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grant.corriveau(at)TELUS.
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 Posted: Tue Nov 11, 2008 9:37 am Post subject: Wires and fuses and such |
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Shouldn't fuses/cbs be matched to protect the wire in the circuit?
So matching the fuse to the amp draw of the load item seems to be
skipping a step - no?
The wire gauge should be selected to match the load, cooling
requirements, distance of the run, voltage loss over that distance
etc. Then the fuse/cb is matched to the wire gauge. Isn't that the
way it's "supposed" to be done?
Having said that, after wiring my plane according to Bob Nucholl's
excellent manual, if I did it over again I might do like most car
manufacturers do and use nothing less than 16 gauge wire w 10 amp
fuses. This would vastly simplify the whole thing, simplify the fuse
layout/ need for extras; and would add only a negligible amount of
weight on a simple aircraft like this.
fwiw
Grant
C-GHTF w/ CAM100
(now into winter works projects/upgrades)
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psm(at)att.net
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| Posted: Tue Nov 11, 2008 9:59 am Post subject: Wires and fuses and such |
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Hi Grant,
I think your procedure is OK but a bit of overkill. It would work,
but so would using fuses that are sufficiently large to not blow
under normal use. For example, a 10 amp fuse will do a fine job on a
circuit that only draws 1 amp under normal use.
I have separate fuses for each major electrical or electronic
device. I put them in nice little fuse blocks I got from NAPA.
My idea is if a fuse blows then it only takes out one device and
repairs should be delayed until after the flight is over. That means
I mounted the fuse blocks behind the instrument panel, the way it is
normally done in cars, rather than cluttering the panel front with them.
Paul
XL getting close
At 09:27 AM 11/11/2008, you wrote:
| Quote: |
Shouldn't fuses/cbs be matched to protect the wire in the circuit?
So matching the fuse to the amp draw of the load item seems to be
skipping a step - no?
The wire gauge should be selected to match the load, cooling
requirements, distance of the run, voltage loss over that distance
etc. Then the fuse/cb is matched to the wire gauge. Isn't that the
way it's "supposed" to be done?
Having said that, after wiring my plane according to Bob Nucholl's
excellent manual, if I did it over again I might do like most car
manufacturers do and use nothing less than 16 gauge wire w 10 amp
fuses. This would vastly simplify the whole thing, simplify the fuse
layout/ need for extras; and would add only a negligible amount of
weight on a simple aircraft like this.
fwiw
Grant
C-GHTF w/ CAM100
|
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maarten versteeg
Joined: 15 May 2007
Posts: 37
Location: San Antonio
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| Posted: Wed Nov 12, 2008 6:35 am Post subject: Wires and fuses and such |
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Hello Paul,
I agree with you that messing with fuses in flight seems a hazardous
activity and
only should be considered if really needed. But I have a question
regarding you
clean solution of placing the fuses out of sight.
The FAR Sec. 23.1357 Circuit protective devices. says: "(d) If the
ability to reset
a circuit breaker or replace a fuse is essential to safety in flight,
that circuit breaker
or fuse must be so located and identified that it can be readily reset
or replaced in
flight.".
Do you know how a DAR would interpret the above rule with respect to you
panel design? Clearly the word open for interpretation is "safety in
flight", would
you consider all electrical systems served by the fuses to fall outside
the safety
in flight category?
Regards,
Maarten
plans building XL, getting close to closing the second wing
| Quote: | Time: 09:59:45 AM PST US
From: Paul Mulwitz <psm(at)att.net>
Subject: Re: Wires and fuses and such
Hi Grant,
I think your procedure is OK but a bit of overkill. It would work,
but so would using fuses that are sufficiently large to not blow
under normal use. For example, a 10 amp fuse will do a fine job on a
circuit that only draws 1 amp under normal use.
I have separate fuses for each major electrical or electronic
device. I put them in nice little fuse blocks I got from NAPA.
My idea is if a fuse blows then it only takes out one device and
repairs should be delayed until after the flight is over. That means
I mounted the fuse blocks behind the instrument panel, the way it is
normally done in cars, rather than cluttering the panel front with them.
Paul
XL getting close
|
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_________________
Maarten Versteeg
601XL scratch building wings |
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psm(at)att.net
Guest
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| Posted: Wed Nov 12, 2008 8:03 am Post subject: Wires and fuses and such |
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Hi Maarten,
I guess the regulation you cited explains why so many panels are
crowded with circuit breakers. In their great wisdom, the FAA seems
to have dictated that solution.
Fortunately, I don't think part 23 regulations apply to experimental
- amateur built airplanes. This may be one of many examples of the
notion that the FAA regulations are overly restrictive on certified planes.
To directly answer your question, my plans are to limit my flights to
Day/VFR. I suspect I could safely conduct such flights without any
electrical equipment operating at all. The only really essential
piece of electrical gear is the starter motor. My Jabiru is not
likely to start any other way.
Best regards,
Paul
At 06:34 AM 11/12/2008, you wrote:
| Quote: | Hello Paul,
I agree with you that messing with fuses in flight seems a hazardous
activity and
only should be considered if really needed. But I have a question
regarding you
clean solution of placing the fuses out of sight.
The FAR Sec. 23.1357 Circuit protective devices. says: "(d) If the
ability to reset
a circuit breaker or replace a fuse is essential to safety in
flight, that circuit breaker
or fuse must be so located and identified that it can be readily
reset or replaced in
flight.".
Do you know how a DAR would interpret the above rule with respect to you
panel design? Clearly the word open for interpretation is "safety in
flight", would
you consider all electrical systems served by the fuses to fall
outside the safety
in flight category?
Regards,
Maarten
plans building XL, getting close to closing the second wing
|
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