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Circuit breaker life as switch.

S

Sid Lambert

Well Known Member
I'm planning more of my wiring and I will have dual P-Mags.

My question is more electrical than EIS but here goes.

In making a test switch for the P-Mag system, is it acceptable to just have a pullable breaker? I am worried that pulling the breaker during every pre-flight will wear it out. I also won't have any other breakers, all fuses.

My other alternative is to wire a DPDT switch that is wired Off(grounded)- On(Test-No power) - On(Normal). I worry this will add unneeded complexity to the EI wiring though.

Any tips from people who have done it?
 
P&B Breakers

Sid,
The garden variety P&B W23/W31 breakers are rated at 10K mechanical operations, (6K under full load) and are specifically called out for use as an on/off switch. That's comparable to a regular toggle switch.

Reliability is an issue if you are driving your ignition system and a few of the W series I've seen failed due to the little zigzag heater wire breaking (vibration?). Might want to consider the Klixon Mil-Spec stuff for a critical circuit.

Other than that, using it as a switch should be OK.
 
Heat may be an issue...

The only issue I've had with my ignition system is the switch breakers I installed. On real hot days, one of them won't turn on, it's like the heat "fools" the breaker into thinking it's seeing too much resistance, so it goes into the tripped condition. In Idaho last year on my way back from Oshkosh I went to restart after a fuel stop and was unable to turn on the breaker. The temperature on the ramp was 105 degrees and the plane sat in the sun for 30 minutes. I did all the diagnostic stuff on the ignitions themselves, but the problem was the switch. Next morning, when it was cool, the switch breaker functioned normally. The same thing happened last year when I parked the plane on the ramp for a static display. It was real hot that day and in the afternoon, I went to taxi the plane back home and couldn't turn on that same breaker. After it cooled off, it worked fine. I can't remember where I ordered these switch breakers from, but I'm looking for a better alternative.
 
Part numbers?

Bob Brown said:
The only issue I've had with my ignition system is the switch breakers I installed. ....
After it cooled off, it worked fine. I can't remember where I ordered these switch breakers from, but I'm looking for a better alternative.
Click to expand...

Bob... do you know the part number of the breakers you installed?

gil A
 
Bob Brown said:
On real hot days, one of them won't turn on, it's like the heat "fools" the breaker into thinking it's seeing too much resistance, so it goes into the tripped condition...
Click to expand...
This happend to me on my fuel pump switch. I replaced it and never looked back. That is the sign of a defective breaker.
 
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