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01-09-2011, 09:23 AM
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Join Date: Aug 2006
Location: santa barbara, CA
Posts: 1,682
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Here is a wire size chart.
From the product documentation, get the current requirements for each light (amps). Find that value in the chart under the 10degree current rise column and the appropriate wire size is found in the left side column.
http://www.matronics.com/aeroelectri...Wire_Chart.pdf
Contrary to an earlier post, the length of the circuit DOES matter, since resistance and voltage loss increase with length. However for the relatively short lengths used in our planes you should be ok. There is a healthy safety margin built in to the chart numbers.
Erich
Ps
The answer to Every electrical question you will ever have for your plane can found somewhere here:
http://www.matronics.com/aeroelectric/articles.html
Last edited by erich weaver : 01-09-2011 at 09:27 AM.
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01-09-2011, 09:41 AM
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Join Date: Jan 2010
Location: PAWS (Wasilla, Alaska)
Posts: 136
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Electrical guidance
If you download AC43.13-1B Chapter 11 it has usefull guidance for practily any electrical aplication it is available free here: http://rgl.faa.gov/Regulatory_and_Gu...r%2011.pdf Section 4&5 discuss circut breakers and wiring Good luck, Russ
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Russell Brown
A&P/IA
"Happiness may never be sensibly pursued as an end in itself, because happiness is the by-product of achievement." -- Northcote Parkinson (paraphrase)
Wasilla, Alaska
Last edited by AK4x4 : 01-09-2011 at 09:45 AM.
Reason: udate info
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01-09-2011, 11:56 AM
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Join Date: Feb 2006
Posts: 276
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Thanks for the help
I have one switch and one 10A circuit breaker for the HID landing lights. There really is no logical place to put either an additional switch or circuit breaker so my plan is to use a bigger circuit breaker. I have not confirmed the wire size yet so if I have to use a larger guage wire I will just rerun that wire (which would be a lot easier than trying to add another switch or cb).
My best guess is that the panel builder missed the instruction to use two 10A fuses, but since he is no longer available to comment I can only guess that.
One odd thing is that the taxi lights (the standard ones from Van's) are apparently on a 15A breaker. Do the standard incandescent lights draw more current than the HID lights?
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Bruce
Richmond, VA (KFCI)
RV-10 (520+ hours since first flight in Nov 07)
RV-8 (500 hours, sold Sept 07)
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01-09-2011, 01:25 PM
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Join Date: Apr 2009
Location: USA
Posts: 1,499
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For DW 50 Watt HID...
you need 14 ga wire with 10 amp breaker running to each light. I am using 3 switches...one for taxi, landing and wig wag.
All you may have to do is install a dp switch and add another breaker as long as your wires are 14 ga. and you want them both on at the same time.
Another option is to use dp switch, use 20 amp breaker with 10 ga wire running to 6 circuit fuse block, install two 10 amp fuses and run your 14 ga wires from there to switch then out to lights.
DW HID's draw about 4 amps continuously, but more on start up- reason for larger wire size.
75 watt incandescent draws about 5.3 amps.
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Good judgment comes from experience, and a lot of that comes from bad judgment.
Last edited by Wayne Gillispie : 01-09-2011 at 01:37 PM.
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01-09-2011, 01:41 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
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Contrary to an earlier post, the length of the circuit DOES matter, since resistance and voltage loss increase with length. However for the relatively short lengths used in our planes you should be ok. There is a healthy safety margin built in to the chart numbers.
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True, but I believe that was covered by "(upsized for voltage drop if necessary)"
L.Adamson ---- RV6A
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01-09-2011, 01:52 PM
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Join Date: Feb 2005
Posts: 110
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bigger is better myth
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There really is no logical place to put either an additional switch or circuit breaker so my plan is to use a bigger circuit breaker. - MSFT-1
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There must be some place you can add a fuse holder and a 10 amp fuse? Change the switch for the DP per Wayne....done!
Your alternative of a bigger wire and breaker doesn't fix any small wires in the light itself. The manufacturer was clear on the fuse or breaker needed, have you determined that the circuit in the light can tolerate more current?
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Jim Peck
San Francisco Bay Area
RV-7
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01-09-2011, 02:00 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by Lux Wrangler
Your alternative of a bigger wire and breaker doesn't fix any small wires in the light itself. The manufacturer was clear on the fuse or breaker needed, have you determined that the circuit in the light can tolerate more current?
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If that was the golden rule.............. we'd be screwed, in regards to a lot of appliances and machinery. I know what you're saying, but it just doesn't happen.
edit: Personally, I'd rather have the two breakers........one to each wing.
L.Adamson ---- RV6A
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01-09-2011, 03:20 PM
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Join Date: Feb 2005
Posts: 110
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golden rule?
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If that was the golden rule.............. we'd be screwed, in regards to a lot of appliances and machinery. I know what you're saying, but it just doesn't happen. - L.Adamson
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You know what I am saying, but you lost me about what you are saying. I am not putting forth any "golden rules". The Duckworks lights have wires, such as those between the ballast and the bulb; or those wires leading to the ballast, from the connection to ship's power. What are the size of those wires? I haven't looked at mine. I would make sure while increasing the breaker size and wire size to the wing tip, that I wasn't ending up with a circuit with the capacity to fry those Duckworks wires which are part of the light assembly, for instance; or, internal circuit within the ballast? In either case a short circuit could be a concern. So, what is it that doesn't "happen"?
We do agree on two, current limiting devices.
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Jim Peck
San Francisco Bay Area
RV-7
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01-09-2011, 07:42 PM
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Join Date: Apr 2008
Location: California
Posts: 652
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Quote:
Originally Posted by Lux Wrangler
You know what I am saying, but you lost me about what you are saying.
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Jim,
Current is a function of voltage and resistance. The formula is I = E/R, or current equals voltage/divided by resistance.
If a light bulb has one ohm of resistance, then if you supply 14 volts across the lamp, it draws 14 amps. Increasing wire size of breaker size has no effect on this relationship. The only way to increase the current and possibly damage the device would be to increase the voltage.
Bruce,
Another option might be to install a DPST (double pole single throw) switch. Feed one side of the switch and one light from your current 10 amp breaker. Feed the other side of the switch and the other light from another breaker that services an intermittent use device, such as a starter, or cigar lighter outlet. Perhaps you have one that is already 10 amps. I doubt that you would have your landing lights on while you are starting the airplane. Maybe this approach could work for you, depending on what you already have installed.
I might add that the intermittent popping of the breaker could be a) it's a weak breaker, but this is unlikely b) depending on the environment, as the lights get hot their resistance drops a bit and the current increases (pretty likely) or c) your buss voltage could be intermittently going up a bit which would also increase the current (less likely) or d) a, b. and c above.
One way to know is to put an ammeter in line and see what the current draw is. If it's close to 10 amps you would need to make a change as has been discussed before (bigger breaker AND wire or separate circuits).
Don
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WW200RV Dynon D180 HS34 AP74
GNS430 SL30 GTX327 PS8000B Uavionix Echouat
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Last edited by cfiidon : 01-09-2011 at 07:54 PM.
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01-09-2011, 11:16 PM
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Join Date: Feb 2005
Posts: 426
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I think we can conclude that each light draws about 5 amps normally. So under normal use each wire if 18 ga is plenty, remember one wire goes right and one goes left. I would just put in a 15 amp breaker. I look at the breaker protecting you against fire caused by shorts. The length of time it takes to trip a 15 amp breaker if a short occurs is probably a micro second longer than tripping a 10 amp breaker. Both will cause one spark and the breaker is tripped. If you have the unlikely condition where one light draws 10amps steady state, the 18ga wire will handle it. Why only 10 amps? because the other side on the same circuit is drawing 5amps. Any more than 10 on one side and the 15 amp breaker goes.
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John Adams
Seattle
RV7 600+hrs
Paid 12/2014
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