using a MANL30 protecting a heavy duty E-Bus. Builders keep
adding more and more loads to an E-bus that was originally designed for minimum
loads.
A person I know was working on an apartment kitchen range outlet. He stuck a
screwdriver in where it should not have been and tripped not only the circuit
breaker for the range, but also the main breaker for the whole building. He
had to get the apartment manager to unlock the utility room and reset the building
main breaker.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484248#484248
Message 7
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Subject: | Re: E-Bus Fuse Size |
> A person I know was working on an apartment kitchen range
> outlet. He stuck a screwdriver in where it should not have been
> and tripped not only the circuit breaker for the range, but also
> the main breaker for the whole building. He had to get the
> apartment manager to unlock the utility room and reset the building
> main breaker.
Defective or mis-applied breaker . . . it's
a fundamental design REQUIREMENT to prevent fault
effects from propagating outward or upward
in a complex system.
Bob . . .
Message 8
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Subject: | Re: Splice wires |
Thank you Bob -
The two wires come from a heated Garmin pitot tube system. Garmin twisted a
nd soldered the two wires together at the factory. The Garmin G3X manual cal
ls for 14 gauge wire for the length required (>21 feet). The manual also cal
ls for a 20 amp fuse for power onto the control box. The max current draw is
listed at 12 amps.
I measured the provided twisted and soldered wire to obtain a 12 gauge equiv
alent.
Where can I learn about a soldered lap joint with heat shrink
Than you again
Dick
Sent from my iPhone
> On Nov 2, 2018, at 11:57 AM, Robert L. Nuckolls, III <nuckolls.bob@aeroele
ctric.com> wrote:
>
> At 10:09 AM 11/2/2018, you wrote:
>>
>> What is the proper technique for splicing two #14 wires to one #16 wire. S
orry for the newbie question. Thank you
>>
>> Sent from my iPhone
>
> Lots of ways work just fine. you can use a crimped
> butt splice, although you'd have to use a yellow
> splice and double up one of the wires.
>
> You can do a soldered lap-joint covered
> in heat shrink.
>
> But I'm curious as to the mixture
> of wire sizes. What power do these wires carry and
> what is the circuit protection for those wires?
>
>
==========================
==========================
==========================
==========================
==========================
==========================
==========================
====
Message 9
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Subject: | Re: E-Bus Fuse Size |
. . . you are certainly right; I didn't consider that you were talking
about "branches".
My email gets staged with the earlier first and I did not see your
follow-up until I had already stepped on my xxx with a reply. "Must
remember to read the entire thread. . .=F0=9F=99=84 "
On Fri, Nov 2, 2018 at 10:25 AM user9253 <fransew@gmail.com> wrote:
>
>
> > Joe, . . . didn't you mean "parallel" instead of series. . . ??
>
> No, I meant series. There is a fuse protecting the E-Bus and there are
> individual loads on the E-Bus each protected by a fuse. The fuse for the
> whole E-bus and a load fuse are in series. The fuse protecting the whole
> E-Bus needs to be chosen so that a hard short to ground on an individual
> load does not blow both the load fuse and the main E-Bus fuse. Bob has
> addressed this issue with his proposed Z-36 using a MANL30 protecting a
> heavy duty E-Bus. Builders keep adding more and more loads to an E-bus
> that was originally designed for minimum loads.
> A person I know was working on an apartment kitchen range outlet. He
> stuck a screwdriver in where it should not have been and tripped not only
> the circuit breaker for the range, but also the main breaker for the whol
e
> building. He had to get the apartment manager to unlock the utility room
> and reset the building main breaker.
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=484248#484248
>
>
===========
===========
===========
===========
===========
===========
>
>
Message 10
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Subject: | Dual Battery Dual Alternator Power Distribution System |
Im looking for some help in reviewing a draft Dual Battery/ Dual Alternator (DBDA)
power distribution architecture for an RV-14A. I started with Bob Nuckolls
Z-14 system and Ive attempted to modify it to capitalize on the dual power feed
capabilities of the newest generation of avionics.
My mission is IFR in the Pacific Northwest where theres lot of clouds and lots
of rocks in those clouds. Accordingly, the proposed system utilizes two alternators
and two EarthX batteries. The 60W primary alternator will handle all normal
loads at 60% capacity. The 20-30W accessory-pad mounted auxiliary alternator
will handle its normal loads at 50% capacity, and when called upon, all IFR
critical loads indefinitely at 66%+ loading. The two batteries provide a third
level of redundancy.
The batteries are not wired for cross connection for starting. I removed that from
Bob's Z-14 - if I cant start the engine with just the primary battery, its
time to get a new battery.
Power is distributed through two buses:
1. The Primary Bus feeds all dual feed components as well as the non-critical single
feed components. Ive elected to use the Vertical Power X Pro to control
these loads. I realize the VPX does somewhat increase the risk of a single point
of failure (not withstanding its two independent controllers and two buses)
but even if the VPX did go dark, I could still get home on the completely independent
Aux Bus with at least as much capability and safety as I get flying spam
cans now.
2. The Aux Bus provides redundant power to all critical IFR dual feed components
(PFD, ADAHRS) as well as to several always-nice-to-have dual feed components
(MFD, AP, Transponder). It also provides sole power to the WAAS GPS/NAV/COM (which
only has a single power feed) and several other redundant loads.
The Aux Bus will be set to run at a slightly lower voltage than the Primary Bus,
so the Primary Alternator will normally carry the full load (excepting the GTN650,
stall warning, and optical fuel level detector). Should Primary Bus voltage
fall during starting, or due to a Pri Alternator failure, the dual feed components
will automatically be picked up by the Aux Bus with no pilot intervention
required.
Regarding the ubiquitous always-hot battery bus, my hypothesis is that its no longer
necessary given advances in technology. In Z-14 (and earlier in Chapter
17 or The AeroElectric Connection), Bob lists the following loads as worthy of
a direct connection to the battery:
Ignition
Fuel pump(s)
Dome light
Clock
Radio mem
My initial attempts at developing an architecture included a battery bus for those
loads. However, as I started to work through failure modes, the list of battery
bus-worthy loads got smaller and smaller. For instance, with dual P-mags
(which the manufacturer recommends not connecting to an always hot battery bus)
you only need power to one P-mag at start. Above 700 RPM both with self-excite
so even in the unlikely event you lose both bus contactors, the plugs will
fire and the engine will spin.
The only recommended battery bus load that gives me a little pause is the fuel
pump. But, as shown, a simple single pole double throw switch should let me connect
to either bus. I would need to lose both buses and the mechanical fuel pump
to lose fuel to the engine. Absent battle damage, it seems like the chance
of fuel starvation due to an electrical problem is pretty remote.
Regarding bus management, normal operation would be to turn on the G5 (to check
G5 back-up battery operation) then the Aux Bus during pre-start to check voltage
and set up the avionics. The Primary Bus, electric fuel pump and P-mags would
be turned on just prior to engine start-up. If the twirley thingy in front
spins, youre good to go.
When done flying, the procedure would be to turn off the Primary Bus (to confirm
load pick-up by the Aux Alt), then secure the Aux Bus, then the G5 which has
its own battery, and finally the P-mags.
In the event of an electrical fire in IMC, opening the Primary Battery relay would
dump about 70% of loads and feeds. I would still have a full complement of
IFR critical equipment running on the Aux Bus. If opening the Primary Battery
Relay doesnt isolate power to the fire, opening the Aux Battery relay would dump
the balance of loads and feeds. At that point, Id still have self-excite power
to run the P-mags and the back-up battery to power the G5 EFIS to keep the
plane upright. In VFR conditions, I would dump both Pri and Aux buses immediately.
So, what I have I missed? Or misunderstood? Or miscalculated? Does eliminating
the battery bus increase risk in some unintended way? Im 100% sure Ive missed
something small, complex, and nuanced. Im also pretty sure Ive missed something
really, really big. Any feedback would be much appreciated. Thanks.
Lance
Beaverton, OR, RV-14A - Emp & Fuse Done, Finish Kit in Progress, QB Wings Ordered
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484257#484257
Attachments:
http://forums.matronics.com//files/rv_power_distribution_v4_137.pdf
Message 11
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Subject: | Re: Splice wires |
On Fri, Nov 2, 2018 at 2:21 PM Dick Gurley <rngurley@att.net> wrote:
> Where can I learn about a soldered lap joint with heat shrink
>
Dick,
I wrote it up with photos in my blog post Physical & Electrical
Considerations when Mounting Avionics
<https://cheerfulcurmudgeon.com/2016/07/19/physical-electrical-considerations-when-mounting-avionics/>.
That post also includes a link to Bob's shop notes on "Poor Man's Solder
Sleeves" which have all of the detailed instructions that you will need.
Also see my photos near the bottom of my blog post Wiring Harness Installed
<https://cheerfulcurmudgeon.com/2016/11/28/wiring-harness-installed/>
because there are some splices with 1 wire coming into the splice and 2
wires going out the other side.
Cheers,
-- Art Z.
--
https://CheerfulCurmudgeon.com/
*"Be kind, for everyone you meet is fighting a hard battle."*
Message 12
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Subject: | Re: Splice wires |
At 11:59 AM 11/2/2018, you wrote:
>Thank you Bob -
>
>The two wires come from a heated Garmin pitot tube system. Garmin
>twisted and soldered the two wires together at the factory. The
>Garmin G3X manual calls for 14 gauge wire for the length required
>(>21 feet). The manual also calls for a 20 amp fuse for power onto
>the control box. The max current draw is listed at 12 amps.
>
>I measured the provided twisted and soldered wire to obtain a 12
>gauge equivalent.
>
>Where can I learn about a soldered lap joint with heat shrink
https://tinyurl.com/c5v2xvm
Bob . . .
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