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Author Topic: Recommended wire size for equipment to ground buss bar?  (Read 1166 times)

N4WRO

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Recommended wire size for equipment to ground buss bar?
« on: December 18, 2019, 05:25:25 PM »

Putting together a new shack, and was trying to find the correct wire size to connect equipment to a central ground buss bar. 

The central buss is connected to the outside ground rod with #6 copper.  This rod is also connected/bonded to the main house ground rod with #6 copper.

Equipment manuals say just connect the ground lug, but give no advise to the correct wire size to accomplish this.

Thanks!

Bill
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KB7TT

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #1 on: December 18, 2019, 05:46:54 PM »

I strip the shield from RG8X and use that for grounding.  That's what it does in the coax and braided shield is low inductance....

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KW9WK

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #2 on: December 18, 2019, 07:44:51 PM »

There's plenty of ways to skin that cat...

Braid off of RG8X like you mentioned,  or RG8, It's all good. Even some stranded 12 to 10 gauge wire will do the trick. 

Myself, the station ground bus is 1/2 copper pipe and I run some 3/8" wide copper braid from my equipment to the pipe, and secure it with hose clamps. 
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Lenny, KW9WK, formerly AC9RN, formerly KB2NYA....

K4IA

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #3 on: December 18, 2019, 07:55:36 PM »

RF travels on the surface of a conductor.  This is called the skin effect.  For that reason, flat strap is preferred as it has more surface area than wire.  There is a debate about solid strap vs braided.  The braided is flexible and easy to work with so you can move your equipment around.  But, not quite as effective and can corrode outdoors.  If you use braided, make sure it is tinned to reduce the corrosion.  Coax shield is not tinned and will deteriorate quickly with unpredictable results. 

I use 1 inch tinned braided strap to bond all my components. 

ARRL has a book on Grounding and Bonding for the Radio Amateur.  K9YC has written several articles on RFI and grounding.  They are available on Al Gore's amazing Internet.
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WB4SPT

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #4 on: December 19, 2019, 08:09:15 AM »

A curious question.   Is the mission to increase RF current on the non-coax conductors??

I actually do use AWG12 green for the AC/60Hz bonding on my BA's.   But, it might seem better to use ferrite around each wire to make to carry LESS rf, no?  I don't want RF to flow into my house wiring or even some random ground rod near the operating position. 
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W4MSL

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #5 on: December 19, 2019, 09:20:23 AM »

I use 1 inch tinned braided strap to bond all my components. 

Tinned copper braid is nice because of its very large surface area and flexibility. The end for equipment connection can be rolled, inserted into the sleeve of a large terminal lug, and then soldered. Makes for a very tidy connection to an existing equipment ground terminal. You can solder the edge of the other end to prevent fraying, if you like. My bus bar is a 1" section of copper pipe, with copper stand-offs and copper-plated  screws to mount to the studs beneath the drywall. The braids will terminate on the tubing, as will a 3" copper strap coming into the station from the nearby ground rod. I placed a snugly-fitting wooden dowel in the pipe to provide support against crush pressure from clamps, but I'm considering soldering both strap and braids to the pipe, once I have equipment where I want it, (and after removing the dowel). I imagine (and may be quite mistaken) that I can roll the strap tightly around the pipe one and one half turns, secure it with sheet metal screws, and then sweat it with a torch as you would any copper pipe joint. All will be well-prepared and coated with rosin flux. Using 63/37 Sn/Pb (eutectic) solder should reduce the heating required, but it's still a very large "joint," so may need a so-called MAPP gas torch. And suitably placed heat shields while working! If my plumber friend says, "Are you kidding?" and refuses to help, I'll take the hint and stick with just the clamps and sheet metal screws.
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KD0REQ

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #6 on: December 19, 2019, 10:14:07 AM »

I'm using 3/4 type L copper on insulators made from plastic Tarzhay wine glasses for the shack ground buss. shined it up with a Scotch pad, then skin coated it with Vaseline to guard against corrosion. attaching the rig ground braids with Ideal hose clamps, and it's all good the past few years. inside grounding of the cabinets for RF is basically to prevent signal loops causing differential currents. you still need the AC safety ground of your power cords to meet code and avoid roasting yourself between machines in case something fails inside.

atmospheric nasties should be stopped on the outside and dumped to a low impedance ground via nice fat straps or heavy wire, and the antenna switches inside should be shorting when not connected to the antenna farm.

the polyphaser website is a good place to find out how uninterruptible services avoid being set on fire by near or direct strikes.
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VK5ISO

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #7 on: December 20, 2019, 10:32:21 PM »

Bus bar is indoors, a large rectangular, pre-drilled slab of copper.

Tinned copper braid indoors, copper flat strap outdoors!

Keep your connecting straps as short as realistically possible, same is true for the connection from the bus to the ground.
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K5LXP

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #8 on: December 21, 2019, 07:42:20 AM »

Back up the bus a second.  What is the goal of all this "grounding"?  Because technically you don't need to separately ground any station equipment at all.  Determining the requirement would drive the solution, not what the popular opinion is on a public forum.  Unless you have a really unusual station setup, you shouldn't need any at all.

Mark K5LXP
Albuquerque, NM
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K6BRN

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #9 on: December 22, 2019, 09:39:50 AM »

Mark:

A station ground, if done well, is always a good idea.  Doing it well is the trick.  But it's not REQUIRED at most stations, either.  So if the O.P. wants to put in a good station ground and is in the process of doing so, that's fine.

Reasons for doing so:

1.  Safety (always a good reason)
2.  To minimize stray RF in the shack (ummm.. yes, this really DOES work if done correctly - I don't want to argue it, I "live" there with my own station ground at QTH#1 and in the lab, daily)
3.  Lightning protection (this is a hot topic - it takes MORE than an everyday grounding system to protect against lightning - and if done poorly can make things worse)

The all-knowing ARRL :) states:

Quote
The first thing to know is that there are three functions served by grounding in ham shacks: 1. Electrical Safety 2. Stray RF Suppression (or simply RF Grounding) 3. Lightning Protection. Each has it's own set of requirements, but not all station setups need every kind of ground. In fact, some setups don't use a ground at all!

They have a decent station grounding guide on-line and sell a detailed book on this.  A good .pdf to start with is:

http://www.arrl.org/files/file/Technology/tis/info/pdf/49680.pdf

Brian - K6BRN
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WW5F

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #10 on: December 23, 2019, 06:19:20 AM »

1.  Safety
2.  RF
3.  Lightning protection
You beat me to it.  First question to ask:  purpose of ground?

I tried to answer all three of these questions about 10 years ago by "clamping" seven 8-foot ground rods (spaced 8 feet apart) (along with the ground in in my 50 amp sub-panel) with 1 inch tinned strap.  Recently, I measured resistance from my sub-panel ground to the end of my string of ground rods and saw about 10 ohms.  10 years ago, it was almost zero.

I noticed about 5 years ago issues starting to slowly appear when transmitting.  My computer would lock up, keyboard/mouse would freeze.  Kept getting worse and worse.

I assume corrosion.  And God knows how well each of my clamps were doing since they're all outside and at dirt level.

About a month ago, I removed the 1 inch tinned ground strap, cleaned up the tops of all my ground rods, ran #4 solid and used cadweld one-shots to "bond" all my ground rods.

Guess what?  No more computer lock up issues.

Lesson:  use cadweld one-shots, make sure there are no ground loops (or minimum ground loops...) and use a big solid copper wire.

(My AL-80B has a ground loop, I believe.  Grounding the case and the ground/neutral coming in from the power cord creates a ground loop, but I don't see how to remove this ground loop and maintain safety.)

I use a 1 inch copper pipe as a ground bus behind all the equipment at my operating desk.  Some very short #10 stranded to connect all equipment to the 1 inch copper pipe.

I'm happy with what I did.  Of course, this is my situation.  Grounding is an art form.  There's all kinds of theories on how it works.  There are all kinds of examples that shows what works for some folks.  And there are several false prophets who claim to be experts on it.  As an individual, make sure you understand the electrical code (safety), keep things as short as possible, and try it.

That's my story and I'm sticking to it.
« Last Edit: December 23, 2019, 06:24:32 AM by W5UAA »
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N8FVJ

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #11 on: December 24, 2019, 07:43:27 AM »

Most use a 1/4" to 3/8" tinned copper braid wire for grounding in-between equipment. Apparently it is better than stranded #12 or #10 gauge wire for RF. Braided wire is somewhat rare, a few rolls exist for sale on ebay.
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VK2LEE

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #12 on: February 07, 2020, 05:57:42 PM »

I have read that lightning runs on the outside of metal, so a wide braid is good.Copper Braided wire is available off ebay in different sizes. Looks like good quality too... and the braid should be bolted on not soldered etc as the lightning will melt the solder..  Naturally none of US Want to be hit by Lightning, but some of Us have been. It can melt N connectors and PL-259s etc...  So,  Grounding and bus bars etc are all there for Grounding the radio, Power Supplies, & antennas etc and not really for a lightning strike.... best to keep the lightning outside Your House...
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28 years as VK2LEE - The 1st 3 letter L call ever issued - in 1986 -

N6YFM

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #13 on: March 06, 2020, 10:33:17 PM »

I needed a 3 foot piece of copper wire to go between my garage shack buss-bar and the outside ground rod.
Went to home depot.  The only thing that day in their scrap bargin price left-overs bin was a piece of large
stranded wire at least the same diameter of the ground rod.  Turn's out if was not such a bargin because it
was hard as all hell to bend and route.  But now, it's like one solid continuous ground rod coming into the shack
ground bus-bar.  From the bus-bar, I just use the 1/2 inch stranded flat cable that HRO sells, with gromet/screw
holes at each end.   EVERYthing gets grounded.  Power meters, rotor controller, PC chassis, tuner, WestMountain
DSP audio, everything.   I don't have any RFI issues, no computer crashes, even on 40m, nothing.  Rock solid.

Antenna coax lines all come into Alpha-Delta lightning arrestors mounted on the ground bus-bar in the shack.
They really belong out-side, but that is another storey for another day.

Point is;  from day one, I don't have any issues with this shack for the three years I am operating.  I have
a rotating dipole and an end-fed EFHW wire antenna.   I drive 500 watts.   No PC issues, no equipment issues,
no neighbor issues.   On 40 meters, it always turns on a touch-lamp in the house, and used to open the garage
door until I put a few mix-30 toroids on the garage door controller wires.    Very happy with the station. 
Reliable and no unexpected problems.

When grounding all your station equipment DO NOT forget to attach a braided ground wire to a screw on the PC,
and connect that to your ground bus-bar.   Without doing this, especially if using a random wire or EFHW, where RF
comes back on the coax shield, you are likely to eventually blow out the USB port on your PC main board.
If using a laptop for your shack, you can accomplish the same by cutting up a USB cable, and soldering your
braided ground wire in the shack, onto the outer shell USB connection.  Plug it into a USB port on the laptop and
that will provide a really good effective ground connection to the laptop, preventing potential USB port damage.

Good grounding is the difference between solid reliability and constant problems.

Cheers,

Neal
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K8AC

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Re: Recommended wire size for equipment to ground buss bar?
« Reply #14 on: March 08, 2020, 06:42:41 AM »

Having experienced equipment damage from a couple of nearby lightning strikes, I know that in my case the damage done was due to pieces of gear being at different potentials and not because of heavy current from a direct strike.  My purpose for grounding everything to a common ground buss in the station is to ensure that all cabinets/chassis are as close to a common potential as possible.  Just about any wire size will fill the bill in that case.  If you're grounding everything together with heavy braid to try and solve RF problems, I think you'd be more successful if you spent some time determining the cause of "RF in the shack". 
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