The 5/8 Earth rod debate

[huntos33]

Did a re wire on a village hall TT system , after reading the threads on rods i went for it, chucked away the 3/8 twig coupled together 3 5/8 rods and away i went driving away with my 4lb lump hammer 3.6m of depth and got my ZE down to 14 ohms so i guess thats a ok reading for a TT well bellow the 200 ohms , but was hoping it would be a lot lower...

 

[Engineer54]

Did a re wire on a village hall TT system , after reading the threads on rods i went for it, chucked away the 3/8 twig coupled together 3 5/8 rods and away i went driving away with my 4lb lump hammer 3.6m of depth and got my ZE down to 14 ohms so i guess thats a ok reading for a TT well bellow the 200 ohms , but was hoping it would be a lot lower...

I bet that when you first started driving in the first rod, it was swinging around all over the place using a lump hammer!! lol!! Anyway now for the good news, ...Because the rod couplers have a greater diameter than the rods themselves, the ground soil, is not as yet consolidated around the top two rods. So you can expect that 14 ohm Ra value to get considerably better over the next 12 to 18 months as that ground compacts and consolidates around those two upper rods... One things for sure, you will have created a very stable TT system, and a system that will only improve over the coming months....

Well Done!!!

 

[edexlab]

yep....dig a pit first ...just to be sure......

That was a serious question , a friend of mine lives on the south coast and told me he knew of a case where someone knocking a rod in went through a 240mm cable, it penetrated 2 phases and he received serious burns and some fragments of the exploding cable injured his legs,
for example if you are digging a trench then the obvious thing is to use a cable locator to check for hidden utilities yet no one seems to think twice about knocking a rod in without checking whats below them.

 

[somersetsparks]

That was a serious question , a friend of mine lives on the south coast and told me he knew of a case where someone knocking a rod in went through a 240mm cable, it penetrated 2 phases and he received serious burns and some fragments of the exploding cable injured his legs,
for example if you are digging a trench then the obvious thing is to use a cable locator to check for hidden utilities yet no one seems to think twice about knocking a rod in without checking whats below them.

surely he would have penetrated the earthed sheath first?

 

[needasparks]

I also dig at least 2 ft and usually a meter to make sure there's no services.

Dig a metre ! or use a meter ? you sure your not just digging for diamonds

 

[Engineer54]

That was a serious question , a friend of mine lives on the south coast and told me he knew of a case where someone knocking a rod in went through a 240mm cable, it penetrated 2 phases and he received serious burns and some fragments of the exploding cable injured his legs,
for example if you are digging a trench then the obvious thing is to use a cable locator to check for hidden utilities yet no one seems to think twice about knocking a rod in without checking whats below them.

A 240mm SWA cable is in all likelihood, going to be a DNO cable, unless on an industrial or large commercial site. So in that instance there should have been cable protection tiles (usually 10'' X 10'' concrete paver's) so he should have known that he had hit something quite solid. Bit foolish to carry on thumping away, without making some kind of investigation. It's not as if he'd gone down that far before hitting that protection tile....

 

[StuSpiers]

Just created a blog of my last Spike install.

How To install An Adequate Earth Spike - Blogs - Electricians Forum | Electrical Advice Forum | An electrical forum for electricians in the UK | Electricians Forum

Was a beauty!

 

[Guitarist]

I'm sure that a few members may pull this apart a bit, but well done mate. You did a great job creating this for people who don't know what to do (but are too afraid to ask)

 

[StuSpiers]

yup I sure it doesn't tick every box, after all it's only my humble opinion.


It's got to be better than installing a stick though, and will result in a fairly stable and safe TT system.

 

[Marvo]

I'm glad people are getting a bit more excited about achieving a decent TT earth, I think it's a worthwhile thing not to put all your eggs in one basket relying on the RCD because of a poor Ra.

Maybe with the growing interest they'll do end users everywhere a favour and amend the regs at some stage in the future.

 

[PEG]

Congratulations on a belting article.Such a vital component of that system has now been fitted well and to last.Small comfort i know,but future sparks will very likely now only have to wave a tester about and not a hammer.Respect due :flowers:

 

[KevinS]

"all the force just causes a lot of vibration and not much penetration."

Nothing worse!

Read more: http://www.electriciansforums.net/e...62028-5-8-earth-rod-debate.html#ixzz23wNSb5ie

 

[MarkieSparkie]

..Nothing worse!

Read more: http://www.electriciansforums.net/e...62028-5-8-earth-rod-debate.html#ixzz23wNSb5ie

Err, something worse, you have referenced the thread we are all reading!

 

[trev]

Just created a blog of my last Spike install.

How To install An Adequate Earth Spike - Blogs - Electricians Forum | Electrical Advice Forum | An electrical forum for electricians in the UK | Electricians Forum

Was a beauty!

Good article mate, one criticism though. The ones who don't know how to create a good TT system may have a few why questions.
Such as, why come away from the building 2 metres? Well we know that the area you're avoiding will probably be filled with the builder's rubble but the uninitiated may not.

 

[Engineer54]

Just created a blog of my last Spike install.

How To install An Adequate Earth Spike - Blogs - Electricians Forum | Electrical Advice Forum | An electrical forum for electricians in the UK | Electricians Forum

Was a beauty!

A good effort at bringing some important factors together for the benefit of those that are inexperienced in providing a TT system...

I am however, having problems with the Ra values you gained. The only exception, would be if the area is or was at one time a salt marshland. I see that you were using a MFT to measure Ra values, one that i take has a 3 pole earth test facility. Did you check these values you gained, with a Ze type ELI test at the service head position (MET) with the bonding conductors disconnected etc?? Without knowing what distance your axillary/temporary current test rod (Y) was placed and the distances your voltage test rods (Z / Z1 / Z2) were placed, i can't really comment. Only that they do need to be placed in a relatively straight line, the greater the distances, and the more points the Z rod/spike is tested (normally 3 points but better with 5, ...''eg 50% -10 / -20% / +10% / + 20%'') the more accurate the values obtained will be. It's fine to water in the temporary rods, but never the earth rod/electrode under test!! I doubt very much that your Ra value will half in the course of just one day, it takes a number of months for ground soils to consolidate around driven rods.

 

[imago]

why come away from the building 2 metres? Well we know that the area you're avoiding will probably be filled with the builder's rubble but the uninitiated may not.

True, but there's another factor to consider with the distance from where builing work was carried out. Most of the chemicals and mixes used (cement, plaster etc) are alkaline. Not only are they affecting the soil pH level during building work, but the affect the pH level as the rain runs through the brickwork and concrete. Alkaline soil has less hydrogen ions in it and is less conductive than acid soils. So the distance away from the building is more about chemical differences in the soil as it is about rubble.

At two metres from the building you are at a point where you can reasonably expect the soil conditions to be at 'normal' levels for the area.