Can't get earth rod under 200ohms

[M107]

Or dropped through the waste water pipe :innocent

 

[Larnacaman]

always double up on depth before putting a second rod in,as Apache says, deeper holds moisture more(closer to water table),

also remember that if you do need to drive a 2nd rod in to go twice the distance of depth of the deepest rod.

hope that makes sense....

Good solid advise, that should be taken into consideration the next time anyone needs to install a TT system. You can't expect miracle's from those short 1.2m x 3/8'' rods. The longer the separate rods the better, and never less than 5/8'' Dia.....

 

[Lee321]

wont it trip all the way upto 1667? it should

 

[Manator]

DEEP EARTH GROUNDING

Interesting reading from a Nebraska company

 

[Revved Up Sparky]

[quote name='Lee

 

[Andy™]

to keep touch voltage below 50v, max Zs testing at 150mA would be 333.3 ohms

some test kits may detect that Zs is too high and will have a greater touch voltage, and wont do the test

 

[Larnacaman]

I done one last week but had to break up a concrete path as nowhere else to put it. I decided to bang a thin rod through the expansion joint in the concrete path to test if I was going to get a decent reading. Banged it in a foot and took reading of 437 ohms then banged it in another 6 inches and it went down to 198 ohms. So broke some concrete then put in the 5/8 rod and got my best reading yet. 7.40 ohms. I was amazed bit then client told me the supply tx was 2 garages away lol.

Now just think what you may of got, with coupling another rod on to that 7.4 ohm rod??

 

[Andy™]

Now just think what you may of got, with coupling another rod on to that 7.4 ohm rod??

gas leak from going through the pipe instead of touching it?

 

[m4tty]

The supply transformer was 2 garages away so 20 foot roughly. Is that why it's such a good reading. YOur getting me worried now lol.

 

[steptoe]

it will be fine as long as you dont pull it out.

 

[Sidewinder]

DEEP EARTH GROUNDINGInteresting reading from a Nebraska company

Manator,

Yes interesting reading, though typical of the "other side" of the Atlantic.

We used to get loads of grief with our kit over there that performed faultlessly over here & in mainland Europe and across much of the rest of the globe!

It does seem that contractors have scant regard for the NEC.

Also though some of these systems are "propper" TT!

Rod spacing of at least depth is normal over here is it not unless the rods are to be considered a single device, e.g. a group of 4 rods in 4 places giving 4 earth electrodes.

I am thinking about getting hold of some Bentonite and doing a TT experiment.

I have access to a TT supplied property with a single stable rod below the NIC guidelines but not as low as I would like to see.

I am seriously thinking about changing it and driving it deeper, at least twice the depth it is now if not 3-4 times, then adding a few parallel rods to check the affect and taking readings at each point.

 

[Manator]

There have been a few experiments over here using Bentonite I also remember some environmental agency guy saying it should not be used on deep rod installations because of the unknown leakage into the water, I am not sure of the location of this information, its just from memory.

Substations in this country use both mesh and deep rod, some are very similar to the American set up, but we tend to go one step further.

 

[steptoe]

I know a lot of houses where the rebar in the founds has been bonded via a loop left for this sole purpose,

as well as the ubiquitous rod of course,

was a quite common method in norn iron during the late '80s early '90s , dunno if its still done that way though.

 

[Manator]

Very true, I still come across redundant rods that have never been used but installed at the time the building went up, I have also seen multiple rods installed for the purpose of lightening protection that again was never installed. Looks like the world is full of redundant rods

 

[steptoe]

addresses Manator,

ADDRESSES !!!!!!

you cant leave a man hanging!!!! :|

 

[Larnacaman]

There have been a few experiments over here using Bentonite I also remember some environmental agency guy saying it should not be used on deep rod installations because of the unknown leakage into the water, I am not sure of the location of this information, its just from memory.Substations in this country use both mesh and deep rod, some are very similar to the American set up, but we tend to go one step further.

You sure about Bentonite being un-environmentally friendly?? It's basically only a naturally occurring clay that has conductive properties of holding high levels of moisture for extended periods of time. We've used it extensively, on the Great Man Made River Project in Libya directly over the natural underground reservoirs to ground the pumping stations. That Project had environmental water Engineers crawling over everything.

It was also used extensively, on the cathodic protection of buried 7m x 4m pipe sections where the pipeline passed through particually corrosive areas using magnesium anode strings dropped in Bentonite filled boreholes.

Recently, we've been using quite a lot of Portland and carbon particle cement, for rod enhancement, which also has given some pretty decent results.

 

[Manator]

Its all from memory Larnicaman, I am unsure if it was Bentonite on its own or another type of mixture combined, If I have time I will troll through and see if I can find it. It is as you say a natural slurry type of clay and as far as I am aware has many applications. I just remember at the back of my memory an environmental report about water table and the use of Bentonite. For all I know it may have been the type of alloy used for the rod.

 

[CHICKI]

rods spaced less than two rod-lengths apart will interfere with each other because their effective resistance areas will overlap. The overlap increases the net resistance of each rod, making the grounding electrode system less effective than if the rods were spaced farther apart.