Ground rod in every light pole?

[hillbilly1]

Well dirt isn't a good conductor either. If it makes you sleep better at night then make sure the anchor bolts are connected to the rebar cage

It is not for a fault return path, it is for reducing transient voltages, just like a ufer ground.

 

[winnie]

As @hillbilly1 is describing things, the rebar cage is not being used as an UFER, and a ground rod might help for coupling lightning spikes to ground. But it seems like a huge wasted opportunity, because a connection to the rebar cage would likely provide a much better earth connection than a driven rod.

In fact, given the problems being considered (damage caused by lightning), having a good ground electrode (the rebar cage embedded in the concrete) very close to, but _not_ solidly bonded to the metal pole might be a recipe for disaster.

-Jon

 

[LarryFine]

Adding a pigtail to the rebar a la a Ufer would assure pole-to-rebar continuity.

 

[mtnelect]

When I was doing traffic signal work for the County of Los Angeles, we started converting our controllers from electromechanical to digital. We were installing "170 Controllers" which were all solid state. Our electrical service started on a utility pole and went underground to the controller where we installed a second ground rod. After installing several cabinets, we started getting calls that the intersections were going on "Flash". I discovered that there was a difference in potential between the two ground rods. So, I disconnected the second ground rod at the controller cabinet and pulled a grounding conductor back to the service, and that corrected the problems.

 

[hillbilly1]

As @hillbilly1 is describing things, the rebar cage is not being used as an UFER, and a ground rod might help for coupling lightning spikes to ground. But it seems like a huge wasted opportunity, because a connection to the rebar cage would likely provide a much better earth connection than a driven rod.

In fact, given the problems being considered (damage caused by lightning), having a good ground electrode (the rebar cage embedded in the concrete) very close to, but _not_ solidly bonded to the metal pole might be a recipe for disaster.

-Jon

I agree, bonding to the rebar cage would be more effective, but for some reason the engineers spec the ground rod instead. Maybe a straighter path to earth?

 

[jim dungar]

Maybe a straighter path to earth?

It wouldn't be straighter to get to the rebar, unless the ground rod is installed in the concrete of the base. Lighting does not manage 90°bends very well.

 

[jaggedben]

I agree, bonding to the rebar cage would be more effective, but for some reason the engineers spec the ground rod instead. Maybe a straighter path to earth?

It's not straighter, is the thing.

Maybe they don't trust the construction process. i.e. they worry that the concrete will get poured before the bonding wire is installed and brought above the footing.

Or, maybe the light pole covers the top of the footing in such a way that bringing a bonding wire out of the top of the sonotube gets in the way.

Or maybe they think having a rod outside the footing might direct lightning away from the footing and the wiring within it?

Or maybe they've just always done it that way and have giving up thinking further on it. It's not their money.

The above (other than my first sentence) is all speculation, to be clear.

Do the engineers specify exactly where to put the rod? What do you normally bond it to?

 

[hillbilly1]

It wouldn't be straighter to get to the rebar, unless the ground rod is installed in the concrete of the base. Lighting does not manage 90°bends very well.

That’s what I meant about the ground rod, it being a straighter path.

 

[jim dungar]

That’s what I meant about the ground rod, it being a straighter path.

How many ground rods are installed in pole bases?

 

[rambojoe]

I don't know if an 'electrical design drawing' (OPs words) is the same as an 'engineered drawing'. It makes a difference, to me anyway, if it was stamped by a licensed outside engineer or just drawn up by my fellow employee.

The wording is
Detail drawings.. or spec drawings.. since when can we argue those ?!

 

[hillbilly1]

How many ground rods are installed in pole bases?

Just one, most of the time it is just thrown in the center of the hole, maybe 6” to a foot of actual earth contact. I have not seen very many actually driven at the side of the hole, hence the straighter path.

 

[mtnelect]

We use copper plumbers'(ones with the holes in it) tape to wrap around each conduit entry at the base of the standard, to bond together.

 

[jmellc]

But if the pole is bolted to anchor bolts and the anchor bolt are embedded in concrete, and the concrete is in the earth what is a ground rod going to add to the party? Some critical thinking is required here.

I wonder about that too. I know the anchor bolts aren't 8 feet but there are 4 of them on all poles I've seen, and all metal to metal with brackets, etc.

 

[gadfly56]

I wonder about that too. I know the anchor bolts aren't 8 feet but there are 4 of them on all poles I've seen, and all metal to metal with brackets, etc.

Do we know that the anchor bolts/pole are bonded to the rebar cage?

 

[drcampbell]

We use copper plumbers' ... tape ...

Is that stuff difficult to find? I've only seen copper-plated mild steel.
(I admittedly do very little plumbing work)

 

[petersonra]

Some critical thinking is required here.

If people were doing any critical thinking about this, we would probably not worry all that much about connecting the electrical system to earth.

 

[mtnelect]

Is that stuff difficult to find? I've only seen copper-plated mild steel.
(I admittedly do very little plumbing work)

Now, for traffic signals they use pvc conduit with multi conductor cable pulled to each standard.

 

[jmellc]

Do we know that the anchor bolts/pole are bonded to the rebar cage?

Good thought, probably not. Another thought is if a pole is knocked down but still has power. It should especially be grounded then. We had 1 knocked over about 2 months ago and the light stayed on all through.

 

[mtnelect]

We use copper plumbers'(ones with the holes in it) tape to wrap around each conduit entry at the base of the standard, to bond together. Also, to tighten the copper tape we use a 8-32 brass screw and nut through the holes.

 

[tom baker]

We used disconnect fuse holders in base of. pole incoming power wires were zip tied to conduit. Pole knockdown pulled out wires from fuse holders. Often pole would be thrown over top of car