Today's Message Index:
----------------------
1. 06:42 AM - Re: Question for Bob (GusF16rv8)
2. 08:16 AM - Grounding architecture (Robert L. Nuckolls, III)
3. 12:16 PM - Re: Grounding architecture (Rocketman1988)
4. 07:13 PM - Re: Re: Grounding architecture (FLYaDIVE)
5. 07:57 PM - Re: Re: Grounding architecture (Charlie England)
6. 08:39 PM - Re: Grounding architecture (Rocketman1988)
7. 08:57 PM - Re: Re: Grounding architecture (Charlie England)
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Subject: | Re: Question for Bob |
nuckolls.bob(at)aeroelect wrote:
> Do you have a wire running from battery(-) up to your firewall ground bus?
>
> Yes I do. My guess is that it is an 8AWG wire running from the battery to airframe
ground connection forward to the ground bus. That forward ground bus is
also grounded to the airframe.
>
> Okay . . . the resistance of that wire is probably
> 100 times higher than the airframe. The wire doesn't
> hurt anything but it adds no value.
>
>
Isn't the point of having a bus or 'field of tabs' grounded directly to the negative
batt terminal to prevent ground loops through the airframe? If so, why
then is the wire of no value, because of its length due to being run from the
rear?
>From the explanation above, it sounds like both ends (batt neg terminal and ground
bus) are also grounded to the airframe, is that correct?
Could you specify which wire is 'adds no value' and how the planned system SHOULD
be grounded then? Thanks!
--------
Gus
RV8 SlowBuild (2006-?)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481864#481864
Message 2
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Subject: | Grounding architecture |
Okay . . . the resistance of that wire is probably
100 times higher than the airframe. The wire doesn't
hurt anything but it adds no value . . .
Isn't the point of having a bus or 'field of tabs' grounded directly
to the negative batt terminal to prevent ground loops through the
airframe? If so, why then is the wire of no value, because of its
length due to being run from the rear?
From the explanation above, it sounds like both ends (batt neg
terminal and ground bus) are also grounded to the airframe, is that correct?
Could you specify which wire is 'adds no value' and how the planned
system SHOULD be grounded then? Thanks!
We're talking two separate issues:
(1) Ground path integrity for DC power
distribution and . . .
(2) shared ground paths bet ween potential
antagonists [alternators, strobe supplies,
etc] and potential victims [audio systems,
some avitonics].
This thread is about issue #1. Yes, we'd
like to achieve the lowest practical path
resistance between the battery(-) and the
firewall ground block. For aircraft with the
battery forward, taking battery(-) directly
to the stud is ideal and practical.
For batteries mounted aft in a metal aircraft,
taking battery(-) to structure is the most
practical.
https://goo.gl/28exWU
Now, if one were to measure the airframe
resistance between the battery(-) grounding
location on the airframe and the firewall
ground block stud, one would measure some
exceedingly small resistance . . . generally
under 0.001 ohms (resistance from nose to
tailcone on a Beechjet is right at .001 ohms).
Enhancements to conductivity by adding some bit
of wire in PARALLEL with the structure would
be very difficult to measure.
GROUND LOOPS are a separate discussion unique
to managing grounds for potential victims
and is unrelated to management of DC power.
Bob . . .
Message 3
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Subject: | Re: Grounding architecture |
So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall
stud a bad plan? Would a basic airframe ground be the better option,i.e.
ground the batteries at their aft mounted location?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481866#481866
Message 4
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Subject: | Re: Grounding architecture |
Nothing beats a copper wire ground on a plane.
There is no reason why you can not do both... A wire from the battery to
the Firewall/Ground Buss and a short Ground wire to the airframe.
Barry
On Thu, Jul 26, 2018 at 3:15 PM, Rocketman1988 <Rocketman@etczone.com>
wrote:
> Rocketman@etczone.com>
>
> So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to
> a firewall stud a bad plan? Would a basic airframe ground be the better
> option,i.e. ground the batteries at their aft mounted location?
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=481866#481866
>
>
Message 5
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Subject: | Re: Grounding architecture |
On 7/26/2018 2:15 PM, Rocketman1988 wrote:
>
> So is running a 2 AWG cable from the aft mounted batteries on an RV 10 to a firewall
stud a bad plan? Would a basic airframe ground be the better option,i.e.
ground the batteries at their aft mounted location?
>
I think the idea is that running the extra ground wire forward is not a
*bad* idea; just an unnecessary one, in a metal a/c. The airframe will
be a lower resistance ground path than any practically size wire.
Problems related to the ground loop issue are usually limited to audio
gear. I'm sure Bob can give you a better, more precise description of
what happens. But my layman's description is this: If a low level
signal, like audio, shares its ground return path with much stronger,
'noisy' electrical signals, like a strobe, the strobe noise can
effectively become part of the audio signal, and you get the noise in
the audio system. To prevent that, you use the 'forest of tabs' located
somewhere near the audio (and other low signal level) gear, and run all
low level signals to that spot instead of through the airframe. That
keeps the ground paths of the low level stuff & the 'noisy' stuff separate.
Charlie
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Message 6
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Subject: | Re: Grounding architecture |
If running a large wire ground isn't necessary, how does Z-15 fit in?
Just curious...
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481873#481873
Message 7
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Subject: | Re: Grounding architecture |
On 7/26/2018 10:38 PM, Rocketman1988 wrote:
>
> If running a large wire ground isn't necessary, how does Z-15 fit in?
>
> Just curious...
Are you asking me? (no context for your question in the email version)
If so, did you read the text (pg z-4) that's associated with the drawing?
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