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Thread: switches and circuit breakers

  1. #1
    Senior Member ken nougaret's Avatar
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    Default switches and circuit breakers

    hi all,
    im not too savvy in this area so I am looking for suggestions. my build is an SS, O-200, steam gauges, comm, transponder, lights. im looking at which switches and c/b's to buy. I was looking exclusively at aircraft spruce, but after searching threads on this forum I saw a mention for steinair. I went to their website and it appears much easier to shop. any other good websites or is this the best? it looks like the klixon 7277 c/b's would be best. as far as switches, some give specs for the volts and amps and the less expensive ones don't. i'm just a little confused.
    thanks, ken

  2. #2
    Senior Member Av8r_Sed's Avatar
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    Default Re: switches and circuit breakers

    A lot of builders and light sport manufacturers are using ATC/ATO automotive style fuses in a fuse block over the Klixon type breakers now. This gives a greater selection of switch types, styles and sizes to choose from. It also can make it easier to wire your electrical system.

    Selecting switches is based on the circuit's voltage and current ratings and whether it's AC or DC. Most small aircraft circuits are DC (ignition grounding circuits being the exception). Many switches have decent AC current ratings but much smaller DC ratings.

    It's good to make a listing of your circuits and their respective maximum current draw. You'll use this to determine fuse or breakers ratings, wire sizes and select switches.

    I think SteinAir is a good choice of vendor. They know what they sell and can answer questions about your type of installation. They also offer tools that are sometimes needed for crimp pins and connectors you typically find in aircraft.
    -- Paul S
    Model III SN910
    582 IVO Med

  3. #3
    JohnB's Avatar
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    Default Re: switches and circuit breakers

    Ken,
    I am at the same point in my build. Attached is a spreadsheet document (in pdf format) that I used to list my circuit, breaker, and switch needs. I am planning on using the round rocker switches that Kitfox sells. I thought that they look nice and don't take up too much room on the panel.
    _________________________________
    JohnB
    Charlotte, MI
    Kitfox 7-SS
    Rotax 912ULS / Whirlwind Prop
    Garmin G3X Touch

  4. #4
    Senior Member War Eagle's Avatar
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    Default Re: switches and circuit breakers

    I opted to use the EXP Bus system because of the simplification of the install and the safety of the solid state protection and soft start capability for the electronics.

    It is just another option you can consider.

    http://www.affordablepanels.com/cata...tricalhubs.pdf

    Aircraft Spruce handles the product as well.

    http://www.aircraftspruce.com/catalo...ges/expbus.php

  5. #5
    Senior Member HighWing's Avatar
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    Default Re: switches and circuit breakers

    I know there has been a significant movement toward the fuses vs. circuit breakers. For me personally, I prefer the circuit breakers for the following reason. I will on occasion want to power up with certain circuits or devices off. This is very helpful since many modern electronic devices come with no on/off switch. With circuit breakers, it is as simple as pulling a pin or pins with no chance of mixing things up when going back to fully powered mode. This idea is similar to those who elect to have valves just down stream of each wing tank in the fuel system - which I don't. I have worked on both and don't really see an advantage to either in the wiring phase except having to make my own positive buss. I didn't particularly like the aesthetics of the fuse box which protruded outward from the panel about an inch with its cover and consumed about a 30 inch square piece of panel space. Like Ken, I was using steam gauges and needed the space for a chart box. I used the Klixon 7274 on my most recent project. Installing was simple as drilling spaced holes for each, then drilling similarly spaced holes in a strip of brass that then was screwed to the hot terminals of the breakers as a positive buss.

    Regarding the switches and their current carrying capacities, with the LED lighting - position and anti collision, current capacity requirements have been greatly reduced and i honestly didn't pay too much attention to that.
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    Lowell Fitt
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    Model IV-1200 912 UL

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  6. #6
    Senior Member ken nougaret's Avatar
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    Default Re: switches and circuit breakers

    Thank you. You've all been very helpful. ken

  7. #7
    Senior Member Esser's Avatar
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    Default Re: switches and circuit breakers

    Also new to this and just starting to stick my toe in. If I don't go the VP-X way, can I have all my switches at 20amps lets say as long as my CBs/fuses all all correctly sized?

    If there any reason not to use 20amp automotive rocker switches?
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

  8. #8
    Senior Member jrevens's Avatar
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    Default Re: switches and circuit breakers

    No reason at all, Josh. If you have a chance, try to read Bob Nuckolls' section on switches & circuit breakers in his AeroElectric Connection book.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE

  9. #9
    Senior Member jmodguy's Avatar
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    Default Re: switches and circuit breakers

    What john said...
    As far as fuses vs circuit breakers are concerned, breakers are re-settable in flight. Fuses, not so much. That is why civil and military aircraft typically use CBs over fuses.
    There are bus bars made for circuit breakers that make it easy to separate the different busses you might need, i.e. essential, main, and avionics.
    Yes these are experimental aircraft and I am a fervent supporter of those ideas. However some aircraft based best practices are there for a reason.
    As for switches, there are AC and DC rated switches. At low current (assuming 12VDC) there is no much to worry about. At higher currents you will be dealing with average voltage and arcing. Will any AC rated switch work? yes. How long? Who knows. It wasn't designed or tested for that.
    I opted for NTE 12VDC 20A rated rocker switches. Are they "aircraft grade"? nope. but they are 12V DC rated switches designed and tested to handle 12VDC at 20A. Anything 20A or less should be fine.
    Steinair has a great site. The site has pics of pretty much everything so you know what you are getting. I highly recommend steinair.com if you are unsure of what you need or just need to see what you are asking for.
    For placards I recommend engravers.net. Very nice custom placarding and very reasonable in cost.
    Jeff
    KF 5
    340KF

  10. #10
    Senior Member efwd's Avatar
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    Default Re: switches and circuit breakers

    I just spent my entire trip over from CA to Washington DC reading that very chapter of AeroElectric .."switches, relays and contactors". It was very informative. He covers everything including the "knife blade" switch they depict in Frankenstein. I learned a good deal reading this chapter.
    Eddie

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