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Old 03-02-2018, 06:02 PM   #1
Flybyjim
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Default Circuit breakers

I am having SteinAir produce the wiring harness for my Garmin G3X system as this is one area I am not comfortable with. I must say all the folks at SteinAir have been wonderful to work with. They are very thorough with explanations and suggestions as I am finding out as I go what I do not know about all the glass screen systems. As Joshua and I were talking today about the can buss routing I became aware how important it is to design the system layout and locations of the interconnecting items. I also was surprised to find how many circuit breakers were required for this G3X system. I assumed (wrong thing to do) there would be just a couple of breakers for the system, well, I receive the list from Joshua, 9 circuit breakers for the G3X Screen and all components within the can buss. Plus the ones needed that I knew about for other items such as but not limited to Landing lights, strobes, nav lights, heater fans, and power outlets. Thinking about the Kitfox panels I have seen I am wondering where have folks put all these breakers as many panels only show a few breakers.
Back to the panel drawing board as I work this out.
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Old 03-02-2018, 06:19 PM   #2
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Default Re: Circuit breakers

Put a fuse holder behind the panel. Cheaper, easier and does exactly the same job. Plus you don't have to fill your panel with little black circles.
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Old 03-02-2018, 06:27 PM   #3
Flybyjim
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Default Re: Circuit breakers

If the fuse panel is behind the main panel how do you access it if there is an
issue?
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Old 03-02-2018, 06:55 PM   #4
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Default Re: Circuit breakers

Quote:
Originally Posted by Flybyjim View Post
If the fuse panel is behind the main panel how do you access it if there is an
issue?
In the air? You don't. Anything that can start a fire you troubleshoot on the ground.

Twenty years ago I would take somebody on a Europa demo flight and they would inevitably ask about the EIS system "what do you do if it quits?"

I'd always reply the same, "fly the plane".

"What about RPM, or oil pressure?"

I'd always reply, "It had oil pressure before the engine monitor quit and it will be fine until I land".
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Old 03-02-2018, 07:01 PM   #5
Flybyjim
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Default Re: Circuit breakers

Yes, I get all that maybe I should have asked this in another way. Where do you mount the fuse box or circuit breaker to have easy access?
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Old 03-02-2018, 07:02 PM   #6
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Default Re: Circuit breakers

I agree, Ronin.

There's another thread on the subject; "Breakers". This are my thoughts as expressed in that thread:


Quote:
is a subject much discussed in electronics books and advice and I'm going down the fuse route, instead of CBs (mostly).

Questions that need to be considered are:

What items are there that are so critical to flight that you need to have access to them while up in the air? I have two ('backup battery' circuit for Rotax 912iS and battery isolation for a Lithium battery....madatory for the UK and, I think, a good idea). For these two circuits I'll have 30A CBs in the panel. For everything else, so what if I lose the radio, transponder, EFIS or iPad charger. Look out the window and do what we did before we got all that kit.

To me the more important thing is WHY has that CB popped? They don't do it just for fun and that means there's a snag with that system. Is being up in the air really the time to start trying to second-guess why your iPad charger has shorted? Do you need it so desperately that it needs to be re-set now or can you wait until you're on the ground?

Space, weight and cost are also considerations but I think the two points above are more important.

Because of all this I'm going down the fuses route. I'll have the fuse boxes (I'm using one as the main bus and a second as the avionics bus) under the panel where I can gain access to them but, realistically, only on the ground.

I like the Vertical Power system and I think electronic circuit breakers are a great system (MGL do a reasonably priced one) and if I were building an RV or similar then I'd definitely be looking at one. However, for my aircraft (a Eurofox) the flaps are manual, the trim is manual, wig-wags are pointless because the landing lights are tiny and in the nose and the starting system goes straight from the battery to the engine. Yes, I can use the ECB as a great way of programming and controlling the CBs but a lot of the functionality of the VPX would be wasted and that's why I opted not to go down that route. If I had all the gizmos above then I would be sorely tempted

So, to answer the question, the panels you see either have an ECB or they have fuses hidden behind the panel (or similar).
Edited to add: I will mount my fuse boxes on the firewall so I can see them when I look underneath the panel. Some people have mounted them in the panel itself (but my OCD doesn't like that). Even more creative people have created drop down panels that are hinged under the front of the instrument panel and fall down so you can see the fuses (I quite like that idea), or even put them into the back of a glove box so you can see them by looking into the void. There's some clever people out there
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Old 03-02-2018, 10:33 PM   #7
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Default Re: Circuit breakers

My fuse panel faces down just behind the panel above the passengers knees.
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Old 03-03-2018, 02:07 AM   #8
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Default Re: Circuit breakers

Hi Josh,

Did you do something like make a plate that attaches to the back of panel and cut a hole in it for the fuse box to face down (so the fuses are viewable from below the panel, looking up)? If so, did you just wire out the back of your fuse box or did the wiring still come from the front/sides? I think I know the answer and that sounds like an elegant solution, but would just like to confirm it.

At the moment I'm considering making a 'shelf' behind the panel (mostly on the pax side) onto which I'll mount things like my radio, transponder, Rotax ECU etc. I was thinking of making it out of that aluminium with lots of holes in it as I thought it would be lighter than sheet metal and you could use the holes for the equipment bolts. I quite like the idea of cutting a couple of holes for the fuse boxes to face down and then just have the wires all coming from the bottom of the fuse box (which is facing towards the top of the panel).

HHmmmm, more thinking required
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Old 03-03-2018, 02:45 AM   #9
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Default Re: Circuit breakers

Here’s how mine is. I just took scrap aluminum angle and fabbed something up. Everything is just wired to the back of it.
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Old 03-03-2018, 06:08 AM   #10
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Default Re: Circuit breakers

I have most of mine on the panel, with the really non-critical ones on the backside. Haven't blown any so far.
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