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Two Ground Blocks?

TheFrisco

Member
I am redoing my RV4 panel, with new Dynon avionics and a Vertical Power VPX. So all the + connections are pretty straight forward, plus wiring harnesses are all there but what about the GROUNDS?

I read that they recommend 2 ground blocks, one for the avionics and one for the rest.

Does that make sense? Where do they typically go? Do I connect them just to the frame as the previous connections all were or do I run a heavier gauge wire to the battery directly?

Thanks for your thoughts and comments!
 
You can use as many ground blocks as you need, you just want to make sure that they are all at about the same potential - meaning connected to each other with as little resistance as possible. This connection can be via the airframe or with the right size wire.

I'm sure others will go into more details, and there are a lot, but this is the basic principle.
 
Z-11

The attached Z-11 schematic from the Aeroelectric Connection may be of help for the various ground points. They recommend dedicated wiring between these ground points, rather than through the airframe. It would be typical to have a "forest of tabs" at each of the avionics and panel ground busses.
 

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Ground Loops

So I have several ground blocks on my build (-7).

In the end, I decided that the blocks should be isolated from the airframe and connected with an appropriate size wire to the main ground block on the firewall to help prevent ground loops.

The fire wall ground block is the forest of tabs style that penetrates the firewall and the NEG battery cable is connected to.
 
You can use as many ground blocks as you need, you just want to make sure that they are all at about the same potential - meaning connected to each other with as little resistance as possible. This connection can be via the airframe or with the right size wire.

I'm sure others will go into more details, and there are a lot, but this is the basic principle.

This ^^^. I have four, and I use screw type grounding bar with substantial wire interconnections back to central ground point. No issues for 21 years.
 
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Bob Nuckolls' Aeroelectric Connection

If you choose to reference Bob Nuckolls' Aeroelectric Connection:

  • Some ground bus names have changed over time... I made a cheat sheet.
  • The Z schematics normally show two ground buses, firewall ground bus and avionics ground bus.
  • Bob covers grounds in general in Chapter 5 and the D-sub style avionics ground bus specifically in Chapter 18. A quick quote from Chapter 5: "Ground loops are pretty simple and occur only when two
    components of the same system (victim) are grounded in different places in the airplane."
  • The latest Z schematic revs are not in the Aeroelectric Connection book but are online... I made a cheat sheet for that also.

Many devices that are not victims can be locally grounded: pitot heat, landing lights, interior lights, seat heaters, 12V outlets, USB chargers, defrost fans, PTT buttons, stick buttons... and in my case, the ShowPlanes flap control box which is located next to the flap motor.
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If you choose to reference Bob Nuckolls' Aeroelectric Connection:

...

Many devices that are not victims can be locally grounded: pitot heat, landing lights, interior lights, flap motor, seat heaters, 12V outlets, USB chargers, defrost fans, PTT buttons, stick buttons.
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Minor correction to this post: Both wires on the flap motor are connected to a switch or VP-X or flap controller. Do not ground one of the flap wires directly. :)
 
thanks for the correction Marc

Minor correction to this post: Both wires on the flap motor are connected to a switch or VP-X or flap controller. Do not ground one of the flap wires directly. :)

Thanks Marc, I edited post #6 to state flap control box, not flap motor, can be locally grounded.:)
 
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