---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 01/19/17: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 03:12 AM - Always hot wire to panel (GTH) 2. 06:13 AM - Re: Always hot wire to panel (GTH) 3. 06:54 AM - Re: Always hot wire to panel (user9253) 4. 07:21 AM - Re: Re: Always hot wire to panel (GTH) 5. 08:42 AM - Re: Always hot wire to panel (Robert L. Nuckolls, III) 6. 09:59 AM - Dual Battery design (Hariharan Gopalan) 7. 10:39 AM - Re: Dual Battery design (Hariharan Gopalan) 8. 07:49 PM - Re: Dual Battery design (user9253) ________________________________ Message 1 _____________________________________ Time: 03:12:46 AM PST US From: GTH Subject: AeroElectric-List: Always hot wire to panel Hi all, Could anyone point me to a text or reference document mentioning the rule about limiting the rating of always hot battery wires such as the wire from battery contactor to Master Switch ? Thanks in advance, -- Best regards, Gilles http://contrails.free.fr http://lapierre.skunkworks.free.fr ________________________________ Message 2 _____________________________________ Time: 06:13:19 AM PST US Subject: Re: AeroElectric-List: Always hot wire to panel From: GTH > > > Could anyone point me to a text or reference document mentioning the > rule about limiting the rating of always hot battery wires such as the > wire from battery contactor to Master Switch ? / Hi again, I believe I got them : FAR Part 23-1361 (b)(1) CS 23.1361 (b)(2) -- Best regards, Gilles http://contrails.free.fr http://lapierre.skunkworks.free.fr ________________________________ Message 3 _____________________________________ Time: 06:54:59 AM PST US Subject: AeroElectric-List: Re: Always hot wire to panel From: "user9253" Usually the negative side of the master contactor coil is switched. So there is no always hot wire running into the cockpit from the master contactor. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=465241#465241 ________________________________ Message 4 _____________________________________ Time: 07:21:48 AM PST US Subject: Re: AeroElectric-List: Re: Always hot wire to panel From: GTH Le 19/01/2017 15:52, user9253 a crit : > > Usually the negative side of the master contactor coil is switched. So there is no always hot wire running into the cockpit from the master contactor. > Joe, Thank you for your response. Just to be sure, isn't this wire from the contactor coil to the panel switch permanently "hot", albeit through the contactor coil ? -- Best regards, Gilles http://contrails.free.fr http://lapierre.skunkworks.free.fr ________________________________ Message 5 _____________________________________ Time: 08:42:56 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Always hot wire to panel At 08:10 AM 1/19/2017, you wrote: >> >> >> >>Could anyone point me to a text or reference document mentioning >>the rule about limiting the rating of always hot battery wires such >>as the wire from battery contactor to Master Switch ? The 'rules' pertain only to those wires which elevate risks during MAJOR deformation of the airframe. The contractor-to-master switch wire is not a 'feeder' in any sense . . . rather a control wire. Further, current in that wire is limited by the resistance in the battery contactor coil. In this case, an elevation of risk would be driven by the probability of damage that takes the wire to ground . . . of course, this would RE-CLOSE a contactor that the pilot purposefully OPENED in preparation for the extra-ordinarily hard landing. Probability of this being a factor in post crash scenarios is exceedingly small . . . if things are so badly munched that the wire gets grounded, then consequences for having re-closed the contactor are irrelevant. The rules are not limited to feeders 'to the panel' . . . but to anywhere in the airframe. The 5A limit is more a 'rule of thumb' having history back as far as I can remember . . . heard it first at Cessna in '64. As a matter of demonstrable physics, an artfully crafted rule would limit ENERGY dissipated in the fault . . . as opposed to simply limiting current. I'd feel more comfortable about a 10A fuse off the battery bus than a 5A breaker. Given that energy rates are based on Voltage(squared), the hazards presented by a 5A breaker off a 24 volt battery are 4x those presented by a 12 volts, There is a HUGE range of reaction times for electronic breakers, magnetic breakers, thermal breakers, fuses, current limiters, etc. etc. Hence, the 5A rule is a VERY broad brush. This topic is a VERY tiny concern in the grand scheme of things. I recall a comment by a greybeard in the accident investigation world at Beech who once shared the observation, "If the airplane burns, the battery is likely to still be in the airplane. If the airplane did not burn, go look for where the battery landed after it was ejected." An interesting anecdote for which I have no personal knowledge. But it does re-enforce a notion that risks to airframe and passengers are orders of magnitude greater for reasons not even remotely associated with choices of circuit protection. Bob . . . ________________________________ Message 6 _____________________________________ Time: 09:59:33 AM PST US From: Hariharan Gopalan Subject: AeroElectric-List: Dual Battery design I was originally planning on using the Z19B, but came across a print out of what looks like a much simpler dual batter design. Not sure where I printed this from, but this surely looks like an aeroelectric design and can not find this in the 12th edition book. could someone please see if they recognize this and enlighten me? Thanks Hari ________________________________ Message 7 _____________________________________ Time: 10:39:04 AM PST US From: Hariharan Gopalan Subject: AeroElectric-List: Re: Dual Battery design Forgot the attachment. On Thu, Jan 19, 2017 at 9:55 AM, Hariharan Gopalan wrote: > I was originally planning on using the Z19B, but came across a print out > of what looks like a much simpler dual batter design. Not sure where I > printed this from, but this surely looks like an aeroelectric design and > can not find this in the 12th edition book. > > could someone please see if they recognize this and enlighten me? > > Thanks > Hari > ________________________________ Message 8 _____________________________________ Time: 07:49:05 PM PST US Subject: AeroElectric-List: Re: Dual Battery design From: "user9253" That is not one of Bob N's schematics. It has some major flaws. The starter current goes through the ammeter shunt. The E-bus relay coil appears to be always grounded but is not. The 4 pole switch is a single failure point. The 20 amp circuit breaker for the starter contactor and solenoid seems too big. The 200 amp ANL alternator current limiter seems way too big. The 200 amp ANL battery current limiters are unnecessary and should not be in series with starter motor. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=465264#465264 ------------------------------------------------------------------------------------- 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.