What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Question for AEC Z11 Mod for E-Bus

avrojockey

Well Known Member
Patron
Electrical novice needing help...

My RV-9A does not have an E-bus (endurance/essential), just a switched Battery Bus (master switch) and a Avionics Bus, switched through an avionics switch. All circuits are protected with hard-to-get-to-but-still-inflight-accessible fuses.

If IMC I want the ability to kill power to everything but the essentials to isolate shorts while aviating and communicating...near impossible to do in the current configuration, certainly not quickly while maintaining aircraft control. The new E-bus will have CBs or easily accessible fuses.

I'm using Z11 schematic as a starting point, but I want to change a couple things...see pictures...changes are in red.
  1. I removed the Hot Battery Bus because all I need is the E-Bus feed
  2. I removed the Diode and replaced it's function with the STDP switch thats ON/ON, so the E-Bus is fed by the normal switched Battery Bus OR directly from the battery. This will be a guarded switch.
  3. Increased to 14AWG wire to handle greater load requirements and longer wire runs.

Is there anything I'm missing? Is the diode still required? Do I need further protection somewhere? Will this kill me?

Thanks!
Tim

Z11new.jpg

Z11.jpg
 
In your revised circuit, a diode is not needed because there is no way
for current to flow from the E-Bus to the main power bus.
-
Fuses isolate shorts. No pilot action required.
-
Can it kill you?
What if the 10 amp breaker trips? There is a reason that the main power bus is not protected by a fuse or circuit breaker.
That long 14 AWG wire connected to the battery is always hot. It could make sparks and ignite spilled fuel after a forced landing.
A pilot should have the ability to shut off all electrical power at the source.
 
What if the 10 amp breaker trips? There is a reason that the main power bus is not protected by a fuse or circuit breaker.
Most of the components powered by the E-Bus have dual power inputs with internal diodes, so if the 10A CB pops then the short is in that
circuit and I can repower the Main Power Bus? Is this rational? I was just going by the original Z11 design has a 7A fuse protecting the E-Bus
I just increased the load with the wire gauge.

That long 14 AWG wire connected to the battery is always hot. It could make sparks and ignite spilled fuel after a forced landing.
A pilot should have the ability to shut off all electrical power at the source.

What if I change the SPDT switch to a DPDT to also control an added S704-1 relay forward the firewall similar to the Z13/8 design?
This would eliminate the long run of live 14AWG unless you needed it in an emergency. If things got bad, prior to forced landing
the E-Bus switch would be killed in addition to the Battery Master.
 
Last edited:
Bob's E-Bus was intended to supply power to a small essential load, thus 7 amps. Essential means
different things to different people. Many builders connect loads that are essential to them but
not to others. I would increase the essential bus circuit breaker size to at least 20 amps.
An E-Bus relay will allow the pilot to shut off power near the battery.
 
Back
Top