AeroElectric-List Digest Archive

Tue 12/08/15


Total Messages Posted: 6



Today's Message Index:
----------------------
 
     1. 02:02 AM - Re: Circuit breaker question (John Tipton)
     2. 06:42 AM - Re: Circuit breaker question (user9253)
     3. 11:49 AM - Re: Re: Circuit breaker question (Charlie England)
     4. 05:02 PM - Re: Weak Starter (speedy11@aol.com)
     5. 05:28 PM - Re: Circuit breaker question (user9253)
     6. 09:11 PM - Re: Re: Weak Starter (Justin Jones)
 
 
 


Message 1


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    Time: 02:02:16 AM PST US
    Subject: Re: Circuit breaker question
    From: John Tipton <jmtipton@btopenworld.com>
    Jeff is right: in this situation the ANL fuse is matched to the alternator o utput, not to the wire size John Sent from my iPad ----x--O--x---- > On 8 Dec 2015, at 06:32 am, Jeff Luckey <jluckey@pacbell.net> wrote: > > > Keep in mind that ANL are really current limiters (as opposed to fuses) wh ich 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 f or a fairly long time (like minutes). Google "ANL current curve" for detail s ... > > -Jeff > > > > > > On Monday, December 7, 2015 8:01 PM, Justin Jones <jmjones2000@mindspring. com> wrote: > > > I thought it was strange too. It's table 11-3 on page 11-15 in chapter 11 o f AC 43.13.1B > > > > > > > > On Dec 7, 2015, at 18:19, Charlie England <ceengland7@gmail.com> wrote: > > il.com> > > > > ANL would obviously be fine, but I was assuming that AC43 wouldn't be re commending 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: spring.com> > >> > >> The ANL fuse suggestion came from Bob's Z diagrams (note 10) > >> > >> > >>> On Dec 7, 2015, at 16:16, Charlie England <ceengland7@gmail.com> wrote : > >>> mail.com> > >>> > >>>> On 12/7/2015 6:02 PM, Justin Jones wrote: ndspring.com> > >>>> > >>>> Hangar talk with a neighbor. He is designing a circuit using 4awg wir e for his alternator. He asked me if he could use 2 - 50A circuit breakers w ired in Parallel for this purpose instead of a single 100A breaker. Chapter 1 1 in AC 43 says to use a 100A breaker or a 70A fuse for 4AWG wire. I suggest ed the use of a 70A ANL fuse, but wasn=99t sure what the answer is to t he 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 lo t longer to trip than a standard fuse of the same value; going 30A higher wi th the breaker *and* having slower response sounds really strange. > >>> > >>> Buying 2 50 A a/c breakers (or even one 100 A breaker) would just kil l 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 br eaker (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 > > > > > ========================= > ========================= > ========== > ========================= > ========== > > > > > > >


    Message 2


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    Time: 06:42:27 AM PST US
    Subject: Re: Circuit breaker question
    From: "user9253" <fransew@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 Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=450818#450818


    Message 3


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    Time: 11:49:35 AM PST US
    Subject: Re: Circuit breaker question
    From: Charlie England <ceengland7@gmail.com>
    On December 8, 2015 8:38:56 AM CST, user9253 <fransew@gmail.com> wrote: > >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 > > >Read this topic online here: > >http://forums.matronics.com/viewtopic.php?p=450818#450818 > > 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.


    Message 4


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    Time: 05:02:43 PM PST US
    From: speedy11@aol.com
    Subject: Re: Weak Starter
    John, I had the same issue on my IO-390. Skytec worked okay for five years then got slower and slower. I did all of the same checks you are talking about. Replaced the starter. Problem solved. See if you can borrow a starter from someone and try it on your plane. Stan My Skytec starter barely turns over an IO320. I measured: Battery 13.12 volts. "On" side of master contactor to airframe ground 12.25 volts. "On" side of starter contactor to airframe ground while cranking 8.6 to 9.0 volts. Big wire on starter to airframe ground while cranking is 8.6 volts or less. All this was done with a genuine Harbor Freight $4.00 digital meter. I believe that this points to the starter contactor as the culprit. Correct? john


    Message 5


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    Time: 05:28:48 PM PST US
    Subject: Re: Circuit breaker question
    From: "user9253" <fransew@gmail.com>
    You are right Charlie. I should not have suggested a smaller wire size without knowing the ampacity of the alternator. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=450830#450830


    Message 6


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    Time: 09:11:12 PM PST US
    From: Justin Jones <jmjones2000@mindspring.com>
    Subject: Re: Weak Starter
    Be advised, some if not all lycoming skytec starters have a contactor (solen oid) on the starter as well. > On Dec 8, 2015, at 16:59, speedy11@aol.com wrote: > > John, > I had the same issue on my IO-390. Skytec worked okay for five years then got slower and slower. I did all of the same checks you are talking about. Replaced the starter. Problem solved. > See if you can borrow a starter from someone and try it on your plane. > Stan > > My Skytec starter barely turns over an IO320. > > I measured: > > Battery 13.12 volts. > "On" side of master contactor to airframe ground 12.25 volts. > "On" side of starter contactor to airframe ground while cranking 8.6 to > 9.0 volts. > Big wire on starter to airframe ground while cranking is 8.6 volts or less . > > All this was done with a genuine Harbor Freight $4.00 digital meter. I > believe that this points to the starter contactor as the culprit. Correct? > > john >




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