---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 09/10/09: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:29 PM - Re: ANL current limiters in Z13-8 (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 08:29:22 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: ANL current limiters in Z13-8 At 02:43 PM 9/9/2009, you wrote: >Spent an hour or so trying to visualize where everything is going to >mount on the firewall while studying Z-13/8 and came upon Note 10 >regarding current limiters. I understand that these are replacing >the In-Line Fuses referred to in Chapter 10 of AEC but had these questions: > >1. With a 40A alternator, do I use a 40A ANL current limiter? Yes, or even a 30 - 35 amp device. These are "current limiters", not fuses. They are EXCEEDINGLY robust and VERY slow. Thus they are used not for the protection of feeders to individual accessories like fuses/breakers. They are intended to separate a hard fadeult in a robust feeder (like the alternator b-lead) where shorted diodes in the alternator would offer battery fed fault currents on the order of many hundreds of amps. Cars don't use them and to the best of my knowledge, the risks have been low(?). But one wonders sometimes as to the root cause of some car-fires that start under the hood. In any case, if you co the mini-ANL route, they're small, light and no big deal to install. http://www.knukonceptz.com/productMaster.cfm?category=Mini-ANL%20Fuse You can make your own mounting block with a chunk of phenolic, delrin, etc and some 10-32 hardware. As you can see here . . . http://aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ANL_Specs.pdf the "current limiter" is quite robust. >2. Any reason the 4 AWG wire (and ANL current limiter) from the >alternator B lead can't go to the "downstream" side of the battery >contactor instead of the "upstream" side of the starter >contactor? They both seem to be electrically equivalent >particularly since the wire between them is so short. The current limiter is a hedge against failed alternator diodes. You can put the devise at either end of the b-lead feeder . . . I draw it at the starter contactor end becuase it's more difficult to mount it on the back of the alternator. Of course you can put it in the middle . . . >3. The following is found under Note 10. in AEC: "Alternator >noises in the system are reduced by not mounting the alternator >breaker on the panel in the traditional fashion...consider >installing the breaker as close as possible to the starter >contactor" -- Is this referring to the ANL current limiter >described above or the circuit breaker for the alternator field? If >the latter, I'm confused and hope someone can provide some more explanation. This is referring to the legacy practice of brining alternator b-leads into the cockpit to tie to a 60A or so breaker on the panel. There's no practical, or safety related reason for doing this . . . we quit doing it at Beech years ago. There are reasons to keep it forward of the firewall to reduce the level of magnetic interference to compass and/or coupled to adjacent instrumentation or avionics wires. Bob . . . --------------------------------------- ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) --------------------------------------- ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.