Circuit Breaker Failure

[chuck]

After about a year I had a failure of a 3 amp tyco/potter&brumsfield W23X1A1G-3 breaker. Breaker was purchased new from B&C. The failure got me stranded since my PMag was on it and the other Mag doesn't have the impulse coupler.

I assumed that breakers failed either open or closed or perhaps some jiggly intermittant. This one failed differently. I had battery voltage of 12.5V on the line side and the load side measured 10.5V. This was the case with and without the PMag connected. The impedence across the breaker is 350 Ohms. Putting a new breaker in and of course I had 12.5V on the output and it started on the second blade.

Is this a 'common' way for breakers to fail?

[Walt]

you get the good stuff from the start. B&C has some great stuff but breakers and switches aren't one of them. If you stick with Klixon 7274-2-XX and honeywell TL series switches I can practically guarantee you will never have another failure. I've been working on Boeing/Douglas for the last 22 years and can probably count on one hand the number of times I've seen a breaker fail and never a switch. These are in planes that are used an average of 8 hours a day 7 days a week so in an RV I expect them to outlast the rest of the airframe. These will definately cost you more that the industrial switches I see most folks use but they are well worth it.

[chuck]

Walt:

Thanks for the input. I'll look into the Klixon's.

I took the breaker appart and it doesn't appear that it was a corrosion issue on the contacts. As far as I can tell there is a little part that looks like a resistor (perhaps a small fuse) that is soldered to the load terminal. The resistor leg broke at the solder joint. I can't be sure that I didn't break it while disassembling so take this for what it's worth.


Chuck

Walt, what is your knowledge of the switches sold by B&C? As I recall, they are Carling brand (or at least were when I bought all mine 3+ years ago). So far mine have had no problems, though I only have about 135 hrs on the airplane. I would be interested in knowing what service history or failure data there is on the Carlings, if those are the ones you were referring to......

John

[gmcjetpilot]

Originally Posted by Walt

you get the good stuff from the start. B&C has some great stuff but breakers and switches aren't one of them. If you stick with Klixon 7274-2-XX and honeywell TL series switches I can practically guarantee you will never have another failure.

Ditto, second vote for Texas Instruments Kilxon. To answer your question that is an odd way for a CB to fail. Also I am surprised the P-mag would not work on start up with 10.5 volts? That's I guess the advantage of the CDI ignition (Light speed) verses a Inductive system (Emag), the CDI can run on lower voltage. Either way good on you for finding it. The new CB should last a lifetime even if it's of the same type.

[chuck]

Originally Posted by gmcjetpilot

Ditto, second vote for Texas Instruments Kilxon. To answer your question that is an odd way for a CB to fail. Also I am surprised the P-mag would not work on start up with 10.5 volts? That's I guess the advantage of the CDI ignition (Light speed) verses a Inductive system (Emag), the CDI can run on lower voltage. Either way good on you for finding it. The new CB should last a lifetime even if it's of the same type.

George:

It is my strong belief that the resistance went up when a real load was placed across the breaker and thus further reduced the voltage. Sort of like what happens when you have corrosion on a car battery. It's a theory I can't test since I took it appart. I am told, but have not verified, that a PMag will fire a spark with a 9V battery.

Chuck

[Walt]

Rutus, no scientific data... it's just a suggestion for those looking for a better than average component. I've read on these forums in the last year about more failures with these simple (but critical) items than I have seen in 22 years working on jets. Don't "cheap out" on the small stuff or you may be plagued with problems down the road. If you shop at radio shack for your airplane you're asking for trouble!

[az_gila]

Originally Posted by Walt

Rutus, no scientific data... it's just a suggestion for those looking for a better than average component. I've read on these forums in the last year about more failures with these simple (but critical) items than I have seen in 22 years working on jets. Don't "cheap out" on the small stuff or you may be plagued with problems down the road. If you shop at radio shack for your airplane you're asking for trouble!

If you equate reliability with minimum complexity (or least number of parts)... it's pretty hard to beat the simple fuse...

gil in Tucson

[Walt]

I use the nuckle (sp?) wiring with fuses, however, I do have some breakers for the alt field, OVM on the backup alt and on one of my lightspeeds which has a direct battery feed (the other lighspeed is off the batter bus which uses fuses).