Discussion in 'Instruments / Avionics / Electrical System' started by GESchwarz, Sep 6, 2019.
PTFE insulated wire is available, but ETFE ("Tefzel") has similar properties but is stronger.
Yes I agree with that.
My concern , baseless or not, has always been that wire which is sized for a circuit may deteriorate over time if continuously operated within its range ....but at or very near the peak of that range. Or if a few strands separate, the wire looks fine but actually has a reduced capacity. Breakers operate quickly, but only after the system suffered a problem. So while the system may continue to operate, was there any possible deterioration to the wire by the surge ? Personally I can't say that a circuit that ocassionally trips and has to be reset doesn't gradually cause some deterioration to the wiring, or that it isn't operating near enough to its peak load continuously to be a concern. Obviously the system needs to be checked, but what if readings are within range and the breaker still continues to trip ocassionally? I've just never liked building anything to the minimum spec allowable. I realize sometimes you have to be reasonable about following the designers plans and not use 1/8" wing skins and thicker tubing, but wiring does allow a little room to be flexible.
Circuit breakers, especially those that have operated frequently, can begin to operate at less than set value.
As a follow-up to the LED question : LEDs are current driven, and there are some nasty cheap switchmode LED drivers out there that I wouldn't trust near a radio without thorough testing. A series resistor would be fine.
Wire sizing guidelines like the charts found in 43.13 are based upon millions and millions of hours of real world use - there is no need to add margin on the top to save your 25 hour per year homebuilt from cyclic fatigue.
My Rocket builder apparently got a great deal on surplus wire because every single circuit was #14AWG. Kind of overkill for the LED nav light - I replaced that run with #22. By the time I cut all that bridge cable wiring out and replaced it with correctly sized examples, I realized a net savings of several pounds. And that is not counting the several pounds of #00 starter cable running the length of the fuselage (replaced with #6, and a front mounted battery).
Wiring can be a huge weight penalty if you're not paying attention.
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