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Alternator B-lead circuit protection

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dan(at)syz.com
Guest

Posted: Fri Aug 07, 2015 12:43 am Post subject: Alternator B-lead circuit protection

Hi everyone.  I have a quick question with regards to protecting alternator B-leads.



A lot of people do so with ANL fuses, yet I know some aircraft (like my C150) do so with a circuit breaker.  Of course, a disadvantage of the ANL is that if it blew while on a trip, after fixing whatever caused the problem, a person would have to source a new fuse which could result in the aircraft being grounded waiting for one to be shipped (are ANL fuses that easy to find?  I'm in Canada, so my usual sources of parts are Aircraft Spruce, which doesn't seem to carry them, or "chain" stores like Canadian Tire, which doesn't seem to either.  Though it does appear that Digikey carries them, so at least there is a source here without having to go through the customs hassles of ordering from somewhere like B&C).  The natural advantage of a circuit breaker, of course, is that it can be reset without replacing things once the problem is fixed.



But I don't like much the idea of bringing B-leads into the area behind the panel, or even into the cockpit for that matter, and am unsure as to whether a circuit breaker would cause more problems than it prevents due to nuisance trips.  I know it's not "conventionally" done, but is there any problem with locating a B-lead circuit breaker under the cowling in the engine compartment if a person were to go the circuit breaker route?  After all, if a B-lead were to have a current spike tripping the fuse or breaker, the cowling would likely have to be pulled anyway to see what's going on.



Or is it better to just go the fuse route?  And if so, any advantages of ANL over MIDI style?



Thanks for any advice!



Dan

---

Dan Charrois

President, Syzygy Research & Technology

Phone: 780-961-2213

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email(at)jaredyates.com
Guest

Posted: Fri Aug 07, 2015 4:33 am Post subject: Alternator B-lead circuit protection

My tool bag carries them!Â  They are cheap enough and small enough to bring a spare or two along, as to help mitigate that concern.

[quote]could result in the aircraft being grounded waiting for one to be shipped (are ANL fuses that easy to find?Â  I'm in Canada, so my usual sources of parts are Aircraft Spruce, which doesn't seem to carry them, or "chain" stores like Canadian Tire, which doesn't seem to either. Â [b]

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yellowduckduo(at)gmail.co
Guest

Posted: Fri Aug 07, 2015 5:02 am Post subject: Alternator B-lead circuit protection

I've used a circuit breaker or maxi fuse with 40 amp alternators when 

the battery is in the fuselage.

I would hesitate to use a C/B on the hot side of the FW since they are 

likely more sensitive to the surrounding environment than fuses or an ANL.

Many automotive audio system vendors stock ANLs and they can always be 

hotwired making them into essentially a fusable link.

Ken



On 07/08/2015 4:41 AM, Dan Charrois wrote:

 	  Quote: 	
		   



 Hi everyone.  I have a quick question with regards to protecting alternator B-leads.



 A lot of people do so with ANL fuses, yet I know some aircraft (like my C150) do so with a circuit breaker.  Of course, a disadvantage of the ANL is that if it blew while on a trip, after fixing whatever caused the problem, a person would have to source a new fuse which could result in the aircraft being grounded waiting for one to be shipped (are ANL fuses that easy to find?  I'm in Canada, so my usual sources of parts are Aircraft Spruce, which doesn't seem to carry them, or "chain" stores like Canadian Tire, which doesn't seem to either.  Though it does appear that Digikey carries them, so at least there is a source here without having to go through the customs hassles of ordering from somewhere like B&C).  The natural advantage of a circuit breaker, of course, is that it can be reset without replacing things once the problem is fixed.



 But I don't like much the idea of bringing B-leads into the area behind the panel, or even into the cockpit for that matter, and am unsure as to whether a circuit breaker would cause more problems than it prevents due to nuisance trips.  I know it's not "conventionally" done, but is there any problem with locating a B-lead circuit breaker under the cowling in the engine compartment if a person were to go the circuit breaker route?  After all, if a B-lead were to have a current spike tripping the fuse or breaker, the cowling would likely have to be pulled anyway to see what's going on.



 Or is it better to just go the fuse route?  And if so, any advantages of ANL over MIDI style?



 Thanks for any advice!



 Dan

 ---

 Dan Charrois

 President, Syzygy Research & Technology

 Phone: 780-961-2213

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

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rene(at)felker.com
Guest

Posted: Fri Aug 07, 2015 5:02 am Post subject: Alternator B-lead circuit protection

I used a CB mounted in the engine compartment.



I had a 60 amp alternator and went to a 70 amp alternator.  I did not change

the CB  (you see what is coming).  On a long trip back East (from Utah), I

had the CB trip twice in flight.  I did not think I could draw 60

amps......but I can.  So when I got back I upgraded to a 70 amp CB.....no

trips since.



I have two batteries on board and on reduced load can go an entire flight

without the alternator.



Rene'

801-721-6080



--

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user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Fri Aug 07, 2015 5:23 am Post subject: Re: Alternator B-lead circuit protection

If the ANL fuse is sized right and the terminals are kept tight, it should never blow unless there is a bigger problem.  There is less to go wrong with a fuse compared to a circuit breaker.  I would use a fuse located near the contactors.

The protective device does not have to be resetable for once in a lifetime event.

Joe

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_________________
Joe Gores

tomhanaway

Joined: 12 Aug 2006
Posts: 111
Location: Murphy, NC

Posted: Fri Aug 07, 2015 5:41 am Post subject: Alternator B-lead circuit protection

I agree that if a properly sized ANL fuse blows, you've probably got bigger problems.

However, I just carry a spare one in my kit



Sent from my iPad



 	  Quote: 	
		   On Aug 7, 2015, at 9:23 AM, user9253 <fransew(at)gmail.com> wrote:

 

 

 

 If the ANL fuse is sized right and the terminals are kept tight, it should never blow unless there is a bigger problem.  There is less to go wrong with a fuse compared to a circuit breaker.  I would use a fuse located near the contactors.

 The protective device does not have to be resetable for once in a lifetime event.

 Joe

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=445669#445669

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_________________
RV-10. Built and sold
RV-8a. Building

ARGOLDMAN(at)aol.com
Guest

Posted: Fri Aug 07, 2015 11:50 am Post subject: Alternator B-lead circuit protection

Uh- Yep

  

 When discharged the battery will immediately take all of the available  alternator current if you have underrated the breaker, it will break.

  

 The breaker, in any circuit should be sized to protect the wire, not the  deliverer of electrons nor those things that use them.

  

 Rich

  

  In a message dated 8/7/2015 8:03:45 A.M. Central Daylight Time,  rene(at)felker.com writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: "Rene" <rene(at)felker.com>



I    used a CB mounted in the engine compartment.



I had a 60 amp alternator    and went to a 70 amp alternator.  I did not change

the CB  (you    see what is coming).  On a long trip back East (from Utah), I

had the    CB trip twice in flight.  I did not think I could draw    60

amps......but I can.  So when I got back I upgraded to a 70 amp    CB.....no

trips since.



I have two batteries on board and on reduced    load can go an entire flight

without the    alternator.



Rene'

801-721-6080



-----Original    Message-----

From:    owner-aeroelectric-list-server(at)matronics.com

[mailto:owner-aeroelectric-list-server(at)matronics.com]    On Behalf Of Dan

Charrois

Sent: Friday, August 07, 2015 2:41 AM

To:    aeroelectric-list(at)matronics.com

Subject: Alternator    B-lead circuit protection



--> AeroElectric-List message posted by:    Dan Charrois <dan(at)syz.com>



Hi everyone.  I have a quick    question with regards to protecting alternator

B-leads.



A lot of    people do so with ANL fuses, yet I know some aircraft (like my

C150) do so    with a circuit breaker.  Of course, a disadvantage of the ANL is

that    if it blew while on a trip, after fixing whatever caused the problem,    a

person would have to source a new fuse which could result in the    aircraft

being grounded waiting for one to be shipped (are ANL fuses that    easy to

find?  I'm in Canada, so my usual sources of parts are    Aircraft Spruce,

which doesn't seem to carry them, or "chain" stores like    Canadian Tire,

which doesn't seem to either.  Though it does appear    that Digikey carries

them, so at least there is a source here without    having to go through the

customs hassles of ordering from somewhere like    B&C).  The natural advantage

of a circuit breaker, of course, is    that it can be reset without replacing

things once the problem is    fixed.



But I don't like much the idea of bringing B-leads into the area    behind the

panel, or even into the cockpit for that matter, and am unsure    as to whether

a circuit breaker would cause more problems than it prevents    due to nuisance

trips.  I know it's not "conventionally" done, but is    there any problem with

locating a B-lead circuit breaker under the cowling    in the engine

compartment if a person were to go the circuit breaker    route?  After all, if

a B-lead were to have a current spike tripping    the fuse or breaker, the

cowling would likely have to be pulled anyway to    see what's going on.



Or is it better to just go the fuse route?     And if so, any advantages of ANL

over MIDI style?



Thanks for any    advice!



Dan

---

Dan Charrois

President, Syzygy Research &    Technology

Phone:  ================================================= Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


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