Grounding steps before concrete pour

Firekite

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I need your input on grounding! We’re pouring concrete, and I need to know what to do before that happens.

I have an attic antenna right now, no grounding or lightning arrestors. I’d like to move it to a mast on the roof (no HOA) and likely add more antennas in the future. My office is where I have my radio setup, and it’s not near the corner of the house where the utility power enters and the ground rod is buried under concrete. AT&T fiber currently enters the home through the wall of my office. We’re capping the existing concrete patio and extending it quite a bit. What should I be doing now in preparation for the future? Home was built in 1971 (San Antonio, TX).

Should I have the concrete guys bust up the existing concrete next to the wall of the station and bury a ground rod next to the wall, leaving some sticking up so I can attach to it? Or maybe just leave a 1” PVC section there so I can drive a rod later? Or maybe drive a ground rod near the tree, attach a 6-gauge copper wire to it, and tie that wire to the rebar and stick it up out of the concrete next to the wall?

Either way, should I go get a length of 6-gauge copper wire and run it across where the new concrete will be and around the corner of the house to attach it to the ground wire leading down to the rod? If running through the concrete should the wire be sleeved, and if so what would I use for that?

They finish forming and bending rebar tomorrow and pouring Tuesday. I only just now realized I should be thinking about this stuff to avoid more hassle in the future! Please help.


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prcguy

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That's a tough one. The best thing to do is study NEC article 810 as its not good to give specific recommendations here due to liability. Here is some easy to read article 810 stuff. https://www.mikeholt.com/download.php?file=PDF/Radio_and_Television_2014NEC.pdf

Along similar lines a friend of mine is building a new house in Colorado and we had some discussions on grounding for his hamster stuff as he is on the top of a hill. He was able to install grounding similar but scaled down slightly from what we do at repeater sites and satellite uplink facilities. He installed 10ft ground rods well below grade about 20-25ft apart around the entire perimeter of the foundation and bonded them all with a reasonable size wire. The goal was 500MCM wire which was not affordable but I think he did go with 6 ga. The ground ring terminates where the electrical entry point will be and the new foundation will have a UFER ground which will bond to the new ground ring.

He made provisions for the future towers to ground back to the main house electrical entry point so there will always be a central grounding point for everything, AC power, coax entry, etc. Power to the house will be supplied underground as will other services. The AC power panel will have both MOV and capacitor type surge protection to the central ground. All future antenna lines will be grounded at the tower base (with their own ground ring bonded to the house ground ring) with lightning arrestors at the central point ground at the cable entry point to the house.

This paves the way for a safer than normal hamster house. Its not engineered by a company that specializes in lightning ground and that can guarantee survivability, but it will be a copy of some sites that are, except for the ultimate size of the ground conductors. You can only get close to surviving a direct hit at home if you are starting completely from scratch.
 

RFI-EMI-GUY

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Don't sleeve that copper. Do one better..

Are you installing rebar or steel mat into that concrete pour? If so you have the opportunity for a UFER ground. Polyphaser has an informative white paper for UFER grounds. Concrete never completely cures or dries up so it is a lot of entrapped water, chemicals (ions) in direct contact with soil. All good for a ground system.

Here is what I would plan:

1) Your shack ground, antenna grounds, all need to return to your utility ground in order to have a single point ground system. The goal is that if lightning hits any of your antennas, the electrical potential of all the electrical systems in the house rise and fall at same potential. Metal airliners get hit by lightning all the time and seldom have damage because of equi-potential on all corners of the aircraft parts.

2) Normally one would run a solid #6 or larger copper wire from the shack to the utility ground. Good practice has you drive an 8 foot ground rod for every 10-16 foot run of that conductor. If say I had a shack 32 feet away, I would; a) Install a fresh ground rod next to the existing utility ground rod (the old ground rod may be corroded to only 4 feet) and bond them together. b) install a fresh ground rod at the shack where lines come in c) install fresh ground rods at 16 feet from utility ground rods, (middle) so 3 new fresh ground rods. The reason for this is that the inductance of the conductor will affect its current handling and the maximum 16 foot spacing is a recommended practice.

3) If you are going to have a concrete pad with steel rebar or mat, you could perhaps eliminate one of those ground rods at middle and run solid #6 or larger copper conductors to the steel at maximum 8-16 ft intervals and use the concrete as a UFER.

4) If you are not using a steel mat or rebar, you can still fan out several #6 copper conductors within the pour.

5) If you have ground rods in the middle of the pour, cap them with PVC and flat lids that you can later remove to inspect or tighten the clamp if necessary. You can always countersink them a half inch or so and grout over the PVC to improve appearances. If you brick or tile over. Mark the tile so you can remove later.

6) When attaching copper to steel, use brass wire clamps and penetrate the connection with grease or anticorrosive like that sold to be used with battery terminals, wrap with electricians cloth and rubber electrical tape. Make redundant connections so that it will stand the effects of time. Experts recommend CAD welding the ground system, but that is beyond the expertise of the average person. I am certified but did it only once! It is expensive.

You will sleep better knowing you are grounded well and also you can eliminate noise from your systems by having a better ground system. Dont forget surge protection devices.
 

RFI-EMI-GUY

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"They finish forming and bending rebar tomorrow and pouring Tuesday. "

Run to Home Depot and fill a cart up with #6 solid, brass cable clamps and ground rods. Get more than you need, you can always return excess.
 

prcguy

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Just pull out the old ground rod and replace with a bigger one. They come out easy with vice grips, some chain and a car jack. I did this recently replacing an old 8ft 3/4" rod that measured about 15 ohms and put in a 10ft 5/8" and my ground resistance went down to under 5 ohms. Its handy to have one of these meters to check ground resistance and if your existing or even new ground rods are doing their job.

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I would; a) Install a fresh ground rod next to the existing utility ground rod (the old ground rod may be corroded to only 4 feet) and bond them together.
 

RFI-EMI-GUY

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I am sure you took all the necessary precautions when doing so.

I hesitate to recommend that the average person disconnect and/or remove a ground rod already connected to a utility service entrance because there may be current flowing on the neutral to ground bond in the panel, or the neutral poorly bonded at the utility pole which could lead to problems of safety and unbalanced potential across the 'phases". So I recommend driving a new rod and bonding it to old with new clamps on both, leaving old clamp and wire in place. Belts and suspenders...

Years ago Motorola installed a new trunking radio site in south Florida and the customer's lead technician decided to open up the ground system "to measure the ground system". Suffice to say, the neutral got floated and a lot of pricey /\/\ gear got smoked. An expensive lesson.

I do get a kick measuring the residual voltage between new and old rod. I like seeing a bit of spark when connecting, showing the new rod is doing its bit!

I need to get one of those clamp on DY1200's.

Just pull out the old ground rod and replace with a bigger one. They come out easy with vice grips, some chain and a car jack. I did this recently replacing an old 8ft 3/4" rod that measured about 15 ohms and put in a 10ft 5/8" and my ground resistance went down to under 5 ohms. Its handy to have one of these meters to check ground resistance and if your existing or even new ground rods are doing their job.

View attachment 87314
 

Firekite

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Polyphaser has an informative white paper for UFER grounds.
Is this what you're talking about?




2) Normally one would run a solid #6 or larger copper wire from the shack to the utility ground. Good practice has you drive an 8 foot ground rod for every 10-16 foot run of that conductor. If say I had a shack 32 feet away, I would; a) Install a fresh ground rod next to the existing utility ground rod (the old ground rod may be corroded to only 4 feet) and bond them together. b) install a fresh ground rod at the shack where lines come in c) install fresh ground rods at 16 feet from utility ground rods, (middle) so 3 new fresh ground rods. The reason for this is that the inductance of the conductor will affect its current handling and the maximum 16 foot spacing is a recommended practice.

3) If you are going to have a concrete pad with steel rebar or mat, you could perhaps eliminate one of those ground rods at middle and run solid #6 or larger copper conductors to the steel at maximum 8-16 ft intervals and use the concrete as a UFER.
OK, I think I'm picking up what you're putting down, kind of. From the corner of the house where the utility ground is to the edge of the new concrete pour is about 25 feet. In a straight line from the point where the shack wall is to the corner where new concrete ends is about 30 feet.

It sounds like you're suggesting:

1) Install a new ground rod at the corner of the house next to the utility ground (just a couple feet way).
2) Install a new ground rod near the windowless door in the middle of the garage brick wall.
3) Use 6-gauge bare copper to bond the new corner ground rod to the old utility ground wire.
4) Use 6-gauge bare copper to bond the new corner ground rod to the new center ground grod.
5) Use 6-gauge bare copper to bond the rebar near the closest edge of the pour to the new center ground rod (as no ground rod would be necessary in the new pour).
6) Use 6-gauge bare copper bonded to the rebar at the shack wall and poking up to clamp to.

Is that about right? This is all new to me. Should I be burying the bare copper between ground rods or leave it lying on top of the ground or even fastened to the existing concrete foundation? Should the new ground rod near the existing utility ground actually be a minimum 8 feet from the existing, and if so then is that as the crow flies or the length of copper wire running around the corner to the existing ground rod wire?

In the cocrete/rebar, am bonding solid copper wire all the way from the ground rod through to the shack wall? Or am I just bonding to the rebar nearest the new ground rod and then separately bonding to the rebar with copper at the shack wall, letting the rebar span between the copper?

I'd like to do this right, but I have one of two modes of operation: either I follow instructions from those in the know or I dive deep and try to wrap my head around the entire concept and understand it fully before making a move. Due to time restrictions, I'm hoping to do the former instead of the latter :)
 

prcguy

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I agree you should drive a new rod and put a temporary connection back to your electrical panel before disconnecting the old rod. You should not have connections to both rods when its done as there are rules about spacing between rods and they would be too close and may actually degrade things. # 6 copper meets NEC for bonding ground rods together but there is a length limit and you may have to upsize the wire if the run is over a certain length.

Is this what you're talking about?





OK, I think I'm picking up what you're putting down, kind of. From the corner of the house where the utility ground is to the edge of the new concrete pour is about 25 feet. In a straight line from the point where the shack wall is to the corner where new concrete ends is about 30 feet.

It sounds like you're suggesting:

1) Install a new ground rod at the corner of the house next to the utility ground (just a couple feet way).
2) Install a new ground rod near the windowless door in the middle of the garage brick wall.
3) Use 6-gauge bare copper to bond the new corner ground rod to the old utility ground wire.
4) Use 6-gauge bare copper to bond the new corner ground rod to the new center ground grod.
5) Use 6-gauge bare copper to bond the rebar near the closest edge of the pour to the new center ground rod (as no ground rod would be necessary in the new pour).
6) Use 6-gauge bare copper bonded to the rebar at the shack wall and poking up to clamp to.

Is that about right? This is all new to me. Should I be burying the bare copper between ground rods or leave it lying on top of the ground or even fastened to the existing concrete foundation? Should the new ground rod near the existing utility ground actually be a minimum 8 feet from the existing, and if so then is that as the crow flies or the length of copper wire running around the corner to the existing ground rod wire?

In the cocrete/rebar, am bonding solid copper wire all the way from the ground rod through to the shack wall? Or am I just bonding to the rebar nearest the new ground rod and then separately bonding to the rebar with copper at the shack wall, letting the rebar span between the copper?

I'd like to do this right, but I have one of two modes of operation: either I follow instructions from those in the know or I dive deep and try to wrap my head around the entire concept and understand it fully before making a move. Due to time restrictions, I'm hoping to do the former instead of the latter :)
 

RFI-EMI-GUY

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Is this what you're talking about?





OK, I think I'm picking up what you're putting down, kind of. From the corner of the house where the utility ground is to the edge of the new concrete pour is about 25 feet. In a straight line from the point where the shack wall is to the corner where new concrete ends is about 30 feet.

It sounds like you're suggesting:

1) Install a new ground rod at the corner of the house next to the utility ground (just a couple feet way).
2) Install a new ground rod near the windowless door in the middle of the garage brick wall.
3) Use 6-gauge bare copper to bond the new corner ground rod to the old utility ground wire.
4) Use 6-gauge bare copper to bond the new corner ground rod to the new center ground grod.
5) Use 6-gauge bare copper to bond the rebar near the closest edge of the pour to the new center ground rod (as no ground rod would be necessary in the new pour).
6) Use 6-gauge bare copper bonded to the rebar at the shack wall and poking up to clamp to.

Is that about right? This is all new to me. Should I be burying the bare copper between ground rods or leave it lying on top of the ground or even fastened to the existing concrete foundation? Should the new ground rod near the existing utility ground actually be a minimum 8 feet from the existing, and if so then is that as the crow flies or the length of copper wire running around the corner to the existing ground rod wire?

In the cocrete/rebar, am bonding solid copper wire all the way from the ground rod through to the shack wall? Or am I just bonding to the rebar nearest the new ground rod and then separately bonding to the rebar with copper at the shack wall, letting the rebar span between the copper?

I'd like to do this right, but I have one of two modes of operation: either I follow instructions from those in the know or I dive deep and try to wrap my head around the entire concept and understand it fully before making a move. Due to time restrictions, I'm hoping to do the former instead of the latter :)
That document is very good, they had an older document that was entirely about UFER ground systems.

To add to what you have above. I would install a rod at your shack where you expect to have antennas enter the house so you can ground there.

You want a continuous run of copper from your shack to the utility ground. Lace the copper wire through the clamp, top to bottom and that way you have no breaks to worry about. Connections from that main run to the rebar can be short jumpers with bronze clamps at each end.

As far as the rod near the existing utility , I normally drive it in alongside a foot away and don't worry about it behaving worse than a new single rod, but since yours is buried you could go a few feet away. It is not as ideal as two new rods 16 feet from each other, but then again your old rod might only be 4 feet and then it's sphere is 4 feet plus the new 8 feet. I am more worked up about reducing the inductance at the utility ground. That's why I drive it alongside and bond it to old. In this game, more is merrier.
 

RFI-EMI-GUY

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I agree you should drive a new rod and put a temporary connection back to your electrical panel before disconnecting the old rod. You should not have connections to both rods when its done as there are rules about spacing between rods and they would be too close and may actually degrade things. # 6 copper meets NEC for bonding ground rods together but there is a length limit and you may have to upsize the wire if the run is over a certain length.

Not sure I entirely agree with the old and new interacting. It would be an excellent experiment given you have that impedance meter. Maybe NEC has reasons to pull old rod that are more to do with maintaining the sphere of influence rule than any functional reason.
 

prcguy

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There are rules about multiple ground rods and placing a couple close together is less effective during a lightning strike than just one. The rule is something like twice the distance between them as they are long but don't quote me on that. Two rods right next to each other would probably show lower ground resistance with a meter but for lightning mitigation some things apparently don't work as you would think.

Personally I think its better to leave the old rod disconnected and transfer the main ground wire to the new rod next to it and bond the others to that. But don't quote me on that either!!! Read NEC, it might be you bond additional rods at the service entrance and not at the first or original rod, I don't know that detail right now..

Not sure I entirely agree with the old and new interacting. It would be an excellent experiment given you have that impedance meter. Maybe NEC has reasons to pull old rod that are more to do with maintaining the sphere of influence rule than any functional reason.
 

Firekite

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wrap with electricians cloth and rubber electrical tape.
I’m not familiar with electricians cloth and can’t find anything with a google search, just a bunch of job site clothing. But I can get the battery terminal protection crease and some self-fusing electrical tape. I can also get the liquid tape and have a nearly full can of the NOCO battery terminal spray.

I would install a rod at your shack where you expect to have antennas enter the house so you can ground there.
The hard part is that right next to the house is under the patio roof overhang, which might make it tough to get an 8’ ground rod on there. But I can try. I’m trying to reduce tripling hazards and have the resulting product pass the wife test, so I don’t want to mount it away from the house.

Rather than driving a ground rod at the station wall, would it make sense to use a shorter ground rod or even just leave a piece of copper pipe bonded to the Ufer ground sticking up out of the concrete? The other ground rods I can bury easily.

My other general option is to mount everything on top of the garage roof, but that will add a good 50+ feet to any coax run I do, which means I could end up pushing close to 100’ which doesn’t seem like a good idea, especially for UHF (limits coax options).

I’m not sure how the pros do it, but it sure would be nice to penetrate the roof near the antenna, run the coax along the attic rafters, have it exit the eve down to the grounding point, and then either back up through the eve and poke out of the wall through a low-voltage bracket by the radio or else penetrate the brick to the interior wall.
 
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Firekite

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Firekite

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Got the station ground to go in 5 feet before hitting bedrock. Even put a big Hilti TE3000-AVR jackhammer the concrete guys let me borrow, only got it about 2 or 3 more inches before it just straight stopped and purely mushroomed out the top. I man have to call it good, Ufer bond it, and be happy.

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The other two are going to be a *****. I don’t know what to do. I may have to hire someone to figure it out. I tried using the bucket of the mini Bobcat S70 skidsteer to save my back, but one made it about 18” and the other only about 7 or 8 inches before lifting the Bobcat. Sledgehammer pings off it instead of thunking. Ugh. San Antonio and it’s stupid bedrock.

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RFI-EMI-GUY

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Bedrock! Where I am at, it is soil and sand. An alternate method is to drive the rods out horizontally in the earth. So if you are only going to get down 2 or 3 feet, it is better to angle it in and keep driving so you have earth covering as much of your rod. You will indeed need all that UFER bonding. The tool I use is one of those fence post drivers. The heavy red tube with handles that doubles as a forced entry tool. A hammer drill can do it as well. I think there is a common adapter.
 

RFI-EMI-GUY

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Firekite

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Got it all in and bonded in the concrete, which was the timely part. I’ll figure out the other ground rods later. Thank you both for all your help!

is it a dumb idea to have the roofer add a vent type port in the roof for bringing in coax to run down the inside of the rafters, out the eves, down to the ground rod, and then back up to the eves and over to the radio (straight line down and back, all over the same interior wall)? It would be a neater/tidier result, wouldn’t have to negotiate bending around gutters, and wouldn’t make a dam for leaves to and such from the overhanging trees to get caught on on the roof.
 
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