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Klixon circuit breakers as switches

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12notes

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I'm looking at circuit breakers for the panel, the Klixon 2TC2 seems like they would work fine. I only need 5 circuit breakers. I noticed that they are good for 2500-5000 cycles, which is well over the number of times I would use a switch in 1000+ hours, is there any reason I couldn't use them as a switch and dispense with the external toggle switch?

I am aware that they sell the circuit breakers with an a toggle switch on them, but for $200+ each, that would be over 10% of the cost of the whole plane in 5 circuit breakers, so no thank you.
I also know that a small fuse box/panel is an option, but I would much prefer the breakers.
I've also looked at the Klixon 7277-1 "inexpensive auxiliary switch", this is not an indicator that it is ro be used as a switch, it means that when the circuit breaker is off, it switches on a secondary circuit.

 

Marc Zeitlin

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I also know that a small fuse box/panel is an option, but I would much prefer the breakers.
Slight thread drift, but why the objection to something cheaper and more reliable? If you want reliable switches, something like these:


are great, and automotive ATO fuse blocks:


give you simplicity and flexibility. It's what I recommend to all my customers. Cheap, simple, reliable.
 

12notes

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Slight thread drift, but why the objection to something cheaper and more reliable? If you want reliable switches, something like these:


are great, and automotive ATO fuse blocks:


give you simplicity and flexibility. It's what I recommend to all my customers. Cheap, simple, reliable.
Other than being larger, heavier, more complex than what I'm suggesting, and needing to carry spare fuses, having no good place to put the fusebox on my tiny panel where it is accessible in flight kills it. And I'm not really worried about the reliability of Klixons.

It's not thread drift to suggest fuseboxes when I explicitly stated in my original post that I am aware of fuse boxes and don't want one, it's complete thread derailment. I spent extra time on my post to look up and include the options that I would not consider. I am not looking for reasons how a fuse box could fit, why it's cheaper, or really, any information on fuses or fuse boxes. I'm asking about breakers here, let's keep it on topic.
 

TFF

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Just twist the wires together.

I would go with nice switches and GM style auto fuses because you can land next to a Walmart to find parts. Flying in icing IFR totally with CBs. Most aircraft have a mix of all anyway.
 

wsimpso1

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Other than being larger, heavier, more complex than what I'm suggesting, and needing to carry spare fuses, having no good place to put the fusebox on my tiny panel where it is accessible in flight kills it. And I'm not really worried about the reliability of Klixons.

It's not thread drift to suggest fuseboxes when I explicitly stated in my original post that I am aware of fuse boxes and don't want one, it's complete thread derailment. I spent extra time on my post to look up and include the options that I would not consider. I am not looking for reasons how a fuse box could fit, why it's cheaper, or really, any information on fuses or fuse boxes. I'm asking about breakers here, let's keep it on topic.
I must respectfully disagree. I feel that I must suggest to you and everyone else thinking about ship's power and wiring to consider Bob Nuckoll's book, AeroElectric Connection. It is a compilation from his experience and materials, including example wiring schemes for everything from really simple airplanes on up. Bob has been a go-to guy for airplane power and wiring for a long time for certified ships and has been all over homebuilts for decades. Among other things, he presents his well thought out basis for designing so that when something breaks in flight, it is not an emergency. This includes, among many other things, using simple reliable switches and fuses that are NOT accessable in flight combined with failure tolerant electrical system design and for very good reasons. He is also big on using double pole double throw switches with multiple purposes to improve reliability and reduce weight at the same time. It is very much worthwhile reading for someone about to wire an airplane.

Billski
 

wsimpso1

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I'm looking at circuit breakers for the panel, the Klixon 2TC2 seems like they would work fine. I only need 5 circuit breakers. I noticed that they are good for 2500-5000 cycles, which is well over the number of times I would use a switch in 1000+ hours, is there any reason I couldn't use them as a switch and dispense with the external toggle switch?

...

AeroElectric Connection works extensively in terms of switches and fuses. The book also discusses how to install and use circuit breakers, but I could not find a discussion of circuit breakers as switches. I might have missed it.

I recall but can not find the reference where circuit breakers are contraindicated as switches. IIRC, the reasoning is that circuit breakers are designed for disengagement at high load, but are not usually designed for fast closing of contacts. Engaging a circuit breaker for a large inductive load (motors) or large starting current (lamps) arcs across the contacts - slow closing extends that arcing and seriously shortens breaker life. If you can find breakers rated for engagement under inductive and resistive loads that cover your cases, well, then go for it. Otherwise, the breaker should be firmly on before the switch is thrown as switches and relays are designed to carry the engagement currents across their closing contacts, while the breaker may not.

Billski
 

12notes

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I must respectfully disagree. I feel that I must suggest to you and everyone else thinking about ship's power and wiring to consider Bob Nuckoll's book, AeroElectric Connection. It is a compilation from his experience and materials, including example wiring schemes for everything from really simple airplanes on up. Bob has been a go-to guy for airplane power and wiring for a long time for certified ships and has been all over homebuilts for decades. Among other things, he presents his well thought out basis for designing so that when something breaks in flight, it is not an emergency. This includes, among many other things, using simple reliable switches and fuses that are NOT accessable in flight combined with failure tolerant electrical system design and for very good reasons. He is also big on using double pole double throw switches with multiple purposes to improve reliability and reduce weight at the same time. It is very much worthwhile reading for someone about to wire an airplane.

Billski
I've read it. I disagree that inaccessible fuses are a good idea. You and he and others on here might be fine with them, but I am not. If the engine is still running but I'm in the pattern at a busy airport, while it is not an emergency, I'd rather have the option of trying to get the radio working again if the fuse/breaker pops. Pushing a button is way, way easier than trying to find the right size fuse and changing it. If it's a serious problem, then the end result is the same, the fuse/breaker will trip again, but it's usually not. I've fixed cars many times by replacing a blown fuse. If there is a short, then it blows again and I'll trace the problem, however, that has been the least common outcome. Usually replacing the fuse just fixes it and after years there is no repeat and no discoverable reason why it blew. Transient electrical weirdness happens. Other times a fuse that has never been changed will eventually come loose and arc in its holder. I'd rather have a breaker screwed into place within reach to reset than a fuse wedged into place. And it's a million times better than a fuse I can't reach.

I disagree that they are better than a breaker in this application. I've heard the arguments. I've read the book. No fuses for my plane.
 
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12notes

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AeroElectric Connection works extensively in terms of switches and fuses. The book also discusses how to install and use circuit breakers, but I could not find a discussion of circuit breakers as switches. I might have missed it.

I recall but can not find the reference where circuit breakers are contraindicated as switches. IIRC, the reasoning is that circuit breakers are designed for disengagement at high load, but are not usually designed for fast closing of contacts. Engaging a circuit breaker for a large inductive load (motors) or large starting current (lamps) arcs across the contacts - slow closing extends that arcing and seriously shortens breaker life. If you can find breakers rated for engagement under inductive and resistive loads that cover your cases, well, then go for it. Otherwise, the breaker should be firmly on before the switch is thrown as switches and relays are designed to carry the engagement currents across their closing contacts, while the breaker may not.

Billski
The documentation states the endurance as 2,500 cycles: 30 VDC inductive, 5,000 cycles: 30VDC resistive, 10,000 cycles: no load. I would assume that a cycle is off and on, but do not know for sure.

 

12notes

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Blue Sea Systems A-Series White Toggle Circuit Breaker - Single Pole, 15A https://www.amazon.com/dp/B000K2IKMI/ref=cm_sw_r_cp_apa_i_yPmFEbRNFRYZM

I'm sure these weigh more, but if you only need 5........ I've rarely seen them fail. Common on boats.
I hope the size is wrong on that link, because it says it's 8x8x3 inches. I couldn't fit 3 of those on my panel. Even if that's supposed to be cm, that's still a bit too large for me to consider.

For some reason, your post and TFFs first post did not show up on my computer until a few minutes ago, although you were the second post hours ago. Weird.
 

wsimpso1

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The documentation states the endurance as 2,500 cycles: 30 VDC inductive, 5,000 cycles: 30VDC resistive, 10,000 cycles: no load. I would assume that a cycle is off and on, but do not know for sure.

Went there, the data is all ratings for steady state carrying and for disengagement. No rating for engagement, as I was concerned. Somebody has got to have tried this...
 

Pops

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Slight thread drift, but why the objection to something cheaper and more reliable? If you want reliable switches, something like these:


are great, and automotive ATO fuse blocks:


give you simplicity and flexibility. It's what I recommend to all my customers. Cheap, simple, reliable.

I used a fuse holder like you posted in the JMR.
 
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Marc Zeitlin

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I used a fuel holder like you posted in the JMR.
Yep (although mine don't hold fuel :) ).

I'm always fascinated by folks who, when their airplane it talking to them and telling them that it's trying to set itself on fire, are insistent that they want to give it another chance to so so. "But I'll only reset the breaker once". Well, two chances to set the plane on fire is 100% more than one chance. No thanks. In my airplane's electrical system design (per Bob Nuckoll's Z-14 diagram) ALL fuses are inaccessible in flight, and NO fuse is safety critical, meaning that any one fuse can blow and the plane does not have an emergency situation.

To each their own.
 

Pops

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Yep (although mine don't hold fuel :) ).

I'm always fascinated by folks who, when their airplane it talking to them and telling them that it's trying to set itself on fire, are insistent that they want to give it another chance to so so. "But I'll only reset the breaker once". Well, two chances to set the plane on fire is 100% more than one chance. No thanks. In my airplane's electrical system design (per Bob Nuckoll's Z-14 diagram) ALL fuses are inaccessible in flight, and NO fuse is safety critical, meaning that any one fuse can blow and the plane does not have an emergency situation.

To each their own.
Thanks, fixed it. Fingers mixed up. :)
 
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