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art(at)zemon.name
Guest

Posted: Wed Mar 02, 2016 7:42 pm Post subject: 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,

Â  Â  -- Art Z.



-- 

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

ceengland7(at)gmail.com
Guest

Posted: Wed Mar 02, 2016 9:18 pm Post subject: Newbie Wiring Questions

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(at)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/"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

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Wed Mar 02, 2016 9:42 pm Post subject: Newbie Wiring Questions

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(at)gmail.com (ceengland7(at)gmail.com)> wrote:

 	  Quote: 	
		  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(at)matronics.com (aeroelectric-list(at)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,

Â  Â  -- Art Z.



-- 

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

matronics(at)rtist.nl
Guest

Posted: Wed Mar 02, 2016 10:23 pm Post subject: Newbie Wiring Questions

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:

     

      	  Quote: 	
		         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(at)gmail.com (ceengland7(at)gmail.com)>           wrote:

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

                   Subject: 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,

                     Â  Â  -- Art Z.                       

                       

                       -- 

                                                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

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Thu Mar 03, 2016 6:26 am Post 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

art(at)zemon.name
Guest

Posted: Thu Mar 03, 2016 6:38 am Post subject: 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 to be pretty useful.

Â  Â  -- Art Z.



On Wed, Mar 2, 2016 at 11:40 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:

 	  Quote: 	
		  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.

	
Â 



-- 

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

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Thu Mar 03, 2016 7:46 am Post subject: 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(at)rtist.nl (matronics(at)rtist.nl)> wrote:

 	  Quote: 	
		                     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:

     

      	  Quote: 	
		         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(at)gmail.com (ceengland7(at)gmail.com)>           wrote:

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

                   Subject: 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,

                     Â  Â  -- Art Z.                       

                       

                       -- 

                                                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

rene(at)felker.com
Guest

Posted: Thu Mar 03, 2016 7:48 am Post subject: 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



--

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Thu Mar 03, 2016 8:58 am Post subject: Re: Newbie Wiring Questions

 	  Quote: 	
		  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

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Mar 06, 2016 5:54 pm Post subject: Newbie Wiring Questions

At 09:39 PM 3/2/2016, you wrote:

  	  Quote: 	
		  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.

 	


    Why not run a conduit of pex or nylon tubing through the

    covered tunnel environs? Then you can push/pull wires

    through at any later time at your convenience . . . after

    you've crafted wiring diagrams that comport with manufacturer's

    instructions for each appliance. You can get a LOT

    of wires into a piece of 1/2 or 3/4" pex.



    Here's an exemplar 'bundle' of wires in a piece of

    5/8" tubing . . .



  http://tinyurl.com/hez7eat



    When I install such features, I always pull in one more

    strand of wire than necessary and secure the pigtails

    at each end. Then, when you need to add a wire later,

    use your 'tag wire' to pull in the new wire PLUS

    a new 'tag wire'.  I've got a 20 foot conduit that

    runs from my desk up the wall an out the roof to

    my antennas. The pipe already had 4 coax cables in

    it when I pulled a 5th into the bundle with no

    sweat.



    Running the bundle through a secured conduit eliminates

    concerns for supporting the wires through the inaccessible

    and invisible tunnel environs.



  	  Quote: 	
		  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? 	


    As long as EVERY electron running one way through

    a bundle is exactly paired with another electron

    going the other way, there is no coupling of energy

    from one wire to another.



 

  	  Quote: 	
		  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. 	


   I'd use three conductor shielded where the shield is 

   a fourth, ground conductor for one of the features at the

   far end.



 

  	  Quote: 	
		  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? 	


   Does EACH servo get powered from its own bus-power-tap?

   How many power feeders are depicted on the installation

   instructions? They probably speak to suggested wire

   gages too. Unless your wire runs are especially LONG

   (seldom in OBAM aircraft), then picking wires and

   their respective protective devices is right out

   of the book  5A/22AWG, 7A/20AWG, etc. etc. There's

   no risk for having the wire oversized. There's nearly

   zero risk for being a little 'undersized' wherein the

   risk is for nuisance tripping of a fuse or breaker.



   20AMPS will not burn a 22AWG wire suspended in free

   air. See:



  http://tinyurl.com/6qr72fr



   So even if you found that some transient load on

   the end of a 22AWG wire nuisance trips a 5A fuse,

   then go up to 7A fuse but do not change the wire.



   99* percent of wiring failures are open circuits.

   Wire comes out of terminal, screw comes loose,

   pin pushes back in a connector, etc. Most of

   the remaining failures are HARD faults to ground

   or within loads where the current will be many times

   higher than the wire's installed protection. In

   these instances you're interested in fast response

   that does not overheat the wire. Compared to breakers

   Fuses are VERY fast. Hence upsizing from 5 to

   7A fuse on a 22AWG wire is a yawn.



    But in any case, begin with the manufacturer's 

    recommendations for the appliance being installed.

    They SHOULD know more about achieving efficiency

    and reliability for that device than anyone else.

    Further, when their product falls short of advertised

    performance, root cause will most likely be found

    In shortfalls of quality assurance in production

    or installation as opposed to design.



    Please don't take this as any kind of push-back

    for bringing those questions to the List but

    understand that some well considered answers require

    more knowledge than one might be expected to have

    in their hip pocket. The last two failure analysis

    programs I participated in started with a study of

    the prior art. I read the manuals, looked up patents,

    researched process recommendations for installing

    the parts. All those references were cited in my report 

    bibliography and became part of a foundation 

    for what turned into as simple, two paragraph conclusion/

    recommendation.



    So like you wife admonished as you struggled

    with your kid's new bike on Xmas eve, "Gee

    dear . . . have you read the instructions?"

    Of course, if they were translated from Chinese

    by a second year language student . . . oh well . . .

    bring it to the List and we'll commiserate.



    How did you happen into the BD-4 project? That

    was probably uncle Jim's finest contribution

    to the OBAM aviation community . . . 



        



 

   Bob . . .

ceengland7(at)gmail.com
Guest

Posted: Sun Mar 06, 2016 7:31 pm Post subject: Newbie Wiring Questions

On 3/6/2016 7:47 PM, Robert L.       Nuckolls, III wrote:

     

      	  Quote: 	
		         At 09:39 PM 3/2/2016, you wrote:

               	  Quote: 	
		  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.

         	
       

          Why not run a conduit of pex or nylon tubing through       the

          covered tunnel environs? Then you can push/pull wires

          through at any later time at your convenience . . .       after

          you've crafted wiring diagrams that comport with       manufacturer's

          instructions for each appliance. You can get a LOT

          of wires into a piece of 1/2 or 3/4" pex.

       

          Here's an exemplar 'bundle' of wires in a piece of

          5/8" tubing . . .

       

                http://tinyurl.com/hez7eat

       

          When I install such features, I always pull in one more

          strand of wire than necessary and secure the pigtails

          at each end. Then, when you need to add a wire later,

          use your 'tag wire' to pull in the new wire PLUS

          a new 'tag wire'.  I've got a 20 foot conduit that

          runs from my desk up the wall an out the roof to

          my antennas. The pipe already had 4 coax cables in

          it when I pulled a 5th into the bundle with no

          sweat.

       

          Running the bundle through a secured conduit eliminates

          concerns for supporting the wires through the       inaccessible

          and invisible tunnel environs.

       

        	  Quote: 	
		  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? 	
       

          As long as EVERY electron running one way through

          a bundle is exactly paired with another electron

          going the other way, there is no coupling of energy

          from one wire to another.

       

       

        	  Quote: 	
		  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. 	
       

         I'd use three conductor shielded where the shield is 

         a fourth, ground conductor for one of the features at the

         far end.

       

       

        	  Quote: 	
		  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? 	
       

         Does EACH servo get powered from its own bus-power-tap?

         How many power feeders are depicted on the installation

         instructions? They probably speak to suggested wire

         gages too. Unless your wire runs are especially LONG

         (seldom in OBAM aircraft), then picking wires and

         their respective protective devices is right out

         of the book  5A/22AWG, 7A/20AWG, etc. etc. There's

         no risk for having the wire oversized. There's nearly

         zero risk for being a little 'undersized' wherein the

         risk is for nuisance tripping of a fuse or breaker.

       

         20AMPS will not burn a 22AWG wire suspended in free

         air. See:

       

                http://tinyurl.com/6qr72fr

       

         So even if you found that some transient load on

         the end of a 22AWG wire nuisance trips a 5A fuse,

         then go up to 7A fuse but do not change the wire.

       

         99* percent of wiring failures are open circuits.

         Wire comes out of terminal, screw comes loose,

         pin pushes back in a connector, etc. Most of

         the remaining failures are HARD faults to ground

         or within loads where the current will be many times

         higher than the wire's installed protection. In

         these instances you're interested in fast response

         that does not overheat the wire. Compared to breakers

         Fuses are VERY fast. Hence upsizing from 5 to

         7A fuse on a 22AWG wire is a yawn.

       

          But in any case, begin with the manufacturer's         

            recommendations for the appliance being installed.

            They SHOULD know more about achieving efficiency

            and reliability for that device than anyone else.

            Further, when their product falls short of advertised

            performance, root cause will most likely be found

            In shortfalls of quality assurance in production

            or installation as opposed to design.

         

            Please don't take this as any kind of push-back

            for bringing those questions to the List but

            understand that some well considered answers require

            more knowledge than one might be expected to have

            in their hip pocket. The last two failure analysis

            programs I participated in started with a study of

            the prior art. I read the manuals, looked up patents,

            researched process recommendations for installing

            the parts. All those references were cited in my report         

            bibliography and became part of a foundation 

            for what turned into as simple, two paragraph         conclusion/

            recommendation.

         

            So like you wife admonished as you struggled

            with your kid's new bike on Xmas eve, "Gee

            dear . . . have you read the instructions?"

            Of course, if they were translated from Chinese

            by a second year language student . . . oh well . . .

            bring it to the List and we'll commiserate.

         

            How did you happen into the BD-4 project? That

            was probably uncle Jim's finest contribution

            to the OBAM aviation community . . . 

         

                

         

                

             Bob . . .            	
     For wire raceway, I found this stuff:

     https://www.techflex.com/prod_ccp.asp

     and

     https://www.techflex.com/prod_f6w.asp

     

     As long as you leave a bit of extra length, the 1st can expand     substantially for future wire additions.

     The 2nd allows wire to be added without being pulled through the     tube, and allows wire to exit at any point along the run without     cutting open the tube.

     

     Very flexible, can turn sharp corners, weighs next to nothing, very     thin 'wall', and good abrasion resistance. I used the split stuff to     run down the sides of my RV-7 from behind the instrument panel to     the fuel line/cable chase at the main spar. The unsplit stuff I've     used to bundle runs from subD connectors behind the panel. The 3/4"     diameter version will expand enough to go over a populated subD, if     the shell is removed & the wires bent 90 degrees.

     

     FWIW...

     

     Charlie

art(at)zemon.name
Guest

Posted: Mon Mar 07, 2016 5:45 am Post subject: Newbie Wiring Questions

On Sun, Mar 6, 2016 at 7:47 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 09:39 PM 3/2/2016, you wrote:

  	  Quote: 	
		  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.

 	


 Â Â  Why not run a conduit of pex or nylon tubing through the

 Â Â  covered tunnel environs? 



	




Bob,

Brilliant. Now why didn't I think of that? I ran a 3/8" piece of PVC to the tail "just in case I ever need it" but never thought of doing the same in the tunnel.

There is a lot of value in hashing out even "obvious" questions with other people. Thank you.

Â 

 	  Quote: 	
		  

 Â Â  When I install such features, I always pull in one more

 Â Â  strand of wire than necessary and secure the pigtails

 Â Â  at each end. Then, when you need to add a wire later,

 Â Â  use your 'tag wire' to pull in the new wire PLUS

 Â Â  a new 'tag wire'.



	




I have used string for similar duties in my home, but fastening the new wire to the string has been worrisome. How do you do it with wire, butt splice? That seems like it would be more reliable and with smaller diameter than the tape that I have used at home.

Â 

 	  Quote: 	
		  

 Â Â  Running the bundle through a secured conduit eliminates

 Â Â  concerns for supporting the wires through the inaccessible

 Â Â  and invisible tunnel environs.



	




Good to know. That eliminates my only concern about using a conduit.

Â 

 	  Quote: 	
		  

  	  Quote: 	
		  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? 	


 Â Â  As long as EVERY electron running one way through

 Â Â  a bundle is exactly paired with another electron

 Â Â  going the other way, there is no coupling of energy

 Â Â  from one wire to another.



	




I am building an aluminum airplane. I have not (yet) found guidelines for selecting from three scenarios:Â 

Run a ground wire
Use a shielded wire
Use the fuselage as the ground

Can you point me at something?

Â 

 	  Quote: 	
		   	  Quote: 	
		  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? 	


 Â  Does EACH servo get powered from its own bus-power-tap?

 Â  How many power feeders are depicted on the installation

 Â  instructions? 

	




MGL's instructions are pretty sparse for their servos (at least compared to what they write for their AHRS and magentometer units, where they do specify a circuit breaker size):

 	  Quote: 	
		  In order to accommodate the current required, 18 to 20 gauge wires should be

used for the power wires (positive and negative supply). Thinner wires can be

used for the signal wires.

If the servo is installed onto an bracket that is grounded (for example in an all

metal aircraft), ensure that the area created by the returning ground (thick) power

cable is kept to a minimum â€“ keep the distance between the wire and the metal

construction to a minimum for the full length of the cable up to termination into

the power bus.Â  	


I'm inclined to use a fuse for each servo, mostly because I don't have any reason to cheap out and save a fuse. We had some good discussion about that over the last few days, so I won't rehash it.

Â 

 	  Quote: 	
		  They probably speak to suggested wire

 Â  gages too. Unless your wire runs are especially LONG

 Â  (seldom in OBAM aircraft), then picking wires and

 Â  their respective protective devices is right out

 Â  of the bookÂ  5A/22AWG, 7A/20AWG, etc. etc. There's

 Â  no risk for having the wire oversized. There's nearly

 Â  zero risk for being a little 'undersized' wherein the

 Â  risk is for nuisance tripping of a fuse or breaker.



 Â  20AMPS will not burn a 22AWG wire suspended in free

 Â  air. See:



  http://tinyurl.com/6qr72fr



 Â  So even if you found that some transient load on

 Â  the end of a 22AWG wire nuisance trips a 5A fuse,

 Â  then go up to 7A fuse but do not change the wire.



 Â  99* percent of wiring failures are open circuits.

 Â  Wire comes out of terminal, screw comes loose,

 Â  pin pushes back in a connector, etc. Most of

 Â  the remaining failures are HARD faults to ground

 Â  or within loads where the current will be many times

 Â  higher than the wire's installed protection. In

 Â  these instances you're interested in fast response

 Â  that does not overheat the wire. Compared to breakers

 Â  Fuses are VERY fast. Hence upsizing from 5 to

 Â  7A fuse on a 22AWG wire is a yawn.



	




This is very good to know. I'm a "gotta know why" kind of guy. Understanding the rationale behind fuse selection makes it much easier for me to "size the fuse for the wire" instead of the load. Specifically, I had not thought it through far enough to realize that the current in a failure will be many times higher than the fuse's limit. That explains why using a smaller fuse doesn't offer any additional protection.

Â 

 	  Quote: 	
		  

 Â Â  How did you happen into the BD-4 project? That

 Â Â  was probably uncle Jim's finest contribution

 Â Â  to the OBAM aviation community . . . 



	


Short version: I wanted a fast 4-place X-C airplane with modern avionics for my wife and me to travel in. I wanted to eliminate moving parts, in particular mechanical gyros and vacuum pumps. I didn't want to spend the money on a new factory-built plane or spend the money to completely upgrade my '68 Arrow. I am way more interested in function than beauty so the BD-4C was the natural choice.

Long version:Â How I Chose to Build a Bede BD-4C (on my blog)

Cheers,

Â  Â  -- Art Z.

-- 

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

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 07, 2016 7:33 am Post subject: Newbie Wiring Questions

 	  Quote: 	
		    	  Quote: 	
		  	
For wire raceway, I found this stuff:

  https://www.techflex.com/prod_ccp.asp

 and

  https://www.techflex.com/prod_f6w.asp



 As long as you leave a bit of extra length, the 1st can expand substantially for future wire additions.

 The 2nd allows wire to be added without being pulled through the tube, and allows wire to exit at any point along the run without cutting open the tube.



 Very flexible, can turn sharp corners, weighs next to nothing, very thin 'wall', and good abrasion resistance. I used the split stuff to run down the sides of my RV-7 from behind the instrument panel to the fuel line/cable chase at the main spar. The unsplit stuff I've used to bundle runs from subD connectors behind the panel. The 3/4" diameter version will expand enough to go over a populated subD, if the shell is removed & the wires bent 90 degrees.



 FWIW...



 Charlie 	


   Yeah, we had this stuff around at Hawker-Beech but I'm

   not sure I ever saw it used in the airplanes . . . I'll

   have to ask some guys who had more experience on

   the lines.  We used it a lot for fabricating test harnesses,

   the techs called it 'snake skin'. 



   I'm not sure one could pull new wires in with a tag

   line if the bundle was secured in an inaccessible

   space with adel clamps. The rigid diameter conduit

   approach preserves cross section under the clamps.



   But this makes for VERY flexible test harnesses. A

   string tied bundle can become quite stiff when

   individual strands of wire get bound tightly

   to each other under those constrictor knots.



 

 

   Bob . . .

ashleysc(at)broadstripe.n
Guest

Posted: Mon Mar 07, 2016 8:26 am Post subject: Newbie Wiring Questions

Hi All;



 Recommend putting a nylon pull string into the tubing before burying it in the aircraft. The string can be pulled through with a vacuum cleaner. Tie on a loose fitting ball of foam or cloth at the leading end of the string to help pull the string through.

 Cheers!   Stu.

 



   From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

To: aeroelectric-list(at)matronics.com

Sent: Sunday, March 6, 2016 5:47:56 PM

Subject: Re: Newbie Wiring Questions

 



At 09:39 PM 3/2/2016, you wrote:

  	  Quote: 	
		  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.

	


   Why not run a conduit of pex or nylon tubing through the

   covered tunnel environs? Then you can push/pull wires

   through at any later time at your convenience . . . after

   you've crafted wiring diagrams that comport with manufacturer's

   instructions for each appliance. You can get a LOT

   of wires into a piece of 1/2 or 3/4" pex.

 



   Here's an exemplar 'bundle' of wires in a piece of

   5/8" tubing . . .

 



http://tinyurl.com/hez7eat

 



   When I install such features, I always pull in one more

   strand of wire than necessary and secure the pigtails

   at each end. Then, when you need to add a wire later,

   use your 'tag wire' to pull in the new wire PLUS

   a new 'tag wire'.  I've got a 20 foot conduit that

   runs from my desk up the wall an out the roof to

   my antennas. The pipe already had 4 coax cables in

   it when I pulled a 5th into the bundle with no

   sweat.

 



   Running the bundle through a secured conduit eliminates

   concerns for supporting the wires through the inaccessible

   and invisible tunnel environs.

 



  	  Quote: 	
		  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? 	


   As long as EVERY electron running one way through

   a bundle is exactly paired with another electron

   going the other way, there is no coupling of energy

   from one wire to another.

 

  	  Quote: 	
		  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. 	


  I'd use three conductor shielded where the shield is 

  a fourth, ground conductor for one of the features at the

  far end.

 

  	  Quote: 	
		  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? 	


  Does EACH servo get powered from its own bus-power-tap?

  How many power feeders are depicted on the installation

  instructions? They probably speak to suggested wire

  gages too. Unless your wire runs are especially LONG

  (seldom in OBAM aircraft), then picking wires and

  their respective protective devices is right out

  of the book  5A/22AWG, 7A/20AWG, etc. etc. There's

  no risk for having the wire oversized. There's nearly

  zero risk for being a little 'undersized' wherein the

  risk is for nuisance tripping of a fuse or breaker.

 



  20AMPS will not burn a 22AWG wire suspended in free

  air. See:

 



http://tinyurl.com/6qr72fr

 



  So even if you found that some transient load on

  the end of a 22AWG wire nuisance trips a 5A fuse,

  then go up to 7A fuse but do not change the wire.

 



  99* percent of wiring failures are open circuits.

  Wire comes out of terminal, screw comes loose,

  pin pushes back in a connector, etc. Most of

  the remaining failures are HARD faults to ground

  or within loads where the current will be many times

  higher than the wire's installed protection. In

  these instances you're interested in fast response

  that does not overheat the wire. Compared to breakers

  Fuses are VERY fast. Hence upsizing from 5 to

  7A fuse on a 22AWG wire is a yawn.

 



   But in any case, begin with the manufacturer's 

   recommendations for the appliance being installed.

   They SHOULD know more about achieving efficiency

   and reliability for that device than anyone else.

   Further, when their product falls short of advertised

   performance, root cause will most likely be found

   In shortfalls of quality assurance in production

   or installation as opposed to design.

 



   Please don't take this as any kind of push-back

   for bringing those questions to the List but

   understand that some well considered answers require

   more knowledge than one might be expected to have

   in their hip pocket. The last two failure analysis

   programs I participated in started with a study of

   the prior art. I read the manuals, looked up patents,

   researched process recommendations for installing

   the parts. All those references were cited in my report 

   bibliography and became part of a foundation 

   for what turned into as simple, two paragraph conclusion/

   recommendation.

 



   So like you wife admonished as you struggled

   with your kid's new bike on Xmas eve, "Gee

   dear . . . have you read the instructions?"

   Of course, if they were translated from Chinese

   by a second year language student . . . oh well . . .

   bring it to the List and we'll commiserate.

 



   How did you happen into the BD-4 project? That

   was probably uncle Jim's finest contribution

   to the OBAM aviation community . . . 

 



       

 



 

  Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 07, 2016 9:17 am Post subject: Newbie Wiring Questions

At 10:25 AM 3/7/2016, you wrote:

  	  Quote: 	
		  Hi All;

 Recommend putting a nylon pull string into the tubing before burying it in the aircraft. The string can be pulled through with a vacuum cleaner. Tie on a loose fitting ball of foam or cloth at the leading end of the string to help pull the string through.

 Cheers!   Stu. 	


   Yeah . . . a airhose blow gun works from the supply

   end too. I'll tie a piece of shop rag onto the end

   of the string then stuff about a foot of string in

   with the rag-wad, blow, stuff more string, repeat.



 

 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 07, 2016 10:03 am Post subject: Newbie Wiring Questions

 	  Quote: 	
		  

 I have used string for similar duties in my home, but fastening the new wire to the string has been worrisome. How do you do it with wire, butt splice? That seems like it would be more reliable and with smaller diameter than the tape that I have used at home. 	


   Kinda depends on how tight the bundle is in

   the tube . . . but my personal favorite is to

   do a soldered lap-splice to ALL of the strands

   being pulled. My tag wire is usually 20AWG.

   Overlap about 1/2" of tag wire strands with the

   new wires (+ new tag wire). Put a piece of heat

   shrink over it to 'smooth' the joint and then

   pull them in . . .



 



  	  Quote: 	
		  Good to know. That eliminates my only concern about using a conduit. 	


   Supporting wires hanging out in the breeze is

   intended to eliminate potential vibration/abrasion

   points and just control what otherwise might be

   a floppy bundle. WAaaayyyy back when, cotton over

   rubber insulated wire (Mil-W-76) wire was subject

   to imbrittlement when exposed to ozone, hydrocarbons,

   and just old age.  Adequate support went to extending

   service life of the insulation. Tefzel doesn't suffer

   from this malady so 'floppy' bundles are more an

   issue of craftsmanship as long as the wires don't

   bang on a hard/sharp point.



 

  	  Quote: 	
		  I am building an aluminum airplane. I have not (yet) found guidelines for selecting from three scenarios:Â   Run a ground wire 	
 

   Except for the few examples of 'local grounds' illustrated

   in Figure Z-15, it is ALWAYS good practice to include

   ground returns in the same bundle that carries power

   and signals. Any appliance designer worth his soldering

   iron will do this and it should be obvious in the

   installation manuals.  CAVEAT: when you DO see a local

   ground called out on a wiring diagram for some appliance

   having mixed signals/power wires running elsewhere, it's

   NEVER wrong to extend your ground up to the panel with

   all the other wires.  	  Quote: 	
		    Use a shielded wire 	
 

   Only when called out by the system designer. Shielding

   breaks only one coupling mode for noises that is seldom

   encountered in modern aircraft appliances. If the instruction

   manual doesn't call out shielded wire, adding it is unnecessary.

   I've seen is used many times where it probably doesn't make

   any difference . . . probably by some guy whose solder

   station includes zinc-chloride flux.  Shielding

   never hurts but it is very seldom necessary or beneficial.



   I use shielded trio as 4-conductor wires in audio

   systems only because it's convenient and the wire

   is commonly available . . . usefulness of the 4th

   conductor's qualities as a shield is problematic.



  	  Quote: 	
		    Use the fuselage as the ground 	
 

   . . . only on those devices called out on Z-15



 



 

  	  Quote: 	
		  I'm inclined to use a fuse for each servo, mostly because I don't have any reason to cheap out and save a fuse. We had some good discussion about that over the last few days, so I won't rehash it. 	


   Can the installation manual for this system be

   downloaded? what's the FEMA for this system look

   like? Can the system still be useful with one

   actuator being un-powered?



   Keep in mind that 99.999% of ALL circuit protection

   installed in DC vehicular power systems will go

   the lifetime of the vehicle having NEVER been

   called upon to operate.  This is why I blanch at

   the idea of using breakers vs. fuses. They use up

   a lot of dollars, install time, panel space, weight,

   etc while adding nothing to system safety when 

   compared to the simple out of sight, out of reach fuse.



   See:



  http://tinyurl.com/hbhlv93



  http://tinyurl.com/ht8wtl5



  http://tinyurl.com/j3lfdbr



   



 

  	  Quote: 	
		  This is very good to know. I'm a "gotta know why" kind of guy. Understanding the rationale behind fuse selection makes it much easier for me to "size the fuse for the wire" instead of the load. Specifically, I had not thought it through far enough to realize that the current in a failure will be many times higher than the fuse's limit. That explains why using a smaller fuse doesn't offer any additional protection. 	


    Good for you. Most of the hangar lore about

    breakers and wires seems to impart images of

    smoke and fire pouring out from under the panel

    along with admonitions: "Tho shalt not oversize

    thy breakers less wires melt and open the gates

    to hell-in-the-air." 



    In fact, insulation quality is the wire's limiting

    factor for current rating working hand in hand

    with controlling voltage drop. I've only experienced

    burned wires one time (improperly installed p-leads

    and disconnected crankcase ground). I've experienced

    and/or conducted analysis on dozens of bad smells and

    smoke that came from INSIDE a device and would probably

    never operate the breaker. 



    Looking through the accident reports for TC aircraft,

    it's exceedingly7 difficult to find instances of

    bad days in the cockpit due to electrical faults.

    Many electrical emergencies in OBAM aircraft have

    roots in poor craftsmanship, piloting skills and/or

    system architecture.



    See:



  http://tinyurl.com/ky7szec



    Fuse and wire sizing is pretty straight-forward

    and way down on the list of reliability/safety

    concerns. Just keep in mind that for every

    condition that will open a fuse on some appliance

    useful for comfortable termination of flight,

    there are dozens to hundreds of conditions more

    likely to bring the system down without blowing

    the fuse.



    If loss of any single appliance drives your

    pucker=pressure up, then having a Plan-B for

    continued comfortable flight without that

    appliance.  



 



  	  Quote: 	
		  Â 

  

  Â Â  How did you happen into the BD-4 project? That

  Â Â  was probably uncle Jim's finest contribution

  Â Â  to the OBAM aviation community . . . 



  

 Short version: I wanted a fast 4-place X-C airplane with modern avionics for my wife and me to travel in. I wanted to eliminate moving parts, in particular mechanical gyros and vacuum pumps. I didn't want to spend the money on a new factory-built plane or spend the money to completely upgrade my '68 Arrow. I am way more interested in function than beauty so the BD-4C was the natural choice.



 Long version:Â  How I Chose to Build a Bede BD-4C (on my blog)

 	


     I'll read it . . . thanks for the heads-up . . .



 

 

   Bob . . .

raymondj(at)frontiernet.n
Guest

Posted: Mon Mar 07, 2016 10:58 am Post subject: Newbie Wiring Questions

I don't know if it's applicable to aircraft wire types, but I have found 

wire lube makes pulling wire in a full conduit and/or long runs 

significantly easier.



Raymond Julian

Kettle River, MN



The things we admire in men, kindness and generosity, openness, honesty, 

understanding and feeling are the concomitants of failure in our system. 

And those traits we detest, sharpness, greed, acquisitiveness, meanness, 

egotism and self-interest are the traits of success. And while men 

admire the quality of the first they love the produce of the second. 

-John Steinbeck, novelist, Nobel laureate (1902-1968)



On 03/07/2016 12:01 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		  >

> I have used string for similar duties in my home, but fastening the

> new wire to the string has been worrisome. How do you do it with wire,

> butt splice? That seems like it would be more reliable and with

> smaller diameter than the tape that I have used at home.



    Kinda depends on how tight the bundle is in

    the tube . . . but my personal favorite is to

    do a soldered lap-splice to ALL of the strands

    being pulled. My tag wire is usually 20AWG.

    Overlap about 1/2" of tag wire strands with the

    new wires (+ new tag wire). Put a piece of heat

    shrink over it to 'smooth' the joint and then

    pull them in . . .



> Good to know. That eliminates my only concern about using a conduit.



    Supporting wires hanging out in the breeze is

    intended to eliminate potential vibration/abrasion

    points and just control what otherwise might be

    a floppy bundle. WAaaayyyy back when, cotton over

    rubber insulated wire (Mil-W-76) wire was subject

    to imbrittlement when exposed to ozone, hydrocarbons,

    and just old age.  Adequate support went to extending

    service life of the insulation. Tefzel doesn't suffer

    from this malady so 'floppy' bundles are more an

    issue of craftsmanship as long as the wires don't

    bang on a hard/sharp point.

> I am building an aluminum airplane. I have not (yet) found guidelines

> for selecting from three scenarios:Ã‚

>

>  1. Run a ground wire



    Except for the few examples of 'local grounds' illustrated

    in Figure Z-15, it is ALWAYS good practice to include

    ground returns in the same bundle that carries power

    and signals. Any appliance designer worth his soldering

    iron will do this and it should be obvious in the

    installation manuals.  CAVEAT: when you DO see a local

    ground called out on a wiring diagram for some appliance

    having mixed signals/power wires running elsewhere, it's

    NEVER wrong to extend your ground up to the panel with

    all the other wires.

>

>  1. Use a shielded wire



    Only when called out by the system designer. Shielding

    breaks only one coupling mode for noises that is seldom

    encountered in modern aircraft appliances. If the instruction

    manual doesn't call out shielded wire, adding it is unnecessary.

    I've seen is used many times where it probably doesn't make

    any difference . . . probably by some guy whose solder

    station includes zinc-chloride flux.  Shielding

    never hurts but it is very seldom necessary or beneficial.



    I use shielded trio as 4-conductor wires in audio

    systems only because it's convenient and the wire

    is commonly available . . . usefulness of the 4th

    conductor's qualities as a shield is problematic.



>  1. Use the fuselage as the ground



    . . . only on those devices called out on Z-15





> I'm inclined to use a fuse for each servo, mostly because I don't have

> any reason to cheap out and save a fuse. We had some good discussion

> about that over the last few days, so I won't rehash it.



    Can the installation manual for this system be

    downloaded? what's the FEMA for this system look

    like? Can the system still be useful with one

    actuator being un-powered?



    Keep in mind that 99.999% of ALL circuit protection

    installed in DC vehicular power systems will go

    the lifetime of the vehicle having NEVER been

    called upon to operate.  This is why I blanch at

    the idea of using breakers vs. fuses. They use up

    a lot of dollars, install time, panel space, weight,

    etc while adding nothing to system safety when

    compared to the simple out of sight, out of reach fuse.



    See:



 http://tinyurl.com/hbhlv93



 http://tinyurl.com/ht8wtl5



 http://tinyurl.com/j3lfdbr





> This is very good to know. I'm a "gotta know why" kind of guy.

> Understanding the rationale behind fuse selection makes it much easier

> for me to "size the fuse for the wire" instead of the load.

> Specifically, I had not thought it through far enough to realize that

> the current in a failure will be many times higher than the fuse's

> limit. That explains why using a smaller fuse doesn't offer any

> additional protection.



     Good for you. Most of the hangar lore about

     breakers and wires seems to impart images of

     smoke and fire pouring out from under the panel

     along with admonitions: "Tho shalt not oversize

     thy breakers less wires melt and open the gates

     to hell-in-the-air."



     In fact, insulation quality is the wire's limiting

     factor for current rating working hand in hand

     with controlling voltage drop. I've only experienced

     burned wires one time (improperly installed p-leads

     and disconnected crankcase ground). I've experienced

     and/or conducted analysis on dozens of bad smells and

     smoke that came from INSIDE a device and would probably

     never operate the breaker.



     Looking through the accident reports for TC aircraft,

     it's exceedingly7 difficult to find instances of

     bad days in the cockpit due to electrical faults.

     Many electrical emergencies in OBAM aircraft have

     roots in poor craftsmanship, piloting skills and/or

     system architecture.



     See:



 http://tinyurl.com/ky7szec



     Fuse and wire sizing is pretty straight-forward

     and way down on the list of reliability/safety

     concerns. Just keep in mind that for every

     condition that will open a fuse on some appliance

     useful for comfortable termination of flight,

     there are dozens to hundreds of conditions more

     likely to bring the system down without blowing

     the fuse.



     If loss of any single appliance drives your

     pucker=pressure up, then having a Plan-B for

     continued comfortable flight without that

     appliance.



> Ã‚

>     Ã‚ Ã‚  How did you happen into the BD-4 project? That

>     Ã‚ Ã‚  was probably uncle Jim's finest contribution

>     Ã‚ Ã‚  to the OBAM aviation community . . .

> Short version: I wanted a fast 4-place X-C airplane with modern

> avionics for my wife and me to travel in. I wanted to eliminate moving

> parts, in particular mechanical gyros and vacuum pumps. I didn't want

> to spend the money on a new factory-built plane or spend the money to

> completely upgrade my '68 Arrow. I am way more interested in function

> than beauty so the BD-4C was the natural choice.

>

> Long version:Ã‚ How I Chose to Build a Bede BD-4C

> <https://cheerfulcurmudgeon.com/2013/10/13/how-i-chose-to-build-a-bede-bd-4c/>

> (on my blog)



      I'll read it . . . thanks for the heads-up . . .

    Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 07, 2016 12:37 pm Post subject: Newbie Wiring Questions

At 12:55 PM 3/7/2016, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: rayj <raymondj(at)frontiernet.net>



 I don't know if it's applicable to aircraft wire types, but I have found wire lube makes pulling wire in a full conduit and/or long runs significantly easier. 	


   TC aircraft are generally designed up from a clean

   piece of paper and don't benefit from inclusion of conduits.



   From the TC perspective, it's a weight penalty that

   project management would really argue against. I

   have seen conduits that run through wet-wing tanks and

   occasionally along the rear spar for wing wires.

   Those conduits were never really 'tight' on the

   wires.



   Pex is so slick inside that you would need to

   have it REALLY full of wire before there was

   risk to successful addition of a few

   new wires. 



 

 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 07, 2016 12:37 pm Post subject: Newbie Wiring Questions

At 12:55 PM 3/7/2016, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: rayj <raymondj(at)frontiernet.net>



 I don't know if it's applicable to aircraft wire types, but I have found wire lube makes pulling wire in a full conduit and/or long runs significantly easier. 	


   TC aircraft are generally designed up from a clean

   piece of paper and don't benefit from inclusion of conduits.



   From the TC perspective, it's a weight penalty that

   project management would really argue against. I

   have seen conduits that run through wet-wing tanks and

   occasionally along the rear spar for wing wires.

   Those conduits were never really 'tight' on the

   wires.



   Pex is so slick inside that you would need to

   have it REALLY full of wire before there was

   risk to successful addition of a few

   new wires. 



 

 

   Bob . . .

art(at)zemon.name
Guest

Posted: Wed Mar 09, 2016 5:35 am Post subject: Newbie Wiring Questions

Bob,

I agree with you completely on the fuses vs. circuit breakers choice. I don't have as much experience as you but I have had two CB's pop while I was in flight. One was a CB failure and the other was a failed voltage regulator. Had I had fuses, the first would not have happened. As you can imagine, resetting the CB didn't help in the second failure so a fuse would have been fine there, too. From what I have read, and from my personal experience, I decided to put fuses in my plane.

And given what you and others have written, I will run ground wires, install fuses that are sized for the wires, and spend my time worrying about preventing the more likely failures (like brushing up on my soldering skills).

Gee... I wonder if I can still find my step-father's old soldering iron. The thing was large enough to almost be confused with a cop's Billy club. 

Cheers,

Â  Â  -- Art Z.



-- 

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

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