---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 10/23/18: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:56 AM - Same rating for fuses and circuit breakers? (Mickey Coggins) 2. 11:28 AM - Re: Same rating for fuses and circuit breakers? (user9253) 3. 12:14 PM - Re: Re: Same rating for fuses and circuit breakers? (Art Zemon) 4. 12:41 PM - Re: Re: Same rating for fuses and circuit breakers? (Rick Beebe) 5. 12:53 PM - Re: Re: Same rating for fuses and circuit breakers? (Charlie England) 6. 01:51 PM - Re: Re: Same rating for fuses and circuit breakers? (Kelly McMullen) 7. 02:12 PM - Re: Same rating for fuses and circuit breakers? (user9253) 8. 02:34 PM - Re: Same rating for fuses and circuit breakers? (Robert L. Nuckolls, III) 9. 02:36 PM - Re: Re: Same rating for fuses and circuit breakers? (Robert L. Nuckolls, III) 10. 02:57 PM - Re: Re: Same rating for fuses and circuit breakers? (Robert L. Nuckolls, III) 11. 05:43 PM - Re: Re: Same rating for fuses and circuit breakers? (Robert L. Nuckolls, III) 12. 07:13 PM - Re: Re: Same rating for fuses and circuit breakers? (Sebastien) 13. 07:13 PM - Re: Re: Same rating for fuses and circuit breakers? (Dick Tasker) ________________________________ Message 1 _____________________________________ Time: 07:56:40 AM PST US From: Mickey Coggins Subject: AeroElectric-List: Same rating for fuses and circuit breakers? Hi, I'm curious if we should use the exact same rating for fuses as are recommended for circuit breakers. I have all fuses with one CB as recommended by the AEC, and for most devices they say something "protect with a 1 amp circuit breaker". My understanding is that fuses are "faster", so more likely to blow in a case where a CB might not have time to react - could be I have this wrong. Is there a recommendation to use the exact same value of fuse as recommended for circuit breakers, or should we increase the fuse size? Thanks for any tips. Mickey Coggins ________________________________ Message 2 _____________________________________ Time: 11:28:38 AM PST US Subject: AeroElectric-List: Re: Same rating for fuses and circuit breakers? From: "user9253" Here is my opinion: Use the same size. Do not use fuses smaller than 3 amps. 3 amp fuses and larger are available from Van's that glow when blown. If a fuse nuisance blows for loads that have a high momentary current, use the next larger size. Of course the wire must be able to carry the current. The nice thing about fuses is that it is easy to change amp rating. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=483988#483988 ________________________________ Message 3 _____________________________________ Time: 12:14:40 PM PST US From: Art Zemon Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? Joe, Why do you say not to use a fuse smaller than 3 amps? My backup ASI/altimeter came with installation instructions calling for a 1 amp slow blow fuse . I splurged the $1.02 and installed it. -- Art Z. On Tue, Oct 23, 2018 at 1:52 PM user9253 wrote: > > Here is my opinion: > Use the same size. > Do not use fuses smaller than 3 amps. > -- https://CheerfulCurmudgeon.com/ *"We do not see the world as it is. We see the world as we are."* ________________________________ Message 4 _____________________________________ Time: 12:41:26 PM PST US Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? From: Rick Beebe I think he means because you can't get the glow-when-blown fuses smaller than 3amp. A 3amp fuse is able to protect a 24-gauge wire so I'm not sure there's any reason to use smaller fuses. I don't have any wires smaller than that in my plane anyway. That said, there's nothing wrong with using smaller if a manufacturer calls for it and you don't mind that it doesn't light up. --Rick On 10/23/2018 3:11 PM, Art Zemon wrote: > Joe, > > Why do you say not to use a fuse smaller than 3 amps? My backup > ASI/altimeter came with installation instructions calling for a 1 amp > slow blow fuse > . > I splurged the $1.02 and installed it. > > -- Art Z. > > On Tue, Oct 23, 2018 at 1:52 PM user9253 > wrote: > > > > > Here is my opinion: > Use the same size. > Do not use fuses smaller than 3 amps. > > > -- > https://CheerfulCurmudgeon.com/ > > /"We do not see the world as it is. We see the world as we are."/ ________________________________ Message 5 _____________________________________ Time: 12:53:28 PM PST US Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? From: Charlie England I'll jump in, because that's one of my pet peeves. First, the mfgr of a widget shouldn't be asking the end user to supply protection for their device. Circuit protection protects circuits; not devices. If the mfgr thinks their device needs a 1A fuse, it should be in the device. Ever seen a piece of consumer or industrial electronics that came with a requirement that you supply its fusing? (They tell you the *minimum* size circuit needed; not a spec for device protection.) Second, a 1A fuse isn't going to protect anything; the equipment will either die before the fuse blows, or the fuse will be blowing needlessly on a more or less random (possibly regular) basis. That's likely why Joe said not to use any fusing under 3A; a policy I also use. Charlie On 10/23/2018 2:11 PM, Art Zemon wrote: > Joe, > > Why do you say not to use a fuse smaller than 3 amps? My backup > ASI/altimeter came with installation instructions calling for a 1 amp > slow blow fuse > . > I splurged the $1.02 and installed it. > > -- Art Z. > > On Tue, Oct 23, 2018 at 1:52 PM user9253 > wrote: > > > > > Here is my opinion: > Use the same size. > Do not use fuses smaller than 3 amps. > > > -- > https://CheerfulCurmudgeon.com/ > > /"We do not see the world as it is. We see the world as we are."/ --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 6 _____________________________________ Time: 01:51:42 PM PST US Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? From: Kelly McMullen I seem to recall there is a reason that ammeters call for a 1 amp fuse on each lead from the shunt. It certainly isn't for wire protection, maybe to protect the meter movement. On 10/23/2018 12:44 PM, Charlie England wrote: > I'll jump in, because that's one of my pet peeves. First, the mfgr of a > widget shouldn't be asking the end user to supply protection for their > device. Circuit protection protects circuits; not devices. If the mfgr > thinks their device needs a 1A fuse, it should be in the device. Ever > seen a piece of consumer or industrial electronics that came with a > requirement that you supply its fusing? (They tell you the *minimum* > size circuit needed; not a spec for device protection.) Second, a 1A > fuse isn't going to protect anything; the equipment will either die > before the fuse blows, or the fuse will be blowing needlessly on a more > or less random (possibly regular) basis. That's likely why Joe said not > to use any fusing under 3A; a policy I also use. > > Charlie > > On 10/23/2018 2:11 PM, Art Zemon wrote: >> Joe, >> >> Why do you say not to use a fuse smaller than 3 amps? My backup >> ASI/altimeter came with installation instructions calling for a 1 amp >> slow blow fuse >> . >> I splurged the $1.02 and installed it. >> >> -- Art Z. >> >> On Tue, Oct 23, 2018 at 1:52 PM user9253 > > wrote: >> >> > >> >> Here is my opinion: >> Use the same size. >> Do not use fuses smaller than 3 amps. >> >> >> >> -- >> https://CheerfulCurmudgeon.com/ >> >> /"We do not see the world as it is. We see the world as we are."/ > > > > Virus-free. www.avast.com > > > > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> ________________________________ Message 7 _____________________________________ Time: 02:12:16 PM PST US Subject: AeroElectric-List: Re: Same rating for fuses and circuit breakers? From: "user9253" One reason is to keep the number of spare fuses to a minimum. Another reason is that glow-when-blown fuses are not readily available at less than 3 amps. Wire sizes commonly used to wire home-built airplanes can safely carry 3 amps. But I am not going to argue with the equipment manufacture's recommendation. Evidently your ASI/Altimeter does not have any internal protection. I should not have wrote to not use less than a 3 amps fuse. It sure doesn't hurt to use a smaller fuse than 3 amps. But I prefer not to. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=483993#483993 ________________________________ Message 8 _____________________________________ Time: 02:34:02 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Same rating for fuses and circuit breakers? At 09:54 AM 10/23/2018, you wrote: >Hi, > >I'm curious if we should use the exact same >rating for fuses as are recommended for circuit breakers. generally, yes >I have all fuses with one CB as recommended by >the AEC, and for most devices they say something >"protect with a 1 amp circuit breaker".=C2 My >understanding is that fuses are "faster", so >more likely to blow in a case where a CB might >not have time to react - could be I have this >wrong.=C2 Is there a recommendation to use the >exact same value of fuse as recommended for >circuit breakers, or should we increase the fuse size? I am suspicious of installation instructions that call for 'downsized' protection with respect to wire size. This has the 'look and smell' of a design gaff . . . albeit a minor one. I was taught to make system integration and installation completely independent of contemporary design rules. In this example, suppose your electro-whizzy needs 3.2A maximum at any time. You state that in the specs . . . and stop there. The system integrator would be expected to gravitate to a 22AWG feeder on a 5A breaker . . . and in this case, a 5A fuse (de-rated to 75% per recommended practice) would be a good choice too. But if the box goes all the way in the tail of a Hawker 4000, the feeder might be upsized to 20AWG just to mitigate voltage drop issues . . . and the system integrator might well protect that wire with a 7A breaker. Bottom line is, it shouldn't matter. The 1A breaker requirement sounds like there may be some design feature INSIDE the electro-whizzy at risk for smoke due to some internal failure; a risk mitigated by adjusting installation requirements. Is there risk associated with replacing a breaker with a fuse? Maybe . . . breakers are a low slower than fuses and the electro-whizzy may have some transient draw that would irritate a fuse. If you get nuisance trips, no big deal. Put the next bigger fuse in. But it WOULD be interesting to talk with the engineer that built that feature into his/her design . . . I mean, there ARE worse things you could do . . . like let your electro-whizzy reset during starter inrush events. Bob . . . ________________________________ Message 9 _____________________________________ Time: 02:36:10 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? At 02:44 PM 10/23/2018, you wrote: >I'll jump in, because that's one of my pet peeves. First, the mfgr of a >widget shouldn't be asking the end user to supply protection for their device. Right on! Bob . . . ________________________________ Message 10 ____________________________________ Time: 02:57:06 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? At 03:49 PM 10/23/2018, you wrote: > >I seem to recall there is a reason that ammeters call for a 1 amp >fuse on each lead from the shunt. It certainly isn't for wire >protection, maybe to protect the meter movement Yeah, first saw them do that on the 336/337 series airplanes at the Pawnee plant. That was the idea . . . but the fusing constant for a AGC1 (then a 3AG1) was such that a 5A flow of current would take about 30 milliseconds to pop the fuse. That 1 mA meter movement would be in trouble a lot faster than that! Don't know if anyone tested that decision in the lab. There were some 50mV instruments with lower resistance (maybe 10mA?). The 1 ohm fuse has about 200 mOhms of resistance. Two fuses in series at 10 mA gives you a 4 mV drop at full scale . . . But I don't think anyone really paid much attention to the readings anyhow . . . ammeters are not really useful flight instruments. Bob . . . ________________________________ Message 11 ____________________________________ Time: 05:43:09 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? At 04:10 PM 10/23/2018, you wrote: > >One reason is to keep the number of spare fuses to a minimum. Why would you carry spare fuses in the airplane? Bob . . . ________________________________ Message 12 ____________________________________ Time: 07:13:00 PM PST US From: Sebastien Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? Ha! I know the answer to this one! In case you land away from base after the fuse blows and you have repaired whatever caused the fuse to blow and then want to get home. On Tue, Oct 23, 2018, 17:47 Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > At 04:10 PM 10/23/2018, you wrote: > > > One reason is to keep the number of spare fuses to a minimum. > > > Why would you carry spare fuses in the airplane? > > Bob . . . > ________________________________ Message 13 ____________________________________ Time: 07:13:01 PM PST US Subject: Re: AeroElectric-List: Re: Same rating for fuses and circuit breakers? From: Dick Tasker To use when you get to your destination when you troubleshoot the problem. Dick Tasker Robert L. Nuckolls, III wrote: > At 04:10 PM 10/23/2018, you wrote: >> >> One reason is to keep the number of spare fuses to a minimum. > > Why would you carry spare fuses in the airplane? > > Bob . . . > ------------------------------------------------------------------------------------- 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.