Today's Message Index:
----------------------
1. 06:28 AM - Re: Newbie Wiring Questions (user9253)
2. 06:38 AM - Re: Newbie Wiring Questions (Art Zemon)
3. 07:39 AM - Wire length in aluminum airframes (Charlie England)
4. 07:46 AM - Re: Newbie Wiring Questions (Ken Ryan)
5. 07:48 AM - Re: Re: Newbie Wiring Questions (Rene)
6. 08:34 AM - Fuel Level signal to G3X and Gauge (Dan Olson)
7. 08:59 AM - Re: Newbie Wiring Questions (user9253)
8. 03:03 PM - Re: Selecting a Fuse (Art Zemon)
9. 03:11 PM - Re: Re: Selecting a Fuse (jtortho@aol.com)
10. 03:30 PM - Re: Re: Selecting a Fuse (Larry Mac Donald)
11. 04:19 PM - Re: Re: Selecting a Fuse (Art Zemon)
12. 10:06 PM - Z-1 Magneto Wiring Question (mike)
Message 1
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Subject: | Re: Newbie Wiring Questions |
I agree with kenryan. Fuse sizes in a table are the maximum fuse sizes. There
is nothing wrong with using a smaller fuse size as long as it does not nuisance
blow. If the wire size is increased to reduce voltage drop over a long distance,
the fuse size does not need to be increased. If there are plenty of fuse
slots available, it is preferable to fuse each load separately rather than
to combine loads onto one fuse. If one load blows a fuse, you do not want an
unrelated circuit to be disabled too.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=453383#453383
Message 2
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Subject: | Re: Newbie Wiring Questions |
Thank you for the references, Ken. That was just the sort of information I
was seeking.
BTW, I found this online Voltage Drop Calculator
<http://www.rapidtables.com/calc/wire/voltage-drop-calculator.htm> to be
pretty useful.
-- Art Z.
On Wed, Mar 2, 2016 at 11:40 PM, Ken Ryan <keninalaska@gmail.com> wrote:
> Example: 1.7 amp X 2 = 3.4 amps. Table 11-9 in AC43.13 shows to carry that
> amount of current you will need at least #20 wire. Figure 11-2 shows #20
> wire with 4 amps can only be 12 feet long (otherwise too much voltage
> drop). I would use #18 to be safe. Table 11-3 shows #18 wire being
> protected by 10 amp breaker or 10 amp fuse. That would be the maximum.
> Since the load is only 3.4 amps I would use a 5 amp fuse. Or something like
> that. Consult 43.13 for specifics.
>
--
http://CheerfulCurmudgeon.com/ <http://cheerfulcurmudgeon.com/>
*"If I am not for myself, who is for me? And if I am only for myself, what
am I? And if not now, when?" Hillel*
Message 3
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Subject: | Wire length in aluminum airframes |
Bob, I'm in the midst of wiring my RV-7, & realized that I can't find an
answer in 'the book' for this question. In the book and articles you've
written, you mention total wire distance (out & back), referencing
fiberglass airframes. But how do you compute wire length when you're
using an aluminum airframe for ground return for things like landing
lights, pitot heat, etc? Can the return path be essentially ignored,
since the return 'conductor' is so massively oversized?
And just for the sake of discussion, would the answer change if it's a
steel tube fuselage (significantly higher resistance for steel, but
still massive)?
Thanks,
Charlie
Message 4
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Subject: | Re: Newbie Wiring Questions |
A 5 amp fuse or breaker will certainly protect an 18AWG wire, so yes, the
fuse is sized to protect the wire.
On Wed, Mar 2, 2016 at 9:17 PM, Rob Turk <matronics@rtist.nl> wrote:
> Good example, but you didn't apply the "size the fuse to protect the wire"
> rule. Using a 5A fuse is sized to the load, not to the wire. The table says
> 10A for a #18 wire, so use 10A.
>
> On 3/3/2016 6:40 AM, Ken Ryan wrote:
>
> Example: 1.7 amp X 2 = 3.4 amps. Table 11-9 in AC43.13 shows to carry that
> amount of current you will need at least #20 wire. Figure 11-2 shows #20
> wire with 4 amps can only be 12 feet long (otherwise too much voltage
> drop). I would use #18 to be safe. Table 11-3 shows #18 wire being
> protected by 10 amp breaker or 10 amp fuse. That would be the maximum.
> Since the load is only 3.4 amps I would use a 5 amp fuse. Or something like
> that. Consult 43.13 for specifics.
>
> On Wed, Mar 2, 2016 at 8:16 PM, Charlie England <ceengland7@gmail.com>
> wrote:
>
>> Size the wire for the load. Size the fuse to protect the wire.
>>
>>
>> -------- Original message --------
>> From: Art Zemon
>> Date:03/02/2016 9:39 PM (GMT-06:00)
>> To: aeroelectric-list@matronics.com
>> Subject: AeroElectric-List: Newbie Wiring Questions
>>
>> Hello,
>>
>> I am starting to plan the wiring for my BD-4C. My immediate problem is
>> that I want to install the wires for things which will go in the rear of
>> the plane, and near the floor by the back seat, soon so that I can close up
>> the "tunnel" and (hopefully) not need to get in there again.
>>
>> The autopilot servos and the magnetometer have me wondering what to do.
>> Each needs power + 4 signal wires. The autopilot servos draw up to 1.7 A so
>> I think I use larger wire for the power than the signals. The magnetomer
>> only draws 0.12 A, though, so do I just get a cable with 5 or 6 conductors
>> in it? Or should the power be a separate wire from a 4-conductor signal
>> cable?
>>
>> The rear seat intercomm has me wondering, too. It looks like 4-conductors
>> will do, since there aren't any PTT switches. But shielded or not? I think
>> not but would like some reassurance.
>>
>> Finally, an off the wall question: How do you size a fuse for a circuit?
>> Do you just round up to the next highest integer or do you go bigger? I'm
>> thinking of the autopilot servos, average current of 0.9 A and max current
>> of 1.71 A. Should I use a 2 A fuse? 3 A? Put both on a single 5 A fuse?
>> Something else?
>>
>> Thanks,
>> -- Art Z.
>>
>> --
>> http://CheerfulCurmudgeon.com/ <http://cheerfulcurmudgeon.com/>
>>
>> *"If I am not for myself, who is for me? And if I am only for myself,
>> what am I? And if not now, when?" Hillel*
>>
>
>
Message 5
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Subject: | Re: Newbie Wiring Questions |
Not to start another primer war....
As my old school electrical engineer reminds me every time we are on a
project. The fuse is to protect the wire, size it that way.
If the wire is capable of handling 10 amps, why not use a 10 amp
fuse.......? That might be the question.
I completed my airplane in 2008. Since then I have modified my panel many
times. That has required me to change CBs because I added loads to a line.
I wish I would have followed my EE advice and just set the breaker to the
wire size.
Rene'
801-721-6080
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of user9253
Sent: Thursday, March 03, 2016 7:26 AM
Subject: AeroElectric-List: Re: Newbie Wiring Questions
I agree with kenryan. Fuse sizes in a table are the maximum fuse sizes.
There is nothing wrong with using a smaller fuse size as long as it does not
nuisance blow. If the wire size is increased to reduce voltage drop over a
long distance, the fuse size does not need to be increased. If there are
plenty of fuse slots available, it is preferable to fuse each load
separately rather than to combine loads onto one fuse. If one load blows a
fuse, you do not want an unrelated circuit to be disabled too.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=453383#453383
Message 6
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Subject: | Fuel Level signal to G3X and Gauge |
I have two Rochester fuel gauges in my Glasair. One for the main, one for the
header. These are wired to two float type resistive sensors (30-240ohm). I have
asked the G3X guys if anyone has had success getting both the gauge and G3X
input to work off of one sender. They mentioned the G3X has a pull up resistor
and might interact with the gauge. Any thoughts about how to make this work?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=453391#453391
Message 7
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Subject: | Re: Newbie Wiring Questions |
> If the wire is capable of handling 10 amps, why not use a 10 amp
> fuse.......?
In this particular case where the maximum load is less than 3 amps, I would use
a 3 or 5 amp fuse because, when something shorts out, a smaller fuse will blow
quicker and there will be less spark and smoke. Sizing circuit protection at
the maximum allowed does have the advantage of being able to add future loads
to that circuit.
There was a recent discussion on VansAirforce about the number of fuses that should
be installed. The consensus was: twice as many as the expected need. Fuses
and fuse blocks are relatively inexpensive.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=453393#453393
Message 8
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Subject: | Re: Selecting a Fuse |
This is good stuff. I appreciate all of the opinions.
Here is a "fer instance:" I have an autopilot servo which averages 0.9A
and, at max torque, draws 1.71A. It sounds like I might select a fuse this
way:
1. I need 10' of wire.
2. The manufacturer recommends 18-20 AWG wire. Using 20 AWG wire, 1.7A @
14V will drop 0.3V in 10'. That seems OK to me.
3. Then, rather than fuse to the max current that 20 AWG can carry, I
might try a 2A fuse. If that nuisance blows, I could try either 3A or 2A
slow-blow.
Reasonable?
Thanks,
-- Art Z.
On Thu, Mar 3, 2016 at 8:26 AM, user9253 <fransew@gmail.com> wrote:
>
> I agree with kenryan. Fuse sizes in a table are the maximum fuse sizes.
> There is nothing wrong with using a smaller fuse size as long as it does
> not nuisance blow. If the wire size is increased to reduce voltage drop
> over a long distance, the fuse size does not need to be increased.
--
http://CheerfulCurmudgeon.com/ <http://cheerfulcurmudgeon.com/>
*"If I am not for myself, who is for me? And if I am only for myself, what
am I? And if not now, when?" Hillel*
Message 9
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Subject: | Re: Selecting a Fuse |
The next question is how many types of wire do you want to buy?
A roll of 18ga will serve most purposes,some as overkill. It is minimally stiffer
to handle.
The weight increase for the plane is neglibable. Decreases the number of connecter
sizes to buy
Jim Timoney
-----Original Message-----
From: Art Zemon <art@zemon.name>
Sent: Thu, Mar 3, 2016 6:05 pm
Subject: AeroElectric-List: Re: Selecting a Fuse
This is good stuff. I appreciate all of the opinions.
Here is a "fer instance:" I have an autopilot servo which averages 0.9A and, at
max torque, draws 1.71A. It sounds like I might select a fuse this way:
I need 10' of wire.
The manufacturer recommends 18-20 AWG wire. Using 20 AWG wire, 1.7A @ 14V will
drop 0.3V in 10'. That seems OK to me.
Then, rather than fuse to the max current that 20 AWG can carry, I might try a
2A fuse. If that nuisance blows, I could try either 3A or 2A slow-blow.
Reasonable?
Thanks,
-- Art Z.
On Thu, Mar 3, 2016 at 8:26 AM, user9253 <fransew@gmail.com> wrote:
I agree with kenryan. Fuse sizes in a table are the maximum fuse sizes. There
is nothing wrong with using a smaller fuse size as long as it does not nuisance
blow. If the wire size is increased to reduce voltage drop over a long distance,
the fuse size does not need to be increased.
--
http://CheerfulCurmudgeon.com/
"If I am not for myself, who is for me? And if I am only for myself, what am I?
And if not now, when?" Hillel
Message 10
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Subject: | Re: Selecting a Fuse |
I'll take a shot at this.
The N. electrical code requires you to to size the wire to 125% of its a
mpacity and then size the fuse at 80% of that, or less. Again its over s
ize the wire for the load and under size the fuse to protect the wire. I
f you want to protect the appliance, put protection at the appliance.
Larry
On Mar 3, 2016, at 6:02 PM, Art Zemon wrote:
> This is good stuff. I appreciate all of the opinions.
>
> Here is a "fer instance:" I have an autopilot servo which averages 0.9
A and, at max torque, draws 1.71A. It sounds like I might select a fuse
this way:
> I need 10' of wire.
> The manufacturer recommends 18-20 AWG wire. Using 20 AWG wire, 1.7A @
14V will drop 0.3V in 10'. That seems OK to me.
> Then, rather than fuse to the max current that 20 AWG can carry, I mig
ht try a 2A fuse. If that nuisance blows, I could try either 3A or 2A sl
ow-blow.
> Reasonable?
>
> Thanks,
> -- Art Z.
>
> On Thu, Mar 3, 2016 at 8:26 AM, user9253 <fransew@gmail.com> wrote:
>
>
> I agree with kenryan. Fuse sizes in a table are the maximum fuse size
s. There is nothing wrong with using a smaller fuse size as long as it
does not nuisance blow. If the wire size is increased to reduce voltage
drop over a long distance, the fuse size does not need to be increased.
>
>
> --
> http://CheerfulCurmudgeon.com/
>
> "If I am not for myself, who is for me? And if I am only for myself, w
hat am I? And if not now, when?" Hillel
>
>
> ____________________________________________________________
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Message 11
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Subject: | Re: Selecting a Fuse |
So actually reading AC43-13 was illuminating.
11-48. DETERMINATION OF CIRCUIT BREAKER RATINGS. Circuit protection devices
> must be sized to supply open circuit capability. *A circuit breaker must
> be rated so that it will open before the current rating of the wire
> attached to it is exceeded, or before the cumulative rating of all loads
> connected to it are exceeded, whichever is lowest.* A circuit breaker
> must always open before any component downstream can overheat and generate
> smoke or fire.
I added the emphasis.
It looks like using a 2A breaker to protect a 1.7A device on a 20 AWG wire
can be justified by AC43-13.
Cheers,
-- Art Z.
--
http://CheerfulCurmudgeon.com/ <http://cheerfulcurmudgeon.com/>
*"If I am not for myself, who is for me? And if I am only for myself, what
am I? And if not now, when?" Hillel*
Message 12
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Subject: | Z-1 Magneto Wiring Question |
I am wiring my magneto's according to the set-up in the Z-1 diagram.
I have a phobia about leaving the magneto's on and would like to have some type
of sensor to indicate whether the magneto's are on by either a flashing warning
light or buzzer but cannot see how to wire it into the set-up as detailed on Z-1
All ideas welcome
Thanks
Mike
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