Cycling circuit breakers

Dave Siciliano

Dave Siciliano

Final Approach
Joined
Feb 27, 2005
Messages
6,434
Location
Dallas, Texas
Display Name
Display name:
Dave Siciliano
Wondered how many of y'all pulled each circuit breaker annually and recycled it. (only the mushroom topped ones, not those that are flat on older aircraft.)

Seems a study has been done that shows this improves the life of the breaker!!

The recommendation came as a side benefit to the Institute's Aging Aircraft Laboratory life-extension program for the 400-series Cessnas, which was funded by FAA.

There's an article on it in the current issue of ABS (American Bonanza Society) Mag. Never though of it. I've done it, but not as a part of any preventive maintenance program.

Best,

Dave
 
I've never heard of doing this before. Is it to help corrosion on the contacts? Or to make sure they work? The only one that gets pulled on a regular basis for us is the JPI one because we forget to add the proper amount of fuel on startup every so often.
 
Hey Chris. I'd have to go back and read all the details, but if they are cycled at least annually, they seem to work better. Don't recall the technical explaination; if I see it when I read the mag, I'll try to go back and post it.


Dave
 
Dave, what do you mean by recycling the breaker? Just pulling it out and resetting it?
 
The recommendation came as a side benefit to the Institute's Aging Aircraft Laboratory life-extension program for the 400-series Cessnas, which was funded by FAA.

Do the say to only cycle it once a year?

My concerns are that people would cycle more often then once a year (like every flight) and I bet they would fail (not reset). If you cycle a house breaker too much it's not good for it and it will fail. I am not 100% sure if the breaker in the aircraft would, don't know the construction but I would keep that in mind.


Do they say anything about cycling it too much?

Just my thoughts
Bob
 
In the August 2005 issue of ABS it generally said this.


A visit to the Aging Aircraft Laboratory at www.niar.wichita.edu/newniar/researchlabs/aa_overview.asp
the labs's research results on circuit breakers were discussed. ABS reps were in attendance. The manager of the facility stated that 30% of breakers tested didn't trip after installation at their load. 20% didn't pop when warranted after the breaker had been cycled once. "After being cycled a second time, breakers almost universally worked as designed." To prevent electrical fires, NIAR recommends cycling all new circuit breakers two or three times upon installation, and annually thereafter, to ensure they will trip when called for.

Interesting, huh?

Guess I've got another 'xcuse to go out to the hanger once a year!!

Best,

Dave
 
Thanks for the infor. I have never heard of this before. I have had my plane for the last 6 plus years so I know what I am doing later this week. Thanks again.
 
Ive often wondered what is a good way to test a new breaker.
You can't simply overload them safely can you? Have never read a manual on what if anything can be done.
 
I ask an engineering group I belong to about circuit beakers, below is what they provided me. The pdf file at the web site is a big document, but it is full of information.



The referenced FAA document makes it clear that circuit breakers not be used as switches. The recommendation is to "periodically cycle circuit breakers on and off", basically to improve voltage drop at rated current. The period would have to be determined. They should have said "pull and reset" so as not to make it sound like you were operating a switch.


Boeing has a service letter titled Circuit Breaker Reliability that references DOT/FAA/AR-01/118 (http://www.tc.faa.gov/its/worldpac/techrpt/ar01-118.pdf). Boeing states that they are unable to quantify the benefit or common interval for cycling circuit breakers. Some operators of aging Boeing aircraft have opted to include this recommendation in their C check intervals.


It is common practice where I am to pull select breakers after flight for safety purposes. We have not seen these breakers being replaced more than any others. On the other hand, breakers in circuits where tripping has occured due to component or wiring problems do seem to require replacement more often, especially on the higher amperage rated ones.

Stache
 
Let'sgoflying! said:
Ive often wondered what is a good way to test a new breaker.
You can't simply overload them safely can you? Have never read a manual on what if anything can be done.
Click to expand...

Tripping under overload actually shortens the life of most breakers although the manufacturer does test then to insure proper operation. BTW a standard 20A breaker may not trip at 20 or 21 amps for quite a while. The greater the overload the faster they trip. Personally I wouldn't worry about testing a breaker for correct tripping. As long as they carry the expected load (<80% of rated current) they should be fine.

As to cycling breakers, I think it's a good idea and will probably extend their life somewhat if done annually. According to their datasheet, Klixon push-pull aircraft breakers are rated for 10,000 mechanical (no load) cycles and 5000 cycles under load (resistive).

Switches and breakers for DC are usually designed so that the contacts wipe each other when operated to keep the surfaces clean. I suspect that this is the reason behind the recommendation to cycle them once in a while.
 
Stache said:
Boeing has a service letter titled Circuit Breaker Reliability that references DOT/FAA/AR-01/118 (http://www.tc.faa.gov/its/worldpac/techrpt/ar01-118.pdf). Boeing states that they are unable to quantify the benefit or common interval for cycling circuit breakers. Some operators of aging Boeing aircraft have opted to include this recommendation in their C check intervals.


It is common practice where I am to pull select breakers after flight for safety purposes. We have not seen these breakers being replaced more than any others. On the other hand, breakers in circuits where tripping has occured due to component or wiring problems do seem to require replacement more often, especially on the higher amperage rated ones.

Stache
Click to expand...

If your pulling them as a common practice then your using it as a switch.

The KC-135's have about 20 breakers that are pulled and reset every flight and on eng runs. I don't know if that has shortened their useful life, some of them get so hard to pull you can't do it with your fingers. It makes no sense to me to be pulling them, if they are being used that often, put in a switch!
 
Steve said:
At the power plant we'd rack the breakers out, pull them from the bus, and take them to the test bench where a regulated power supply was connected and the actuation current was recorded.

And the power plant would be Grand Gulf??

Bobby Day, ANO Retiree
Click to expand...
 
You must log in or register to reply here.
Back
Top