Grounding

[Archer39J]

Researching electrical grounding I find some advocating local grounds for things like pitot heat and landing/nav lights in the wing. Will this work in our planes? Or is it best to run a ground wire all the way back?

[Chris In Milwaukee]

Always a touchy subject, grounds. For position or area lights, especially LEDs, I don't see any reason why local grounding won't work. It only takes a small amount of current to light one up, so grounding is probably not a big deal. High-current things, like pitot heat, will probably work best when they've got a solid, low-resistance path to ground. In that case, a dedicated ground line back to the grounding block is probably a good idea. Incandescent bulbs, like those in steam gauges are probably okay with local grounds. Higher-current lights, like LED landing lights, I'd probably go with central ground.

Device chargers can be really finicky with their ground preference. I have a couple of Stratus Power USB chargers in my plane. They *really* wanted grounds on the ground block. They didn't like local grounds at all, especially with a higher-current device like an iPad Pro. Any and all avionics, I'd certainly go with central grounding.

A good chunk of my electrics are centrally grounded on the firewall.

Happy to hear about others' experiences as well.

[Archer39J]

I suppose the added weight/cost is minimal enough to just throw a return in with the same bundles. More electrically clean as well.

[Chris In Milwaukee]

Generally speaking, I'd say so. Lessens the likelihood of a funky ground loop that can cause noise. Which reminds me, if you've got something that can be grounded by screwing to something, and you plan on running a dedicated ground wire back to a central location, it's a good idea to isolate that "thing" from ground so when you fasten it to whatever surface it doesn't create multiple ground paths. That's a potential noise generator for sure.

Here's an example of one:

shoulder-washers-2-1.jpg

This way, you've a screw can pass through it without touching the side of the hole, and also isolates it from the surface.

[Chris In Milwaukee]

Google "isolation washer". You'll find all kinds of them :-)

[Bcone1381]

I did not know that about the problems multiple ground paths can cause! Great idea, Chris. Thanks for sharing! Do you have a favorite source for those grommets?

[Chris In Milwaukee]

I’ve only dealt with them in military applications and haven’t had a need to buy any yet. I’m sure Google Shopping or eBay will reveal plenty of options. Just need to make sure you get a washer appropriate for the thickness of material and screw size you intend to use.

[rodsmith]

Garmin instructions for a magnetometer in the wing is that all electrical wiring in the wing be shielded pairs grounded centrally. Interesting that instructions for both my LED landing lights and position/strobe LEDs also recommended shielded wire and central grounding.

[Chris In Milwaukee]

It's a good idea. Especially when you have something as sensitive as a magnetometer in near proximity to a potential noise generator.

[Bcone1381]

My favorite ground block. It attaches to the firewall. One side serves as ground on the engine side, the other side serves the cabin.

http://www.bandc.aero/groundblock2424-tabfirewallkit.aspx

Screen Shot 2018-10-02 at 6.23.21 PM.png

[Chris In Milwaukee]

That’s a cool device. Certainly makes plugging in a ground easy, doesn’t it?