---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 09/12/07: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:20 AM - Re: 1 Amp Fuses (Richard Girard) 2. 07:35 AM - Re: 1 Amp Fuses (Michael T. Ice) 3. 09:56 AM - Re: 1 Amp Fuses (Fiveonepw@aol.com) 4. 02:45 PM - Re: 1 Amp Fuses (Robert L. Nuckolls, III) 5. 03:43 PM - Re: 1 Amp Fuses (Dennis Golden) 6. 06:09 PM - Re: 1 Amp Fuses (Terry Miles) 7. 07:13 PM - Re: 1 Amp Fuses (Robert L. Nuckolls, III) 8. 07:15 PM - Re: 1 Amp Fuses (Robert L. Nuckolls, III) 9. 07:18 PM - 1 AMP Fuses (Ralph Hoover) ________________________________ Message 1 _____________________________________ Time: 06:20:25 AM PST US From: "Richard Girard" Subject: Re: AeroElectric-List: 1 Amp Fuses Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea. Rick On 9/11/07, Michael Petersen wrote: > > G'day Bob and List Members, > > > I have come across a number of equipment manufacturers that specify a 1 > amp fuse for their equipment (eg Ray Allen trim systems) and I am using a > mini blade type fuse block in my aircraft. The smallest fuse I can find is 2 > amps, which leads me towards the following alternatives; > > > 1. Stick to the philosophy of selecting the fuse to suit the wire > (22awg in this case) and ignoring the manufacturer's requirement. > 2. Use the 2 amp blade fuse, being the closest available. > 3. Incorporating some other type of 1 amp circuit protection, for > example a small circuit board being supplied via the main bus/fuse block > that provides several 1 amp circuits protected by a PTC type fuse. > > > My question is, is there a recognized 'correct' way of dealing with this > issue, or what is the preferred solution? > > > Bob, I have read your critique of Greg Richter's "Aircraft Wiring for > Smart People", in which you very briefly mention that PTC fuses are not > suitable for use in aircraft. Could you please elaborate on your research > and findings? By the way, I am half way through reading your book and would > like to thank you for the effort you put into helping people like me > understand these issues! Keep up the good work! > > > Thanks, > > > Michael > > > * > > > * > > -- Rick Girard "Ya'll drop on in" takes on a whole new meaning when you live at the airport. ________________________________ Message 2 _____________________________________ Time: 07:35:37 AM PST US From: "Michael T. Ice" Subject: Re: AeroElectric-List: 1 Amp Fuses Michael, Tech-Tips PTC's vs. Fuses PTC's act as a type of circuit breaker; the resistance increases as the PTC threshold temperature is exceeded due to the load current passing through the device. This causes high resistance which opens the circuit protecting the device in the event of an over current condition. Unlike fuses, ambient temperature plays a role in how long it will be before a PTC reacts to over current. For this reason, careful consideration should be given to when PTC's are used for equipment protection. A PTC is appropriate for battery protection as most battery shorts are heavy shorts quickly tripping the PTC. The PTC is best for devices that can tolerate high current for a substantial amount of time, such as batteries. Because PTC's are slow acting and have a less accurate trip threshold, the PTC may not protect the cameras as reliably as a fast acting fuse. Because PTC's need to cool down to reset and will not do so if the over current condition is not corrected, a service call will probably be needed to address the failure. A one amp PTC may never blow at 2 amps and may require more than 30 seconds to blow at 5 amps. A one-amp fuse should blow at 1.25 amps in about 1 second, regardless of conditions. It is much more economical for the dealer/customer to replace a simple fuse rather than an expensive piece of electronics. This came off of the: www.pthree.com/techtips.aspx Doesn't seem like the PTC is a good idea. Mike ----- Original Message ----- From: Michael Petersen To: aeroelectric-list@matronics.com Sent: Tuesday, September 11, 2007 8:00 PM Subject: AeroElectric-List: 1 Amp Fuses G'day Bob and List Members, I have come across a number of equipment manufacturers that specify a 1 amp fuse for their equipment (eg Ray Allen trim systems) and I am using a mini blade type fuse block in my aircraft. The smallest fuse I can find is 2 amps, which leads me towards the following alternatives; 1.. Stick to the philosophy of selecting the fuse to suit the wire (22awg in this case) and ignoring the manufacturer's requirement. 2.. Use the 2 amp blade fuse, being the closest available. 3.. Incorporating some other type of 1 amp circuit protection, for example a small circuit board being supplied via the main bus/fuse block that provides several 1 amp circuits protected by a PTC type fuse. My question is, is there a recognized 'correct' way of dealing with this issue, or what is the preferred solution? Bob, I have read your critique of Greg Richter's "Aircraft Wiring for Smart People", in which you very briefly mention that PTC fuses are not suitable for use in aircraft. Could you please elaborate on your research and findings? By the way, I am half way through reading your book and would like to thank you for the effort you put into helping people like me understand these issues! Keep up the good work! Thanks, Michael ________________________________ Message 3 _____________________________________ Time: 09:56:25 AM PST US From: Fiveonepw@aol.com Subject: Re: AeroElectric-List: 1 Amp Fuses In a message dated 09/11/2007 10:58:26 PM Central Daylight Time, mpetersen@repsol.com.au writes: Stick to the philosophy of selecting the fuse to suit the wire (22awg in this case) Yes. 2-amp fuse would be fine, IMHO. Mark do not archive ________________________________ Message 4 _____________________________________ Time: 02:45:11 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 1 Amp Fuses At 08:18 AM 9/12/2007 -0500, you wrote: >Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea. > >Rick B&C stocks them too. If you do a google search on "ATC-1" and "fuse" you'll find lots of other folks have them too. Bob . . . ________________________________ Message 5 _____________________________________ Time: 03:43:45 PM PST US From: Dennis Golden Subject: Re: AeroElectric-List: 1 Amp Fuses Robert L. Nuckolls, III wrote: > > > At 08:18 AM 9/12/2007 -0500, you wrote: > >> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea. >> >> Rick > > B&C stocks them too. > > If you do a google search on "ATC-1" and "fuse" you'll > find lots of other folks have them too. I thought the original post stated that the fuse box was for miniature (i.e. ATM) fuses. I've had problems finding anything less that 2 amp also. Dennis -- Dennis Golden Golden Consulting Services, Inc. ________________________________ Message 6 _____________________________________ Time: 06:09:56 PM PST US From: "Terry Miles" Subject: RE: AeroElectric-List: 1 Amp Fuses Just to toss a little more in the mix about fuses. I bought a box of fuses from Harbor Freight about a year ago and went back today for another box. Their ATC (ATO?) sized (the middle size ones that most of us use) have been recalled. Nobody knew any of the circumstances around this decision. I thought everyone ought to know. Terry -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dennis Golden Sent: Wednesday, September 12, 2007 6:43 PM Subject: Re: AeroElectric-List: 1 Amp Fuses Robert L. Nuckolls, III wrote: > > > At 08:18 AM 9/12/2007 -0500, you wrote: > >> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea. >> >> Rick > > B&C stocks them too. > > If you do a google search on "ATC-1" and "fuse" you'll > find lots of other folks have them too. I thought the original post stated that the fuse box was for miniature (i.e. ATM) fuses. I've had problems finding anything less that 2 amp also. Dennis -- Dennis Golden Golden Consulting Services, Inc. ________________________________ Message 7 _____________________________________ Time: 07:13:08 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 1 Amp Fuses At 05:42 PM 9/12/2007 -0500, you wrote: > > >Robert L. Nuckolls, III wrote: > > > > > > At 08:18 AM 9/12/2007 -0500, you wrote: > > > >> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea. > >> > >> Rick > > > > B&C stocks them too. > > > > If you do a google search on "ATC-1" and "fuse" you'll > > find lots of other folks have them too. > >I thought the original post stated that the fuse box was for miniature >(i.e. ATM) fuses. I've had problems finding anything less that 2 amp also. Opps. My bad. Yes, the ATM spec sheet http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATM_Specs.pdf says 2A is as small as they go in that form-factor unlike the ATC sheet http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATC_Specs.pdf which takes us down to 1A. I didn't go back to the original post. Sooooo . . . G'day Bob and List Members, I have come across a number of equipment manufacturers that specify a 1 amp fuse for their equipment (eg Ray Allen trim systems) and I am using a mini blade type fuse block in my aircraft. The smallest fuse I can find is 2 amps, which leads me towards the following alternatives; Stick to the philosophy of selecting the fuse to suit the wire (22awg in this case) and ignoring the manufacturer's requirement. Use the 2 amp blade fuse, being the closest available. This would probably be just fine. I've always had a bit of heartburn about manufacturer's "suggestions" that their device would benefit from some degree of protection by installation . . . which the installer is expected to supply. Having said that - I HAVE designed systems using appliances with very light draw (under 1A) where their 22AWG feeders were protected with small fuses. This is pretty easy when the system is wired with the ATC fuseblocks. Harder as you've noted in alternative fuseblock products. Incorporating some other type of 1 amp circuit protection, for example a small circuit board being supplied via the main bus/fuse block that provides several 1 amp circuits protected by a PTC type fuse. The 2A fuse will be fine. As you've already noted, the PTC is not easily integrated into a system. The small, solid wire lead components are designed to be integrated inside a device and demand some appliance design, fabrication and installation (i.e., super-whippy power distribution assembly boards). My question is, is there a recognized 'correct' way of dealing with this issue, or what is the preferred solution? Bob, I have read your critique of Greg Richter's "Aircraft Wiring for Smart People", in which you very briefly mention that PTC fuses are not suitable for use in aircraft. Could you please elaborate on your research and findings? I'm not sure I've ever used the words "not suitable" but there have been many a discussion between myself an individuals who were touting products that incorporated the PTC (aka polyswitch, and polyfuse). A few documents in addition to the Richter discussion include: http://www.aeroelectric.com/FAQ/AeroElectric-List/AeroElectric-List_FAQ.pdf http://www.aeroelectric.com/articles/expbusthd.html http://www.aeroelectric.com/articles/expbusad.html The polyswitch was first presented to me about 1982 by my very good friend Jim West who at the time was a Raychem rep with Thunderbird aviation. I had the electrical/ avionics group on the GP-180 and Jim thought perhaps this nifty device would find useful applications in the airframe arena. First, let me be quite clear that incorporation of the polyswitch NEVER raised questions with respect to safety. It was never pushed aside for failure to do the tasks that fuses, breakers and other FIRE PROTECTION devices have accomplished for over a century. The questions about PTC circuit protection have to do with (1) $value$ of the trade-off and (2) integration into the overall system design philosophy. PTC's are loose components intended to solder to an etched circuit board. This means that unlike a collection of fuses or breakers (which are easily integrated into a wide variety of designs as individual components) an array of PTC devices becomes an appliance - an assembly that in the TC aircraft world requires qualification. Those qualification test would most certainly include vibration and operation over temperature extremes. In the OBAM aircraft world, the appliance grows features like pre-assembled switch panels, avionics bus noise filters and power management, voltage regulators, etc. The more features that are added, the less adaptable becomes the appliance. What you see is what you get . . . take it or leave it. And whether or not you want or need all those features, the cost is not insignificant. In the TC world, I participated in three explorations with others. Once at Learjet and twice at Beech to see if the PTC offered any features attractive to our program managers and customers . . . and the FAA. Had more than one FAA type objecting to the "self re-setting feature of PTCs . . . when a hazardous fault operates the circuit protection, present conventions call for the system to open and stay open pending repairs. Many have read my writings about the various products that feature PTCs and have mis-interpreted the down-side observations to be an attack on PTCs as protective devices. Again, they do the job they were designed to do in the manner described in their sales literature. The BIG picture speaks to poor $value$ and loss of some operational and architecture control when appliances (perhaps combined with other components) are used to replace loose breakers or inexpensive fuseblocks. By the way, I am half way through reading your book and would like to thank you for the effort you put into helping people like me understand these issues! Keep up the good work! You HAVE already thanked me by purchasing the work. I'm pleased that you're finding it useful. Bob . . . ________________________________ Message 8 _____________________________________ Time: 07:15:50 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: 1 Amp Fuses At 09:06 PM 9/12/2007 -0400, you wrote: > > >Just to toss a little more in the mix about fuses. I bought a box of fuses >from Harbor Freight about a year ago and went back today for another box. >Their ATC (ATO?) sized (the middle size ones that most of us use) have been >recalled. Nobody knew any of the circumstances around this decision. I >thought everyone ought to know. >Terry A number of wanna-be's in the fuse business have attempted to clone the ATC and similar products only to find that the simple little fuse was more complex than molding some handy metal stamping inside a plastic housing. Folks like Cooper- Bussman and Littlefuse have been in this business for a very long time and have optimized the recipe for success in the creation of a product that performs as advertised. You're never treading at the edge by purchasing devices with these brands on them. Bob . . . ________________________________ Message 9 _____________________________________ Time: 07:18:01 PM PST US From: Ralph Hoover Subject: AeroElectric-List: 1 AMP Fuses Littlefuse lists 1A minimum in the 257 series ATO fuses and 2A minimum in the 297 mini series. -- Ralph C. Hoover RV7A hooverra at verizon dot net ------------------------------------------------------------------------------------- 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.