Today's Message Index:
----------------------
1. 07:57 AM - Re: Primary Power Diagram RV-14 (Mudfly)
2. 11:35 AM - Re: FAT Wire Pt Implementation Question (jcohen@post.com)
3. 11:49 AM - Re: Building fusible links for FAT wires (jcohen@post.com)
4. 01:41 PM - Re: Re: Building fusible links for FAT wires (Charlie England)
5. 02:08 PM - Re: Building fusible links for FAT wires (jcohen@post.com)
6. 02:30 PM - Re: Re: Building fusible links for FAT wires (Charlie England)
7. 03:54 PM - Re: Building fusible links for FAT wires (johnbright)
8. 04:52 PM - Re: Re: Building fusible links for FAT wires (Robert L. Nuckolls, III)
9. 04:55 PM - Re: Re: Building fusible links for FAT wires (Robert L. Nuckolls, III)
10. 06:26 PM - Re: Building fusible links for FAT wires (johnbright)
11. 07:39 PM - Re: Primary Power Diagram RV-14 (johnbright)
12. 08:15 PM - Re: Primary Power Diagram RV-14 (user9253)
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| Subject: | Re: Primary Power Diagram RV-14 |
Gentlemen,
In todays episode of my Primary Power System design I have moved the Hot
Battery Bus FWF, and created the new Main Power Bus B (it's actually the old
HBB).
My question is the power feed to the new Main Power Bus B.
(Wire length approx. 2.5 ft from MPBA to MPBB)
The attached drawing shows it fed from MPBA through a 10A CB and 18AWG wire.
Is this acceptable or would direct run to battery contactor
be preferred? Currently, there will be approx. 7.5A on MPBB.
The main reason for MPBB is to reduce CBs on
MPBA. I would prefer to keep the CB number on MPBA to 25.
I'm still deciding on the wire protection for the HBB now located FWF. I only
plan on two items on that bus. Right now I'm leaning towards using some
type of in-line fuse holders. Plan B would be mounting a four place
fuse holder.
Sorry for the spaghetti chart and small print. I know it's hard on the eyes.
It's just the quickest way for me right now to do this planning.
Thanks
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510215#510215
Attachments:
http://forums.matronics.com//files/primary_power_system_feb17_734.pdf
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| Subject: | Re: FAT Wire Pt Implementation Question |
thank you for the replies! Very helpful!
--------
Jeff
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510216#510216
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| Subject: | Re: Building fusible links for FAT wires |
Now that I am having fun building fusible links for my Pri and Aux Alternator wires,
I am using off the shelf Pico fusible link wire (12AWG and 14AWG) to build
my FAT wire links, should I still cover the wire with Fiberglass Sleeving?
How does the off-the shelf FAT wire fusible link normally respond when it operates/
burns? If the link can flame and is not covered by fiberglass sleeve,
shouldn't the physical routing be considered, like not routing near/below the
battery or other components?
My thought is, if one event causes the fusible link to operate ( burn), couldn't
a flame from a FAT wire take out a nearby critical component (like the Master
in Z101) and cause a second failure?
--------
Jeff
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510218#510218
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| Subject: | Re: Building fusible links for FAT wires |
On 2/17/2023 1:49 PM, jcohen@post.com wrote:
>
> Now that I am having fun building fusible links for my Pri and Aux Alternator
wires, I am using off the shelf Pico fusible link wire (12AWG and 14AWG) to build
my FAT wire links, should I still cover the wire with Fiberglass Sleeving?
How does the off-the shelf FAT wire fusible link normally respond when it operates/
burns? If the link can flame and is not covered by fiberglass sleeve,
shouldn't the physical routing be considered, like not routing near/below the
battery or other components?
>
> My thought is, if one event causes the fusible link to operate ( burn), couldn't
a flame from a FAT wire take out a nearby critical component (like the Master
in Z101) and cause a second failure?
>
> --------
> Jeff
Hi Jeff,
If you're buying purpose-built fuse-link wire, the insulation should be
designed to contain the 'event'. Look at the difference in both material
and thickness of the insulation. It's probably good practice to avoid
bundling the short segment of fuselink wire into a larger bundle, but
there usually wouldn't be any need to do that, anyway. If you have
serious doubts/questions, then make yourself a test rig and test a
segment (common sense protections for yourself and other stuff obviously
applies).
The fiberglass sleeving trick is typically used for the small gauge
links that are user-fabbed from regular small gauge wire that has
typical aircraft insulation.
Charlie
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| Subject: | Re: Building fusible links for FAT wires |
Ceengland wrote:
> On 2/17/2023 1:49 PM, jcohen@post.com wrote:
>
> >
> >
> > Now that I am having fun building fusible links for my Pri and Aux Alternator
wires, I am using off the shelf Pico fusible link wire (12AWG and 14AWG) to
build my FAT wire links, should I still cover the wire with Fiberglass Sleeving?
How does the off-the shelf FAT wire fusible link normally respond when it
operates/ burns? If the link can flame and is not covered by fiberglass sleeve,
shouldn't the physical routing be considered, like not routing near/below
the battery or other components?
> >
> > My thought is, if one event causes the fusible link to operate ( burn), couldn't
a flame from a FAT wire take out a nearby critical component (like the
Master in Z101) and cause a second failure?
> >
> > --------
> > Jeff
> > Hi Jeff,
> >
>
>
> If you're buying purpose-built fuse-link wire, the insulation should be
> designed to contain the 'event'. Look at the difference in both material
> and thickness of the insulation. It's probably good practice to avoid
> bundling the short segment of fuselink wire into a larger bundle, but
> there usually wouldn't be any need to do that, anyway. If you have
> serious doubts/questions, then make yourself a test rig and test a
> segment (common sense protections for yourself and other stuff obviously
> applies).
>
> The fiberglass sleeving trick is typically used for the small gauge
> links that are user-fabbed from regular small gauge wire that has
> typical aircraft insulation.
>
> Charlie
>
> --
> This email has been checked for viruses by Avast antivirus software.
> www.avast.com
Thank you Charlie. I will bench test the link to understand more of how the link
reacts. Would there be any downside to attaching the 6 link at the B terminal
of the pri alternator , rather than at the terminal on the starter contactor
as depicted on Z101? That could help with fire proximity issues with contactors
and/or battery. That implementation still protects the entire wire the same
way, even when the protection is on the other end , right?
--------
Jeff
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510221#510221
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| Subject: | Re: Building fusible links for FAT wires |
On 2/17/2023 4:08 PM, jcohen@post.com wrote:
>
>
> Ceengland wrote:
>> On 2/17/2023 1:49 PM, jcohen@post.com wrote:
>>
>>>
>>>
>>> Now that I am having fun building fusible links for my Pri and Aux Alternator
wires, I am using off the shelf Pico fusible link wire (12AWG and 14AWG)
to build my FAT wire links, should I still cover the wire with Fiberglass Sleeving?
How does the off-the shelf FAT wire fusible link normally respond when
it operates/ burns? If the link can flame and is not covered by fiberglass sleeve,
shouldn't the physical routing be considered, like not routing near/below
the battery or other components?
>>>
>>> My thought is, if one event causes the fusible link to operate ( burn), couldn't
a flame from a FAT wire take out a nearby critical component (like the
Master in Z101) and cause a second failure?
>>>
>>> --------
>>> Jeff
>>> Hi Jeff,
>>>
>>
>> If you're buying purpose-built fuse-link wire, the insulation should be
>> designed to contain the 'event'. Look at the difference in both material
>> and thickness of the insulation. It's probably good practice to avoid
>> bundling the short segment of fuselink wire into a larger bundle, but
>> there usually wouldn't be any need to do that, anyway. If you have
>> serious doubts/questions, then make yourself a test rig and test a
>> segment (common sense protections for yourself and other stuff obviously
>> applies).
>>
>> The fiberglass sleeving trick is typically used for the small gauge
>> links that are user-fabbed from regular small gauge wire that has
>> typical aircraft insulation.
>>
>> Charlie
>>
>> --
>> This email has been checked for viruses by Avast antivirus software.
>> www.avast.com
>
> Thank you Charlie. I will bench test the link to understand more of how the
link reacts. Would there be any downside to attaching the 6 link at the B terminal
of the pri alternator , rather than at the terminal on the starter contactor
as depicted on Z101? That could help with fire proximity issues with contactors
and/or battery. That implementation still protects the entire wire the
same way, even when the protection is on the other end , right?
>
> --------
There is a downside to placing it at the alternator. Remember, the fuse
(whether CB, link, or actual fuse) is there to protect the wire. The
alternator B lead wire should be big enough to handle the highest
current the alternator can create (usually a small percentage higher
than its 'rated' output), so there's no need to protect the wire from
the alternator. The danger to the B lead is from the *battery*. So the
fusing device should be on the 'dangerous' end, to protect the wire. (It
is confusing, when you have devices at both ends that are both capable
of producing current.)
Charlie
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| Subject: | Re: Building fusible links for FAT wires |
jcohen@post.com wrote:
> ... I will bench test the link to understand more of how the link reacts. Would
there be any downside to attaching the 6 link at the B terminal of the pri
alternator , rather than at the terminal on the starter contactor as depicted
on Z101? That could help with fire proximity issues with contactors and/or battery.
That implementation still protects the entire wire the same way, even
when the protection is on the other end , right?
The way I put it is the protection (relay, contactor, fuse, current limiter, CB,
fusible link) should be as close as possible to the power source which in this
case is the battery. The battery can put out hundreds of amps and the alternator
can only put out its rating (plus a little more if it's cold) so it is not
capable of damaging itself or the B lead.
Suppose the alternator B leads gets pinched to ground somehow... one wants the
fuselink to open before the battery self-destructs.
I don't imagine a melted B lead fuselink will create enough fire to burn the contactor
case. Bob Nuckolls shows the fuselink at the contactor for a reason. I
look forward to your experiment of burning one. A 12 awg wire will burn at ~235A
and a 14 awg at ~166A.
BTW, what is the rating of your alternator?
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/folderview?id=1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510225#510225
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| Subject: | Re: Building fusible links for FAT wires |
>Suppose the alternator B leads gets pinched to ground somehow... one
>wants the fuselink to open before the battery self-destructs.
Wire damage is unlikely. Shorted diodes in alternator
is more likely but still rare.
>I don't imagine a melted B lead fuselink will create enough fire to
>burn the contactor case.
The definition of any fusible circuit protection is
"a means by which a conductor can be protected
from catastrophic failure due to hard fault
down stream of a potentially hazardous energy
source."
In our cases, potentially hazardous energy sources
start with a battery (1000 amps) joined in relatively
minor concert with alternator(s) (40 to 125A?).
Circuit protection should function to clear the
faulted feeder with MINIMAL damage to adjacent
hardware and zero propagation to other systems.
Oh yeah, any by-products of fault clearance activity
should not become a hazard to occupants of the
machine (smoke). This applies to all vehicles
including but not limited to rail locomotives,
trucks and yeah, airplanes.
> Bob Nuckolls shows the fuselink at the contactor for a reason. I
> look forward to your experiment of burning one. A 12 awg wire will
> burn at ~235A and a 14 awg at ~166A.
The wire to be protected in this instance
is the alternator b-lead itself. The energy
source is the battery. The fault will most
likely be failed rectifier in the alternator.
I've 'smoked' a number of COTS (commercial off
the shelf) fusible link wires. Those current
'ratings' are irrelevant in the face of probable
fault conditions probably exceeding 1000 amps.
The smoke generated was not 'pleasant' but not
debilitating and short lived. Damage to said insulation
was remarkably minor. Fusible link insulation
is intended to contain the effects of a fused
wire such that damage to materials and components
outside that insulation is minimized. See "Hypalon"
insulation history.
>BTW, what is the rating of your alternator?
Relevant only to the extent of sizing b-lead
wire conductor size to limit voltage drop
to design goals . . . generally on the order
of a few hundred millivolts at full load.
I've got some videos of fusible link burns
that I'll try to dig up . . . or perhaps
duplicate.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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| Subject: | Re: Building fusible links for FAT wires |
>There is a downside to placing it at the alternator. Remember, the
>fuse (whether CB, link, or actual fuse) is there to protect the
>wire. The alternator B lead wire should be big enough to handle the
>highest current the alternator can create (usually a small
>percentage higher than its 'rated' output), so there's no need to
>protect the wire from the alternator. The danger to the B lead is
>from the *battery*. So the fusing device should be on the
>'dangerous' end, to protect the wire. (It is confusing, when you
>have devices at both ends that are both capable of producing current.)
B-lead protection is ALWAYS designed to deal
with BATTERY faults as the potentially hazardous
condition. An alternator is physically incapable
of opening its own b-lead protection.
BATTERIES are always the driving consideration for
placement and sizing of fusible links and/or current
limiters (ANL, ANN, MANL, etc).
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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| Subject: | Re: Building fusible links for FAT wires |
nuckolls.bob(at)aeroelect wrote:
>
>
>
> > BTW, what is the rating of your alternator?
>
> Relevant only to the extent of sizing b-lead
> wire conductor size to limit voltage drop
> to design goals . . . generally on the order
> of a few hundred millivolts at full load.
>
> Bob . . .
Im just curious the OP chose 8 awg main alternator B lead. I have the impression
main alternators are usually 60A with 6 awg B lead. This is an RV-7 with SDS
EFI+I so current demands are higher than without EFI+I. I understand conductor
sizing is not an exact science and the smaller wire will just get a little warmer
and drop a little more voltage without being a safety issue.
My notes show 8 awg rated 40A and 6 awg 54A for the 10C rise criteria. I understand
this is conservative when not in a bundle.
My load analysis for four cylinder SDS EFI+I ship shows 44A with both pumps running
in addition to pitot heat, seat heat, lambda sensor, landing nav and strobe
lights, dual Skyview and its accessories so in reality 8 awg is not a problem.
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/folderview?id=1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510230#510230
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| Subject: | Re: Primary Power Diagram RV-14 |
Any chance of a future episode switching the acres of breakers for fuses? (except
for alternator fields with crowbar OV) Would make the physical implementation
easier and save panel space.
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/folderview?id=1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510231#510231
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| Subject: | Re: Primary Power Diagram RV-14 |
Agree with John. I once tested a breaker on the bench and it literally
smoked instead of tripping. Fuses never fail to open with excessive current.
All of the fuses and fuse block(s) can be purchased for the price of one or two
breakers.
There is no temptation to reset a blown fuse while airborne and give the fire a
second chance.
--------
Joe Gores
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