Date: Thu, 27 Jun 1996 06:10:16 -0500 From: JerryKennel Subject: COZY: Electrical Shunt I am in the process of doing the electrical wiring on my Cozy. The plans talk about a "shunt" What is a shunt and what does it do? In the plans it looks like a piece of aluminum with two holes in it with two wires attached. I'm not real good at electricity. Help!! Jerry Kennel #241 From: Ken Reiter Date: Thu, 27 Jun 96 08:15:20 CDT Subject: COZY: Electrical System - How Much Wire Hello TO All, With Hope I will start wiring my CozyIII this coming week and need to get the wire and etc. Question: How much wire and what sizes does the typical COZY require. I am thinking of using the P&B comb Switch and Circuit breaker. (Most likely a off-brand to save money). Thanks, Ken Reiter - Dallas Area From: Rob Cherney Date: Thu, 27 Jun 1996 09:18:11 -0400 (EDT) Apparently-To: Jerry Kennel asks: >I am in the process of doing the electrical wiring on my Cozy. The plans >talk about a "shunt" >What is a shunt and what does it do? In the plans it looks like a piece of >aluminum with two holes in it with two wires attached. A shunt is a resistor -- in this case, a very low value resistor. A shunt is typically placed in series with the battery to allow charge/discharge current to be measured. Rob- Date: Thu, 27 Jun 96 08:45:48 EST From: MISTER@neesnet.com Subject: Re: COZY: Electrical Shunt Jerry Kennel asked: >>"What is a shunt and what does it do? "<< Jerry: Typically, we don't use direct reading ammeters in the panel to display amperes. Doing so would require bringing the heavy current carrying lead up to the instrument panel and then back. Instead to display amperes, we use a device that actually measures a small voltage that is proportional to the current. To do this you need a device that takes current and converts it to a proportional voltage. That is a shunt. It is really just a resistor. Using ohm's law E=IR, one ampere of current through a one ohm resistor generates a voltage drop of one volt. Using a shunt, the heavy current carrying wires are kept short and in the back and you can run skinny wires up to the instrument in front. The shunt and the ammeter must be matched to work correctly. Look at Wick's catalog page 291. It shows both the Westach shunt unit and the Mitchell direct reading type. If you don't understand this electrical stuff, I'd strongly suggest you invest in the material available from Bob Nuckolls at Aeroelectric Connection. It explains all of the complicated electrical stuff very clearly and has several good ideas. He also includes complete schematics. He also has a few kits for things like lamp dimmers and overvoltage sensors. It is well worth the money. With his help I managed to get a nice quiet and electrical system which I am very pleased with. Take a look at his stuff before you get too far into your wiring. He can be reached at 72770.552@compuserve.com. Bob Misterka N342RM From: "Dewey Davis" Date: Thu, 27 Jun 1996 10:44:34 -0400 Subject: Re: COZY: Electrical Shunt -Reply On Jun 27, 8:17, DAVID B MONK wrote: > Subject: COZY: Electrical Shunt -Reply > Jerry Kennel writes: > plans talk about a "shunt" What is a shunt and what does it do? > In the plans it looks like a piece of aluminum with two holes in it > with two wires attached. > > > > A shunt is just a fancy name for a short between two wires or two > contacts. So when the plans call for a shunt, anything that shorts > the two wires (contacts) together will do, hence, the aluminum > block with two holes with the two wires attached. > > Dave Monk > >-- End of excerpt from DAVID B MONK Not exactly. It is a very low resistance, like a short, but it is also a known, calibrated value of resistance so the meter will indicate correctly. You can either pay the price for a calibrated shunt, or you can build your own. Several people have simply used the proper length of rolled up wire. But that is going to add weight. Probably our best choice is to buy the shunt from Spruce or Wicks. Dewey Davis Date: Thu, 27 Jun 1996 08:17:46 -0700 From: DAVID B MONK Subject: COZY: Electrical Shunt -Reply Jerry Kennel writes: A shunt is just a fancy name for a short between two wires or two contacts. So when the plans call for a shunt, anything that shorts the two wires (contacts) together will do, hence, the aluminum block with two holes with the two wires attached. Dave Monk Date: Thu, 27 Jun 1996 17:20:48 -0400 From: PBurkha238@aol.com Subject: Re: COZY: Electrical System - How Much Wire In a message dated 96-06-27 12:26:58 EDT, you write: >Question: How much wire and what sizes does the typical COZY >require. I am thinking of using the P&B comb Switch and Circuit >breaker. (Most likely a off-brand to save money). > > Ken, you should contact BOB nuckolls from aeroelectric connection. for approximately 40 bucks he has an excellent manual covering all the aspects of electrical installations, in particular in the cozy type aircraft . Paul Burkhardt-- he had an e-mail address in you want it ill look it up Date: Thu, 27 Jun 1996 17:42:32 -0400 From: CCady@aol.com Subject: COZY: Electric Heater I found a nice little 12 volt ceramic heater that looks nice. It's only 7" long and puts out 340 BTU at 100 watts or about 9 amps. It has it's own little blower in it but it doesn't really blow a large volume of air. It puts out pretty good heat however. This one is only 19.99 and I found it in a mail order catalog, Heartland America (800) 229-2901 the part number for the heater is #3815. It's made by a company called Cafranmo of Ontario Canada (800) 567-3556 (519) 1080, Fax (519) 534-1088. Their Model # for it is 9303. It's made in Taiwan and is mostly plastic but it's very light weight and compact. I'm going to put one in my project before next winter. Date: Thu, 27 Jun 1996 22:52:38 -0400 From: StetsonE@aol.com Subject: Re: COZY: Electrical System - How Much Wire In a message dated 96-06-27 17:23:33 EDT, Paul writes: << Ken, you should contact BOB nuckolls from aeroelectric connection. for approximately 40 bucks he has an excellent manual covering all the aspects of electrical installations, in particular in the cozy type aircraft . Paul Burkhardt-- he had an e-mail address in you want it ill look it up>> I wholeheartedly agree! Bob Nuckolls' book is a wealth of information for those (like me) who's knowledge of things electrical is nearly non-existent. His book also has wiring schematics for wiring various type of aircraft, including composite canards. I've been a subscriber of his for the past few years. He puts out the book, and updates to the book if you subscribe. As a subscriber, he's also been VERY helpful in answering all my stupid questions, mostly by email. I don't know about the Cozy plans, but the Long-EZ plans for the electrical system are extremely basic, so I needed additional help. For about $50.00 or so, he'll design your wiring schematic on his CAD computer based on your requirements. It sounds like everytime I've called him on the phone he called up my schematic on the computer and made changes as we talk. Once it's finalized he'll print it out for you. His email address is 72770.552@CompuServe.COM. But rather than all of you sending him an email about pricing, etc, let me do that and I'll post his reply. That way he won't get buried in email asking the same question. Stet Elliott stetsone@aol.com Perpetual Long-EZ builder Date: Fri, 28 Jun 1996 07:37:17 -0400 From: RonKidd@aol.com Subject: Re: COZY: Electric Heater You don't say where you live, so I hope you are in a warm climate. If not, you are wasting your money and time. I installed two different electric heaters in my Cozy 3, and neither one did much in cold weather (especially at 10K feet). I finally bit the bullet and redesigned the heat muff. It works very well. Still not enough for the extremes (I live in Ohio) but far better than the electrical heaters. The last one I used was $170 and pulled 15 amps. For what it's worth, Ron Date: Sat, 29 Jun 1996 19:06:31 -0400 From: StetsonE@aol.com Subject: COZY: Bob Nuckolls Reply As I promised, I asked Bob Nuckolls an email describing his products. Here is his reply. Stet Elliott stetsone@aol.com Perpetual Long-EZ Builder =========================================================================== Bibliography of Printed Works by Bob Nuckolls "No Juice." Aviation Consumer, February 1995 "Aircraft Electrical Systems: A philosophy for Reliability." Sport Aviation, February 1993, Page 80. "Fuses or Circuit Breakers?" Sport Aviation, March 1993, Page 86. "Brushes for Aircraft." Sport Aviation, April 1993, Page 62. "Solid State Light Dimming." Sport Aviation, June 1993, Page 50. "Magneto Switch Options." Sport Aviation, July 1993, Page 56. "The Batteries are Coming, the Batteries are Coming!!!!" Sport Aviation, August 1993, Page 90. "Crowbar Over Voltage Protection." Sport Aviation, December 1993, Page 68. "Ignition Battery Manager: Reliable Aircraft Operations with Battery Powered Ignition Systems." Sport Aviation, January 1994, Page 84. "Failure Mode Effects Analysis: Confidence by design." Sport Aviation, June 1994, Page 83. "Avionics Master Switches." Sport Aviation, July 1994, Page 80. "Battery Alternatives for Hand-held Radios." Sport Aviation, March 1995, Page 30. "Ignition Battery Manager - Revisited" Sport Aviation, August 1995, Page 99. "Aircraft Electrical Systems for Homebuilders", SportPlane Resource Guide, 1995/1996 edition published by Kindred Spirit Press, 3001 21st Street NW, Winterhaven, FL 33881. "When is a Good Ground Not?" Kit Airplane Builder, February 1996. "Anatomy of a Close Call" will appear soon in Kitplanes magazine. The AeroElectric Connection, an Information Service and Guide to Theory, Operation, Design and Fabrication of Aircraft Electrical Systems. A book (200+ pages), newsletter and consulting service offered through Medicine River Press, 6936 Bainbridge Road, Wichita, KS 67226-1008. Phone (316) 685- 8617. e-mail to 72770.552ompuserve.com. Be sure to check out Bob's forums in the tents at Oshkosh every year. There's at least one daytime forum on a specific topic and an evening, open Q&A marathon. The AeroElectric Connection In development for over 10 years, the AeroElectric Connection is a definitive work on electrical systems for light aircraft. Over 1000 readers in 12 countries. Written, illustrated and published by an engineer and educator with over 35 years experience in electrical and electronics systems design. Possible the only book you'll ever buy with the author's name, address and phone number on the front cover; questions, comments and criticisms welcome! If you don't talk to use we don't now what to write about! Rapid response e-mail feedback. We try to check our mailbox two or three times per day and answer immediately. Yearly updating and periodical newsletters keep your documentation up to date by subscription. Newsletters: Hot Flashes from the AeroElectric Connection are mailed periodically to cover timely topics and error corrections in other printed materials. When the book is finished, the newsletters will step up to a quarterly publication rate. Wiring Diagram Services: How are you going to remember where all those wires go five years from now? When the time comes to sell your airplane, how are you going to tell your prospective buyer where all the wires go? Readers may wish to take advantage of customized power distribution diagrams and/or complete page per system wire books and wire marking tailored to your airplane and equipment . . . contact us for details. Weekend Seminars: It's difficult to beat a face-to-face tutorial with question and answer sessions. Bob's services are available for intensive, all-day Saturday and half-day Sunday seminars. Depending on distance traveled and other expenses a minimum of 40 attendees at $75/person are necessary. A number of companies offering aviation related services donate to the door prizes for these seminars. Curently, the AeroElectric Connection is giving away a hand-held GPS receiver! Drop us a note with your snail-mail address for a sample flyer and details on how to organize a weekend seminar in your area. Procurement Services: Ten years experience working with thousands of amateur airplane builders has shown that locating sources for suitable parts can waste hours of time that would be better spent bolting parts to the airplane. We're doing the planning and artwork now on a catalog of recommended products and supplies to be stocked by the 'Connection. The catalog should be ready for publication by OSH '96. In addition, the 'Connection will offer to locate and arrange shipping for parts not in our catalog charging only a nominal service fee for time and expenses. Let us help you with difficult or otherwise time consuming procurement activities. The Book: Materials in print now total over 200 pages with lots of illustrations. Unlike books nailed between hard covers which cannot change, the 'Connection is a dynamic work that grows with new technology and advancement of our collective experience . The book is 3-ring, loose-leaf binder format to permit timely updates. Chapters presently cover: Chapter Topic 1 . . . . . . . . . DC Fundamentals 2 . . . . . . . . . Batteries 3 . . . . . . . . . Engine Driven Power Sources 4 . . . . . . . . . Voltage Regulators 5 . . . . . . . . . Grounding 6 . . . . . . . . . Over Voltage Protection 7 . . . . . . . . . Electrical System Instrumentation 8 . . . . . . . . . Wire Selection and Installation 9 . . . . . . . . . Wire Termination and Connectors 10 . . . . . . . Circuit Protection 11 . . . . . . . Switches Relays and Contactors 12 . . . . . . . Lighting and Lighting Controls 13 . . . . . . . Antennas and Feedlines 14 . . . . . . . Temperature Instrumentation Appendix C Catalog of Products and Services Appendix Z Power Distribution Diagrams ========================= Order Form ====================================== Name _____________________________________________ Address:__________________________________________ City:_____________________State:_____ Zip:________ Phone(s): (______) _______________________________ Please enter my ( )NEW or ( ) RENEWAL subscription to the AeroElectric Connection. I enclose US funds as follows: >>>>>NOTE THE DIFFERENT PRICES FOR NORTH AMERICA AND OVERSEAS ORDERS<<<<< N. America (Overseas) ( ) Revision 6 (Current edition) . . . $32 ($40) ______ ( ) Revision 7 update subscription . . $13 ($17) ______ ( ) Revision 8 update subscription . . $13 ($17) ______ Total Enclosed . . . . . . . . . . . . . . . . . . . ._______ Charge my (MstrCrd)(Visa) |_________||_________||_________| |_________| My Card Expires |____|____| |____|____| I own/am building a: ____________________________________________ REFERRED BY:_______________________________________________________________ Make checks payable to Medicine River Press. Mail with form to 6936 Bainbridge Road, Wichita, KS 67226-1008. Orders may also be placed by phone (316) 685-8617 or e-mail to 72770.552@Compuserve.com 1/96 Date: Sun, 08 Sep 1996 14:45:49 From: RSiebert1@gnn.com (Reid Siebert) Subject: Re: COZY: CS Prop Governor? >Date: Sun, 8 Sep 1996 00:16:58 -0400 >From: CheckPilot@aol.com > Gee Reid, how about the fully redundant dual electrical system of > the Mooney PFM, wouldn't want a failure now!!!! :-) > >Jim Hi Jim, Since talking to you at Oshkosh I've been real busy over at Amoco, not any early morning departures though, so haven't seen you "Learjet away". I already have a dual bus electrical system under construction, since I will have dual electronic ignition. The extra battery in the nose will help counteract the weight of the heavy prop, too. I use alot of Bob Nuckolls' ideas, including using copper water pipe as the aircraft ground, noise-shielding electrical conduit, and cabin exhaust air duct, all in one. It runs from the nose to the engine compartment. Later, Reid Date: Tue, 10 Sep 1996 22:13:56 From: RSiebert1@gnn.com (Reid Siebert) Subject: COZY: Copper Water Pipe >Date: Mon, 09 Sep 1996 14:20:18 MDT >From: Lee Devlin >> I use alot of Bob Nuckolls' ideas, including using copper water >> pipe as the aircraft ground, noise-shielding electric conduit, >> and cabin exhaust air duct, all in one. It runs from the nose >> to the engine compartment. >What diameter/wall thickness pipe do you intend to use for this? >I have thought about doing something like this on my LongEZ. > >Thanks, > >Lee Devlin Lee, I use the one-inch copper tubing found in the local Home Depot. I also bought plenty of elbows, couplings, and tee's to snake my way into the cabin. Soldering my be a bit tricky, so I plan to assemble it in sections, and paint it, before installing. I haven't installed any of it yet, just making room for the runs. I even have some 1/2" tubing for short branches, like under the front seats. They are connected to the main line with adapting tees. So far the weight isn't too bad. I just can't get carried away. Be sure to make each section of it removeable for servicing. Reid Date: Wed, 11 Sep 96 07:50:59 EST From: MISTER@neesnet.com Subject: Re: COZY: Copper Water Pipe Reid Siebert wrote: >>I use the one-inch copper tubing found in the local Home Depot. I also bought plenty of elbows, couplings, and tee's to snake my wayinto the cabin. Soldering my be a bit tricky, so I plan to assemble it in sections, and paint it, before installing. << My $.02 You should consider using the seamless soft copper tubing that comes in coils instead of the straight copper tube which is tempered and doesn't bend easily. I used 3/4" and it worked fine. I'm not sure if 1" is available. It bends very easily. Also, I wouldn't paint it because you might want to have the ability to easily make a conductive connection by clamping on to it in the future. Bob Misterka N342RM Date: Sat, 14 Sep 1996 16:09:12 -0400 From: StetsonE@aol.com Subject: COZY: Fwd: "Solid state" electrical system Cozy and Eracer builders: The below is an email I sent to Bob Nuckolls (AeroElectric Connection) which included a post from the ERacer mailing list about the new "solid state" fuse panel currently being marketed by Control Vision. Although opinions about the suitability of this product for our use is going to vary, I thought Bob's reply might be of interest to the members of both the Cozy and ERacer lists. Stet Elliott Perpetual Long-EZ builder -------------------------------- Bob: I thought this post from the ERacer mailing list might be of interest to you. Are these current limiting devices suitable for our use? Rather than purchasing one of these prebuilt panels, is it possible to use these PTC devices in, say, the fuse panel you've been recommending? Stet Elliott Perpetual Long-EZ Builder ------------------------------------- In a message dated 96-09-05 18:23:19 EDT, JJay5@aol.com writes: > Subj: [ERACER-L:102] "Solid state" electrical system > Date: 96-09-05 18:23:19 EDT > From: JJay5@aol.com > Sender: eracer-l@listproc.eracer.org > Reply-to: eracer-l@listproc.eracer.org > To: eracer-l@listproc.eracer.org (Multiple recipients of list) > > The EXP Bus is certainly not a scam. The term "solid state electrical > system" is not our term, and it not entirely accurate, however we do offer a > PC board containing most of the electrical system of a small aircraft on one > board. Traditional circuit breakers are replaced by solid state current > limiters. For more information on the specific product, see our web page at > http://www.controlvision.com. > > HOW DO "SOLID STATE FUSES" WORK? > The purpose of the limiter is identical to that of the breaker, to shut off > whenever too much current is being drawn from a particular circuit. > Technically, the devices used are very non-linear thermistors with a > positive temperature coefficient (PTC). When excess current is drawn, the > PTC device heats up and becomes a poor conductor of electricity. This shuts > down the offending circuit. These components are UL recognized, and > manufactured by a major US component manufacturer. > > AN EXAMPLE > Suppose that a wire leading to a nav light is chafing against a grounded > metal part in a wing, such as a rib. If the light is on, and the insulation > abrades away, the wire will intermittently or permanently short to ground. > With a fuse, the overcurrent will blow the element in the fuse, before the > wire can get hot and start a fire (although the spark could ignite fuel > vapors before the fuse blows). With a breaker, the bimetallic element in > the > breaker heats up (more slowly than the fuse) and trips the breaker. With > the > solid state device, the PTC device gets hot, increasing it's resistance, and > shutting down current flow to the nav lights. Actually, about 1/30th of an > amp continues to flow, which is not enough current to heat up any wiring. > The > voltage drop across the PTC device keeps the device hot (about 100 degrees > C), and the device stays "tripped". The load presented to the circuit by > the nav lights will keep the device tripped even if the short is > intermittant. > > The devices used are made to perform this function, and can do this over and > over, thousands of times without damage. To reset the device, power is > removed from the circuit for about 10 seconds (by switching off the nav > light) , the device cools and switches back on, and the circuit is restored. > If the short still exists, the device will immediatly trip again. > > We demonstrated this scenario literally hundreds of times at Oshkosh this > year. These devices are used in automibiles and also in military > electronics > manufactured by Control Vision. No smoke and no mirrors used here. Using > these devices, we have produced a PC board with switches mounted on it that > replaces up to 16 fuses and circuit breakers in a small aircraft. Because > these devices are quite inexpensive, we are able to offer the entire > assembly > for $249,. slightly less than the cost of the individual circuit breakers > it > replaces. > > This is not a scam, we are offering this product with a 90 day money back > guarantee, and a 1 year warranty. A builder can save time, money, panel > space, troubleshooting, and weight. Remember: "Simplicate and save weight". > > > Email me if you have any questions: > jay@controlvision.com In a message dated 96-09-07 23:28:15 EDT, 72770.552@CompuServe.COM (Robert L. Nuckolls, III) writes: > Subj: "Solid state" electrical system > Date: 96-09-07 23:28:15 EDT > From: 72770.552@CompuServe.COM (Robert L. Nuckolls, III) > To: StetsonE@aol.com (INTERNET:StetsonE@aol.com) > > Stet, > > I was looking for a rather extensive analysis I'd done > for the rv-list on this product. Basically, it's got > too many parts, unsupported soldered wires, poorly > designed mountings with respect to vibration and > maintenance and last . . . costs much too much. > > The self-reseting "fuse" may hide intermittant problems. > I just can't justify using them except in very > specialized applications. We looked them over > pretty carefully about ten years ago at Learjet > and let 'em go by then. I ran the traps on two > products of this type at OSH and still can see > that they're applicable. Fuse blocks and switches > are the lightest, lowest cost, lowest parts count > and easiest to install of ANY system I've see thus > far. > Bob . . . > AeroElectric Connection > > ********************************* > * Go ahead, make my day . . . * > * Show me where I'm wrong. * > ********************************* > --------------------- Forwarded message: From: 72770.552@CompuServe.COM (Robert L. Nuckolls, III) To: StetsonE@aol.com (INTERNET:StetsonE@aol.com) Date: 96-09-07 23:28:15 EDT Stet, I was looking for a rather extensive analysis I'd done for the rv-list on this product. Basically, it's got too many parts, unsupported soldered wires, poorly designed mountings with respect to vibration and maintenance and last . . . costs much too much. The self-reseting "fuse" may hide intermittant problems. I just can't justify using them except in very specialized applications. We looked them over pretty carefully about ten years ago at Learjet and let 'em go by then. I ran the traps on two products of this type at OSH and still can see that they're applicable. Fuse blocks and switches are the lightest, lowest cost, lowest parts count and easiest to install of ANY system I've see thus far. Bob . . . AeroElectric Connection ********************************* * Go ahead, make my day . . . * * Show me where I'm wrong. * ********************************* From: Ken Reiter Date: Thu, 3 Oct 96 08:52:28 CDT Subject: Re: COZY: Breaker Switches Hello Builders, I must second the breaker/switch(B/S) solution for our panels. I am building a CozyIII and have the layout below at the top center of the panel. WarningLight B/S B/S B/S B/S B/S B/S B/S B/S B/S B/S PrimeSwitch I and other pilots like the look and the B/S are easy to hook up - with the DC buss across the bottom and the circuit hook-up at the top. I used Potter & Brumfield 5 and 10 amps. Aircraft Spruce has them for about $15 - this does add up. However, in my case I had talked about them at a family gathering and a family member got them for me. How do you return a gift (that you want)? Any way they are easy to hook-up and work very well. p.s. After I finish the wiring, I will list the amount of wire that it takes and a great source (low cost) of milspec wire in the Dallas Area (they will ship). Thanks, Ken Reiter > > To All Builders, > > I have come across a great deal for the builder group. I found a surplus > supply of AIRPAX 5 amp toggle breaker/switches (they are toggle switches > that have a circuit breaker built in and kick off when overloaded). The > same items at Sun-Fun or Oshkosh run $14-20 each or $?? plus shipping if > you order from cataloges. These will be priced @ $5 each including > shipping(in the USA). If you build more or less to plans and use just 7 (I > bought 10) of these in your panel you save $63-105 plus the weight of the > extra wiring & breakers. They are .94 oz each and measure 11/16"W 1 3/16"H > & 1 1/2" D behind the panel and are "aircraft quality" 50 Volt DC Rated > (i.e. made for the job). These have to be ordered in large quantity so I > am putting together an order at this time. I will be bringing samples with > me to the Central States gathering at Rough River KY on Oct 11-13th so if > you are coming you can see'em before you buy'em. If anyone outside of USA > is interested I'll Be glad to find out shipping cost & mail direct to you. > > > Michael.Amick@Nashville.com > MkIV #317 Chapter 5 > > > > by Npt.NUWC.Navy.Mil (PMDF V5.0-5 #13155) id <01IA7HQ5NAQU94DTPY@Npt.NUWC.Navy.Mil> for cozy_builders@hpwarhw.an.hp.com; Thu, 03 Oct 1996 13:26:55 -0400 (EDT) (4.1/SMI-4.1) id AA27072; Thu, 03 Oct 1996 13:27:17 -0400 (EDT) Date: Thu, 03 Oct 1996 13:27:17 -0400 (EDT) From: triley@C38FS0.NPT.nuwc.navy.mil (Tom Riley) Subject: COZY: Breaker switches I'm far from needing switches for my instrument panel yet, but I have looked at some of the readily available circuit breakers and have one concern about a popular model made by Potter-Brumfield. If anyone could comment on the following, it would be much appreciated. The P-B W31 series (thermal breaker with built-in toggle) seems to be very susceptible to being fliped OFF by shock - and it doesn't take much. Try it, take a W31 and set it to the ON (up) position, then hold it upright in your right hand with the toggle away from you and strike the palm of your left hand. It doesn't take too much of a blow to flip the switch to the OFF position. It would seem to me that a good bang in bad turbulence could result in shutting off several such breakers --- not fun. Does anyone have any experience with these breakers or care to comment? Am I way off base here, or is this a valid concern? Tom Riley Cozy MKIV, S/N 113, Chap 9 Date: Thu, 03 Oct 96 14:15:29 est From: "Larry Schuler" Subject: COZY: Breaker switches Tom Riley wrote: >The P-B W31 series (thermal breaker with built-in toggle) >seems to be very susceptible to being fliped OFF by shock >..... Try it, take a W31 and set it to the ON (up) >position, then hold it upright in your right hand with the >toggle away from you and strike the palm of your left >hand. It doesn't take too much of a blow to flip the >switch to the OFF position. >It would seem to me that a good bang in bad turbulence >could result in shutting off several such breakers --- >not fun. Does anyone have any experience with these >breakers or care to comment? Am I way off base here, or >is this a valid concern? Just a couple of thoughts FWW: I work in electronics; you might have a valid concern. I have seen quite a few breakers that seem to trip from the least movement (ie a mechanical rather than electrical {normally thermal} trip) and some of the same ones wouldn't trip until they reached 150% or more of rated current. Can't help on the specific P-B model, but here's some food for thought: How many Gs was the "plam bang"? And how do you relate that to the Gs of turbulence and "peak" stress rating of the Cozy? Might try taping one to the dashboard of your car and drive over some rough railroad tracks just for kicks........ P-B should have full spec info available. The info "should" contain the specs on vibration sensitivity as well as electrical performance. If they don't have apprpriate info for our aircraft application, I'd be inclined to stear clear. Larry Schuler MKIV-#500 Date: Thu, 03 Oct 1996 12:42:06 -0700 From: berkut@loop.com Subject: Re: COZY: Breaker switches > Tom Riley wrote: > >The P-B W31 series (thermal breaker with built-in toggle) >>seems to be very susceptible to being fliped OFF by shock >>..... Try it, take a W31 and set it to the ON (up) >>position, then hold it upright in your right hand with the >>toggle away from you and strike the palm of your left >>hand. It doesn't take too much of a blow to flip the >>switch to the OFF position. > > >It would seem to me that a good bang in bad turbulence >>could result in shutting off several such breakers --- >>not fun. Does anyone have any experience with these >>breakers or care to comment? Am I way off base here, or >>is this a valid concern? > I've used the toggle breakers in the past, and won't again. They are too tempting to use as on/off switches, and they seem to have a lifespan of a few hundred cycles. Better to use a plunger breaker and a conventional toggle switch that has a life of millions of cycles. -- Richard Riley Experimental Aviation, Inc "The important things 3025 Airport Ave are always simple. Santa Monica, CA 90405 The simple things 310.391.1943 are always hard." 310.391.8645 fax See the Berkut at http://www.berkut.com by Npt.NUWC.Navy.Mil (PMDF V5.0-5 #13155) id <01IA7MJ7V03694DTPY@Npt.NUWC.Navy.Mil> for cozy_builders@hpwarhw.an.hp.com; Thu, 03 Oct 1996 15:44:04 -0400 (EDT) (4.1/SMI-4.1) id AA29109; Thu, 03 Oct 1996 15:44:32 -0400 (EDT) Date: Thu, 03 Oct 1996 15:44:32 -0400 (EDT) From: triley@C38FS0.NPT.nuwc.navy.mil (Tom Riley) Subject: COZY: Breaker switches > Just a couple of thoughts FWW: > > I work in electronics; you might have a valid concern. I have seen > quite a few breakers that seem to trip from the least movement (ie a > mechanical rather than electrical {normally thermal} trip) and some of > the same ones wouldn't trip until they reached 150% or more of rated > current. > > Can't help on the specific P-B model, but here's some food for > thought: > > How many Gs was the "palm bang"? And how do you relate that to the Gs > of turbulence and "peak" stress rating of the Cozy? > > Might try taping one to the dashboard of your car and drive over some > rough railroad tracks just for kicks........ > > P-B should have full spec info available. The info "should" contain > the specs on vibration sensitivity as well as electrical performance. > If they don't have apprpriate info for our aircraft application, I'd > be inclined to stear clear. > > Larry Schuler > MKIV-#500 > ------------------------------------------------------------------------------ Larry, Thanks for your reply. I can't say how many g's it takes to trip one of these as I don't have a "calibrated palm", but it isn't much, just a gentle strike is all that's needed. I've got a copy of P&B's technical specs on the breaker and they don't talk about shock & vib at all. The only environ- mental specs they cover is temp and humidity. The thing that makes me think it may not be an issue is that this particular model has been sold through Wicks & Aircraft Spruce for years. It would seem to me that if shock were a problem, someone would have reported it by now and neither distributor would be offering them for aircraft apps ........ then again, maybe not. I think I'll try your auto road test and will place one rigidly on the dash of my truck. I'll let you know what happens. Tom Riley, MKIV #113 Date: Fri, 04 Oct 1996 08:25:51 +0200 From: Rego Burger Subject: COZY: Circuitbreakers vs Fuses Hi All, It's nice to have things at your finger tips! One could get brand new circuit breakers at Gulfcoast Avionics for $9-95 10 of these would cost $99-50. By the time I get it here in South Africa it will cost me R 971-75 excl. VAT. Having read about vibration triping etc. I wondered if high quality automotive fuses would not be a beter option for me. One has the choice of selecting fast or slow blow for various priority cicuits. I believe that even the SPACE SHUTTLE uses fuses. I could kit out my electrical system for about R 150-00 in this manner. Like everything in life there is a pro and a con or two. e.g. Flying is fun but you need to arrange a car at your destination etc. Now for a field day, what has general aviation got against fuses? Please respond for the benefit of all in a similar "boat" as me. Rego Burger P.E. S.A. Cozy Mk IV #139 Date: Fri, 04 Oct 96 08:35:35 EST From: MISTER@neesnet.com Subject: Re: COZY: Circuitbreakers vs Fuses Subject: Re: COZY: Circuitbreakers vs Fuses Author: MISTERKA 'R6M' ROBERT M at WBROF07 Date: 10/4/96 8:34 AM Rego Burger asked: "I wondered if high quality automotive fuses would not be a beter option for me. One has the choice of selecting fast or slow blow for various priority cicuits." Rego: I used ATO auto type fuses for all of my electrical circuits except for one breaker. That breaker is for the alternator field. I like the way it came out. Bob Nuckolls (Aeroelectric Connection 72770.552@compuserve.com) had suggested their use. He also has some excellent written materials on all aspects of aviation electrical issues. I am very happy with my fuse arrangement. It is neat and clean and I didn't have to worry about finding room for and paying for all those breakers. The fuse block that Bob sells also incorporates an essential bus concept that allows you to cut the power to everything but the essentials by simply opening the electrical master and closing the essential bus switch. This is used if you should lose your alternator and have to conserve battery power. I would say that in 95% of the instances where a fuse blows or a breaker trips the problem is a permanent fault that won't be resolved by merely closing the breaker or replacing the fuse. In fact, more problems may result from reclosing the circuit. One exception to this is the alternator field breaker. In my aircraft, I have an overvoltage crowbar circuit that deliberately shorts the field to ground if there is a high voltage excursion by the alternator. I'd highly recommend Bob Nuckoll's approach. I have found him very helpful and willing to answer my question. Bob Misterka N342RM From: "Dalrymple, Mark J" Subject: COZY: Fuses Vs Circuit breakers Date: Fri, 04 Oct 96 06:50:00 PDT Hi to all, In reference to previous discussions pertaining to circuit breakers verses fuses, I would have to agree with Richard Riley's comments and then some. I have also attended Bob Nuicoles (SP?) seminar on aircraft electrical systems. A few points to ponder are: 1. Nuisance trips are difficult to troubleshoot. If you had fuses, you might burn out/replacement alot before you isolate the problem. I have seen nuisance trips now and then on our flight test aircraft at McDonnell Douglas (These aircraft use the switch/circuit breaker method all over. There are only a few fuses installed). The period between resets can be a short time or a long time. With Long time between nuisance trip events, an aircraft might be able to make it home by merely resetting the circuit breaker. Also having tested and troubleshot large aircraft electrical systems (up to 120kva per engine), I happy to have circuit breakers to aid in troubleshooting quickly. I use also a clamp-on ac/dc amp meter to clamp on to wires in question. 2. Care must be taken if you use a fuse. I have read that someone had used a fuse for the electric landing brake. Their fuse had blown and the landing brake choked the flow of air to the engine cowl and they had to tear down their engine. Regards, Mark Dalrymple 2. Date: Fri, 04 Oct 96 11:09:09 est From: "Larry Schuler" Subject: COZY: Circuitbreakers vs Fuses Rego Burger wrote >.... >Now for a field day, what has general aviation got against fuses? >Please respond for the benefit of all in a similar "boat" as me. Rego, good question. Here's my thoughts: Fuses "REQUIRE" replacements when they blow; breakers don't. Breakers DO wear out though, ...... eventually. Other than that, there isn't a major difference. They both generally do exactly what is intended which is to protect the equipment and systems. Just a different flavor. Your idea of using automotive fuses is, in my opinion, a sound one. They are cheap, plentiful, and reliable. If you go in that direction, you have basically two choices: 1) the older glass types; or, 2) newer plastic "U" fuses. Either one will work, but I like the newer ones because of space savings and no glass to break. Either type fuse panel could be obtained from a junk yard and provide all the fuse positions you might need in an aircraft. Something to think about anyway. Choices..... Larry Schuler MKIV-#500 Date: Fri, 04 Oct 96 11:41:37 EST From: MISTER@neesnet.com Subject: Re: COZY: Fuses Vs Circuit breakers Mark Dalrymple writes:"Nuisance trips are difficult to troubleshoot." I guess I have a problem with the term "nuisance trips". Doesn't that really translate into "improper design". Maybe I'm naive but I think that if the circuit and the protection are properly sized there should be no such thing as a nuisance trip. The fuse or breaker should be sized to protect the wire against overload. If it trips, the wire has been overloaded. I also think that trying to find the reason for a trip by replacing the fuse or reclosing the breaker is literally playing with fire. He also wrote:"Care must be taken if you use a fuse. I have read that someone had used a fuse for the electric landing brake. Their fuse had blown and the landing brake choked the flow of air to the engine cowl and they had to tear down their engine." I think the issue here is not whether a fuse or a breaker was used. Who can say that reclosing the breaker in this instance would have cured the problem? In fact, it could have resulted in a fire in addition to an overheated engine. I think the real issue in this instance was ,again, proper design. Shouldn't all flight critical systems have a backup? In this case, a mechanical release or override to allow the brake to close was in order. Bob Misterka N342RM Date: Fri, 04 Oct 1996 11:08:04 -0700 From: Michael Antares Subject: COZY: Fuses vs Circuit Breakers... Just to add a couple of comments coming from one of the resident EE's... Nuisance tripping can come from (obviously) many causes. Not all of the causes are the result of design problems or could be corrected by design improvements. The choice of a value for a circuit breaker or a fuse depends on the balance between the protection level desired and not wanting to trip the breaker or blow the fuse unnecessarily. Without going into a huge effort most of us will empirically choose a value and that value will often be hundreds of percent greater than the nominal current flowing through the breaker/fuze. Startup currents may have to be accommodated so the fuse/breaker has to be sized accordingly. Nuisance tripping/blowing will result from transients and transients come from? Very often extremely difficult to trace. Well designed circuit breakers will trip at a more consistent current setting than a fuse and thus can have a lower current rating than a fuse protecting the same circuit. Also a fuse operated close to its fuzing point will have an unpredictable lifetime; each on-off cycle will cause the fuse material to sag a little until the fuse fails even in normal use. As an EE I will opt for breakers in my Cozy. I don't think that it is BAD to use fuses and probably no harm would come from using them in place of breakers but part of that probability is the fact that an electrical failure causing either a fuse or a breaker to go is very rare (I've never experienced it). The reason for me is that my conservative nature says that spending a few dollars more on breakers gives just that much more safety margin. In my experience (almost 5 decades of working in electronics) I have not come across an instance where a fuse would have been preferable to a breaker except for a cost benefit and a hundred dollars extra compared to $30 to $40K is pretty negligible! My two cents... 6077 Old Redwood Highway Penngrove CA 94951 707.664.1171 Cozy#413 Finished through chap 14 except chap 13. Chaps 16 & 24 mostly finished. Now on chap 19. by SERV05.SLAC.STANFORD.EDU (PMDF V5.0-6 #10979) id <01IA8V1M6ZK8000HHM@SERV05.SLAC.STANFORD.EDU> for cozy_builders@hpwarhw.an.hp.com; Fri, 04 Oct 1996 12:58:48 -0800 (PST) Date: Fri, 04 Oct 1996 13:00:05 -0700 From: hrogers@SLAC.Stanford.EDU (Howard Rogers) Subject: COZY: breakers vs. fuses Hi, I just thought I'd introduce myself as a new member of your esteemed group. My name is Howard Rogers. I live in the Sierra foothills, in "Gold Country", and commute, with my wife, back and forth to Palo Alto, California (103 NM, one-way) in a Grumman Cheetah. We both work at the Stanford Linear Accelerator Center. I am an A&P, and a former EAA tech counselor. I have had a Long EZ under construction for more years than I'd be willing to admit. It has been languishing in the garage for over a year, but I think I have enough other projects and crises under control to begin working on it again (possibly this weekend, in fact). There really isn't much remaining glass work to do to, and when the structure is complete, I guess I am 50% finished? I dream of replacing our 4-place Grumman with a Cozy Mk. IV, some day. I would like to respond, with a couple of points, to Michael Antares who wrote: >Without going into a huge >effort most of us will empirically choose a value and that value will often >be hundreds of percent greater than the nominal current flowing through the >breaker/fuze. Startup currents may have to be accommodated so the >fuse/breaker has to be sized accordingly. Nuisance tripping/blowing will >result from transients and transients come from? Very often extremely >difficult to trace. All very true, and may I suggest that *EVERYONE* who is building an airplane should own a copy of AC 4313, the A&P's "bible". You will find a vast resource of information in there that will darn near make you an A&P :-), including a ton of good information on how to select appropriate wire and breaker/fuse sizes for your circuits. This publication is available through places like Sporty's and also from the Government Printing office. >Well designed circuit breakers will trip at a more consistent current >setting than a fuse and thus can have a lower current rating than a fuse >protecting the same circuit. Also a fuse operated close to its fuzing point >will have an unpredictable lifetime; each on-off cycle will cause the fuse >material to sag a little until the fuse fails even in normal use. Good points, both. >As an EE I will opt for breakers in my Cozy. I don't think that it is BAD >to use fuses and probably no harm would come from using them in place of >breakers but part of that probability is the fact that an electrical failure >causing either a fuse or a breaker to go is very rare (I've never >experienced it). I have. It happened in my Grumman, about 6 years ago. What failed? My main 60 amp circuit breaker! It bacame an open, and wouldn't reset. Mechanically, it seemed fine, and *appeared* to reset, but remained open. In this particular case, I would have been better off with a fuse. It would have been obvious that it had failed, and I could have dealt with it in flight, insead of on the ground, after an hour of sun-baked sleuthing and muttered curses. It was about the last thing I suspected as the culprit that stole my entire electrical system, but systematic trouble-shooting eventually ruled out everything else. I certainly don't consider this to be a compelling reason to use a fuse, in this application. I will still use a "main" breaker in the EZ. >The reason for me is that my conservative nature says that >spending a few dollars more on breakers gives just that much more safety >margin. In my experience (almost 5 decades of working in electronics) I >have not come across an instance where a fuse would have been preferable to >a breaker except for a cost benefit and a hundred dollars extra compared to >$30 to $40K is pretty negligible! I agree that cost is not much of an issue, here, but there are two more that could be: Space and weight. I realize that you Cozy guys, with your acres of panel-area, don't worry about the space as much as us single-wide types, but weight is certainly an issue for all aircraft. You know the saying: "If you worry about the grams, the pounds will take care of themselves" (or something to that effect). I have seen a very elegant and *LIGHT* fuse setup, employing the automotive 2-prong plastic-topped fuses, that fit into a fraction of the space that would have been required for the equivilent breakers. What am I going to use? I haven't decided on every detail, but I suspect it will be a combination of fuses and breakers, even though I already own enough breakers for the whole job. I look forward to reading the postings from this group, and I will dig through the archives, just as soon as I can figure out how to download and read "Zipped" files. Not to worry--I'm surrounded by computer gurus here, so as soon as I can pin one of them down....... Regards, hrogers@slac.stanford.edu (Howard Rogers: pilot, aircraft mechanic, saddle maker, high energy physics R+D handyman) _____________________________________________________________________ Do your part: Help stamp out the mindless, indiscriminate use of impersonal, cutesy "rubber-stamp" E-mail signatures. _____________________________________________________________________ Opinions are strictly mine, and are usually not those of my employer. Date: Fri, 04 Oct 1996 15:55:18 -0700 From: Michael Antares Subject: COZY: Fuses/Circuit Breakers May I add a couple of obvious things to consider in your choice of fuse vs circuit breaker? 1) When a fuse blows you need some way of knowing which one it is! In a hurry! Some fuses have built in indicators--many do not. 2) When a fuse blows you need a replacement--again in a hurry. You probably can't afford to go thumbing through your glove compartment (there ain't one anyway), map holder or whatever, so you need to consider where to stash the spares. You don't have these concerns with circuit breakers. However I certainly agree that when a circuit breaker fails we can have big time problems, we need to select a reliable one to minimize that possibility. More 2 cent comments... 6077 Old Redwood Highway Penngrove CA 94951 707.664.1171 Cozy#413 Finished through chap 14 except chap 13. Chaps 16 & 24 mostly finished. Now on chap 19. Date: Fri, 4 Oct 1996 19:23:25 -0500 From: csmith@siue.edu (Curt Smith) Subject: COZY: Fuses vs. Breakers One of my regular stops at Oshkosh each year is to check out Mike Melville's Long to see what he's done to it lately. Mike has a pretty good rep for thinking things through pretty carefully and , obviously, is well-connected. Anyway, one of the things he has recently added is a fuse panel using the newer, spade-type automotive fuses. As I recall, he used to have breakers. It looks good, and is very space-efficient. I've decided that's the way I'll go when wiring my Cozy III. Curt --------------------------------------------------------------- Curtis A. Smith, Ph.D. Associate Professor & Educational Administration Program Director Southern Illinois University at Edwardsville Department of Educational Leadership Box 1125 Edwardsville, IL 62026-1125 Phone: 618/692-3970 FAX: 618/692-3359 ---------------------------------------------------------------- From: "Rob Cherney" Organization: Ellicott City, Maryland Date: Sat, 5 Oct 1996 00:01:56 -0400 Subject: COZY: Circuitbreakers vs Fuses Hi, y'all: >Now for a field day, what has general aviation got against fuses? >Please respond for the benefit of all in a similar "boat" as me. As an electrical enginerd, my feelings are that radios or circuit loads that are primarily resistive could be connected through fuses. Inductive loads, i.e. motors and solenoids, should have circuit breakers since the electrical load is much more a function of starting current, friction, and normal operation. As such, these loads are more prone to operational variations and true overcurrent faults. That said, my experience has been that nuisance trips are caused either by a mis-sized breaker or workmanship issues. Wormanship problems have been traced to whiskers of stranded wire touching another conductor, loose crimps on ring lugs, mis-mated connectors, frayed wires, and/or generally poor wiring technique. When everything is done "right" and a properly sized fuse has done it's job, there is a high probability of a fault which would not have been resolved in flight. Rob- +--------------------------------------------------------+ |Robert Cherney Home Phone: (410)465-5598 | |Ellicott City, Maryland e-mail: cherney@clark.net | +--------------------------------------------------------+ Date: Sat, 5 Oct 1996 08:31:50 -0400 (EDT) From: "George A. Graham" Subject: COZY: Fuses & Breakers & Links What with the discussion of the merits of fuses and breakers, why have we ignored what the automotive industry uses for important circuits, fused wire links ? Of course you know that if one does burn, there is probably nothing you can do about it in the air. But on the other hand, they are much more reliable, vibration tolerant, corrosion proof, even lighter than breakers or fuses. I've used them in race cars with good success (never had one blow). Modified E-Racer #206 Mazda Engine next George Graham {ca266@freenet.buffalo.edu} Date: Mon, 7 Oct 1996 07:20:17 -0400 From: CheckPilot@aol.com Subject: Re: COZY: Circuitbreakers vs Fuses In a message dated 96-10-04 07:41:54 EDT, you write: << Having read about vibration triping etc. I wondered if high quality automotive fuses would not be a beter option for me. >> A lot of older airplanes have fuses. The biggest downside that I always saw was that you need to have spares, and if one blows you need to replace it versus just pushing it back in. Check your local regs for what you need to carry for spares. I know that the US FARs say a full set of spares or three of each type used (rating and slow/fast, etc.) BTW, what is a "high quality" auto fuse, we all know that the auto stuff is probably better quality than aircraft stuff, right??? Jim III #455 Date: Mon, 7 Oct 1996 18:23:52 -0400 From: C537130@aol.com Subject: Re: COZY: Fuses Vs Circuit breakers Bob Misterka writes-I guess I have a problem with "nuisance trips". Doesn't that really translate into "improper design". Maybe I'm naive................ Maybe so. I'm privileged to get to operate airplanes that are considered to be the best available. The more sophisticated the electrical system, avionics, etc., the more likely the occasional "nuisance trip","alert" or whatever flag a particular airplane sends up. From an operator standpoint, the industry standard fix for a system you want/need to have back, is one reset after allowing for a cooldown period. If it trips again, further resets are usually not recommended. You have to use your best judgement as to how bad you need the system back. More and more homebuilts are becoming awfully hi-tech in the electrical department. Cessna 150's probably suffer precious few nuisance trips. But throw in all the goodies and it's a fact of life. Thanks , Mark Holley by Npt.NUWC.Navy.Mil (PMDF V5.0-5 #13155) id <01IAE9ML1GA094DQC3@Npt.NUWC.Navy.Mil> for cozy_builders@hpwarhw.an.hp.com; Tue, 08 Oct 1996 09:50:28 -0400 (EDT) (4.1/SMI-4.1) id AA04795; Tue, 08 Oct 1996 09:51:00 -0400 (EDT) Date: Tue, 08 Oct 1996 09:51:00 -0400 (EDT) From: triley@c38fs0.npt.nuwc.navy.mil (Tom Riley) Subject: COZY: Breaker switches, revisited About a week ago I sent the following message. It may have been responsible for unleashing a lengthy discussion on circuit breakers vs. fuses, but that wasn't the issue. The issue is ARE POTTER & BRUMFIELD TYPE W31 BREAKERS SUBJECT TO BEING TRIPPED BY HIGH G'S? How about it guys? Doesn't anyone out there have any views/experience with these very popular breakers? --------------------------------------------------------- I'm far from needing switches for my instrument panel yet, but I have looked at some of the readily available circuit breakers and have one concern about a popular model made by Potter-Brumfield. If anyone could comment on the following, it would be much appreciated. The P-B W31 series (thermal breaker with built-in toggle) seems to be very susceptible to being fliped OFF by shock - and it doesn't take much. Try it, take a W31 and set it to the ON (up) position, then hold it upright in your right hand with the toggle away from you and strike the palm of your left hand. It doesn't take too much of a blow to flip the switch to the OFF position. It would seem to me that a good bang in bad turbulence could result in shutting off several such breakers --- not fun. Does anyone have any experience with these breakers or care to comment? Am I way off base here, or is this a valid concern? Tom Riley Cozy MKIV, S/N 113, Chap 9 Date: Wed, 9 Oct 1996 10:33:22 -0500 (CDT) From: Steven A Eberhart Subject: COZY: --WARNING-- W31 Circuit Breaker --WARNING-- I just got off the phone with an old friend that still works at P&B and got the following information. 1. The W31 breakers are not now specified in reguards to shock tripping. The old spec. used to be 15 to 25 G's. The low Amp. breakers up to about 4 Amps were good for 15 G's, above 4 Amps were good for 25 G's. Rapping on your hand is not a valid test. 2. From date code 9550 to present should be returned to your supplier for replacement!!!! There is a manufacturing defect that has, as of today, not been corrected. When the breakers trip, they can NOT be reset. Breakers made before date code 9550 should be OK. Just passing along the information I was told by the now anonymous source. Steve Date: Sat, 19 Oct 1996 16:36:29 -0400 (EDT) From: Randy Crutfield Subject: Re: COZY: --WARNING-- W31 Circuit Breaker --WARNING-- I've been on the sidelines on this one, and behind in my E-mail so I waited until this string "played out" to post. Just my opinion, and please don't restart the string, merely add this point to your decision process in choosing between breakers and fuses. One of the key points that I keep in mind is KISS. Now think about KISS when considering breakers versus fuses. One is a very simple device with no moving parts, the other is not that complex, but does contain a few more parts, some of which have to move. My fear is not that I may not be able to reset it because it has mechanically failed, but rather that it may not trip because of a mechanical failure. I'm sure that someone has seen a fuse that did not open under overload (I have seen one), but I have seen quite a few molded case breakers in power distribution systems mechanically fail and could not be switched off. I'm not sure if they would have tripped with an overload, but they definitely could not be "switched" off. Again, before you post I realize that molded case breakers (these are the cheap kind that are in your house and in larger form in most power distribution panels in industry) are not the same as mil-spec aircraft quality breakers. But, as Steven's post indicated, even a higher quality breaker suffers from some of the same problems. Regarding the troubleshooting aspect, that needs a little more consideration on my part. My background is electronic\electrical and also considering that I am the builder I feel confident that I will be able to logically deduce which is the problem fuse. My pilot wife for all her virtues may not apply the same logic. ^randy