Question on Adding Avionics buss to Z11

[Don Patterson]

I am starting the wiring of my 7a and was thinking of using the aeroelectric Z-11 drawing. I would like to add an avionics buss to the print and my thinking was to add a switch breaker to the endurance buss in the same fashion as the endurance alt feed from the main battery buss. The switch breaker would protect the wire feeding the avionic buss and also act as my avionic master switch. Any feedback on the subject would be appreciated.

[dan]

Sounds like a single point of failure to me. Why not just distribute your avionics on the existing main bus & e-bus as per endurance needs?

[PaigeHoffart]

You can still use the main and endurance buss concept, and switch off your avionics with a single switch, if you get a 4PST switch. Digikey and Mouser both carry 4 pole switches. You could argue that it's still a single point of failure, but you have 4 contacts, and 4 breakers / fuses, so the risk of losing everything is lower.

I have not seen anything bigger than a 4 pole switch and using a relay would defeat the purpose (many more failure modes than even a simple bus)

In my case I needed more than 4 contacts, so I used 3 contacts to switch the avionics on the endurance bus, and I fed a small fuse block with the 4th contact for everything else.

Another option would be to provide a backup feed for the avionics bus just like you do for the endurance bus.


Paige
RV-8A

[az_gila]

Originally Posted by PaigeHoffart

....
Another option would be to provide a backup feed for the avionics bus just like you do for the endurance bus.

Paige
RV-8A

I agree with Dan's earlier post....

But... if you do make an additional Avionics Bus, make it identical to the Endurance Bus, but with a switch ("Avionics Master") in series with a second diode.

If you install an additional alternate feed switch just like the endurance bus, you should have no single point failures...

....again, I still like Dan's answer better....

gil A

[PaigeHoffart]

If you install an additional alternate feed switch just like the endurance bus, you should have no single point failures...

Instead of two alternate feed switches, why not just one 2 pole alternate feed switch? Hook one side to the endurance, and one to the avionics. Would there be a situation where you would want endurance but not avionics?

Paige

[az_gila]

Originally Posted by PaigeHoffart

Instead of two alternate feed switches, why not just one 2 pole alternate feed switch? Hook one side to the endurance, and one to the avionics. Would there be a situation where you would want endurance but not avionics?

Paige

Depends on the failure, two separate switches would give isolation of the buses...

But, your question echoes Dan's posting... normally some of the avionics would be on the regular bus, and some on the endurance bus.

With a separate avionics bus, you would have to do manual load shedding, not a big deal, but might take time and concentration in an emergency situation...

gil A

[Don Patterson]

Thanks for all the input on the avionic buss question. There seems to be a few ways of wiring this buss to prevent a any one failure, causing a loss in the avionics.
Thanks again.