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ccwacker(at)HOTMAIL.COM
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 Posted: Sat Nov 10, 2007 9:41 pm Post subject: Avionics Master Switch: To install, or not to install |
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I have a dual electrical system. Seperate master relay, alternator, voltage regulator and battery. I have a full panel and and was concerned about the load on the Jabiru alternator wih so much stuff.
By the way do not use a Cessna type master switch. They are prone to failure.
Chuck Wacker
N601XL, Quick Build
| Quote: | Subject: Re: Avionics Master Switch: To install, or not to install
From: wr.giacona(at)suddenlink.net
Date: Fri, 9 Nov 2007 23:21:24 -0800
To: zenith-list(at)matronics.com
--> Zenith-List message posted by: "Gig Giacona" <wr.giacona(at)suddenlink.net>
All I can say is I've never flown and aircraft that had an electrical system that didn't have one. That doesn't make it right but...
txpilot wrote:
> I'm currently working on my electrical system using Bob Nuckoll's 'Aeroelectric Design' book as a guide. This book is an excellent resource, but I'm not sure about his suggestion not to install an avionics master switch. He claims it causes more problems than it solves because the switch itself can be a single point of failure for all avionics.
>
> He also says modern avionics are robust enough to take voltage fluctuations and therefore don't need an AMS. I'm planning on installing relatively old technology radios: KX-155, KT-76A and a standard sigtronics intercom.
>
> Any thoughts? What's everyone else doing? BTW - I'm not intending on installing a secondary AMS. This is a day VFR only airplane and I'm trying to keep it simple.
>
> Thanks,
>
> Dan Ginty
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W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=144874#144874>
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dredmoody(at)cox.net
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| Posted: Mon Nov 12, 2007 8:04 am Post subject: Avionics Master Switch: To install, or not to install |
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If absolute simplicity is not the goal, you should have the avionics master switch supply an avionics bus as you said, but coming from that bus, each electrical consumer should have its own breaker or fuse with the appropriate amp rating to protect the one appliance it serves. I know from painful experience burning out a Ray Allen servo system that lumping things in under one breaker rated for the sum of all the users is not a great idea.
Dred
---- ashontz <ashontz(at)nbme.org> wrote:
| Quote: |
Actually, if anything it may may the installation cleaner, you have everything going back to a common terminal strip anyway, I would hope anyway, not a big deal to just add a switch to that whole terminal strip. Or how about if you're doing maintenance later in and around one of those instruments, instead of disconnecting the whole battery you can just flip the switch off and be able to work around the instruments without worrying about shorting something out. Plus you can add a breaker to the whole terminal block that services the instruments. Seems like a "best practices" thing to me to add a master switch.
When I get to the point of doing my instrument panel I'd like the whole thing to be able to just slide out and have the terminal block and everything on a tray along with the instruments, that way I can install all the instruments on my work bench and then just slide the tray in and connected one or two wiring harnesses. Nothing beats clean installations. Make it easier to work on for sure.
do not archive.
jetboy wrote:
> I went with simple, no avionics master, and I never bother turning the stuff I normally run (KY97a) on or off either. That just wears out the controls. I have run this same radio in 2 planes over the last 15 years, no problems. It was in a C150A with the pull starter and generator, no avionics master, not even the 'dump the radios while the keyswitch is cranking' facility.
>
> Those 'older' radios are compliant to DOD 160, something that some of the newer round hole mount types seem to be lacking. You can tell the cheap ones by the messages on their websites about "must install after avionics master and xx,000 uF capacitor" The problem with these is they actually have no physical switch of their own, and the electronic switch is 'susceptible', so this class of device does benefit from a separate switch.
>
> I'm with Bob's philosophy here, and if things go bad on a murky day you really just want to fly the airplane without getting mixed up in complicated systems that lead to more troubles than you started with. Sorry it doesnt make for a very impressive cockpit, bit like when I got into a Piper Cub after training in C172's and literally wondered if I could safely fly this machine because it lacked almost every item that I thought was needed for the journey. And it didnt have an avionics master.
>
> Ralph
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Andy Shontz
CH601XL - Corvair
www.mykitlog.com/ashontz
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=145388#145388
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Mon Nov 12, 2007 5:42 pm Post subject: Avionics Master Switch: To install, or not to install |
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The fuses are there to protect the wiring, not the devices that are connected to it. A fuse or breaker will not prevent an electrical device from shorting out internally and frying, but it will prevent that short circuited device from overheating the wiring and filling the cockpit with smoke. A fuse or circuit breaker rating is determined by the size of the smallest interconnect wiring supplied by that fuse. The biggest advantage of dividing up the electrical load into smaller chunks with more fuses is that you may save weight overall by using smaller supply wire on all those circuits since modern fuse blocks with mini fuses are much lighter than the old style individual sockets for glass fuses.
On Nov 12, 2007, at 11:03 AM, <dredmoody(at)cox.net (dredmoody(at)cox.net)> <dredmoody(at)cox.net (dredmoody(at)cox.net)> wrote:
| Quote: | --> Zenith-List message posted by: <dredmoody(at)cox.net (dredmoody(at)cox.net)>
If absolute simplicity is not the goal, you should have the avionics master switch supply an avionics bus as you said, but coming from that bus, each electrical consumer should have its own breaker or fuse with the appropriate amp rating to protect the one appliance it serves. I know from painful experience burning out a Ray Allen servo system that lumping things in under one breaker rated for the sum of all the users is not a great idea.
Dred
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--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
[quote][b]
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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