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Z-13/8 Question

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kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Apr 27, 2018 8:36 am Post subject: Z-13/8 Question

On Z-13/8 given that there is already a 5A breaker in the wire from the main bus to the master switch, what is the purpose of the 22AWG fusible link in that same wire?

ceengland7(at)gmail.com
Guest

Posted: Fri Apr 27, 2018 8:54 am Post subject: Z-13/8 Question

On Fri, Apr 27, 2018 at 11:33 AM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:

 	  Quote: 	
		  On Z-13/8 given that there is already a 5A breaker in the wire from the main bus to the master switch, what is the purpose of the 22AWG fusible link in that same wire?

 	


The breaker the reset-able option (nuisance trips) for the OV protection circuit. It is remote from the bus ('unlimited' current source) to allow access by the pilot. Without the fusible link, the 18 ga wire would be unprotected between the bus and the breaker.

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Apr 27, 2018 9:10 am Post subject: Z-13/8 Question

Okay, that makes sense. But it spurs other questions, like why is the 18 gauge there at all, when the rest of the run is 20 gauge?



On Fri, Apr 27, 2018 at 8:53 AM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

 	  Quote: 	
		  



On Fri, Apr 27, 2018 at 11:33 AM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:

 	  Quote: 	
		  On Z-13/8 given that there is already a 5A breaker in the wire from the main bus to the master switch, what is the purpose of the 22AWG fusible link in that same wire?

 	


The breaker the reset-able option (nuisance trips) for the OV protection circuit. It is remote from the bus ('unlimited' current source) to allow access by the pilot. Without the fusible link, the 18 ga wire would be unprotected between the bus and the breaker.

user9253

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

Posted: Fri Apr 27, 2018 11:15 am Post subject: Re: Z-13/8 Question

Good catch.  I think there is a typo in the drawing.  The wire size should be 18 AWG between the 5 amp circuit breaker and the master switch.  That wire will carry over-voltage module current when the module shorts to ground.  20 AWG is OK between the master switch and the voltage regulator.

_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Fri Apr 27, 2018 3:19 pm Post subject: Z-13/8 Question

On 4/27/2018 2:15 PM, user9253 wrote:

 	  Quote: 	
		   



 Good catch.  I think there is a typo in the drawing.  The wire size should be 18 AWG between the 5 amp circuit breaker and the master switch.  That wire will carry over-voltage module current when the module shorts to ground.  20 AWG is OK between the master switch and the voltage regulator.



 --------

 Joe Gores

Well...the 20 awg is protected by the CB. Current will likely never get 
	


above 3 amps in normal operation, and in an OV event, the overcurrent 

duration from the crowbar firing would be measured in milliseconds. I 

wouldn't be worried about a 5A CB protecting a 20 awg wire; I think I 

probably have some short runs of 20 that are fused with 5A.



Charlie



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user9253

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

Posted: Fri Apr 27, 2018 4:11 pm Post subject: Re: Z-13/8 Question

I was wrong in my post above.  The fuselink protects the 18 AWG from shorting out.  The circuit breaker protects everything down steam from there.

_________________
Joe Gores

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Apr 27, 2018 4:40 pm Post subject: Z-13/8 Question

So, is the reason for the 18AWG section perhaps to set the size of the fuselink at 22AWG?



On Fri, Apr 27, 2018 at 4:11 PM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 I was wrong in my post above.  The fuselink protects the 18 AWG from shorting out.  The circuit breaker protects everything down steam from there.

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=479613#479613

 

 

 

 

 

 

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user9253

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

Posted: Fri Apr 27, 2018 5:16 pm Post subject: Re: Z-13/8 Question

The rule of thumb for a fuselink is 4 wire sizes smaller than the protected conductor. So I agree with you.

_________________
Joe Gores

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri Apr 27, 2018 6:50 pm Post subject: Z-13/8 Question

And what would be the argument against all 20AWG with a 24AWG fuselink?



On Fri, Apr 27, 2018 at 5:16 PM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 The rule of thumb for a fuselink is 4 wire sizes smaller than the protected conductor.  So I agree with you.

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=479616#479616

 

 

 

 

 

 

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ceengland7(at)gmail.com
Guest

Posted: Fri Apr 27, 2018 8:50 pm Post subject: Z-13/8 Question

For me, it would be availability (I       don't keep 24 awg on hand) and physical strength of the link. 22       is pretty tough; 24 is marginal.

       

       No doubt it will work, though, if you want to use it.

       

       Charlie

       

       On 4/27/2018 9:48 PM, Ken Ryan wrote:

     

      	  Quote: 	
		         And what would be the argument against all 20AWG         with a 24AWG fuselink?

       

         On Fri, Apr 27, 2018 at 5:16 PM,           user9253 <fransew(at)gmail.com (fransew(at)gmail.com)>           wrote:

            	  Quote: 	
		  -->             AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

             

             The rule of thumb for a fuselink is 4 wire sizes smaller             than the protected conductor.  So I agree with you.

             

             --------

             Joe Gores

             

             

             

             

             Read this topic online here:

             

             http://forums.matronics.com/viewtopic.php?p=479616#479616

             

             

             

             

             

             

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Apr 28, 2018 5:37 am Post subject: Z-13/8 Question

At 11:48 PM 4/27/2018, you wrote:

  	  Quote: 	
		  For me, it would be availability (I don't keep 24 awg on hand) and physical strength of the link. 22 is pretty tough; 24 is marginal.



 No doubt it will work, though, if you want to use it. 	


   This bigger-but-not-fat wire is a 'bus feeder'

   to a distribution point of one. You could

   use 18/22 or even put a maxifuse of, say

   30-40A at the fuse-link location.



   The fuse link seems a bit more 'elegant'

   tied into the wire bundles as opposed to

   sticking out like a sore thumb.



 

 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Apr 28, 2018 5:38 am Post subject: Z-13/8 Question

At 11:48 PM 4/27/2018, you wrote:

  	  Quote: 	
		  For me, it would be availability (I don't keep 24 awg on hand) and physical strength of the link. 22 is pretty tough; 24 is marginal.



 No doubt it will work, though, if you want to use it. 	


   This bigger-but-not-fat wire is a 'bus feeder'

   to a distribution point of one. You could

   use 18/22 or even put a maxifuse of, say

   30-40A at the fuse-link location.



   The fuse link seems a bit more 'elegant'

   tied into the wire bundles as opposed to

   sticking out like a sore thumb.



 

 

   Bob . . .

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Sat Apr 28, 2018 7:33 am Post subject: Z-13/8 Question

Bob, I don't follow your language "this bigger but not fat wire is a 'bus feeder' to a distribution point of one." Specifically, why use the 18/22 when the rest of the run is 20. Why not just use 20/24?



Ken





On Sat, Apr 28, 2018 at 5:37 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 11:48 PM 4/27/2018, you wrote:

  	  Quote: 	
		  For me, it would be availability (I don't keep 24 awg on hand) and physical strength of the link. 22 is pretty tough; 24 is marginal.



 No doubt it will work, though, if you want to use it. 	


   This bigger-but-not-fat wire is a 'bus feeder'

   to a distribution point of one. You could

   use 18/22 or even put a maxifuse of, say

   30-40A at the fuse-link location.



   The fuse link seems a bit more 'elegant'

   tied into the wire bundles as opposed to

   sticking out like a sore thumb.



 

 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Apr 28, 2018 9:08 am Post subject: Z-13/8 Question

At 10:24 AM 4/28/2018, you wrote:

  	  Quote: 	
		  Bob, I don't follow your language "this bigger but not fat wire is a 'bus feeder' to a distribution point of one." Specifically, why use the 18/22 when the rest of the run is 20. Why not just use 20/24? 	


   Forgive me. "FAT wires" refers to feeders that

   carry major battery/starter currents and generally

   require no fault protection.  If one is using

   a fuse block as opposed to breaker panel, then

   we would like to have the crowbar ov protection

   breaker crew accessible. This requires runing an

   extension of the power distribution on something

   less than a fat-wire to the single breaker on the

   panel.



   As a practical matter, one could make that total

   run from the fuse block to regulator with 20AWG

   wire and no other consideration bit it fusible

   link or other CPD (circuit protective device).



   The fusible link suggestion simply honored the

   legacy rule-of-thumb allowing small, short wires

   to attach unprotected to a fat-wire fed bus. The

   notion was that a hard fault on such wires would

   terminate quickly and not generate much smoke.

   

   We're sifting the really fine sands of risk here.

   99.99% of all circuit breakers/fuses installed 

   on all manner of vehicle goes to the salvage yard

   never being called upon to do its job to protect

   vehicle and occupants from smoke/fire.



   If we were boarding your airplane for a $100 hamburger

   trip and you confessed to me that the feeder to the

   crowbar ov breaker was 'unprotected' . . . my response

   is most likely to be, "Where are we going? Ponca City

   or Hutch?"



 

   Bob . . .

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Sat Apr 28, 2018 9:29 am Post subject: Z-13/8 Question

Thanks Bob. That clears some things up for me. You have not commented on using 20AWG with a 24AWG fuselink. I'm sure at some point the mechanical properties of the wire become an issue. Is 24AWG too small to be messing with for a fuselink?



Ken





On Sat, Apr 28, 2018 at 9:07 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 10:24 AM 4/28/2018, you wrote:

  	  Quote: 	
		  Bob, I don't follow your language "this bigger but not fat wire is a 'bus feeder' to a distribution point of one." Specifically, why use the 18/22 when the rest of the run is 20. Why not just use 20/24? 	


   Forgive me. "FAT wires" refers to feeders that

   carry major battery/starter currents and generally

   require no fault protection.  If one is using

   a fuse block as opposed to breaker panel, then

   we would like to have the crowbar ov protection

   breaker crew accessible. This requires runing an

   extension of the power distribution on something

   less than a fat-wire to the single breaker on the

   panel.



   As a practical matter, one could make that total

   run from the fuse block to regulator with 20AWG

   wire and no other consideration bit it fusible

   link or other CPD (circuit protective device).



   The fusible link suggestion simply honored the

   legacy rule-of-thumb allowing small, short wires

   to attach unprotected to a fat-wire fed bus. The

   notion was that a hard fault on such wires would

   terminate quickly and not generate much smoke.

   

   We're sifting the really fine sands of risk here.

   99.99% of all circuit breakers/fuses installed 

   on all manner of vehicle goes to the salvage yard

   never being called upon to do its job to protect

   vehicle and occupants from smoke/fire.



   If we were boarding your airplane for a $100 hamburger

   trip and you confessed to me that the feeder to the

   crowbar ov breaker was 'unprotected' . . . my response

   is most likely to be, "Where are we going? Ponca City

   or Hutch?"



 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Apr 28, 2018 11:44 am Post subject: Z-13/8 Question

At 12:26 PM 4/28/2018, you wrote:

  	  Quote: 	
		  Thanks Bob. That clears some things up for me. You have not commented on using 20AWG with a 24AWG fuselink. I'm sure at some point the mechanical properties of the wire become an issue. Is 24AWG too small to be messing with for a fuselink? 	


    Actually, no . . . 



    We used a lot of 24AWG in the airframe wiring

    on Premier . . . lots of grumbling at the outset

    but I think if proved to be pretty much a non

    issue. When crimping 24AWG into the red pidg

    terminals, I do double the strip length and

    fold the strands back to double the copper

    in the crimp . . . and i'm not sure that

    offers demonstrable benefit.



    Play around with it on the bench and see

    what YOU think . . . 



 

   Bob . . .

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Fri May 04, 2018 8:40 am Post subject: Z-13/8 Question

Bob,



From my limited experience, I see no demonstrable benefit to working with wire as fine as 24AWG. Certainly the weight is a non-issue. 24AWG is downright dainty compared to 20AWG. I think it is criminal that Ray Allen uses such fine wire in its servo pigtails. To me, using such fine wire is just asking for trouble. 

On Sat, Apr 28, 2018 at 11:43 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 12:26 PM 4/28/2018, you wrote:

  	  Quote: 	
		  Thanks Bob. That clears some things up for me. You have not commented on using 20AWG with a 24AWG fuselink. I'm sure at some point the mechanical properties of the wire become an issue. Is 24AWG too small to be messing with for a fuselink? 	


    Actually, no . . . 



    We used a lot of 24AWG in the airframe wiring

    on Premier . . . lots of grumbling at the outset

    but I think if proved to be pretty much a non

    issue. When crimping 24AWG into the red pidg

    terminals, I do double the strip length and

    fold the strands back to double the copper

    in the crimp . . . and i'm not sure that

    offers demonstrable benefit.



    Play around with it on the bench and see

    what YOU think . . . 



 

   Bob . . .

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