AX-O

AX-O

Well Known Member
Guys,
like many of you. I know nothing about electrical systems. That is why we build our own aircraft right? I put this picture up and requested feedback last week but it was in a different post. Could you please throw some rocks at it? I don't have that big of an electrical system but I want to do it right.


site1072.JPG
 
What comments are you looking for?

This is about 90% of Bob Nuckolls design from figure Z-11 of his book. So what kind of comments are you looking for?

Paul
N694BP reserved
 
Looks pretty standard to me. A lot of RV's are flying around with a system very much like this. I didn't look in detail at your choice of wire gauges, but I assume you'll be going by the tables.

One thought I had... you have a bunch of lights connected to your always-hot battery bus. Sure you want to have that many chances to run your battery down? :)

mcb
 
Comments:

Need a question answered for my comments.
Is there an oil pressure switch for the HOBBS?

If there is NO oil pressure switch on the hobbs, I would move the HOBBS/VOLTMETER fuse to the Essential Bus. IF there is a Hobbs Oil Pressure Switch, I would move the Voltmeter to the Essential Bus. It really does not matter IMHO if the hobbs runs during an emergency so it would not matter if the circuit was moved to the Essential Bus. I also like to have the 12V accessory power outlet (what you call a 12V Cig Lighter) hot off the battery. If it is only used for a backup GPS, then place it on the Essential Bus. Why two voltmeters? I see one on the Essential Bus and one on the E-Bus.

Move Engine Instruments to the Essential Bus.

Like someone else said, Do you really need all those lights on the E-Bus? Ask yourself the question: What will happen if I leave them on for over a week between flying sessions?

One suggestion I have on the Strobe light circuit. (Wish I would have done this.) Do not put the Strobe Lights on a switch. Use a PULL type Circuit Breaker instead. This will then act as an alarm as you walk away from the airplane with the master on. IF you are ever working on the airplane with power, just pull the breaker.

I would increase the wire gauge on the Nav/Com to 18 AWG. May need 18 AWG on the Transponder and stobe lights depending on how far the run is. Could start getting too much voltage drop on the smaller gauge wire. I would recommend 12 AWG on the accessory power and E-Bus. Maybe overkill but you may make changes that need it later.
You may get lots of comments on electrical systems that differ from me.
 
Last edited:
mburch said:
One thought I had... you have a bunch of lights connected to your always-hot battery bus. Sure you want to have that many chances to run your battery down? :)

mcb
Click to expand...

I had the same thought. The reason I did that was so when I do a pre flight during night conditions, I can turn the lights on without having to find the Batt switch. Also my wife is no familiar with night ops and it will facilitate her experience (especially loading bags). The lights are small LEDs. I know I know, I can use a flashlight and so can she. Just trying to make it easier for us. If there is no benefit, I can take some of the lights off. Thanks for the feed back
 
RV6_flyer said:
Comments:

Need a question answered for my comments.
Is there an oil pressure switch for the HOBBS?

If there is NO oil pressure switch on the hobbs, I would move the HOBBS/VOLTMETER fuse to the Essential Bus. IF there is a Hobbs Oil Pressure Switch, I would move the Voltmeter to the Essential Bus. It really does not matter IMHO if the hobbs runs during an emergency so it would not matter if the circuit was moved to the Essential Bus. I also like to have the 12V accessory power outlet (what you call a 12V Cig Lighter) hot off the battery. If it is only used for a backup GPS, then place it on the Essential Bus. Why two voltmeters? I see one on the Essential Bus and one on the E-Bus.

Move Engine Instruments to the Essential Bus.

Like someone else said, Do you really need all those lights on the E-Bus? Ask yourself the question: What will happen if I leave them on for over a week between flying sessions?

One suggestion I have on the Strobe light circuit. (Wish I would have done this.) Do not put the Strobe Lights on a switch. Use a PULL type Circuit Breaker instead. This will then act as an alarm as you walk away from the airplane with the master on. IF you are ever working on the airplane with power, just pull the breaker.

I would increase the wire gauge on the Nav/Com to 18 AWG. May need 18 AWG on the Transponder and stobe lights depending on how far the run is. Could start getting too much voltage drop on the smaller gauge wire. I would recommend 12 AWG on the accessory power and E-Bus. Maybe overkill but you may make changes that need it later.
You may get lots of comments on electrical systems that differ from me.
Click to expand...

Gary,
thanks for reviewing the electrical system. I took the RV building first class that Dan Checkoway and you over 2 years ago.

The Hobbs meter is not connected to a pressure sensor. It is the GT-50 (g-meter, clock, timer, voltmeter). The instructions say to hook up the red wire to the battery. That is why the GT-50 is connected to the main Batt bus. The green wire should be connected to the instrument power source or master switch.

I will move the 12V Cig lighter to the Batt bus. The GPS will have it?s own source of power.

The Voltmeter on the essential bus should not be there. I did not catch it.

Will move the engine instruments to the Essential bus.

I will look into moving some of the light off the Batt bus.

Good Idea regarding the C/B.

Will change the wire size as well.

Once again thanks. That is the type of info I was looking for.
 
fuel boost

Just one quick thought, I had the fuel boost pump (and primer) on the ESS bus as you have. I just moved it to the main bus after running my engine for the first time a couple of weeks ago as it meant you had to power up the avionics bus to prime the engine for starting rather than start just from the main bus. This means I can now start with just the Dynon EMS and then power up the avionics after start.
Downside is you lose the ability to run the pump if you lose the main bus which I believe is the reason it is on the ESS in the Z-11 circuit.
This failure mode would mean that I would have to lose the main bus and the engine driven fuel pump to be a problem which I hope would be very unlikely.
Another one of those choices we have to make.
 
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