Today's Message Index:
----------------------
1. 07:55 AM - Re: Unprotected Feeder in Z Drawings (Robert L. Nuckolls, III)
2. 08:21 AM - Re: Unprotected Feeder in Z Drawings (Jeff Luckey)
3. 08:42 AM - Re: Unprotected Feeder in Z Drawings (Ken)
4. 09:04 AM - Re: Unprotected Feeder in Z Drawings (Jeff Luckey)
5. 09:40 AM - Re: Unprotected Feeder in Z Drawings (Ken)
6. 10:17 AM - Re: Unprotected Feeder in Z Drawings (Jeff Luckey)
7. 03:21 PM - Re: Unprotected Feeder in Z Drawings (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Unprotected Feeder in Z Drawings |
At 11:00 PM 12/4/2013, you wrote:
Bob,
I have been reviewing some of the Z drawings in the back of "The
Aeroelectric Connection" and I have a question. (specifically Z-11,
Z-12, & Z-14)
I notice that the 6 awg wire which connects the load side of the
Battery Contactor to the Main Power Distribution bus is not
fused. That seems like an un-protected feeder and gives me a little
heart burn.
I think of the Main Power Distribution bus as the bus bar which runs
across the back of the breakers in my distribution panel which lives
in my instrument panel. With the Battery Contactor on the firewall,
the run from it to the distribution panel penetrates the firewall
then snakes its way to the back of my panel. That #6 wire will be
between 6 & 8 feet in length.
What happens if that wire gets into trouble along its route. Without
a fuse it will get very hot and bad things will happen.
I'm curious about the criteria used in this design. Perhaps I'm
missing something?
TIA,
-Jeff
Okay,
Get out your toolbox and take a position to contemplate this 'risky'
piece of wire. What process and tools are needed to 'get this wire
into trouble'? Yes, it's attached to a battery with potential for
spectacular fault currents, but so too is your propeller thrashing
around in the breeze with a potential for serious bodily harm.
It's easy to get bogged down worrying about things that have low to
exceedingly small probability of happening. This is a fundamental
component of Failure Modes Effects Analysis. The artfully crafted
FMEA not only considers "what happens if . . .?" you're well advised
to consider HOW that condition became a thing to consider in the
first place. The goal is to decide which has more value: (1)
protecting against a condition or (2) reducing probability of that
condition to an acceptably low value.
In the case of your fat-wire, which design goal offers the lowest
level of risk and greatest boost of system reliability? (1) protect
the wire loaded to some gawd-awful fault or (2) reduce probability of
such an event to levels that says your worry-capital is better
invested elsewhere? This thought process convinces us that building
a safety cage around the propeller is not a useful/necessary
expenditure of weight/cost/performance budget.
There are exposed conductors that run across the back of most circuit
breaker panels. These bus bars are legacy features of all manner of
vehicle not the least of which are airplanes. Is there value in
expending worry-capital on risk for faulting a bus bar? You can
answer this question with pretty simple observation and
contemplation. With a box full of tools at your disposal, what parts
of the airplane do you have to hammer, pry or saw in order to get
that bus bar . . . or your fat-wire into trouble?
Once those actions are discovered and evaluated, what is the
likelihood that such an event is going to befall the potential victim
over the lifetime of your airplane? It's fairly predicable that your
study will produce some combination of discoveries that fall in to
two categories: (1) there are no features of structure or installed
hardware likely to dislodge and attack the potential victim; (2)
Oops! Some feature of installation of the wire or surrounds has not
been installed with attention to good practices . . . and you're
going to fix it.
This same analysis (and incorporation of lessons-learned) produced
the following excerpt from FAR23 for TC aircraft:
Sec. 23.1357 Circuit protective devices.
(a) Protective devices, such as fuses or circuit breakers, must be
installed in all electrical circuits other than--
(1) Main circuits of starter motors used during starting
only; and
(2) Circuits in which no hazard is presented by their omission.
<continued>
The controlling idea here is 23.1357(a)(2) where you're going to
manage the installation of this 6AWG wire and its surrounds such that
"no hazard is presented" by omission of a fuse or breaker.
Bob . . .
Message 2
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| Subject: | Re: Unprotected Feeder in Z Drawings |
Thank you for the explanation.- I get it - the assumption is: very low pr
obability of the wire getting into trouble assuming that it's well-installe
d w/ intelligence and craftsmanship.=0A=0ABut staying with the original the
me, is there any down side to putting a big current limiter (ANL?) in that
lead at its origin?=0A=0A-Jeff=0A=0APS - I'm also thinking about ways to pr
otect that buss bar ;)=0A=0A=0A=0A________________________________=0A From:
"Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>=0ATo: aeroelectr
ic-list@matronics.com =0ASent: Thursday, December 5, 2013 7:54 AM=0ASubject
: Re: AeroElectric-List: Unprotected Feeder in Z Drawings=0A =0A=0A--> Aero
Electric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob@ae
roelectric.com>=0A=0AAt 11:00 PM 12/4/2013, you wrote:=0ABob,=0A=0AI have b
een reviewing some of the Z drawings in the back of "The Aeroelectric Conne
ction" and I have a question.- (specifically Z-11, Z-12, & Z-14)=0A=0AI n
otice that the 6 awg wire which connects the load side of the Battery Conta
ctor to the Main Power Distribution bus is not fused.- That seems like an
un-protected feeder and gives me a little heart burn.=0A=0AI think of the
Main Power Distribution bus as the bus bar which runs across the back of th
e breakers in my distribution panel which lives in my instrument panel.-
With the Battery Contactor on the firewall, the run from it to the distribu
tion panel penetrates the firewall then snakes its way to the back of my pa
nel.- That #6 wire will be between 6 & 8 feet in length.=0A=0AWhat happen
s if that wire gets into trouble along its route.- Without a fuse it will
get very hot and bad things will happen.=0A=0AI'm curious about the criter
ia used in this design.- Perhaps I'm missing something?=0A=0ATIA,=0A=0A-J
eff=0A=0AOkay,=0A=0AGet out your toolbox and take a position to contemplate
this 'risky' piece of wire. What process and tools are needed to 'get this
wire into trouble'? Yes, it's attached to a battery with potential for spe
ctacular fault currents, but so too is your propeller thrashing around in t
he breeze with a potential for serious bodily harm.=0A=0AIt's easy to get b
ogged down worrying about things that have low to exceedingly small probabi
lity of happening.- This is a fundamental component of Failure Modes Effe
cts Analysis.- The artfully crafted FMEA not only considers "what happens
if . . .?" you're well advised to consider HOW that condition became a thi
ng to consider in the first place. The goal is to decide which has more val
ue: (1) protecting against a condition or (2) reducing probability of that
condition to an acceptably low value.=0A=0AIn the case of your fat-wire, wh
ich design goal offers the lowest level of risk and greatest boost of syste
m reliability? (1) protect the wire loaded to some gawd-awful fault or (2)
reduce probability of such an event to levels that says your worry-capital
is better invested elsewhere?- This thought process convinces us that bui
lding a safety cage around the propeller is not a useful/necessary expendit
ure of weight/cost/performance budget.=0A=0AThere are exposed conductors th
at run across the back of most circuit breaker panels. These bus bars are l
egacy features of all manner of vehicle not the least of which are airplane
s. Is there value in expending worry-capital on risk for faulting a bus bar
? You can answer this question with pretty simple observation and contempla
tion. With a box full of tools at your disposal, what parts of the airplane
do you have to hammer, pry or saw in order to get that bus bar . . . or yo
ur fat-wire into trouble?=0A=0AOnce those actions are discovered and evalua
ted, what is the likelihood that such an event is going to befall the poten
tial victim over the lifetime of your airplane? It's fairly predicable that
your study will produce some combination of discoveries that fall in to tw
o categories: (1) there are no features of structure or installed hardware
likely to dislodge and attack the potential victim; (2) Oops! Some feature
of installation of the wire or surrounds has not been installed with attent
ion to good practices . . . and you're going to fix it.=0A=0AThis same anal
ysis (and incorporation of lessons-learned) produced the following excerpt
from FAR23 for TC aircraft:=0A=0A=0ASec. 23.1357- Circuit protective dev
ices.=0A=0A(a) Protective devices, such as fuses or circuit breakers, must
be=0Ainstalled in all electrical circuits other than--=0A=0A- - - -
(1) Main circuits of starter motors used during starting only; and=0A-
- - - (2) Circuits in which no hazard is presented by their omission.
=0A=0A<continued>=0A=0AThe controlling idea here is 23.1357(a)(2) where you
're going to manage the installation of this 6AWG wire and its surrounds su
ch that "no hazard is presented" by omission of a fuse or breaker.=0A=0A=0A
=================
Message 3
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| Subject: | Re: Unprotected Feeder in Z Drawings |
Additional voltage drop and connections that could fail.
What size ANL would you propose?
A 200 amp ANL would start most engines but would it increase safety if
it limited a short to only 2 or 300 amps of arcing for only say 10 seconds?
A 200 amp arc will almost certainly melt airframe material which will
increase the arc length and self extinguish within that time frame anyway.
Ken
On 05/12/2013 11:20 AM, Jeff Luckey wrote:
> Thank you for the explanation. I get it - the assumption is: very low
> probability of the wire getting into trouble assuming that it's
> well-installed w/ intelligence and craftsmanship.
>
> But staying with the original theme, is there any down side to putting a
> big current limiter (ANL?) in that lead at its origin?
>
> -Jeff
>
> PS - I'm also thinking about ways to protect that buss bar ;)
>
> ------------------------------------------------------------------------
> *From:* "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
> *To:* aeroelectric-list@matronics.com
> *Sent:* Thursday, December 5, 2013 7:54 AM
> *Subject:* Re: AeroElectric-List: Unprotected Feeder in Z Drawings
>
> <nuckolls.bob@aeroelectric.com <mailto:nuckolls.bob@aeroelectric.com>>
>
> At 11:00 PM 12/4/2013, you wrote:
> Bob,
>
> I have been reviewing some of the Z drawings in the back of "The
> Aeroelectric Connection" and I have a question. (specifically Z-11,
> Z-12, & Z-14)
>
> I notice that the 6 awg wire which connects the load side of the Battery
> Contactor to the Main Power Distribution bus is not fused. That seems
> like an un-protected feeder and gives me a little heart burn.
>
> I think of the Main Power Distribution bus as the bus bar which runs
> across the back of the breakers in my distribution panel which lives in
> my instrument panel. With the Battery Contactor on the firewall, the
> run from it to the distribution panel penetrates the firewall then
> snakes its way to the back of my panel. That #6 wire will be between 6
> & 8 feet in length.
>
> What happens if that wire gets into trouble along its route. Without a
> fuse it will get very hot and bad things will happen.
>
> I'm curious about the criteria used in this design. Perhaps I'm missing
> something?
>
> TIA,
>
> -Jeff
>
> Okay,
>
> Get out your toolbox and take a position to contemplate this 'risky'
> piece of wire. What process and tools are needed to 'get this wire into
> trouble'? Yes, it's attached to a battery with potential for spectacular
> fault currents, but so too is your propeller thrashing around in the
> breeze with a potential for serious bodily harm.
>
> It's easy to get bogged down worrying about things that have low to
> exceedingly small probability of happening. This is a fundamental
> component of Failure Modes Effects Analysis. The artfully crafted FMEA
> not only considers "what happens if . . .?" you're well advised to
> consider HOW that condition became a thing to consider in the first
> place. The goal is to decide which has more value: (1) protecting
> against a condition or (2) reducing probability of that condition to an
> acceptably low value.
>
> In the case of your fat-wire, which design goal offers the lowest level
> of risk and greatest boost of system reliability? (1) protect the wire
> loaded to some gawd-awful fault or (2) reduce probability of such an
> event to levels that says your worry-capital is better invested
> elsewhere? This thought process convinces us that building a safety
> cage around the propeller is not a useful/necessary expenditure of
> weight/cost/performance budget.
>
> There are exposed conductors that run across the back of most circuit
> breaker panels. These bus bars are legacy features of all manner of
> vehicle not the least of which are airplanes. Is there value in
> expending worry-capital on risk for faulting a bus bar? You can answer
> this question with pretty simple observation and contemplation. With a
> box full of tools at your disposal, what parts of the airplane do you
> have to hammer, pry or saw in order to get that bus bar . . . or your
> fat-wire into trouble?
>
> Once those actions are discovered and evaluated, what is the likelihood
> that such an event is going to befall the potential victim over the
> lifetime of your airplane? It's fairly predicable that your study will
> produce some combination of discoveries that fall in to two categories:
> (1) there are no features of structure or installed hardware likely to
> dislodge and attack the potential victim; (2) Oops! Some feature of
> installation of the wire or surrounds has not been installed with
> attention to good practices . . . and you're going to fix it.
>
> This same analysis (and incorporation of lessons-learned) produced the
> following excerpt from FAR23 for TC aircraft:
>
>
> Sec. 23.1357 Circuit protective devices.
>
> (a) Protective devices, such as fuses or circuit breakers, must be
> installed in all electrical circuits other than--
>
> (1) Main circuits of starter motors used during starting only; and
> (2) Circuits in which no hazard is presented by their omission.
>
> <continued>
>
> The controlling idea here is 23.1357(a)(2) where you're going to manage
> the installation of this 6AWG wire and its surrounds such that "no
> hazard is presentedution link below to find out more
> ronics.com/contribution"
> target="_blank">http://www.matronics.com/contribst ->
> http://www.matronics.com/Navigator?AeroElectric-List
> _ref="http://forums.matronics.com/"
> target="_blank">http://forums.matron==================
>
>
Message 4
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| Subject: | Re: Unprotected Feeder in Z Drawings |
Ken,=0A=0AIn the circuit that I'm thinking about the ANL would not be in th
e starter circuit - only in the feed to the distribution panel and maybe in
the 60-80 amp range.=0A=0AI think voltage drop will be very minimal.- Ad
ditional failure points, sure, but if we are assuming quality components &
workmanship that risk is also minimal.=0A=0A-Jeff=0A=0A=0A=0A______________
__________________=0A From: Ken <klehman@albedo.net>=0ATo: aeroelectric-lis
t@matronics.com =0ASent: Thursday, December 5, 2013 8:42 AM=0ASubject: Re:
AeroElectric-List: Unprotected Feeder in Z Drawings=0A =0A=0A--> AeroElectr
ic-List message posted by: Ken <klehman@albedo.net>=0A=0AAdditional voltage
drop and connections that could fail.=0A=0AWhat size ANL would you propose
?=0AA 200 amp ANL would start most engines but would it increase safety if
=0Ait limited a short to only 2 or 300 amps of arcing for only say 10 secon
ds?=0AA 200 amp arc will almost certainly melt airframe material which will
=0Aincrease the arc length and self extinguish within that time frame anyw
ay.=0A=0AKen=0A=0AOn 05/12/2013 11:20 AM, Jeff Luckey wrote:=0A> Thank you
for the explanation.- I get it - the assumption is: very low=0A> probabil
ity of the wire getting into trouble assuming that it's=0A> well-installed
w/ intelligence and craftsmanship.=0A>=0A> But staying with the original th
eme, is there any down side to putting a=0A> big current limiter (ANL?) in
that lead at its origin?=0A>=0A> -Jeff=0A>=0A> PS - I'm also thinking about
ways to protect that buss bar ;)=0A>=0A> ---------------------------------
---------------------------------------=0A> *From:* "Robert L. Nuckolls, II
I" <nuckolls.bob@aeroelectric.com>=0A> *To:* aeroelectric-list@matronics.co
m=0A> *Sent:* Thursday, December 5, 2013 7:54 AM=0A> *Subject:* Re: AeroEle
ctric-List: Unprotected Feeder in Z Drawings=0A>=0A> --> AeroElectric-List
message posted by: "Robert L. Nuckolls, III"=0A> <nuckolls.bob@aeroelectric
.com <mailto:nuckolls.bob@aeroelectric.com>>=0A>=0A> At 11:00 PM 12/4/2013,
you wrote:=0A> Bob,=0A>=0A> I have been reviewing some of the Z drawings i
n the back of "The=0A> Aeroelectric Connection" and I have a question.- (
specifically Z-11,=0A> Z-12, & Z-14)=0A>=0A> I notice that the 6 awg wire w
hich connects the load side of the Battery=0A> Contactor to the Main Power
Distribution bus is not fused.- That seems=0A> like an un-protected feede
r and gives me a little heart burn.=0A>=0A> I think of the Main Power Distr
ibution bus as the bus bar which runs=0A> across the back of the breakers i
n my distribution panel which lives in=0A> my instrument panel.- With the
Battery Contactor on the firewall, the=0A> run from it to the distribution
panel penetrates the firewall then=0A> snakes its way to the back of my pa
nel.- That #6 wire will be between 6=0A> & 8 feet in length.=0A>=0A> What
happens if that wire gets into trouble along its route.- Without a=0A> f
use it will get very hot and bad things will happen.=0A>=0A> I'm curious ab
out the criteria used in this design.- Perhaps I'm missing=0A> something?
=0A>=0A> TIA,=0A>=0A> -Jeff=0A>=0A> Okay,=0A>=0A> Get out your toolbox and
take a position to contemplate this 'risky'=0A> piece of wire. What process
and tools are needed to 'get this wire into=0A> trouble'? Yes, it's attach
ed to a battery with potential for spectacular=0A> fault currents, but so t
oo is your propeller thrashing around in the=0A> breeze with a potential fo
r serious bodily harm.=0A>=0A> It's easy to get bogged down worrying about
things that have low to=0A> exceedingly small probability of happening.-
This is a fundamental=0A> component of Failure Modes Effects Analysis.- T
he artfully crafted FMEA=0A> not only considers "what happens if . . .?" yo
u're well advised to=0A> consider HOW that condition became a thing to cons
ider in the first=0A> place. The goal is to decide which has more value: (1
) protecting=0A> against a condition or (2) reducing probability of that co
ndition to an=0A> acceptably low value.=0A>=0A> In the case of your fat-wir
e, which design goal offers the lowest level=0A> of risk and greatest boost
of system reliability? (1) protect the wire=0A> loaded to some gawd-awful
fault or (2) reduce probability of such an=0A> event to levels that says yo
ur worry-capital is better invested=0A> elsewhere?- This thought process
convinces us that building a safety=0A> cage around the propeller is not a
useful/necessary expenditure of=0A> weight/cost/performance budget.=0A>=0A>
There are exposed conductors that run across the back of most circuit=0A>
breaker panels. These bus bars are legacy features of all manner of=0A> veh
icle not the least of which are airplanes. Is there value in=0A> expending
worry-capital on risk for faulting a bus bar? You can answer=0A> this quest
ion with pretty simple observation and contemplation. With a=0A> box full o
f tools at your disposal, what parts of the airplane do you=0A> have to ham
mer, pry or saw in order to get that bus bar . . . or your=0A> fat-wire int
o trouble?=0A>=0A> Once those actions are discovered and evaluated, what is
the likelihood=0A> that such an event is going to befall the potential vic
tim over the=0A> lifetime of your airplane? It's fairly predicable that you
r study will=0A> produce some combination of discoveries that fall in to tw
o categories:=0A> (1) there are no features of structure or installed hardw
are likely to=0A> dislodge and attack the potential victim; (2) Oops! Some
feature of=0A> installation of the wire or surrounds has not been installed
with=0A> attention to good practices . . . and you're going to fix it.=0A>
=0A> This same analysis (and incorporation of lessons-learned) produced the
=0A> following excerpt from FAR23 for TC aircraft:=0A>=0A>=0A> Sec. 23.1357
- Circuit protective devices.=0A>=0A> (a) Protective devices, such as fus
es or circuit breakers, must be=0A> installed in all electrical circuits ot
her than--=0A>=0A>- - - - - (1) Main circuits of starter motors u
sed during starting only; and=0A>- - - - - (2) Circuits in which
no hazard is presented by their omission.=0A>=0A> <continued>=0A>=0A> The c
ontrolling idea here is 23.1357(a)(2) where you're going to manage=0A> the
installation of this 6AWG wire and its surrounds such that "no=0A> hazard i
s presentedution link below to find out more=0A> ronics.com/contribution"
=0A> target="_blank">http://www.matronics.com/contribst ->=0A> http://www
.matronics.com/Navigator?AeroElectric-List=0A> _ref="http://forums.matron
ics.com/"=0A> target="_blank">http://forums.matron=======
====
Message 5
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| Subject: | Re: Unprotected Feeder in Z Drawings |
Jeff
In that case if you decide to do it I'd suggest that something like a
maxi fuse would be more appropriate than a very slow acting ANL. I'd
still lean towards no protection but you are obviously more familiar
with your wire routing. I'd make sure that it isn't going to present a
major problem though if you get a nuisance trip after takeoff.
Ken
On 05/12/2013 12:03 PM, Jeff Luckey wrote:
> Ken,
>
> In the circuit that I'm thinking about the ANL would not be in the
> starter circuit - only in the feed to the distribution panel and maybe
> in the 60-80 amp range.
>
> I think voltage drop will be very minimal. Additional failure points,
> sure, but if we are assuming quality components & workmanship that risk
> is also minimal.
>
> -Jeff
>
> ------------------------------------------------------------------------
> *From:* Ken <klehman@albedo.net>
> *To:* aeroelectric-list@matronics.com
> *Sent:* Thursday, December 5, 2013 8:42 AM
> *Subject:* Re: AeroElectric-List: Unprotected Feeder in Z Drawings
>
> <mailto:klehman@albedo.net>>
>
> Additional voltage drop and connections that could fail.
>
> What size ANL would you propose?
> A 200 amp ANL would start most engines but would it increase safety if
> it limited a short to only 2 or 300 amps of arcing for only say 10 seconds?
> A 200 amp arc will almost certainly melt airframe material which will
> increase the arc length and self extinguish within that time frame anyway.
>
> Ken
>
> On 05/12/2013 11:20 AM, Jeff Luckey wrote:
> > Thank you for the explanation. I get it - the assumption is: very low
> > probability of the wire getting into trouble assuming that it's
> > well-installed w/ intelligence and craftsmanship.
> >
> > But staying with the original theme, is there any down side to putting a
> > big current limiter (ANL?) in that lead at its origin?
> >
> > -Jeff
> >
> > PS - I'm also thinking about ways to protect that buss bar ;)
> >
> > ------------------------------------------------------------------------
> > *From:* "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com
> <mailto:nuckolls.bob@aeroelectric.com>>
> > *To:* aeroelectric-list@matronics.com
> <mailto:aeroelectric-list@matronics.com>
> > *Sent:* Thursday, December 5, 2013 7:54 AM
> > *Subject:* Re: AeroElectric-List: Unprotected Feeder in Z Drawings
> >
> > <nuckolls.bob@aeroelectric.com <mailto:nuckolls.bob@aeroelectric.com>
> <mailto:nuckolls.bob@aeroelectric.com
> <mailto:nuckolls.bob@aeroelectric.com>>>
> >
> > At 11:00 PM 12/4/2013, you wrote:
> > Bob,
> >
> > I have been reviewing some of the Z drawings in the back of "The
> > Aeroelectric Connection" and I have a question. (specifically Z-11,
> > Z-12, & Z-14)
> >
> > I notice that the 6 awg wire which connects the load side of the Battery
> > Contactor to the Main Power Distribution bus is not fused. That seems
> > like an un-protected feeder and gives me a little heart burn.
> >
> > I think of the Main Power Distribution bus as the bus bar which runs
> > across the back of the breakers in my distribution panel which lives in
> > my instrument panel. With the Battery Contactor on the firewall, the
> > run from it to the distribution panel penetrates the firewall then
> > snakes its way to the back of my panel. That #6 wire will be between 6
> > & 8 feet in length.
> >
> > What happens if that wire gets into trouble along its route. Without a
> > fuse it will get very hot and bad things will happen.
> >
> > I'm curious about the criteria used in this design. Perhaps I'm missing
> > something?
> >
> > TIA,
> >
> > -Jeff
> >
> > Okay,
> >
> > Get out your toolbox and take a position to contemplate this 'risky'
> > piece of wire. What process and tools are needed to 'get this wire into
> > trouble'? Yes, it's attached to a battery with potential for spectacular
> > fault currents, but so too is your propeller thrashing around in the
> > breeze with a potential for serious bodily harm.
> >
> > It's easy to get bogged down worrying about things that have low to
> > exceedingly small probability of happening. This is a fundamental
> > component of Failure Modes Effects Analysis. The artfully crafted FMEA
> > not only considers "what happens if . . .?" you're well advised to
> > consider HOW that condition became a thing to consider in the first
> > place. The goal is to decide which has more value: (1) protecting
> > against a condition or (2) reducing probability of that condition to an
> > acceptably low value.
> >
> > In the case of your fat-wire, which design goal offers the lowest level
> > of risk and greatest boost of system reliability? (1) protect the wire
> > loaded to some gawd-awful fault or (2) reduce probability of such an
> > event to levels that says your worry-capital is better invested
> > elsewhere? This thought process convinces us that building a safety
> > cage around the propeller is not a useful/necessary expenditure of
> > weight/cost/performance budget.
> >
> > There are exposed conductors that run across the back of most circuit
> > breaker panels. These bus bars are legacy features of all manner of
> > vehicle not the least of which are airplanes. Is there value in
> > expending worry-capital on risk for faulting a bus bar? You can answer
> > this question with pretty simple observation and contemplation. With a
> > box full of tools at your disposal, what parts of the airplane do you
> > have to hammer, pry or saw in order to get that bus bar . . . or your
> > fat-wire into trouble?
> >
> > Once those actions are discovered and evaluated, what is the likelihood
> > that such an event is going to befall the potential victim over the
> > lifetime of your airplane? It's fairly predicable that your study will
> > produce some combination of discoveries that fall in to two categories:
> > (1) there are no features of structure or installed hardware likely to
> > dislodge and attack the potential victim; (2) Oops! Some feature of
> > installation of the wire or surrounds has not been installed with
> > attention to good practices . . . and you're going to fix it.
> >
> > This same analysis (and incorporation of lessons-learned) produced the
> > following excerpt from FAR23 for TC aircraft:
> >
> >
> > Sec. 23.1357 Circuit protective devices.
> >
> > (a) Protective devices, such as fuses or circuit breakers, must be
> > installed in all electrical circuits other than--
> >
> > (1) Main circuits of starter motors used during starting
> only; and
> > (2) Circuits in which no hazard is presented by their omission.
> >
> > <continued>
> >
> > The controlling idea here is 23.1357(a)(2) where you're going to manage
> > the installation of this 6AWG wire and its surrounds such that "no
> > hazard is presentedution link below to find out more
> > ronics.com/contribution"
> > target="_blank">http://www.matronics.com/contribst ->
> > http://www.matronics.com/Navigator?AeroElectric-List
> > _ref="http://forums.matronics.com/"
> >
> target="_blank">http://forums.matron==============p://www.matronics.com/contribution"
> target="_blank">http://www.matronics.nbsp; -Matt Dralle,
> List Atric-List"
> target="_blank">http://www.matronics.com/Navigator?AeroElectrip; -->
> <http://forums.matron===================/>http:=======================
>
>
> <http://forums.matronics.com/>
> <http://forums.matronics.com/>
> <http://forums.matronics.com/>
> <http://forums.matronics.com/>
> <http://forums.matronics.com/>
>
> *
>
> *
>
Message 6
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| Subject: | Re: Unprotected Feeder in Z Drawings |
Ken,=0A=0AI think you put your finger on it - I'm interested in analyzing t
he potential for events which are non-catastrophic & transient in nature th
at might cause the fuse to pop un-necessarily (nuisance trip).=0A=0AI think
that's a pretty small universe and at the moment I can't think of an examp
le of such an event - perhaps that's because there are none.- I'm hoping
the brain trust on this list can think of such an event that I may be overl
ooking.=0A=0A=0A-Jeff=0A=0A=0A=0A________________________________=0A From:
Ken <klehman@albedo.net>=0ATo: aeroelectric-list@matronics.com =0ASent: Thu
rsday, December 5, 2013 9:39 AM=0ASubject: Re: AeroElectric-List: Unprotect
en <klehman@albedo.net>=0A=0AJeff=0AIn that case if you decide to do it I'd
suggest that something like a =0Amaxi fuse would be more appropriate than
a very slow acting ANL. I'd =0Astill lean towards no protection but you are
obviously more familiar =0Awith your wire routing. I'd make sure that it i
sn't going to present a =0Amajor problem though if you get a nuisance trip
after takeoff.=0AKen=0A=0AOn 05/12/2013 12:03 PM, Jeff Luckey wrote:=0A> Ke
n,=0A>=0A> In the circuit that I'm thinking about the ANL would not be in t
he=0A> starter circuit - only in the feed to the distribution panel and may
be=0A> in the 60-80 amp range.=0A>=0A> I think voltage drop will be very mi
nimal.- Additional failure points,=0A> sure, but if we are assuming quali
ty components & workmanship that risk=0A> is also minimal.=0A>=0A> -Jeff=0A
>=0A> ---------------------------------------------------------------------
---=0A> *From:* Ken <klehman@albedo.net>=0A> *To:* aeroelectric-list@matron
ics.com=0A> *Sent:* Thursday, December 5, 2013 8:42 AM=0A> *Subject:* Re: A
eroElectric-List: Unprotected Feeder in Z Drawings=0A>=0A> --> AeroElectric
-List message posted by: Ken <klehman@albedo.net=0A> <mailto:klehman@albedo
.net>>=0A>=0A> Additional voltage drop and connections that could fail.=0A>
=0A> What size ANL would you propose?=0A> A 200 amp ANL would start most en
gines but would it increase safety if=0A> it limited a short to only 2 or 3
00 amps of arcing for only say 10 seconds?=0A> A 200 amp arc will almost ce
rtainly melt airframe material which will=0A> increase the arc length and s
elf extinguish within that time frame anyway.=0A>=0A> Ken=0A>=0A> On 05/12/
2013 11:20 AM, Jeff Luckey wrote:=0A>- > Thank you for the explanation.
- I get it - the assumption is: very low=0A>- > probability of the wire
getting into trouble assuming that it's=0A>- > well-installed w/ intelli
gence and craftsmanship.=0A>- >=0A>- > But staying with the original th
eme, is there any down side to putting a=0A>- > big current limiter (ANL?
) in that lead at its origin?=0A>- >=0A>- > -Jeff=0A>- >=0A>- > PS
- I'm also thinking about ways to protect that buss bar ;)=0A>- >=0A>-
> ------------------------------------------------------------------------
=0A>- > *From:* "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com
=0A> <mailto:nuckolls.bob@aeroelectric.com>>=0A>- > *To:* aeroelectric-li
st@matronics.com=0A> <mailto:aeroelectric-list@matronics.com>=0A>- > *Sen
t:* Thursday, December 5, 2013 7:54 AM=0A>- > *Subject:* Re: AeroElectric
-List: Unprotected Feeder in Z Drawings=0A>- >=0A>- > --> AeroElectric-
List message posted by: "Robert L. Nuckolls, III"=0A>- > <nuckolls.bob@ae
roelectric.com <mailto:nuckolls.bob@aeroelectric.com>=0A> <mailto:nuckolls.
bob@aeroelectric.com=0A> <mailto:nuckolls.bob@aeroelectric.com>>>=0A>- >
=0A>- > At 11:00 PM 12/4/2013, you wrote:=0A>- > Bob,=0A>- >=0A>- >
I have been reviewing some of the Z drawings in the back of "The=0A>- >
Aeroelectric Connection" and I have a question.- (specifically Z-11,=0A>
- > Z-12, & Z-14)=0A>- >=0A>- > I notice that the 6 awg wire which co
nnects the load side of the Battery=0A>- > Contactor to the Main Power Di
stribution bus is not fused.- That seems=0A>- > like an un-protected fe
eder and gives me a little heart burn.=0A>- >=0A>- > I think of the Mai
n Power Distribution bus as the bus bar which runs=0A>- > across the back
of the breakers in my distribution panel which lives in=0A>- > my instru
ment panel.- With the Battery Contactor on the firewall, the=0A>- > run
from it to the distribution panel penetrates the firewall then=0A>- > sn
akes its way to the back of my panel.- That #6 wire will be between 6=0A>
- > & 8 feet in length.=0A>- >=0A>- > What happens if that wire gets
into trouble along its route.- Without a=0A>- > fuse it will get very h
ot and bad things will happen.=0A>- >=0A>- > I'm curious about the crit
eria used in this design.- Perhaps I'm missing=0A>- > something?=0A>-
>=0A>- > TIA,=0A>- >=0A>- > -Jeff=0A>- >=0A>- > Okay,=0A>- >
=0A>- > Get out your toolbox and take a position to contemplate this 'ris
ky'=0A>- > piece of wire. What process and tools are needed to 'get this
wire into=0A>- > trouble'? Yes, it's attached to a battery with potential
for spectacular=0A>- > fault currents, but so too is your propeller thra
shing around in the=0A>- > breeze with a potential for serious bodily har
m.=0A>- >=0A>- > It's easy to get bogged down worrying about things tha
t have low to=0A>- > exceedingly small probability of happening.- This
is a fundamental=0A>- > component of Failure Modes Effects Analysis.- T
he artfully crafted FMEA=0A>- > not only considers "what happens if . . .
?" you're well advised to=0A>- > consider HOW that condition became a thi
ng to consider in the first=0A>- > place. The goal is to decide which has
more value: (1) protecting=0A>- > against a condition or (2) reducing pr
obability of that condition to an=0A>- > acceptably low value.=0A>- >
=0A>- > In the case of your fat-wire, which design goal offers the lowest
level=0A>- > of risk and greatest boost of system reliability? (1) prote
ct the wire=0A>- > loaded to some gawd-awful fault or (2) reduce probabil
ity of such an=0A>- > event to levels that says your worry-capital is bet
ter invested=0A>- > elsewhere?- This thought process convinces us that
building a safety=0A>- > cage around the propeller is not a useful/necess
ary expenditure of=0A>- > weight/cost/performance budget.=0A>- >=0A>-
> There are exposed conductors that run across the back of most circuit=0A
>- > breaker panels. These bus bars are legacy features of all manner of
=0A>- > vehicle not the least of which are airplanes. Is there value in
=0A>- > expending worry-capital on risk for faulting a bus bar? You can a
nswer=0A>- > this question with pretty simple observation and contemplati
on. With a=0A>- > box full of tools at your disposal, what parts of the a
irplane do you=0A>- > have to hammer, pry or saw in order to get that bus
bar . . . or your=0A>- > fat-wire into trouble?=0A>- >=0A>- > Once t
hose actions are discovered and evaluated, what is the likelihood=0A>- >
that such an event is going to befall the potential victim over the=0A>-
> lifetime of your airplane? It's fairly predicable that your study will=0A
>- > produce some combination of discoveries that fall in to two categori
es:=0A>- > (1) there are no features of structure or installed hardware l
ikely to=0A>- > dislodge and attack the potential victim; (2) Oops! Some
feature of=0A>- > installation of the wire or surrounds has not been inst
alled with=0A>- > attention to good practices . . . and you're going to f
ix it.=0A>- >=0A>- > This same analysis (and incorporation of lessons-l
earned) produced the=0A>- > following excerpt from FAR23 for TC aircraft:
=0A>- >=0A>- >=0A>- > Sec. 23.1357- Circuit protective devices.=0A>
- >=0A>- > (a) Protective devices, such as fuses or circuit breakers, m
ust be=0A>- > installed in all electrical circuits other than--=0A>- >
=0A>- >- - - - - (1) Main circuits of starter motors used durin
g starting=0A> only; and=0A>- >- - - - - (2) Circuits in which
no hazard is presented by their omission.=0A>- >=0A>- > <continued>=0A>
- >=0A>- > The controlling idea here is 23.1357(a)(2) where you're goin
g to manage=0A>- > the installation of this 6AWG wire and its surrounds s
uch that "no=0A>- > hazard is presentedution link below to find out more
=0A>- > ronics.com/contribution"=0A>- > target="_blank">http://www.ma
tronics.com/contribst ->=0A>- > http://www.matronics.com/Navigator?AeroEl
ectric-List=0A>- > _ref="http://forums.matronics.com/"=0A>- >=0A> tar
get="_blank">http://forums.matron=============
=p://www.matronics.com/contribution"=0A> target="_blank">http://www.mat
ronics.nbsp;- - - - - - - -Matt Dralle,=0A> List Atric-List"
=0A> target="_blank">http://www.matronics.com/Navigator?AeroElectrip; -->
=0A> <http://forums.matron================
===/>http:===================
======0A>=0A>=0A>=0A>=0A>=0A> <http://forums.matronics.com/>=0A>
<http://forums.matronics.com/>=0A> <http://forums.matronics.com/>=0A> <http
://forums.matronics.com/>=0A> <http://forums.matronics.com/>=0A>=0A> *=0A>
===============
Message 7
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| Subject: | Re: Unprotected Feeder in Z Drawings |
At 10:20 AM 12/5/2013, you wrote:
>Thank you for the explanation. I get it - the assumption is: very
>low probability of the wire getting into trouble assuming that it's
>well-installed w/ intelligence and craftsmanship.
>
>But staying with the original theme, is there any down side to
>putting a big current limiter (ANL?) in that lead at its origin?
>
>-Jeff
>
>PS - I'm also thinking about ways to protect that buss bar ;)
. . . as you wish.
Bob . . .
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