A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Soaring
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Fuse for radio



 
 
Thread Tools Display Modes
  #11  
Old July 16th 19, 04:04 AM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
external usenet poster
 
Posts: 1,383
Default Fuse for radio

Bigger wire has less resistance per length. A fuse is basically a wire designed to clear when overloaded.
Fuses and breakers are really to protect the wire from overloads.
A 12ga wire is good for a max load of about 20A. We won't get into free air load vs. in a bundle or conduit (it is rated at less).
Sooo.....a 12ga wire can carry about 20A load. So the fuse would be equal or less so you don't overload the wire and start a fire.
A smaller fuse on a big wire can then help protect the equipment.
Small fuse (amp/A rating) is the same as a lower load. The good thing is it clears when overloaded but no fire.
Downside is voltage drop since it is not designed for a big load.
So a big wire, then fuses that protect the equipment within reason. This gives max power (less voltage drop) to the fuse.

Hope I didn't muddle things.....
  #12  
Old July 16th 19, 11:36 AM posted to rec.aviation.soaring
kinsell
external usenet poster
 
Posts: 546
Default Fuse for radio

On 7/15/19 9:04 PM, Charlie M. (UH & 002 owner/pilot) wrote:

Fuses and breakers are really to protect the wire from overloads.
A 12ga wire is good for a max load of about 20A. We won't get into free air load vs. in a bundle or conduit (it is rated at less).
Sooo.....a 12ga wire can carry about 20A load.


No, it can carry a whole lot more than that. Residential electrical
codes limit it to 20 amps to minimize I*R drops, where the length of the
wiring could reach into hundreds of feet. The wiring will actually
handle over 200 amps before it starts to melt.
  #13  
Old July 16th 19, 04:59 PM posted to rec.aviation.soaring
John DeRosa OHM Ω http://aviation.derosaweb.net
external usenet poster
 
Posts: 276
Default Fuse for radio

Fuse resistance and voltage drop - Yep, each fuse size has a different resistance and thus a voltage drop. Who knew??

Small values of fuses (and breakers) have a bigger/worse voltage drop. For the widely used Bussman brand fuses here are some examples (at a 1A load)*;

1A 0.190Vdc drop
2A 0.078Vdc drop
3A 0.045Vdc drop
5A 0.024Vdc drop

So bigger is certainly better and 3A and higher is recommended.

Thanks, John

*Reference: http://www.cooperindustries.com/cont...AGC_Series.pdf

  #14  
Old July 16th 19, 05:37 PM posted to rec.aviation.soaring
John DeRosa OHM Ω http://aviation.derosaweb.net
external usenet poster
 
Posts: 276
Default Fuse for radio

On Tuesday, July 16, 2019 at 5:36:33 AM UTC-5, kinsell wrote:
On 7/15/19 9:04 PM, Charlie M. (UH & 002 owner/pilot) wrote:

Fuses and breakers are really to protect the wire from overloads.
A 12ga wire is good for a max load of about 20A. We won't get into free air load vs. in a bundle or conduit (it is rated at less).
Sooo.....a 12ga wire can carry about 20A load.


No, it can carry a whole lot more than that. Residential electrical
codes limit it to 20 amps to minimize I*R drops, where the length of the
wiring could reach into hundreds of feet. The wiring will actually
handle over 200 amps before it starts to melt.


Not to be pedantic but ... FAA Advisory Circular AC43-13-1B defines the maximum current along 20ft of 12ga mil-spec (Tefzel) wire across 14Vdc as ~12amps (fig 11-2 continuous current flow) or ~22 amps (fig 11-3 intermittent current flow).

Reminder that this is DC, not AC, current we are talking about. Edison pushed DC systems but was beat out (trounced) by Tesla/Westinghouse and their long-haul AC systems due to exactly what we are talking about here. Just sayin'. ;-)

Thanks, John

References:
https://en.wikipedia.org/wiki/War_of_the_currents
https://www.faa.gov/documentLibrary/...-1B_w-chg1.pdf
  #15  
Old July 16th 19, 09:16 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
external usenet poster
 
Posts: 1,383
Default Fuse for radio

Thanks.....

My comment was not, "what can it carry before becoming a lightbulb", but what is acceptable for continuous load at a voltage.
Basics......small wire carries low load.....fuse keeps wiring from igniting.
Big wire carries larger load and/or less voltage drop.
Fuse/breaker keeps from a wiring fire.

Huge wire is a minor weight penalty.
Huge wire may be a PITA to run/fit/connect.
Huge wire does NOT "overwork" a device.....the device only uses what it needs until failure...thus.....a fuse or breaker.

Would anyone here use a 12ga jumper cable when car has a dead battery?!?!
Well.....off in neverland, cold, rainy, etc......I would try rather than quibble.
Going to welding cable with suitable clamps would likely yield a better result.....

Have a great day....
  #16  
Old July 17th 19, 03:11 AM posted to rec.aviation.soaring
John DeRosa OHM Ω http://aviation.derosaweb.net
external usenet poster
 
Posts: 276
Default Fuse for radio

UH - I am with you on this. My pedantic comments were needlessly complicated for soaringjac's simple initial request. RAS at its best in the weeds.

Light bulbs? Welding cables? What a thought. ;-)

- John

  #17  
Old July 17th 19, 03:42 AM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
external usenet poster
 
Posts: 1,383
Default Fuse for radio

From now on, please all peeps label me as Charlie.....I wish nothing negative to "UH" if I do a FUBAR. I know him and fly his ships at times, I do not speak for him.

Whatever......while a 12ga wire "may" handle a lot more than 20A, for how long, what insulation (yes, I am sorta versed from PVC/MTW through Tefzel and above....;-)).
As stated before, big wire from battery to buss is great.....
Fuses are basically the resistance and should fail before wire becomes a "heating element/light bulb".,...
So, specking (SP) a low amp fuse can/will drop voltage to devices.

To others......do you want to use a 12ga jumper cable to get home?, or maybe 4O welding cable to handle the current?
High load WILL roast a small cable/wire. Short very high load may pass, not our issue.....we want to know the downside of very small fuses/breakers versus voltage supplied to devices....
My thought.....big wire, great connections, protection (fuse or breaker...), and have fun.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Cambridge 302 fuse [email protected] Soaring 6 December 18th 18 04:36 PM
ASW 27 Fuse ballast tank FS pat Soaring 0 July 22nd 12 05:56 PM
B40 fuse question Tuno Soaring 3 December 8th 08 08:43 PM
KR-2 fuse for sale Turbo Tiger Home Built 3 December 17th 05 07:27 PM
Fuse the Wire or Fuse the Device? ContestID67 Soaring 11 April 27th 05 03:13 AM


All times are GMT +1. The time now is 03:33 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.