andrew.d.zachar(at)gmail.
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 Posted: Tue Jan 11, 2011 7:01 pm Post subject: Very Simple Question about landing lights, wire size, and c |
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On Tue, Jan 11, 2011 at 9:29 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> But do they DRAW 55 Watts of power in operation?
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A gentlemen on the VAF forums was kind enough to point me to these lights, and at $30, even if they don't perform well in an airplane, I figured it would be a good investigative exercise for me (and the aeroeletric list). I'll try to gather up some data on the lights and report back.
| Quote: | You cited 24 foot runs, is this a round-trip for power+ground?
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Yes, it was for round trip, but only because I was ignoring the convention that these kinds of loads can be locally grounded. I know this next question can open up a pretty large (and already covered in some of your articles) conversation about the pro and cons of running grounds back.
Even if these loads, which are typically grounded locally don't normally contribute to noise, if I have the room (and presumably excess useful load) for it, is it bad to run the grounds back? I'm guessing it's no worse than grounding locally, it may even be negligibly better in terms of noise, but more of a "bad form" given that I'm adding more weight and complexity for a small (if anything other than perceived) benefit. I'm getting stuck on the "normally these aren't suspects for noise generation" and "maybe I can absolutely prevent any noise by running the grounds back." My lack of knowledge about potential noise issues is showing again. Sorry. (I need to brush up on the section of AEC again...)
| Quote: | This isn't a current ratings discussion. It's
a failure tolerance discussion. If you'd like to
have no single point of failure for both lamps,
then separate fuses is called for. A single 2-pole
switch adds some risk for single-point failure but
its tiny. |
For me, it is actually failure tolerance versus aesthetics and switch space. I'm using your philosophy that I should assume everything in the airplane will fail, and the failure of anything in the airplane doesn't prevent me from safely continuing (or just completing) a flight. I prefer one switch for the landing lights and I think I'm okay with a single point of failure (whether it be a DPDT switch or a switch-breaker) given that the failure is just a no-landing-light landing. (I may still put a taxi light out in the wing tip separate from these HIDs...that would provide me at least a little light in the case of my single failure. I better be careful though, I may end up being lit up like a Christmas tree.)
| Quote: | Your HID lamps almost certainly don't exhibit this magnitude
of inrush. So a pair of 7A fuses/breakers driving 20AWG wires
is just fine. |
My lack of experience all things electrical is showing here. I think an investigation of the lamps and their inrush versus steady state loads when they arrive will yield some education on my side and some data for the list.
| Quote: | The only suggestion I have is to confirm there REAL running current.
But in any case stay with 20AWG/7A protection.
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I'll do just that.
Thank you for the great guidance, as usual. I'll report back soon.
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Andrew Zachar
andrew.d.zachar(at)gmail.com (andrew.d.zachar(at)gmail.com)
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