Ground wire length

[Mynameismcgyver 10+ year member]

I would have used the search option but it hasn't worked for me in a day or so. Anywho, I read somewhere that the ground wire on the Amp should be __ as long as the power wire or some crap. Is this a myth or....?

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[PESteele 10+ year member]

I would have used the search option but it hasn't worked for me in a day or so. Anywho, I read somewhere that the ground wire on the Amp should be __ as long as the power wire or some crap. Is this a myth or....?

my power wire is like 12 feet long and my ground is like 3 and it works fine

 

[jgarcia9102 10+ year member]

im pretty sure the ground should be as short as possible....

 

[davidfre21 5,000+ posts]

you want the ground as short as possible..

 

[Mynameismcgyver 10+ year member]

Alright I guess it was BS then. thanks

 

[Perdonic 10+ year member]

I heard keep it under 30 inchs.

 

[JimJ 5,000+ posts]

No set number to keep it under, but if you're grounding to the chassis, you want it as short as you can make it to reduce the overall length of the ground return.

If you're running a seperate wire back to the negative post on the battery, obviously, it's going to be the same length as the positive lead //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Prowler573 5,000+ posts]

The commonly accepted wisdom is to keep it as short as possible - but it does not have to be very, very short to provide good results.

My main ground is spot-welded to the spare tire mount underneath my trunk floor (no possibility of loose connections later, tyvm //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif ) and from there to the distribution block it feeds may be a 5 foot long length of cable. I have absolutely zero inducted noise.

 

[KaeZoo 10+ year member]

There's no rule of thumb. The assumption is that you'll lose more voltage through a wire than through the chassis of the vehicle, so you should keep the wire portion of the ground as short as possible. That's an assumption that's been challenged a bit lately, though.

You're definitely better off with a long ground wire to a good grounding point, compared with a short ground wire to a poor grounding point.

 

[JimJ 5,000+ posts]

OT technical alert...ignore if you want

Short grounding is nowhere near as important at DC as it is once you get to RF frequencies...I have a 4 inch lead grounding the antenna tuner to the chassis, and on the lower frequencies (80 meters and below), it still isn't enough to get a decent SWR. When I get around to it, I'm going to be upgrading everything to 2/0 cable to both the ground and the radiating element - even though it's such a short connection, the fact that the antenna element itself is so short relative to the wavelength (9 feet vs. 262 feet for the 3.5mHz band) the voltage, and therefore the losses, are huge. On 10/11 meters it it's so bad because the tuner doesn't have to work hard to get a 50 ohm load, but when there's tons of radiation resistance, those things can hurt you dead if you happen to be in the way //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[theCybe 5,000+ posts]

current follows the path of least resistance. is a ground lead back to the negative post on your battery less resistive than grounding to the chassis?

who wants to test?

another argument for trunk-batteries.

 

[squeak9798 5,000+ posts]

current follows the path of least resistance. is a ground lead back to the negative post on your battery less resistive than grounding to the chassis?
who wants to test?

Depends on who you talk to, and the gauge of wire you are using.

I've seen valid tests that arrive at the conclusion that an average vehicle chassis has a resistance equivalent to 4ga wire...which would mean if your ground wire is larger than 4ga, you would be better off running the ground wire back directly to the battery (regardless of where the battery is located).

Then I've seen other valid tests which show that the average vehicle's chassis has a resistance equivalent to that of 2/0ga, which would mean running the ground wire directly to the negative battery terminal (regardless of where said battery is located) would only be beneficial if using wire larger than 2/0ga.

As to the original question....pretty much as JimJ (I'll never get used to your new name Jack //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif ) and KaeZoo said....there's no real set limit, you just want to minimize the amount of resistance. In which case, it's typically thought that the chassis has less resistance than most wire, and hence you want the wire (the most resistive part of the path) to be as short as possible.

 

[JimJ 5,000+ posts]

Testing would be inconclusive, because it would completely depend on your vehicle.

My van would have a significantly better ground return than a Saturn would, for example, but the amount of metal involved is vastly different //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif