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jmjones2000(at)mindspring
Guest

Posted: Mon Dec 07, 2015 4:04 pm Post subject: Circuit breaker question

Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had.



Any insight?



Justin

ceengland7(at)gmail.com
Guest

Posted: Mon Dec 07, 2015 5:17 pm Post subject: Circuit breaker question

On 12/7/2015 6:02 PM, Justin Jones wrote:

 	  Quote: 	
		   



 Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had.



 Any insight?



 Justin

No. (To using 2 breakers in parallel.)
	




And that's a weird recommendation, too, unless the fuse mentioned is a 

special long-time-constant 'slow blow' type fuse. A breaker would take a 

lot longer to trip than a standard fuse of the same value; going 30A 

higher with the breaker *and* having slower response sounds really strange.



Buying 2  50 A a/c breakers (or even one 100 A breaker) would just kill 

my (wallet's) soul. A fuse-able link would be lighter, take no panel 

space, a *lot* cheaper, and if soldered in place, a *lot* more reliable 

than a breaker (no joints to corrode or contacts to fail). If it's 

properly sized, it shouldn't need attention for the life of the a/c, 

unlike a CB.



FWIW,



Charlie

jmjones2000(at)mindspring
Guest

Posted: Mon Dec 07, 2015 6:04 pm Post subject: Circuit breaker question

The ANL fuse suggestion came from Bob's Z diagrams (note 10)

 	  Quote: 	
		   On Dec 7, 2015, at 16:16, Charlie England <ceengland7(at)gmail.com> wrote:

> On 12/7/2015 6:02 PM, Justin Jones wrote:

> 

> 

> Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had.

> 

> Any insight?

> 

> Justin

 No. (To using 2 breakers in parallel.)

 And that's a weird recommendation, too, unless the fuse mentioned is a special long-time-constant 'slow blow' type fuse. A breaker would take a lot longer to trip than a standard fuse of the same value; going 30A higher with the breaker *and* having slower response sounds really strange.

 Buying 2  50 A a/c breakers (or even one 100 A breaker) would just kill my (wallet's) soul. A fuse-able link would be lighter, take no panel space, a *lot* cheaper, and if soldered in place, a *lot* more reliable than a breaker (no joints to corrode or contacts to fail). If it's properly sized, it shouldn't need attention for the life of the a/c, unlike a CB.

 FWIW,

 Charlie

ceengland7(at)gmail.com
Guest

Posted: Mon Dec 07, 2015 7:21 pm Post subject: Circuit breaker question

ANL would obviously be fine, but I was assuming that AC43 wouldn't be 

recommending ANL fuses. Even with ANL, it's still weird that they would 

equate a 100A breaker to a 70A fuse.



On 12/7/2015 8:02 PM, Justin Jones wrote:

 	  Quote: 	
		   



 The ANL fuse suggestion came from Bob's Z diagrams (note 10)



   



> On Dec 7, 2015, at 16:16, Charlie England <ceengland7(at)gmail.com> wrote:

>

> 

>

>> On 12/7/2015 6:02 PM, Justin Jones wrote:

>> 

>>

>> Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had.

>>

>> Any insight?

>>

>> Justin

> No. (To using 2 breakers in parallel.)

>

> And that's a weird recommendation, too, unless the fuse mentioned is a special long-time-constant 'slow blow' type fuse. A breaker would take a lot longer to trip than a standard fuse of the same value; going 30A higher with the breaker *and* having slower response sounds really strange.

>

> Buying 2  50 A a/c breakers (or even one 100 A breaker) would just kill my (wallet's) soul. A fuse-able link would be lighter, take no panel space, a *lot* cheaper, and if soldered in place, a *lot* more reliable than a breaker (no joints to corrode or contacts to fail). If it's properly sized, it shouldn't need attention for the life of the a/c, unlike a CB.

>

> FWIW,

>

> Charlie

>

jmjones2000(at)mindspring
Guest

Posted: Mon Dec 07, 2015 7:47 pm Post subject: Circuit breaker question

I thought it was strange too. It's table 11-3 on page 11-15 in chapter 11 of AC 43.13.1B



 

 



 	  Quote: 	
		   On Dec 7, 2015, at 18:19, Charlie England <ceengland7(at)gmail.com> wrote:

 

 

 

 ANL would obviously be fine, but I was assuming that AC43 wouldn't be recommending ANL fuses. Even with ANL, it's still weird that they would equate a 100A breaker to a 70A fuse.

 

> On 12/7/2015 8:02 PM, Justin Jones wrote:

> 

> 

> The ANL fuse suggestion came from Bob's Z diagrams (note 10)

> 

>  

>> On Dec 7, 2015, at 16:16, Charlie England <ceengland7(at)gmail.com> wrote:

>> 

>> 

>> 

>>> On 12/7/2015 6:02 PM, Justin Jones wrote:

>>> 

>>> 

>>> Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had.

>>> 

>>> Any insight?

>>> 

>>> Justin

>> No. (To using 2 breakers in parallel.)

>> 

>> And that's a weird recommendation, too, unless the fuse mentioned is a special long-time-constant 'slow blow' type fuse. A breaker would take a lot longer to trip than a standard fuse of the same value; going 30A higher with the breaker *and* having slower response sounds really strange.

>> 

>> Buying 2  50 A a/c breakers (or even one 100 A breaker) would just kill my (wallet's) soul. A fuse-able link would be lighter, take no panel space, a *lot* cheaper, and if soldered in place, a *lot* more reliable than a breaker (no joints to corrode or contacts to fail). If it's properly sized, it shouldn't need attention for the life of the a/c, unlike a CB.

>> 

>> FWIW,

>> 

>> Charlie

 

 

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jluckey(at)pacbell.net
Guest

Posted: Mon Dec 07, 2015 10:34 pm Post subject: Circuit breaker question

Keep in mind that ANL are really current limiters (as opposed to fuses) which have a different (slower acting) current curve  than a regular fuse and/or breaker (faster acting).  They can hold a little over their rated value for a fairly long time (like minutes).  Google "ANL current curve" for details ...

-Jeff

 



    On Monday, December 7, 2015 8:01 PM, Justin Jones <jmjones2000(at)mindspring.com> wrote:



  



 I thought it was strange too. It's table 11-3 on page 11-15 in chapter 11 of AC 43.13.1B



 

 



 	  Quote: 	
		   On Dec 7, 2015, at 18:19, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

 

 --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

 

 ANL would obviously be fine, but I was assuming that AC43 wouldn't be recommending ANL fuses. Even with ANL, it's still weird that they would equate a 100A breaker to a 70A fuse.

 

> On 12/7/2015 8:02 PM, Justin Jones wrote:

> --> AeroElectric-List message posted by: Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)>

> 

> The ANL fuse suggestion came from Bob's Z diagrams (note 10)

> 

>  

>> On Dec 7, 2015, at 16:16, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

>> 

>> --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

>> 

>>> On 12/7/2015 6:02 PM, Justin Jones wrote:

>>> --> AeroElectric-List message posted by: Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)>

>>> 

>>> Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had.

>>> 

>>> Any insight?

>>> 

>>> Justin

>> No. (To using 2 breakers in parallel.)

>> 

>> And that's a weird recommendation, too, unless the fuse mentioned is a special long-time-constant 'slow blow' type fuse. A breaker would take a lot longer to trip than a standard fuse of the same value; going 30A higher with the breaker *and* having slower response sounds really strange.

>> 

>> Buying 2  50 A a/c breakers (or even one 100 A breaker) would just kill my (wallet's) soul. A fuse-able link would be lighter, take no panel space, a *lot* cheaper, and if soldered in place, a *lot* more reliable than a breaker (no joints to corrode or contacts to fail). If it's properly sized, it shouldn't need attention for the life of the a/c, unlike a CB.

>> 

>> FWIW,

>> 

>> Charlie

 

 

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 	  Quote:

JOHN TIPTON

Joined: 17 Sep 2006
Posts: 239
Location: Torquay - England

Posted: Tue Dec 08, 2015 2:02 am Post subject: Circuit breaker question

Jeff is right: in this situation the ANL fuse is matched to the alternator output, not to the wire size

John



Sent from my iPad



     ----x--O--x----

On 8 Dec 2015, at 06:32 am, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote:

 	  Quote: 	
		  



Keep in mind that ANL are really current limiters (as opposed to fuses) which have a different (slower acting) current curve  than a regular fuse and/or breaker (faster acting).  They can hold a little over their rated value for a fairly long time (like minutes).  Google "ANL current curve" for details ...

-Jeff

 



    On Monday, December 7, 2015 8:01 PM, Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)> wrote:



  



 I thought it was strange too. It's table 11-3 on page 11-15 in chapter 11 of AC 43.13.1B



 

 



 	  Quote: 	
		   On Dec 7, 2015, at 18:19, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

 

 --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

 

 ANL would obviously be fine, but I was assuming that AC43 wouldn't be recommending ANL fuses. Even with ANL, it's still weird that they would equate a 100A breaker to a 70A fuse.

 

> On 12/7/2015 8:02 PM, Justin Jones wrote:

> --> AeroElectric-List message posted by: Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)>

> 

> The ANL fuse suggestion came from Bob's Z diagrams (note 10)

> 

>  

>> On Dec 7, 2015, at 16:16, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

>> 

>> --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

>> 

>>> On 12/7/2015 6:02 PM, Justin Jones wrote:

>>> --> AeroElectric-List message posted by: Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)>

>>> 

>>> Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had.

>>> 

>>> Any insight?

>>> 

>>> Justin

>> No. (To using 2 breakers in parallel.)

>> 

>> And that's a weird recommendation, too, unless the fuse mentioned is a special long-time-constant 'slow blow' type fuse. A breaker would take a lot longer to trip than a standard fuse of the same value; going 30A higher with the breaker *and* having slower response sounds really strange.

>> 

>> Buying 2  50 A a/c breakers (or even one 100 A breaker) would just kill my (wallet's) soul. A fuse-able link would be lighter, take no panel space, a *lot* cheaper, and if soldered in place, a *lot* more reliable than a breaker (no joints to corrode or contacts to fail). If it's properly sized, it shouldn't need attention for the life of the a/c, unlike a CB.

>> 

>> FWIW,

>> 

>> Charlie

 

 

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 	  Quote:

user9253

Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan

Posted: Tue Dec 08, 2015 6:38 am Post subject: Re: Circuit breaker question

Circuit breakers should not be connected in parallel.  An ANL fuse is fine.  Circuit protection should be located near the source of power.  One might think that the alternator is the source of power.  But in this case, the battery and wires are what need protection in case the alternator or its "B" lead shorts out.  A disadvantage of using a circuit breaker for this application is that it would be located inside of the cockpit and fed with a hot unprotected wire.  An ANL fuse can be located near the contactors on the engine side of the firewall, thus eliminating at least one heavy wire from running into the cockpit.  Is 4 AWG wire really needed?  Maybe 6 AWG or even 8 AWG could be used, depending on the expected load.  Modern avionics and LED lights use less current than older equipment.

_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Tue Dec 08, 2015 11:49 am Post subject: Circuit breaker question

On December 8, 2015 8:38:56 AM CST, user9253 <fransew(at)gmail.com> wrote:[quote] [quote]--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>Circuit breakers should not be connected in parallel.  An ANL fuse is fine.  Circuit protection should be located near the source of power.  One might think that the alternator is the source of power.  But in this case, the battery and wires are what need protection in case the alternator or its "B" lead shorts out.  A disadvantage of using a circuit breaker for this application is that it would be located inside of the cockpit and fed with a hot unprotected wire.  An ANL fuse can be located near the contactors on the engine side of the firewall, thus eliminating at least one heavy wire from running into the cockpit.  Is 4 AWG wire really needed?  Maybe 6 AWG or even 8 AWG could be used, depending on the expected load.  Modern avionics and LED lights use less current than older equipment.--------Joe GoresRead this topi  c   The  Wire must be large enough to handle max possible current from alt (which is > rated output). Fuse must be sized to protect wire. Otherwise there will be nuisance trips. I think that it's covered in the 'book'.

 -- 

 Sent from my Android device with K-9 Mail. Please excuse my brevity.

user9253

Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan

Posted: Tue Dec 08, 2015 5:25 pm Post subject: Re: Circuit breaker question

You are right Charlie. I should not have suggested a smaller wire size without knowing the ampacity of the alternator.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Dec 10, 2015 8:18 am Post subject: Circuit breaker question

At 06:02 PM 12/7/2015, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Justin Jones <jmjones2000(at)mindspring.com>



 Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had. 	


   Few OEMs (if any) in the certified iron business

   use circuit breakers in the alternator b-lead.

   At Beech, current limiters on the firewall have

   protected the b-lead for 30 or more years.



   Check out the products on this webpage



  http://tinyurl.com/by5qnop



   These are miniature, high current fuses

   and matching holders widely available through

   automotive and mobile sound system dealers.

   You can find all sizes along with mounting

   bases on ebay.



  http://tinyurl.com/jn9k9nu



   One caveat . . . AVOID the fuse holders

   that grip the fat-wires with mash-screws.

   You want a holder with captive, male studs

   which are used to place the fuse-tab into

   intimate contact with the ring-terminal on

   the end of your b-lead wiring.



   A holder like this one



  http://tinyurl.com/54fk



   can be 'modified' to a satisfactory aviation

   fuse holder by discarding the mash-screws

   and dropping your ring terminals over the

   fuse attach screws.



   Consider making your own fuse holder . . .

   A block carved from phenolic, delrin, micarta

   or other high temp, machinable plastic.



  http://tinyurl.com/jdatd3e



   These parts combined with some 10-32 stainless

   steel screws, nuts and washers from a hardware

   store will produce a robust alternative

   to purchased/modified fuse holders.

  

   Pick a MIDI fuse rating at or just above

   the alternator rating. If the guy wants to

   use a breaker, the rating should be 20-50%

   LARGER than the alternator output. Finally,

   DO NOT parallel breakers.



 

 

   Bob . . .

millner(at)me.com
Guest

Posted: Thu Dec 10, 2015 10:31 am Post subject: Circuit breaker question

On 12/10/2015 8:16 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   Few OEMs (if any) in the certified iron business

   use circuit breakers in the alternator b-lead.


	


Hey Bob!



You're overlooking our friends at Cessna, responsible for almost half 

the single engine land aircraft out there! From the first installation 

of alternators through, I believe, today, they put a breaker at the main 

bus where the alternator power enters... in my '76 Cardinal (12 volt) 

that's a 60 amp beast which is hard to come by, and subject of several 

service bulletins over the years (aluminum bus heating causing false 

tripping, etc.)



Paul

jmjones2000(at)mindspring
Guest

Posted: Thu Dec 10, 2015 12:22 pm Post subject: Circuit breaker question

Convinced him to go with ANL fuses. Where is the best place to locate them? Close to the alternator or close to the battery?

Bob's Z diagrams show them near the battery. If protecting against a short, wouldn't the battery end of the b lead be best? Or are we simply protecting from an over amperage condition?

Justin



 



On Dec 10, 2015, at 07:16, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 06:02 PM 12/7/2015, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)>



 Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had. 	


   Few OEMs (if any) in the certified iron business

   use circuit breakers in the alternator b-lead.

   At Beech, current limiters on the firewall have

   protected the b-lead for 30 or more years.



   Check out the products on this webpage



  http://tinyurl.com/by5qnop



   These are miniature, high current fuses

   and matching holders widely available through

   automotive and mobile sound system dealers.

   You can find all sizes along with mounting

   bases on ebay.



  http://tinyurl.com/jn9k9nu



   One caveat . . . AVOID the fuse holders

   that grip the fat-wires with mash-screws.

   You want a holder with captive, male studs

   which are used to place the fuse-tab into

   intimate contact with the ring-terminal on

   the end of your b-lead wiring.



   A holder like this one



  http://tinyurl.com/54fk



   can be 'modified' to a satisfactory aviation

   fuse holder by discarding the mash-screws

   and dropping your ring terminals over the

   fuse attach screws.



   Consider making your own fuse holder . . .

   A block carved from phenolic, delrin, micarta

   or other high temp, machinable plastic.



  http://tinyurl.com/jdatd3e



   These parts combined with some 10-32 stainless

   steel screws, nuts and washers from a hardware

   store will produce a robust alternative

   to purchased/modified fuse holders.

  

   Pick a MIDI fuse rating at or just above

   the alternator rating. If the guy wants to

   use a breaker, the rating should be 20-50%

   LARGER than the alternator output. Finally,

   DO NOT parallel breakers.



 

 

   Bob . . .

ceengland7(at)gmail.com
Guest

Posted: Thu Dec 10, 2015 2:13 pm Post subject: Circuit breaker question

On December 10, 2015 3:21:06 PM EST, Justin Jones <jmjones2000(at)mindspring.com> wrote: 	  Quote: 	
		   Convinced him to go with ANL fuses. Where is the best place to locate them? Close to the alternator or close to the battery?



Bob's Z diagrams show them near the battery. If protecting against a short, wouldn't the battery end of the b lead be best? Or are we simply protecting from an over amperage condition?



Justin

 

On Dec 10, 2015, at 07:16, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 06:02 PM 12/7/2015, you wrote:  	  Quote: 	
		  --> AeroElectric-List message posted by: Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)> Hangar talk with a neighbor. He is designing a circuit using 4awg wire for his alternator.  He asked me if he could use 2 - 50A circuit breakers wired in Parallel for this purpose instead of a single 100A breaker. Chapter 11 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggested the use of a 70A ANL fuse, but wasnâ€™t sure what the answer is to the CB question he had. 	
   Few OEMs (if any) in the certified iron business   use circuit breakers in the alternator b-lead.   At Beech, current limiters on the firewall have   protected the b-lead for 30 or more years.   Check out the products on this webpage  http://tinyurl.com/by5qnop   These are miniature, high current fuses   and matching holders widely available through   automotive and mobile sound system dealers.   You can find all sizes along with mounting   bases on ebay.  http://tinyurl.com/jn9k9nu   One caveat . . . AVOID the fuse holders   that grip the fat-wires with mash-screws.   You want a holder with captive, male studs   which are used to place the fuse-tab into   intimate contact with the ring-terminal on   the end of your b-lead wiring.   A holder like this one  http://tinyurl.com/54fk   can be 'modified' to a satisfactory aviation   fuse holder by discarding the mash-screws   and dropping your ring terminals over the   fuse attach screws.   Consider making your own fuse holder . . .   A block carved from phenolic, delrin, micarta   or other high temp, machinable plastic.  http://tinyurl.com/jdatd3e   These parts combined with some 10-32 stainless   steel screws, nuts and washers from a hardware   store will produce a robust alternative   to purchased/modified fuse holders.     Pick a MIDI fuse rating at or just above   the alternator rating. If the guy wants to   use a breaker, the rating should be 20-50%   LARGER than the alternator output. Finally,   DO NOT parallel breakers.  

   Bob . . .   

	
	


Battery end. Battery can melt the wire; alt cannot.

 -- 

 Sent from my Android device with K-9 Mail. Please excuse my brevity.

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Dec 10, 2015 6:50 pm Post subject: Circuit breaker question

At 12:30 PM 12/10/2015, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Paul Millner <millner(at)me.com>



 



 On 12/10/2015 8:16 AM, Robert L. Nuckolls, III wrote:

  	  Quote: 	
		  Few OEMs (if any) in the certified iron business

   use circuit breakers in the alternator b-lead. 	


 Hey Bob!



 You're overlooking our friends at Cessna, responsible for almost half the single engine land aircraft out there! From the first installation of alternators through, I believe, today, they put a breaker at the main bus where the alternator power enters... in my '76 Cardinal (12 volt) that's a 60 amp beast which is hard to come by, and subject of several service bulletins over the years (aluminum bus heating causing false tripping, etc.) 	


   Yes, that's where they were when I worked there

   too . . . but I thought those were moved off the

   panel when the Lamar power distribution box went

   into production . . . and that's been some time

   ago.



   I'll have to check my G2 sources . . .



 

 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Dec 10, 2015 6:51 pm Post subject: Circuit breaker question

At 02:21 PM 12/10/2015, you wrote:

  	  Quote: 	
		  Convinced him to go with ANL fuses. Where is the best place to locate them? Close to the alternator or close to the battery?



 Bob's Z diagrams show them near the battery. If protecting against a short, wouldn't the battery end of the b lead be best? Or are we simply protecting from an over amperage condition?

  	  Quote: 	
		  	
	
 

   Close to the battery. An alternator is physically

   incapable of burning its own b-lead . . . but the

   BATTERY is good for 1000+ amps in a fault condition.



 

 

   Bob . . .

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