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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Sat Mar 01, 2014 2:26 pm Post subject: grounds

hi all,



 i have 2 questions about the led landing light and led strobe i am installing in a metal wing.



 #1 is it acceptable to use next size smaller groung wire compared to power supply??

 

 #2 is it acceptable to ground these lights to the airframe?



  thanks for any info.



 bob noffs



  [quote][b]

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jluckey(at)pacbell.net
Guest

Posted: Sat Mar 01, 2014 3:19 pm Post subject: grounds

Bob,

I put my comments in with your questions:

-Jeff



        From: bob noffs <icubob(at)gmail.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Saturday, March 1, 2014 2:25 PM

 Subject: grounds

  

 

 hi all,



 i have 2 questions about the led landing light and led strobe i am installing in a metal wing.



 #1 is it acceptable to use next size smaller groung wire compared to power supply??



When you say "..power supply.." I assume you mean positive lead.  

If that is the case then the answer is no.  The current flowing in

the positive lead is the same in the negative lead therefore the wires 

should be the same size.

 

 #2 is it acceptable to ground these lights to the airframe?



Lots of airplanes do, but if it were mine, I wouldn't.  Keeping

accessories grounded at 1 or possibly 2 properly-installed

grounding busses helps reduce the potential for ground loops 

to affect sensitive equipment.



Anecdote: 

I'm aware of a certificated metal airplane that was

having problems w/ some electronic equipment.  This aircraft

was equipped w/ video cameras & recorders and there was

a fair amount of noise on the video.  



After years of maintenance and new avionics & accessories 

being installed/removed/upgraded etc the aircraft had grounds

all over the place. Some things were grounded to a central

ground.



The fix was to move some of the ground wires for existing

accessories (don't know which ones) to the central ground  buss.

For further reading I recommend Bob Nuckoll's book. It has a whole

chapter on the subject.



  thanks for any info.



 bob noffs



  [quote][b]

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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Sat Mar 01, 2014 3:45 pm Post subject: grounds

thanks for the info. as a past builder of a dakota hawk ground wires were the norm. had a ''forest of tabs''on both sides of the firewall. will do it again with the rv.



 bob noffs

 

On Sat, Mar 1, 2014 at 5:19 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote:

 [quote]Bob,

 



I put my comments in with your questions:

 



-Jeff



         From: bob noffs <icubob(at)gmail.com (icubob(at)gmail.com)>

  To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com) 

 Sent: Saturday, March 1, 2014 2:25 PM

  Subject: AeroElectric-List: grounds

  

 

 hi all,



 i have 2 questions about the led landing light and led strobe i am installing in a metal wing.



 #1 is it acceptable to use next size smaller groung wire compared to power supply??

 



When you say "..power supply.." I assume you mean positive lead.  

If that is the case then the answer is no.  The current flowing in

the positive lead is the same in the negative lead therefore the wires 

 should be the same size.

 

 #2 is it acceptable to ground these lights to the airframe?

Lots of airplanes do, but if it were mine, I wouldn't.  Keeping

accessories grounded at 1 or possibly 2 properly-installed

 grounding busses helps reduce the potential for ground loops 

to affect sensitive equipment.



Anecdote: 

I'm aware of a certificated metal airplane that was

having problems w/ some electronic equipment.  This aircraft

 was equipped w/ video cameras & recorders and there was

a fair amount of noise on the video.  



After years of maintenance and new avionics & accessories 

being installed/removed/upgraded etc the aircraft had grounds

 all over the place. Some things were grounded to a central

ground.



The fix was to move some of the ground wires for existing

accessories (don't know which ones) to the central ground  buss.

For further reading I recommend Bob Nuckoll's book. It has a whole

chapter on the subject.



  thanks for any info.



 bob noffs



   	  Quote: 	
		  	




 

 

  

  	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	




[b]

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kleh(at)dialupatcost.ca
Guest

Posted: Sat Mar 01, 2014 5:18 pm Post subject: grounds

Short answer 1. No  2. Yes



Long answer:

It is good practice and in most cases a requirement that the ground wire 

should be the same size as the supply if they carry the same current. 

Exceptions can occur such as when the supply is part of a bundle whereas 

the ground is exposed with good cooling, and voltage drop is not an 

issue. I doubt there is much of that occurring in a Rebel.



There is little reason not to use airframe grounds for continuous loads 

on a metal aircraft. Indeed it often reduces weight and 

resistance/voltage drops. Obviously not good to pass current through a 

hinge though if you have a position light on a rudder or something like 

that.



The problem is only when airframe grounds are also used (shared) by 

noise sensitive receptors such as audio wires or antennae. The sensitive 

devices may pick up tiny voltage changes caused by other loads if they 

share grounds. That phenomenon is commonly called ground loops and is 

why avionics grounds should go to a common ground point.



Ken



On 01/03/2014 5:25 PM, bob noffs wrote:

 	  Quote: 	
		   hi all,

   i have 2 questions about the led landing light and led strobe i am

 installing in a metal wing.

   #1 is it acceptable to use next size smaller groung wire compared to

 power supply??

   #2 is it acceptable to ground these lights to the airframe?

    thanks for any info.

   bob noffs

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jmjones2000(at)mindspring
Guest

Posted: Sat Mar 01, 2014 6:43 pm Post subject: grounds

Bob,



As for the wire size, the best option is to go with a 10A breaker and 18 gauge wire. Remember that a circuit breaker or fuse protects the wire and not the device. Your LEDs will likely pull just a few amps, but this leaves your options open in the future if you decide to go with something other than LEDs.  I would also use shielded wire. Ground the shield at the airframe end and leave it ungrounded at the load end.

As far as the grounding to the airframe is concerned I would say it depends.  It is never a good idea to ground anything to the airframe and not a ground bus.  The lights will work if you do this, but it may help contribute to noise in the system.  The power supply for LEDs are notorious for creating noise so grounding is imperative.  I would also consider using a ferrite filter. These can be had from radio shack. They often come with new electronics and are cylinder shaped.  It is a magnet in plastic that clips around your wire and helps eliminate noise.

Hope this helps

Justin



On Mar 1, 2014, at 1:25 PM, bob noffs <icubob(at)gmail.com (icubob(at)gmail.com)> wrote:

[quote]hi all,



 i have 2 questions about the led landing light and led strobe i am installing in a metal wing.



 #1 is it acceptable to use next size smaller groung wire compared to power supply??

 

 #2 is it acceptable to ground these lights to the airframe?



  thanks for any info.



 bob noffs



   	  Quote: 	
		  



href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List

href="http://forums.matronics.com/">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/contribution



	
[b]

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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peter(at)sportingaero.com
Guest

Posted: Sun Mar 02, 2014 1:10 am Post subject: grounds

In general 1 No, 2 Yes, but,

     

     The power supply wire to a wing tip will be 15 or 20' long, so you     may choose to use a thicker wire size because of volts drop, rather     than current carrying, considerations. If the ground wire is     grounded to the spar 1' away then the volts drop considerations are     not relevant and a thinner ground wire may be used.

     

     Using airframe ground return for the kind of wing tip mounted     devices you mention is standard practice in a metal airframe and can     result in significant weight savings (which are always important) -     always assuming you have a good ground path back to the battery.     Take care of potential ground loops for items in the panel that are     sensitive (eg audio devices).

     

     Just my opinion,

     Peter

     

     On 01/03/2014 22:25, bob noffs wrote:

     

     [quote]                                                                        hi all,

                 

                  i have 2 questions about the led landing light and led                 strobe i am installing in a metal wing.

               

                #1 is it acceptable to use next size smaller groung wire               compared to power supply??

             

              #2 is it acceptable to ground these lights to the airframe?

           

             thanks for any info.

         

          bob noffs

       

        	  Quote: 	
		  

	
     [b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Mar 02, 2014 1:12 pm Post subject: grounds

At 04:25 PM 3/1/2014, you wrote:

 	  Quote: 	
		  hi all,

  i have 2 questions about the led landing light and led strobe i am 

 installing in a metal wing.

  #1 is it acceptable to use next size smaller groung wire compared 

 to power supply??

  #2 is it acceptable to ground these lights to the airframe?

   thanks for any info.

  bob noffs


	


   The current demand of LED replacement for legacy

   lighting is generally much smaller. You should tailor

   your wire selections to those values . . . assuming

   of course . . . that larger wires are not already

   installed to service a legacy system being replaced.

   In the later case, leave old wires in place.



   Have you read chapter 5 of the 'Connection and

   reviewed Z-15 and in particular, this drawing?



http://tinyurl.com/6w87rvb



   Voltage drop is not a big issue with modern

   LED fixtures fitted with constant current

   power supplies . . . and the BRIGHT fixtures

   fall into this category. The electronics in

   the fixture insures proper lamp drive over a

   wide range of input voltages.



   Concerns for ground-loop induced noises have

   foundation in poorly crafted grounds for VULNERABLE

   systems. You can generally ground potentially

   antagonistic systems anywhere as long as the

   potential victims (generally all on the panel)

   share a local common ground as depicted in the

   Z-15 drawings.





   Bob . . .

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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Sun Mar 02, 2014 6:28 pm Post subject: grounds

thanks for the advice. i built my last plane using your diagrams. i now have a plan!



 bob noffs



On Sun, Mar 2, 2014 at 3:11 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 [quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> 

 

 At 04:25 PM 3/1/2014, you wrote:

  	  Quote: 	
		   hi all,

  i have 2 questions about the led landing light and led strobe i am installing in a metal wing.

  #1 is it acceptable to use next size smaller groung wire compared to power supply??

  #2 is it acceptable to ground these lights to the airframe?

   thanks for any info.

  bob noffs

 	
 



   The current demand of LED replacement for legacy

   lighting is generally much smaller. You should tailor

   your wire selections to those values . . . assuming

   of course . . . that larger wires are not already

   installed to service a legacy system being replaced.

   In the later case, leave old wires in place.

 

   Have you read chapter 5 of the 'Connection and

   reviewed Z-15 and in particular, this drawing?

 

 http://tinyurl.com/6w87rvb

 

   Voltage drop is not a big issue with modern

   LED fixtures fitted with constant current

   power supplies . . . and the BRIGHT fixtures

   fall into this category. The electronics in

   the fixture insures proper lamp drive over a

   wide range of input voltages.

 

   Concerns for ground-loop induced noises have

   foundation in poorly crafted grounds for VULNERABLE

   systems. You can generally ground potentially

   antagonistic systems anywhere as long as the

   potential victims (generally all on the panel)

   share a local common ground as depicted in the

   Z-15 drawings.

 

 

 

 

   Bob . . . 

 

 ====================================

 -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ====================================

 http://forums.matronics.com

 ====================================

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ====================================

 

 

 

 



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