Resetting tripped circuit breaker

Cardboard box and crayon explanation here. (I loved ConAir)

A bit bigger breaker than you really need for the load, supplying said load with a bit bigger wire than you really need, in order to get the job done safely.

You determine the load you are dealing with, you then choose the breaker to properly handle that load.

Then you choose the wire to supply said load safely..

Show me where you see 5..

I had to leave in the Conair quip.

Show your math.

I drew this concept out for my Wife who is a CHFC and not proficient in this field, she got it.

I'm not trying to contradict an over complicated document, I'm merely trying to simplify it's concept.

Perhaps explain it where more can understand its intent.
 
Bob Weber said:
...
A bit bigger breaker than you really need for the load, supplying said load with a bit bigger wire than you really need, in order to get the job done safely.

You determine the load you are dealing with, you then choose the breaker to properly handle that load.

Then you choose the wire to supply said load safely..

....
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Bob, as a self-described "why" and "how" guy.... "why" is there a breaker needed in the first place? Answer... to protect the wire. "How" does the breaker protect the wire? Answer .. by tripping before the wire's capacity to safely carry the current present is exceeded. "Why" does 41.13 state that the breaker is there to protect the wire and not the black boxes? "How" does one ensure that the breaker protects the wire, as instructed in 41.13?

I understand what you're saying so relatively cryptically, and am not in need of cardboard/crayon explanations. Your method (paraphrased) of "Load determines breaker determines wire" may end up with the same results, but it ignores the "why" and "how" of the function and flow within the circuit.... not to mention 41.13.

Practical experience and working end results are great, but as you implied in an earlier posts, the "why"s and "how"s are the foundation from from which all of this springs... the theory and engineering principals behind electrical design. Answering the "why" with "because it works for me and because it makes sense to me that way" and the "how" with "the way I do it or was taught" are simply insufficient answers.
 
"How" does one ensure that the breaker protects the wire, as instructed in 41.13?

upload_2019-11-4_18-43-35-png.79416


"whichever is lowest"

"A circuit breaker must always open before any component ( I interpret this including both the wire and the load) downstream can overheat and generate smoke or fire.

"Wires must be sized to carry continuous current in excess of the circuit protective device rating."

I always use the old adage " what comes first, the cart or the chicken"...( I will always leave my quips in)

The radio will smoke faster than the wire feeding it, by design, if your doing it right...

The size of wire is determined by the breaker that prevents the radio from going up in smoke, and is designed to handle the current requirements of the breaker.

"why" is there a breaker needed in the first place?

Why would you use a 2 amp breaker with an 18ga wire?

yet here we are with 2 amp breakers in the aircraft.
 
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Super interesting post. This above was posted on page 2. So it says," that the circuit breaker must open before the current rating of the wire is exceeded OR before the cumulative rating of all loads connected to it are exceeded, whichever is lowest. "

Also,"A circuit breaker must always open before any component downstream can overheat and generate smoke or fire."

So you must take both into account and consider the most limiting. So essentially it is what both sides of the discussion are pointing out. The breaker must be sized to protect the wire, but also protect against overheat and smoke. You must consider if you have a 2 amp load and you wire it with 6 gauge wire, you can put a large trip circuit breaker. Let's say 20 amps. But does this meet the limitation of overheat and generate smoke? Probably not. Better maybe with a 5 amp breaker and then adjust the wire size that a 5 amp breaker will protect the wire.

So you are both right. You must size the breaker to protect the wire, that goes with out saying, but you must also take into consideration the component downstream overheating and smoking with a breaker that is oversized for the circuit but protects the wire.

So no matter how you come to your conclusion you must take both into consideration so you don't have large circuit breaker protecting a large cable powering a very small load.

But my opinion on the original question/post: there is no reason in flight to reset a circuit breaker in flight. Period... unless there is an emergency, it is not worth the risk of why it popped in the first place. Maybe it was an anomaly. But, is have smoke or fire in the cockpit worth the chance. I know my plane and most others I can turn off the master and the motor will continue to run just fine and I can land safely. So if a breaker trips for say your landing light. Land. Troubleshoot on the ground. Even if you loose all you avionics, land. Troubleshoot on the ground. If the airplane is running and flying correctly, land asap. Troubleshoot on the ground. Your life is the most important. Not much different than losing a vacuum pump, only a vacuum pump can't be reset.
 
THANK YOU!!!
 
GeneC said:
View attachment 79537


Also,"A circuit breaker must always open before any component downstream can overheat and generate smoke or fire."
Click to expand...


So how does a CB meet this criteria with respect to a cigarette lighter? When it's properly operating it's purpose is to provide sufficient heat so as to be a direct cause of smoke.

;)

(and with that helpful contribution, you'll find me hiding behind a sofa.)
 
I Love it!!!

Refer to the Cessna service bulletin that addressed this.... 30 some years ago.
 
GeneC said:
So you must take both into account and consider the most limiting.
Click to expand...
Not exactly. But if you are looking for a single reference then paragraph 11.51 would be it as it refers to Paragraph 11.48 also. Bob can put this all to rest by providing an acceptable reference to his "150% rating comment" and "that CBs protect equipment." Unfortunately, he has yet to provide this.
 
Bob Weber said:
I have worked with A/P's, I/A's, ASE certified mechanics, and every other certification out there, I found the certification does not make the man. Results are what I look for.
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Unfortunately your results become a moot point unless you can find someone with a certificate to sign them off per Part 43. Right? However, considering by your own admission that you lack any type of certificate that allows you to approve aircraft for return to service, then perhaps your failure to understand the significance of AC43.13 and other reference requirements vs opinion is based on your lack of experience with this part of the process??
Bob Weber said:
I have one simple question to ask you, what part of my concept explanation goes against your 43.13 mumbo jumbo I'm so glad to be able to put in my library archives?
Click to expand...
As answered several times earlier: "I was taught a breaker should be rated at 150% of the max load.." and "the breaker is designed to prevent the radio from going up in smoke."
 
Bell206 said:
Unfortunately your results become a moot point unless you can find someone with a certificate to sign them off per Part 43. Right? However, considering by your own admission that you lack any type of certificate that allows you to approve aircraft for return to service, then perhaps your failure to understand the significance of AC43.13 and other reference requirements vs opinion is based on your lack of experience with this part of the process??

As answered several times earlier: "I was taught a breaker should be rated at 150% of the max load.." and "the breaker is designed to prevent the radio from going up in smoke."
Click to expand...


Perhaps you might visit my website webairconsulting.com and see that I merely offer money saving advice, complete with the statement that I do not in fact return any aircraft to service any more by design, and I love it that way.

Twist your interpretations of 43.13 however makes you comfortable, I try to simplify.

It creates a bit better understanding to many.

KISS

It's cheaper quite often!
 
I am not an electrician, but if I was to wire something, my logic would be something like this. Intended load will be 8 amps, so I will use a 10 amp breaker, and wire good for 15 amps. That for me would feel like a safe, and sane, thing to do.
 
Bob Weber said:
I merely offer money saving advice...I do not in fact return any aircraft to service...and I love it that way.
Click to expand...
Ha! I guess life is grand on your side when you have zero responsibility or accountability for what you believe, or say, or do on an aircraft. I think you've summed up the entire thread rather splendidly. But buyer beware....
 
Shuswap BC said:
my logic would be something like this.
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The "best" part of aviation is you can usually leave the "logic" side of things on standby as there is more than enough of FAA acceptable/approved guidance out there to answer/predicate your requirements. In the case of aircraft electrical systems there are probably more than a dozen charts that will provide you several options/answers for the example you mention. The "better" part is that the FAA actually prefers you follow that guidance to the letter vs over-simplifying or modifying that guidance to your fit your personal narrative.;)
 
Shuswap BC said:
I am not an electrician, but if I was to wire something, my logic would be something like this. Intended load will be 8 amps, so I will use a 10 amp breaker, and wire good for 15 amps. That for me would feel like a safe, and sane, thing to do.
Click to expand...

That sounds like a rational choice for most wiring projects.

But in aircraft, weight is critical, and wire gauge is chosen very carefully with that in mind.
 
FastEddieB said:
That sounds like a rational choice for most wiring projects.

But in aircraft, weight is critical, and wire gauge is chosen very carefully with that in mind.
Click to expand...

Now your thinking about it like me.

I need X amps of current, set the breaker rating, how small of wire can we select to supply the load with a safety margin.

All of this is clearly stated, and lies within 43.13.

All the manufacturers allow the "headroom" for the breaker rating above the current draw of the component you are working with.

Generally the AML STC calls out for both the breaker, and the wire gauge.

I never found the need to create any extra thought in a project, I always felt my head should be on a swivel for any other issues.

You know, on this same subject, how many wires are in your aircraft that are unused/abandoned.

Better start a new thread...
 
"Good engineers design the bridge to stand up to normal and any reasonably foreseeable overload."

"Great engineers design the bridge to stand up to normal and any reasonably foreseeable overload -- just barely."

Jim
 
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