Today's Message Index:
----------------------
1. 07:34 AM - Re: Wiring: Burned (Discover)
2. 08:30 AM - Wiring: Burned (923te@att.net)
3. 09:02 AM - Fw: Wiring: Burned (923te@att.net)
4. 09:29 AM - Re: Wiring: Burned (Discover)
5. 11:07 AM - Re: Re: Wiring: Burned (Gary L Vogt)
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| Subject: | Re: Wiring: Burned |
Gary,
What gage is the 51LD3 wire?
I've looked at all your pictures to try and see the AWG indicated in the wire but
can't make it out. Also, I spent an hour looking in the nainmrnance manual
and parts manual and just can't find it.
Ned
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=444362#444362
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| Subject: | Fwd: Wiring: Burned |
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| Subject: | Re: Wiring: Burned |
Gary,
Just thinking out loud about your finding of several examples of Nav Light wires
being toasted....
According to the Grumman Maintenance Manual it appears that the Navigation lights
may be designed to be able to run continuously:
image1.jpeg
You can see from this chart that Navigation Lights are listed under things with
"CONTINUOUS LOADS"
According to this chart the Nav lights, which basically is 3 light bulbs, pull
4.52 amps. Looking at the chart if you assume this fuse handles everything listed
under Continuous except Battery Relay, Flashing Beacon and Pitot Heat you
can figure the fuse sees 8.39 amps with the lights turned on. (26.49-18.1=8.39
amps)
Doesn't leave much room on the fuse.
Your wiring diagram schematic shows more than one wire connected to the 10 amp
fuse in the buss bar:
http://www.aucountry.com/ACA_Folder/Technical/Wire_76-77.html
Fuel Gauge, Radio and Compass lights and 4 other Resistive loads denoted by an
"R" that are not labeled that I'm guessing are lights in the panel.
Without knowing the AWG the factory used for the wire I can't really continue doing
any load analysis but I don't think you can properly protect one wire when
two wires are connected to one fuse.
AC 43.13-1B TABLE 11-3. DC wire and circuit protector chart.
Shows for a 20 gauge wire you need a 5 amp fuse
18 gauge needs a 10 amp
But our fuse is "protecting" more than one wire. We could have one 20 gauge wire
pulling 0 amps and the other pulling 9.9 amps. That would burn up the wire
and not blow the fuse....
I'm not sure the fuse was the culprit here. I'm thinking that while good design
would require it to protect the wire it doesn't always do it in this case.
I would suspect there are several culprits all due to age. Corrosion in the switch
and connections and bulb holders all will make the resistance higher and cause
more Amps to be drawn. The switches are really cheap to replace with new.
I've had experience with switches causing resistance. Especially the master switch
but also accessory switches. You can actually get pulsing panel/instrument
lights from a corroded master switch....
I've seen lots of bulb sockets that are corroded. And a few connectors where the
actual metal spades inside the plastic are corroded. Ground wires get corroded
where they are attached to the airframe. I've seen the fuse holders get corroded
too. Adding more wires to a tightly packed bundle doesn't help either.
I'd be curious how all these things look on the planes you've found the burnt wires
Regards,
Ned
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=444371#444371
Attachments:
http://forums.matronics.com//files/image_626.jpg
Message 5
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| Subject: | Re: Wiring: Burned |
My personal opinion is that whoever made up the wiring diagram knew they were limited
by panel space to put fuses/circuit breakers. The wire from the switch
to the branch that splits off for the wing and tail lights should be at least
18 AWG and I would have gone higher. Each of the wires after the split could
be 20 AWG. Id still use 18 AWG. The ground wire on the tail Nav and beacon
is just a screw through the ELT tray. Not great.
The plastic wire cracks and corrosion within the wiring adds to the current draw.
Its just not a great design. Its OK. Probably State-of-the-art in 1969.
> On Jul 4, 2015, at 9:29 AM, Discover <923te@cox.net> wrote:
>
>
> Gary,
> Just thinking out loud about your finding of several examples of Nav Light wires
being toasted....
>
> According to the Grumman Maintenance Manual it appears that the Navigation lights
may be designed to be able to run continuously:
> image1.jpeg
> You can see from this chart that Navigation Lights are listed under things with
"CONTINUOUS LOADS"
>
> According to this chart the Nav lights, which basically is 3 light bulbs, pull
4.52 amps. Looking at the chart if you assume this fuse handles everything listed
under Continuous except Battery Relay, Flashing Beacon and Pitot Heat you
can figure the fuse sees 8.39 amps with the lights turned on. (26.49-18.1=8.39
amps)
> Doesn't leave much room on the fuse.
>
> Your wiring diagram schematic shows more than one wire connected to the 10 amp
fuse in the buss bar:
> http://www.aucountry.com/ACA_Folder/Technical/Wire_76-77.html
>
> Fuel Gauge, Radio and Compass lights and 4 other Resistive loads denoted by an
"R" that are not labeled that I'm guessing are lights in the panel.
>
> Without knowing the AWG the factory used for the wire I can't really continue
doing any load analysis but I don't think you can properly protect one wire when
two wires are connected to one fuse.
> AC 43.13-1B TABLE 11-3. DC wire and circuit protector chart.
>
> Shows for a 20 gauge wire you need a 5 amp fuse
>
> 18 gauge needs a 10 amp
>
> But our fuse is "protecting" more than one wire. We could have one 20 gauge
wire pulling 0 amps and the other pulling 9.9 amps. That would burn up the wire
and not blow the fuse....
>
> I'm not sure the fuse was the culprit here. I'm thinking that while good design
would require it to protect the wire it doesn't always do it in this case.
>
> I would suspect there are several culprits all due to age. Corrosion in the switch
and connections and bulb holders all will make the resistance higher and
cause more Amps to be drawn. The switches are really cheap to replace with new.
I've had experience with switches causing resistance. Especially the master
switch but also accessory switches. You can actually get pulsing panel/instrument
lights from a corroded master switch....
> I've seen lots of bulb sockets that are corroded. And a few connectors where
the actual metal spades inside the plastic are corroded. Ground wires get corroded
where they are attached to the airframe. I've seen the fuse holders get corroded
too. Adding more wires to a tightly packed bundle doesn't help either.
>
> I'd be curious how all these things look on the planes you've found the burnt
wires
>
> Regards,
> Ned
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=444371#444371
>
>
>
>
> Attachments:
>
> http://forums.matronics.com//files/image_626.jpg
>
>
>
>
>
>
>
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