---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 07/13/18: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:34 AM - Re: Z-* Question (jonlaury) 2. 05:20 AM - Re: Making your own fuseable links (JOHN TIPTON) 3. 06:50 AM - Re: Re: Making your own fuseable links (Robert L. Nuckolls, III) 4. 01:33 PM - Re: Re: Making your own fuseable links (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 12:34:44 AM PST US Subject: AeroElectric-List: Re: Z-* Question From: "jonlaury" barber_seville(at)msn.com wrote: > Charles Boyer and ? > > Ingrid Bergman Read this topic online here: http://forums.matronics.com/viewtopic.php?p=481626#481626 ________________________________ Message 2 _____________________________________ Time: 05:20:35 AM PST US Subject: AeroElectric-List: Re: Making your own fuseable links From: "JOHN TIPTON" Hi Bob I can see where we are now with Z11 rev: P (thank you user9253-Joe Gores for the link), I'm sticking with Rev: M (no 30 amp in-line fuse or or E-Bus alternate feed relay) - so it's a fusible link off the live side of the Battery contactor Regards: John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=481630#481630 ________________________________ Message 3 _____________________________________ Time: 06:50:29 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Making your own fuseable links At 07:19 AM 7/13/2018, you wrote: > > >Hi Bob > >I can see where we are now with Z11 rev: P (thank you user9253-Joe >Gores for the link), I'm sticking with Rev: M (no 30 amp in-line >fuse or or E-Bus alternate feed relay) - so it's a fusible link off >the live side of the Battery contactor > >Regards: John > > Wouldn't do that myself but as you wish . . . Bob . . . ________________________________ Message 4 _____________________________________ Time: 01:33:33 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Making your own fuseable links > > Wouldn't do that myself but as you wish . . . Got a private email seeking clarification of what was correctly perceived as a terse reply. My apologies. Recall that the legacy 'rule of thumb' for always hot feeders in TC aircraft suggested they be protected at not more than 5A. This HAD to be a rule of thumb . . . cause the 5A figure was a constant whether we were talking about 28 vs. 14v and breakers vs. fuses. I've asked if analysis was offered for mitigating potential energy dissipation that drove the 5A figure . . . nobody I knew was aware of any such study. Nonetheless, FMEA deliberations confirmed the notion that such wires SHOULD be of some limited ability to conduct post-crash energy. So for the Z-figures, we adopted 7A in fuses and 5A in breakers in 14v systems. The 7A fuse seemed to give good coverage for most boost pumps and electronic ignition systems of the time. A little later on, the Endurance Bus came along. At that time, it was possible to craft an endurance load that did not exceed the 7A-rule for always hot feeders. At some later time, Z-13/8 came along which offered an opportunity to support e-bus/battery bus loads up to and including 10A. We also had builders wanting to support e-bus loads in excess of 10A. At this time, the e-bus alternate feed relay was added to become a mini-battery contactor that supported only e-bus loads. At that time, protection of that feed path was boosted to 15A . . . and COULD be larger still. This because crash safety for the feed path changed from ALWAYS HOT protected at 7A to CREW CONTROLLED with no practical limit. Emacs! If one does not require a battery bus but with 'larger' e-bus loads, then the alternate feed relay is still recommended. The relay is mounted close to the battery contactor hence a short jumper between the two devices. That jumper is easily fabricated with an in-line fuse holder. the in-line fuse is MANY times faster than a fusible link. As we've discussed quite a few times over the years, fusible links behave more like current limiters . . . very slow compared to fuses. They are not recommended for in situations other than those illustrated in the Z-figures. 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