first time I have run across this, but I have a company insisting I use a braided type ground wire to ground my rack mounted IP Office. I didn't have much luck searching the internet. Anyone got a source? Ed???

Try putting "grounding bond braid" in google, I found several types and sources.

Amazon sells braided copper wire on spools and premade braided ground straps. Prices are not bad.

just needed the right terminology. Thanks guys!

A braided ground strap is normally used to ground a componet to a rack or ground multiple racks to each other, not to a cold water pipe or ground rod.

What's the advantage of the braided cable, as opposed to a stranded or solid wire?

Justin

More surface area, thus a better ground. Electricity travels on the surface of a wire not through its center. So stranded is better than solid, braided is better than stranded in therory.

Do a search for ladder rack grounding kits. I use the braided bonds to join rack sections. Black Box or Panduit come to mind.

More surface area, thus a better ground. Electricity travels on the surface of a wire not through its center. So stranded is better than solid, braided is better than stranded in therory.

Stop listening to those IT weanies! They don't know s***!

That's BS unless you are talking about RF. Besides, the ground screw on the IPO chassis is just a UL requirement, not something required for operation. It's required by the listing in case someone pulls the line cord of a wall mounted system thereby removing the ground provided through the electrical receptacle, allowing the premises wiring to "float". If the system equipment (any equipment) is rack mounted, the ground from the other rack components (including the PDU or outlet strips) will be in common with the rack through their mounting screws and provided to all other equipment. Providing a separate ground for a rack of equipment can actually cause problems if the rack ground is derived elsewhere than that of the electrical supply grounds due to stray currents. Those currents can damage equipment as I have related many times.

Further, if a rack contains no powered equipment, such as would be the case with a rack full of patch panels, a ground is neither required by the NEC or even necessary. The premises wiring has no electrical connection to the rack.

-Hal

God bless you, Hal. I'm so tired of companies selling hardware by creating potential hazards in their own minds. They do this in an effort to spook the IT bunch into buying their snake oil.

Exactly. So with their mindset, I should also be bonding a metal 183A1 backboard that carries four 66 blocks? What about the metal BIX frames? Should those be bonded as well? Oh, and don't forget those metal shelving units in the warehouse. This whole thing is quickly becoming more of a joke on a daily basis.

A manufacturer comes up with a potential risk, develops a potential fix for this 'risk', sets up a booth at a seminar and the next thing you know, we have a new hazard. Such BS, yet so many people (even those who I thought were professionals) are falling for it.

The NEC is comprised of a board that almost completely exists of manufacturer executives. When things get slow, they simply invent some new risk, convince the NEC board of this risk and within a few years, their new toy is mandated. The NEC is one step below the crooked standard that our US Congress uses.

What Hal & Ed both stated!

Just to be clear... you guys are saying that grounding the equipment could cause more issues than not? I can see where the mounting of the equipment to a rack that is grounded should negate the need for a ground, that makes sense.

"More surface area, thus a better ground. Electricity travels on the surface of a wire not through its center."

Hal; Had a friend of mine that is working for Edison as a cable splicer, he told me that was a true statement in so far as the cables used on the high voltage transmission towers. Solid is to heavy; and for this rteason they are hollow and mostly Alumanum.

Looks to me there are two different discussions going on. The need for a ground and the current flow over a wires surface.

It's true current flows over the surface, so the bigger the surface the more current it will handle.

The need for a separate ground on equipment, other than the 3rd prong, has been debated forever. All things being equal the 3rd prong on a plug should be the same potential as any other ground in a building. But should the grounds not be consistent or a bad joint in the ground that's where the trouble lies. That's why I prefer a ground from the power panel all the way to my equipment. Than I know I'm the same potential as the rest of the buildings grounds. If I get a dedicated source of power for my equipment and my equipment only, that also satisfies the grounding requirements. I'm finding more and more that is hard to get.

What causes the harm is mis-grounding. You want your equipment to be the same potential as any other ground, not better, not worse. That's the key.

EDIT: Want to ad. The proper way to check ground potential is to meg it to earth. Nobody does that anymore. A pretty good source is to drive a ground rod and the soil conditions dictate how deep or how many, than check your ground to the rods you've just driven, shouldn't be any more than a half ohm difference in the two, if there is you need to start looking for your grounding problem.

The statement as to how deep or how many relates to the following saying we had back in my Northwestern Bell days. Ground is ground the world around, except in the Nebraska sand hills.

Thank you, Bill. Surface current is NOT isolated to RF.

And yes, mis-grounding IS a big problem...especially in CLEC COLOs. Jesus, these guys don't understand shit.

And if you have to ask why we don't use stranded for long wire runs (instead of just for local grounds, short patch cables and the like), then it's time you go back to class.

Sorry to sound like a dick, but I learned my stuff the real hard way.

I can't see any reason why you would need stranded ground wire other than wanting some flexibility. Skin effect is actually more pronounced with stranded wire, so that can't be the reason for it's use.

Skin Effect is the phenomenon where AC signals will flow only along the outer skin of a conductor. The higher the frequency the more pronounced the effect. This is why coax for high frequency signals can have a copper plated steel core, and microwave transmitters use a hollow waveguide instead of cables. I did a quick search, and the skin depth for 300Mhz is about 4 microns and about 3 microns for 500Mhz, so it actually is an issue at the frequencies used for 10GBase-T.

It's true current flows over the surface... Thank you, Bill. Surface current is NOT isolated to RF.

Skin Effect is the phenomenon where AC signals will flow only along the outer skin of a conductor. The higher the frequency the more pronounced the effect.

At power line frequencies and audio frequencies skin effect is almost unmeasurable so don't even go there. This is the kind of nonsense Monster Cable (and others) use to suck people into spending $$$$ on gold plated oxygen free stranded audio cables.

Had a friend of mine that is working for Edison as a cable splicer, he told me that was a true statement in so far as the cables used on the high voltage transmission towers. Solid is too heavy and for this reason they are hollow and mostly Aluminum.

I've never heard of that. Aluminum yes. Like I said, at 60Hz it would make no difference. If they truly are using a hollow conductor it has to be for some other reason, possibly they are pumping a cooling fluid through it.

-Hal

I share your opinion of "high end" audio cables, but nobody else hear was talking about audio or making claims of skin effect at audio frequencies.

Skin effect also wouldn't be an issue at 60Hz, but a quick Google search does turn up information on high voltage power lines being hollow to reduce the weight. The large diameter of the cable reduces corona losses, but has nothing to do with skin effect.

I share your opinion of "high end" audio cables, but nobody else hear was talking about audio or making claims of skin effect at audio frequencies.

My point was that even though audio (generally up to 20Khz) is much higher in frequency than what we are talking about here, the skin effect is not even a consideration. So why would it be at 60Hz? It's also easier to find information about skin effect as it relates to audio cables than power cables.

-Hal

I was told that if you measure the circumference of a solid number six ground wire and then do the same with each individual strand of a stranded number six you will get a larger over all circumference plus in addition to the flexability of stranded.
PS: I did have a situation where my crew had to change out numerious solid ground wires to stranded per the inspector.

If any of that were true the current carrying capacity of the cable or wire would be increased for stranded. Also, how would you explain a six strand vs a 18 vs a 30? Fact is the cross section is made to be the same regardless of whether the wire is solid or stranded. Plenty of ignorant sparkies out there though and that's probably where your story came from. And the inspector was an idiot for the same reason.

-Hal

There is 1 valid reason for using stranded rather than solid 6ga. IT'S A LOT EASIER TO PLACE! You don't need a mallet to make stranded conform to the variations in surface flatness!

Hal, I'm wondering if the inspector was basing his demand upon the fact that the NEC requires anything larger than #8 to be stranded for building wiring.

Frankly, I base all of my practices in the telecommunications business on Bell System Standards. All they ever used for premise grounding conductors was solid copper. With the exception of FiOS installations, Verizon appears to be holding true to the BSP for everything else.

Hal, I'm wondering if the inspector was basing his demand upon the fact that the NEC requires anything larger than #8 to be stranded for building wiring.

Maybe. We do have #6 solid, bare or with a telephone gray PVC jacket and they don't.

-Hal

I think their request for braided was based solely on two things... Looks and Looks.. these guys care more about it looking pretty than it working right. It is one of those dog and pony locations. The braided wire was just the start..don't get me going on their patch cord requirements.....