lithium366 Posted December 16, 2021 Report Posted December 16, 2021 Looking at an electrical system diagram for my 1966 E there is a gap in a power bus bar (in red on the attached image). In my airplane that last circuit breaker is connected to the bus bar using jumping wire. Does anyone know why bus bar does not go across all circuit breakers and why wiring diagram does not show that jumping wire between 49 and 108 or am I chasing a red herring? 1 Quote
ArtVandelay Posted December 16, 2021 Report Posted December 16, 2021 Can’t answer question, but there’s possible some arcing on the left most switch/CB?Your steel frame is rusted, and the switch on the lower right…was there a leak? 1 Quote
lithium366 Posted December 16, 2021 Author Report Posted December 16, 2021 10 minutes ago, ArtVandelay said: Can’t answer question, but there’s possible some arcing on the left most switch/CB? Your steel frame is rusted, and the switch on the lower right…was there a leak? I am going to re-do an entire panel. It will get all new circuit breakers / wiring Quote
EricJ Posted December 16, 2021 Report Posted December 16, 2021 A diagram drawn that way is a bit ambiguous but usually just means there's a longer distance between 49 and 108 and they're using the break to show that. 3 Quote
lithium366 Posted December 16, 2021 Author Report Posted December 16, 2021 That was my thinking but it is not longer and that jumper wire I have made me think there might be something else Quote
MikeOH Posted December 16, 2021 Report Posted December 16, 2021 Yes, that is quite odd. To add to what EricJ said, that 'break' symbol is also used when part of the bus is shown elsewhere on the schematic (with additional loads). Can you confirm that the 5th CB from the left is for the fuel pump? Quote
lithium366 Posted December 16, 2021 Author Report Posted December 16, 2021 5 minutes ago, MikeOH said: Yes, that is quite odd. To add to what EricJ said, that 'break' symbol is also used when part of the bus is shown elsewhere on the schematic (with additional loads). Can you confirm that the 5th CB from the left is for the fuel pump? Yes it is 1 Quote
MikeOH Posted December 16, 2021 Report Posted December 16, 2021 1 minute ago, lithium366 said: Yes it is In that case, I'm going with "red herring" territory Quote
carusoam Posted December 16, 2021 Report Posted December 16, 2021 That is a nicely hand drawn drawing left from the days before cad… Scaling drawings was a challenge… re-scaling them… impossible. The break says, there is something unimportant between here and there…. But, that’s about it…. before cad…. Engineers would supply details to a person that knew how to draw these details up (draftsmen)…. The system included all kinds of errors in translation…. Then the engineer would supply handwritten notes to a secretary to get them typed up… more losses occurred… So… when you see so little information in an old manual… you get the feeling why it used to occur…. And why everything was kept as basic as possible… An engineer with a cad station is more powerful than the old engineer/tech drawer/typist combination…. Updating a drawing today… is a breeze. And includes who did the change, why, and when… with approvals…. And printing it only takes the push of a button… Now… if you have two actual separate bus bars that are connected together with wires…. Even a hand drawing would want to show that detail… Often some bus bar extensions…. Are just CBs daisy chained together with more wires… (extra failure points…) Again, that level of detail took way to much effort/cost to produce…. Mechanics in the field would get saddled with all the short comings of the old documentation system… Theory vs. real life actual from the 1960s and 70s…. Best regards, -a- 1 Quote
carusoam Posted December 16, 2021 Report Posted December 16, 2021 Ilya, lots of heat damage on that left end circuit breaker…. What’s going on there? Might be time to figure out a replacement strategy for that one… (did I miss the part of the conversation of why you are in there to begin with?) Best regards, -a- Quote
carusoam Posted December 16, 2021 Report Posted December 16, 2021 Take a look at the front of the panel… Were the extra CBs original to the plane, or were they added later? Technically, you would want a bus bar connecting these to eliminate the possibility of a wire break… Assume these were added later… and the mechanic at the time didn’t have a proper bus bar to fit this situation… Or the owner didn’t have the money/desire to replace the old one, with a proper new one…. The cost of the new proper bus bar is near zero… available in many places, cut to fit…. Getting it installed… is a lot of screws behind the panel…. If you have access panels… this is easy and can be done for low cost during annual… Hmmmmmmm….. taking the access panels off the first time after new paint…. Use extra care…. Best Regards, -a- 1 Quote
lithium366 Posted December 16, 2021 Author Report Posted December 16, 2021 28 minutes ago, carusoam said: Ilya, lots of heat damage on that left end circuit breaker…. What’s going on there? Might be time to figure out a replacement strategy for that one… (did I miss the part of the conversation of why you are in there to begin with?) Best regards, -a- I believe this damage is from the unknown past. I saw it and touched and smelled and I believe it’s when this airplane had it’s original landing light (I have LED now) and for some reason this CB was not replaced. Anyways I am replacing an entire panel and I don’t want to miss even a tiny detail this is why I asked this question 2 1 Quote
lithium366 Posted December 16, 2021 Author Report Posted December 16, 2021 This lonely CB is an aux fuel pump and it is in it’s home location. I can say the same about other CBs in a left bus (pitot, exterior lights) so it is a mystery for me why one of them is on a jumper wire Quote
carusoam Posted December 16, 2021 Report Posted December 16, 2021 When going with a new panel… The wiring design typically will get new bus bars… All the wires will be proper type and dimensions… Just another one of the million details avionics guys have in there “tool box”… As the panel user… we look at bus bars as they have some kind of magic… Mostly, why we have two or three separate bus bars…. Main, avionics, and emergency… Using the bus bars themselves… simply cuts out failure points that come with separate wires… In modern Mooneys with an array of CBs on the right end of the panel… there are probably a half dozen bars connecting rows of CBs… Watch for the difference in the part called a bus bar…. And all the small circuits that are collected together and powered by the same master circuit breaker… From the user side… all the CBs one one bus bar… may be connected using a few small pieces of brass ‘bus bars’…. All supported from basic drawings from the 60s… Our CBs are temperature sensitive… that’s how they work… as they age, they wear… and lose their crisp click… Check your old CBs if they are missing their click, like your new ones have…. They probably can’T hold the stated limit anymore… Landing light CBs had a tendency to wear out sooner than lower amperage devices… Often the landing light would warm its CB… then the CB couldn’t hold its place… because no click had to be overcome…. between the loose panel above the switch, and the worn switch… my M20C couldn’t keep its landing light on for a long time (months) before it got replaced… That new panel looks really nice! Do you get to paint the tubes back there while they are exposed? Best regards, -a- Quote
lithium366 Posted December 16, 2021 Author Report Posted December 16, 2021 Yes, I will paint this tube. It really is not that bad as it appears in the image: very light corrosion I have a similar symptom on my pitot CB - it holds for a minute or two and then goes off. I will just replace them all 1 Quote
Yetti Posted December 16, 2021 Report Posted December 16, 2021 Yep because. At least the as built matches the drawing. 1 Quote
Belso Posted December 31, 2021 Report Posted December 31, 2021 Some pictures of my electrical and avionics wiring and schematic 2 Quote
Prior owner Posted December 31, 2021 Report Posted December 31, 2021 There might be one reason why the entire row of circuit breakers is not on the same bus bar- to change one of the CB’s out, the entire row would have to be removed from the panel and pushed back together. A jumper will allow the other CB’s to be removed individually. But I don’t know that this is the reason for the arrangement. It might be part of the reason why? Quote
carusoam Posted December 31, 2021 Report Posted December 31, 2021 +1 for bus bars eliminating many points of failure… -1 for each time you want to swap out a CB on a CB’s budget… -a- Quote
EricJ Posted December 31, 2021 Report Posted December 31, 2021 2 hours ago, Belso said: Some pictures of my electrical and avionics wiring and schematic Nicely done! And kudos for graphic documentation. A shop built mine and I asked for an as-built drawing and they refused to provide any kind of documentation of the wiring. Yet another of many reasons to do it yourself. Quote
carusoam Posted December 31, 2021 Report Posted December 31, 2021 Belso’s awesome art work… rotated! Hey! That is hand drawn… in ink! That’s a skill last seen by engineers in the 80s… See if @Hank is familiar? (Mechanical drawings in ink) Really cool skill to have! -a- Quote
Hank Posted December 31, 2021 Report Posted December 31, 2021 Nice and neat! I still have (and use occasionally for myself) my collegiate laptop drawing board, 18" T-square and triangles. Even have a couple of small pocket-size 30/60/90 triangles, because they sure do come in handy sometimes. Quote
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