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EXPBUS II - versus circuit breakers

Marlonyoung

Well Known Member
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I have acquired a RV4 project that has been stalled for a long time; for over 30 years I have own, maintained (with my I.A. father) and fly a C195 and Citabria.
This is my first foray into Experimental and building, so you might see post from me in the future.

I am just now getting into the electrical system, and it looks like they were planning on using an EXBUS II circuit board in the place of the battery relay (looks like they did plan on a starter relay/solenoid but they were using this circuit board with integrated toggle switchers as the master switch, battery relay and overvoltage protection circuit in leu of circuit breakers. Aircraft spruce does have the EXBUS II listed in their catalogue, but this is something I am completely unfamiliar with. Before just pulling it and replacing it with standard toggle switches and circuit breakers I thought I would reach out to see if anyone had used this system before or had experience with it.
 
I have it in our 6 but I'm not that familiar with it other than it auto resets if it trips a circuit. I've put a few hundred hours on it and so far it's been trouble free.
 
Lots of them still installed. I have one in my 8 which works flawlessly but others have had some problems. The units are no longer manufactured or supported. The EXP II also limits your future options as it only has X number of each amp size breakers.

For those reasons, if I were building a plane today, I'd go with breakers. Seems you're at a point that you can go either way. If you decide to not use it, I'd be interested in buying it as a spare.
 
If you want electronic breakers, Vertical Power seems to be the one everybody is using these days.
 
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If I were to build again, I would use a fuse panel for the majority of items and pullable breakers for the few critical systems that don't otherwise have an "off" switch. Such as: Trim, Flap Motor, Alternator Field, Autopilot, Starter Contactor.

The fuse panel allows for easy upgrades in the future and can be tucked away nicely.
 
I have 2 EXP-buss boards remoted. One board for the avionics and one for the rest of the electrical system. Works as intended and costs 1/5th of what a Vertical Power system costs.
 
Lots of them still installed. I have one in my 8 which works flawlessly but others have had some problems. The units are no longer manufactured or supported. The EXP II also limits your future options as it only has X number of each amp size breakers.

For those reasons, if I were building a plane today, I'd go with breakers. Seems you're at a point that you can go either way. If you decide to not use it, I'd be interested in buying it as a spare.

I have had one installed in my RV6 since 2002. The plane was featured at the Control Vision booth at Oshkosh in 2003. Worked with no issues (other than the time when my leaking tip-up allowed it to get filled with water!!). I was able to wire it with AUX BUSS and BBAT (backup battery) charging.

[Later, for a total rewire on the RV8, I went with FUSE BLOCKS as I wanted a LOT more items protected.]

If it covers everything you would imagine for your mission, it works just fine. For new installations with a LOT MORE electronics these days, especially an IFR setup, I would take a different path. My personal preference just happens to be fuse blocks.
 
Works as intended and costs 1/5th of what a Vertical Power system costs.

Same here… installed one a few years ago in a previous aircraft of mine, and to this day works perfect. Installation was easy, and the physical size small.
 
Worked great, until it didn’t

Had one in my -6. Worked just fine for 10 years and then one day it didn’t. Replaced it with switches and fuse blocks. Agree with the limitations noted above. Doing it again I’d go with fuses or breakers.
 
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Thanks for the info - since they have it wired in (put sitting for 10 years) I will probably try to power it up and see if it still works. I have very little need for electrical (basic VFR only) so redoing would not be significant, but then this may be adequate. Decisions!
 
The problem with them is that most people to not understand them. It took me quite a while to figure out. Once I did, I like it.
 
Ooops!

I have had one installed in my RV6 since 2002. The plane was featured at the Control Vision booth at Oshkosh in 2003. Worked with no issues (other than the time when my leaking tip-up allowed it to get filled with water!!). I was able to wire it with AUX BUSS and BBAT (backup battery) charging.

[Later, for a total rewire on the RV8, I went with FUSE BLOCKS as I wanted a LOT more items protected.]

If it covers everything you would imagine for your mission, it works just fine. For new installations with a LOT MORE electronics these days, especially an IFR setup, I would take a different path. My personal preference just happens to be fuse blocks.

Oops!!!!!

Thought I was typing into a Private Message. Message did show up as sent. Now I know why. :)

The EXP Bus II has worked for me for over 20 years. Don’t know how many more but I give it credit for those.

By the way, I installed the ***REMOTE CONTACTOR***. The little on-board relay did not suit my fancy.
 
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