A grounding question please

[MedMan4040]

I've today run 3/8" copper braid from my 'shack' area through a wall, above a drop ceiling
and to the outside where a copper bus bar awaits.
This bus bar runs to my whole house main electrical grounding bar......so everything will be grounded
at one point.
My question is simply how to connect the copper braid to the copper bus bar.
The copper bus bar has many screws in holes seemingly designed for ring terminals, yet the copper braid
I received has no terminals of any kind.
Suggestions please.

 

[prcguy]

Any reason you chose braid instead of wire? The braid will wick in water and corrode prematurely outdoors. Insulated wire of 10ga or larger should meet code and be much easier to run through walls, etc.

 

[MedMan4040]

Prcguy, for some reason I thought braid had advantages over strap or wire, but I'm game to anything...just wanting to be safe(r) than I was before which was NO grounding at all (been using VHF rigs) but passed my General yesterday and will begin putting up an EFHW soon for an FT-710 which has been sitting here for 2 months never turned on.
The braid wasn't hard to run at all and I could go to Lowes and grab some 10 gauge wire. So how would you terminate it? Simple ring terminal? I suppose one could even use Romex....got plenty of 12/2 in the garage....nope, just Googled. Romex is not even an idea choice for grounding.

 

[KF0NYL]

10 gauge is the minimum size that you should use. bare 6 gauge wire is usually recommended. I did use 10 gauge wire to connect my lightening arrestors to the ground rod. I used 6 gauge for grounding my antenna masts and also to bond everything to my service ground.

I agree that braid is not the best for outdoors use. The main reason it is used on vehicles is the flexibility factor so it doesn't break under constant movement.

 

[prcguy]

Prcguy, for some reason I thought braid had advantages over strap or wire, but I'm game to anything...just wanting to be safe(r) than I was before which was NO grounding at all (been using VHF rigs) but passed my General yesterday and will begin putting up an EFHW soon for an FT-710 which has been sitting here for 2 months never turned on.
The braid wasn't hard to run at all and I could go to Lowes and grab some 10 gauge wire. So how would you terminate it? Simple ring terminal? I suppose one could even use Romex....got plenty of 12/2 in the garage....nope, just Googled. Romex is not even an idea choice for grounding.

Short runs of flat braid is better for RF grounding because it has less inductance than round wire of similar thickness. But the type of grounding you are doing is more for meeting NEC for human safety placing all components of your station at the same ground potential. No real need to go larger than 10ga in my opinion since you won't be protecting from a direct lightning hit, that's not something you can realistically build for.

 

[KF0NYL]

Nothing is going to survive a direct lightening strike.

Here is a good article to read on grounding.

https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

As always, follow NEC regulations and local building codes when installing antenna masts/towers. This includes proper grounding.

 

[AC9KH]

So how would you terminate it? Simple ring terminal?

I wouldn't use ring terminals. Just use screw lugs. They are available with a hole to bolt the lug to your bus bar, then simply insert the end of the wire in the lug and tighten up the screw. Ones like these - they're available in aluminum, bare copper or plated copper. Then treat the connection with some anti-corrosion compound which is used, for instance, when terminating aluminum conductors on a plated copper bus.

 

[AC9KH]

This bus bar runs to my whole house main electrical grounding bar......so everything will be grounded
at one point.

A lot of hams tend to over-think shack grounding and create their own ground loops, which it sounds like you're doing here. If you ohm out the power supply for your equipment, which is likely equipped with a three-prong power plug, that is already grounded to your service entrance. And there's likely an external chassis grounding point on the power supply. Ohm that out from the ground pin on the power plug to the chassis of the power supply and you'll likely find zero ohms.

All that's required to eliminate potential between your radio(s), tuner(s), etc is to run a grounding wire from each of those (daisy chained) to the ground point on the power supply and you're already connected to your service entrance grounding point. Why are you creating a ground loop with a second grounding circuit? The only reason to do what you're doing is if your station equipment runs off a battery so you have a floating ground, or you have some sort of cheap power supply with just a two-prong AC plug.

I would urge you to check this out with your handy ohmmeter before you go to great lengths to create a ground loop. There's a reason on AC power why only one neutral-ground bond is allowed in the system at the service entrance, and all subsequent sub-panels are not bonded. Power only flows on that service ground in the event of a fault, and it flows to that common grounding point. You don't want it flowing in loops, following the path of least resistance to get there - that will create differences in potential.

When you think of electrical grounding in AC power systems, reduce it to the simplest terms - every electrical item in your house or shack is grounded but there's only one path to that common ground from any item. Don 't create two paths or you got a ground loop, same as bonding the ground to neutral in a sub-panel with split-phase power.

RF grounding is different and that can't be bonded to your electrical service ground. So is antenna masts and towers different, they normally have their own grounding system to divert lightning or static buildup without running it thru your electrical service ground.

 

[davidgcet]

I wouldn't use ring terminals. Just use screw lugs. They are available with a hole to bolt the lug to your bus bar, then simply insert the end of the wire in the lug and tighten up the screw. Ones like these - they're available in aluminum, bare copper or plated copper. Then treat the connection with some anti-corrosion compound which is used, for instance, when terminating aluminum conductors on a plated copper bus.

View attachment 178895

those are not made for use in a wet location, though people often do. a true compression lug is best, and it "should" be a properly sized 2 hole lug. that means correct size for the wire, correct hole size for the stainless bolts, and correct hole spacing for the bar. you can roll the end of the braid up tight to crimp on a lug, BUT it will never be perfect. i personally would tin the braid after i rolled it, crimp a lug on and then solder it to the braid. probably overkill but won't hurt in my experience. the lug you posted is for solid wire in a protected area, but if he does have to use one like that i would cold galv it once everything is locked in tight.

 

[AC9KH]

those are not made for use in a wet location, though people often do

They are for stranded or solid wire. They're used all the time in wet or outdoor applications, including in Siemens 600V rated three-phase knife switches right from the factory. This is a Siemens outdoor safety switch that uses lugged fuses instead of blade contact type. The reason they use those is because blade contact fuses will rust the tension springs on the blade contacts, and subsequently melt and burn the contacts.

This is for an application on a 60hp three-phase motor with no soft-start and due to the inertial load it takes it 9 seconds to spool up to operating rpm, drawing 1,000+ starting amps. So they use lugged slo-blows because a conventional three-phase motor starter won't handle the starting amps. There's a safety flash cover that goes over the whole assembly. If the motor loses a phase during spool-up it's about like a 12ga shotgun going off when one of those fuses blow.

The same lugs are used in the top of the box where there's three stranded copper THHN conductors feeding it.

 

[davidgcet]

that is a damp location as it is inside a NEMA enclosure, the OP is connecting to an exposed ground bus bar that will be in the open. read any grounding standard and those are not acceptable for this situation as they are not irreversible and will corrode. will they work fine for several years, yes they will. are they ideal, no they are not. and yes i did misspeak about that being for solid wire, it is rated for both but most commonly used with solid for grounding purposes in my experience over the last 35 years. we used to use the copper/brass versions of those, Moto crawled our butts on a R56 audit because they are not the "correct" lug even though they had no real answer other than they can corrode or loosen over time but agreed that when properly torqued and clean they worked just as good as a crimped lug. that was the point of my post.

 

[AC9KH]

that is a damp location as it is inside a NEMA enclosure, the OP is connecting to an exposed ground bus bar that will be in the open

Virtually everything electrical, including antennas, has a limited lifespan when exposed to the weather. In this case, if the OP actually does need this elaborate grounding system, which I rather doubt if his power comes from utility mains, at the minimum I'd get one of those 12 x 12 x 6 PVC boxes and put it inside the box to keep the connections out of the weather. I'm kinda confused as to why there's braid being used for DC grounding - that's for RF on radio systems. And I'm even more confused as to why this is being done in the first place unless this is a station with a floating DC ground.

 

[MUTNAV]

RF grounding is different and that can't be bonded to your electrical service ground. So is antenna masts and towers different, they normally have their own grounding system to divert lightning or static buildup without running it thru your electrical service ground.

I was under the impression that the RF ground does have to connected to the electrical ground at the ground rod (earth electrode system) along with the lightning proctection system. And generally the power panel is for the fault protection system.

Could be wrong, lots of words in the written guidence(s).

Thanks
Joel

 

[AC9KH]

I was under the impression that the RF ground does have to connected to the electrical ground at the ground rod (earth electrode system) along with the lightning proctection system. And generally the power panel is for the fault protection system.

All you're doing with your DC grounds is bonding the equipment in your shack, most of which is DC-powered from an external power supply, to a common grounding point. This is to eliminate potential between the various pieces of equipment that could give you a shock, same as any electrical equipment in your house.

Radios that operate from power mains, thru any type of power supply, stand a chance of having the power line accidentally fault to the chassis. Worse yet, say you have a linear amplifier with a high voltage power transformer that might develop a secondary to primary short, and that short might cause the chassis to rise to peak secondary voltage plus peak primary. An amplifier can have a chassis voltage as high as 3600 volts from a secondary to primary failure inside the HV transformer. All power mains operated radio gear requires a safety ground. But hams over-think this in many cases. The safety ground does not need a ground rod, it only requires a connection back to the power mains service entrance ground. And you don't want to do this in loops where there's more than one path or you're going to get differences in potential due to different impedances in wire runs.

If you look at the back of your power supply, you'll likely find the chassis grounding terminal that is connected to the ground pin on the wall plug if you ohm it out, and all your station gear must be bonded to that because otherwise all it has is a "floating" ground thru the DC power cable going from the power supply to the equipment.

The RF return-path ground is different and it is not bonded to your DC safety ground. If your station has coaxial or balanced lines feeding antennas this does not require a RF station ground. All currents flowing out to the antenna are matched by equal currents flowing back on the second conductor, be it a shield on a coax cable or the second conductor of a balanced feeder. However some antennas like end-feds are going to use a RF ground in the form of a ground rod. If you have "RF in the shack" due to common mode currents, no RF or DC grounding is gonna fix it. Fix the antenna system instead.

Lightning grounds are another matter yet. No matter what you do, nothing in your station will survive a direct lightning hit on an antenna. The only way to prevent that is to unhook all your antennas, preferably outside someplace. And even then there's no guarantees because the EMF is likely gonna blow your radios anyway, along with your cell phones, computers, TV's and anything else you got. If you want to see proper lightning grounding go visit a commercial AM broadcast station and check it out. You (probably) don't have the money that's going to be required to install a proper lightning grounding system that can survive a direct hit.

 

[prcguy]

RF grounding is different and that can't be bonded to your electrical service ground. So is antenna masts and towers different, they normally have their own grounding system to divert lightning or static buildup without running it thru your electrical service ground.

This would not be legal anywhere in the US, antenna masts, towers, feedlines, etc, must be bonded to the AC electrical panel ground in all cases, otherwise you violate the NEC, specifically article 810. If you look at any commercial broadcast or repeater site there will be ground rods at tower bases but those are bonded back to the building main AC panel, unless a ham did it that doesn't know the rules.

"RF ground" is sort of a misconception, RF doesn't know its supposed to go to an earth ground and in most cases earth grounding an antenna doesn't help with RF problems. It will change the setup and may work better or grounding may not do anything.

 

[cavmedic]

R56 and TIA Standard for your head spinning pleasure.

 

[prcguy]

R56 and TIA Standard for your head spinning pleasure.

They both have in depth methods for grounding antenna systems but neither of those can contradict NEC for human safety.

 

[AC9KH]

If you look at any commercial broadcast or repeater site there will be ground rods at tower bases but those are bonded back to the building main AC panel, unless a ham did it that doesn't know the rules.

Not exactly, because that's open to interpretation due to a radius disclaimer. Like my 120ft tower is not bonded to the service mains ground because it's over 150 ft. So the tower has its own grounding system that sets its potential to earth ground potential. That tower was not installed by a ham. It was installed professionally and signed off on by the engineer that designed it.

 

[prcguy]

Not exactly, because that's open to interpretation due to a radius disclaimer. Like my 120ft tower is not bonded to the service mains ground because it's over 150 ft. So the tower has its own grounding system that sets its potential to earth ground potential. That tower was not installed by a ham. It was installed professionally and signed off on by the engineer that designed it.

Signed off by engineers or the local inspector? If the antenna feedline from the tower connects to anything in the building the tower and feedline must be bonded to the building AC mains per NEC. If the tower feeds an isolated shack run off solar then it comes under different rules.

Running two different grounds almost always increases damage from a lightning strike, central point grounding at the AC mains reduces lightning damage.

 

[AC9KH]

It was put in in 2001, had to have a site engineering survey and design for the building permit for setback from buildings and property lines, etc, which was subsequently rubber stamped by the local inspector. The tower has 18 ground rods around it and being it's free-standing has 22 yards of concrete in the base that goes down into the ground 8ft. It originally had a wind turbine on it - three-phase unit that fed a bridge rectifier that put out 200VDC to a MPPT controller in the utility room in the house. That MPPT controller stepped the 200VDC down to 58VDC for charging a battery bank for the inverters.

I since re-purposed it as a ham radio tower and the feedlines do not come into the house - they go to my shack which is separate from the house. But the shack is powered from a subpanel fed from the house mains. We do have 17.5KW of installed solar capacity as well, but that also charges the battery bank and inverters feed excess back to the grid. We also have a 45 kVA Caterpillar diesel generator that feeds the AC2 input on the inverters (Schneider 6848's) but the generator is isolated from the grid by the transfer switches in the inverters. The generator is in a separate sound-attenuated powerplant building and its grounds are bonded to the AC mains in the house.

But the tower itself is standalone. I had it loaded up as a 160m vertical at one point with a shunt feed to it but the voltages were quite high on it. These days I use it for supporting my wire antennas, which are electrically isolated from the tower. Wind turbine is still on it but the bearings are locked up and it doesn't turn anymore. It wasn't worth fixing because it never generated enough power to justify its $112,000 installation cost.