VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Main > RV General Discussion/News
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #21  
Old 01-10-2011, 07:14 AM
Lux Wrangler Lux Wrangler is offline
 
Join Date: Feb 2005
Posts: 110
Default Ohm's law

Quote:
The only way to increase the current and possibly damage the device would be to increase the voltage. - Don
I dissagree. At a given voltage, current is inversely proportional to resistance. You can increase current by reducing resistance. Voltage can remain constant while the current rises. I understand Ohm's law just fine, what I don't understand is what L. Adamson is saying.
__________________
Jim Peck
San Francisco Bay Area
RV-7
Reply With Quote
  #22  
Old 01-10-2011, 07:48 AM
L.Adamson's Avatar
L.Adamson L.Adamson is offline
 
Join Date: Apr 2005
Location: KSLC
Posts: 4,021
Default

Quote:
Originally Posted by Lux Wrangler View Post
what I don't understand is what L. Adamson is saying.
Simple........

When we get into the devices themselves, many of the wires will be of less size than the main protected lead that services them. In some cases, the device (or sections of) is farther protected with it's own internal or external fuse. But you'll see applications everywhere, in which the breaker/fuse isn't sized to the smallest wire in the electrical path. Just plugging in light cords to a 15 or 20 amp wall outlet is an example. This is a response to where you mentioned protecting the smallest wire in the light setup.

As to my own aircraft............I do have at least three external in-line fuse pacs to protect small wires, that are not in the fuse tray or circuit breaker panel.

L.Adamson
Reply With Quote
  #23  
Old 01-10-2011, 08:29 AM
Lux Wrangler Lux Wrangler is offline
 
Join Date: Feb 2005
Posts: 110
Default the point is that it trips the breaker

Quote:
Just plugging in light cords to a 15 or 20 amp wall outlet is an example. This is a response to where you mentioned protecting the smallest wire in the light setup. - L.Adamson
Fair enough. But we don't plug in two devices which are rated for a 20 amp input into that wall outlet. And when the user says: "the breaker keeps tripping", I say read the instruction manual, were it says "use two 20 amp breaker circuits".

Quote:
In some cases, the device (or sections of) is farther protected with it's (sic) own internal or external fuse. - L.Adamson
Is this the case with the Duckworks? I doubt it.
__________________
Jim Peck
San Francisco Bay Area
RV-7

Last edited by Lux Wrangler : 01-10-2011 at 08:32 AM.
Reply With Quote
  #24  
Old 01-11-2011, 01:57 PM
JETPAUL's Avatar
JETPAUL JETPAUL is offline
 
Join Date: Jan 2011
Location: Peachtree City, GA
Posts: 6
Default WIRE LENGTH VS WIRE SIZE

I think the best reference on this issue is AC43.13-1B

Chapter 11 section 4 is C/B's and Wiring.

Table 11-3 on page 11-15 spells out the rated breaker required for a specific GA of wire as discussed several time above.

But I would hope that everyone is still looking at figures 11-2 and 11-3 on page 11-30/31 to ensure that the GA of the wire is rated for the length of the run and the amps that the unit will draw.

I personally disregard the "Intermittent Flow" chart, and use the "Continuous Flow" chart for a built in level of safety.

Using the CONTINUOUS chart, I find that a 10 amp load on an 18 GA wire should not exceed 7 1/2 ft.

Likewise, a 15 amp load on a 16 GA wire would be good for 7 ft.

ALL ASSUMING A 14V SYSTEM.

Hope that helps!!
__________________
Paul (JETPAUL) Reason
Sales / Tech Support
WWW.GARDNERAVIATION.COM

QUICK!: Name 10 FAMOUS High Wing Fighters??? SO..........I guess there really is something to this Low Wing design!!! HAHAHAHAHA!

Last edited by JETPAUL : 01-11-2011 at 02:09 PM. Reason: update technical data
Reply With Quote
  #25  
Old 01-11-2011, 06:13 PM
fmarino1976 fmarino1976 is offline
 
Join Date: Jan 2007
Location: Tricities, TN
Posts: 166
Default To expand on the wire length issue...

Wires have resistance as well. The smaller the wire, the greater the resistance. The wire lengths given in AC43.13 have to do with the allowable voltage drop in the wire at a given amperage. AC43.13 has further charts to choose the wire size given ambient temperature, allowable wire temperature, altitude and weather the wire is by itself or in a bundle. These later charts are really overkill for our applications, but you get the idea that wire current carrying capacity has other variables, one of the important ones being size and length.

Sorry for the long post, but choosing the right size wire is an important safety issue.
__________________
A&P, IA, Avionics Tech, and finally: Pilot! (12/28/06)
Dying to build an RV10. Not quite ready yet
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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


All times are GMT -6. The time now is 03:59 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.