Hi folks,
Looking for advice here - my boss tells me that an earth stake directly into concrete is non-compliant (residential), but looking at the rules I'm seeing '5.3.6.4 (a) This condition is deemed to be satifisfied by locating the electrode - (a) external to the building in ground that is exposed to the weather'
That reads to me as 'if it's outside and not under a roof it's compliant.'
Is that correct?
Thanks,
Earth stake directly into concrete
Re: Earth stake directly into concrete
Can't read an explanatory / supportive Note and ignore the words of the actual requirement:
" effective contact with moist soil that is not subject to excessive drying out".
Also, item (a) of Note to Condition (a) includes the words "exposed to weather".
So if the ground in question has been paved over with concrete, the condition is not satisfied
The soil won't remain moist, and the electrode (as against the connection of MEC to it) isn't exposed to weather.
Unless we do something about it.
Like using one of the special earth electrode covered pits that are readily available.
Both types I know of allow some rain etc to penetrate around the lid, so helping keep the soil moist ;
and this counts as the electrode being "exposed to weather" enough to met condition (a)
They also meet condition (c) for access; and they provide protection for the MEC connection[5.5.1.2 (c).
No nasty stub sticking up to be tripped over / fallen onto.
A nice tidy solution all round.
" effective contact with moist soil that is not subject to excessive drying out".
Also, item (a) of Note to Condition (a) includes the words "exposed to weather".
So if the ground in question has been paved over with concrete, the condition is not satisfied
The soil won't remain moist, and the electrode (as against the connection of MEC to it) isn't exposed to weather.
Unless we do something about it.
Like using one of the special earth electrode covered pits that are readily available.
Both types I know of allow some rain etc to penetrate around the lid, so helping keep the soil moist ;
and this counts as the electrode being "exposed to weather" enough to met condition (a)
They also meet condition (c) for access; and they provide protection for the MEC connection[5.5.1.2 (c).
No nasty stub sticking up to be tripped over / fallen onto.
A nice tidy solution all round.
- Rating: 16.67%
Re: Earth stake directly into concrete
So a series of holes in the concrete in the near vicinity of the stake would also satisfy this.
There are several clauses in 3000 that allude to the porosity of concrete and it's ability to allow water to soak into and pass through it, could it not also be considered a covering that maintains moist soil that is not subject to excessive drying out as would be the case with bare earth?
There are several clauses in 3000 that allude to the porosity of concrete and it's ability to allow water to soak into and pass through it, could it not also be considered a covering that maintains moist soil that is not subject to excessive drying out as would be the case with bare earth?
Re: Earth stake directly into concrete
In my opinion concrete cannot be considered a covering that maintains moist soil .
Concrete may be slightly porous, but not very.
Note it's used to make water tanks, also boats.
True they put in additives to make it even less porous for those jobs.
For sunken basements they paint it with special paints on the outer face, before back-filling.
And for a house floor slab there's a plastic membrane underneath.
But just a normal mix doesn't readily pass water through, certainly not enough to maintain moisture levels in the ground underneath the paving.
What you can do is use one of the several brands of housing designed for the purpose, the round ones have a hole in the lid, the square ones let in water around the edges of the lid.
Ye,s drilling holes could work. But generally much easier, and tidier, to use the product designed for the job.
Concrete may be slightly porous, but not very.
Note it's used to make water tanks, also boats.
True they put in additives to make it even less porous for those jobs.
For sunken basements they paint it with special paints on the outer face, before back-filling.
And for a house floor slab there's a plastic membrane underneath.
But just a normal mix doesn't readily pass water through, certainly not enough to maintain moisture levels in the ground underneath the paving.
What you can do is use one of the several brands of housing designed for the purpose, the round ones have a hole in the lid, the square ones let in water around the edges of the lid.
Ye,s drilling holes could work. But generally much easier, and tidier, to use the product designed for the job.
Re: Earth stake directly into concrete
Our electrodes are required to be 1.8m into the ground. The top 500mm or so of the electrode is the least effective part. And that's pretty much the only part that will be affected by rain water.
IMO, being installed through something like a concrete path would make little difference. A large area of concrete might be different, but I don't know how much drying out would occur at the 0.5-1.8m depth range
I have installed through paths before, and had them inspected. But that doesn't alway mean the inspector is correct.
But, doing a high current loop test on the electrode will give you an idea of how effective it is. Doing the loop test on all installations in the areas you work in, will give you an idea of average values for the area.
IMO, being installed through something like a concrete path would make little difference. A large area of concrete might be different, but I don't know how much drying out would occur at the 0.5-1.8m depth range
I have installed through paths before, and had them inspected. But that doesn't alway mean the inspector is correct.
But, doing a high current loop test on the electrode will give you an idea of how effective it is. Doing the loop test on all installations in the areas you work in, will give you an idea of average values for the area.
Re: Earth stake directly into concrete
Agree with Doug on pretty much all his points.
But to me the question isn't really about effectiveness of the electrode; it's more compliance with the requirement.
Which is "effective contact with moist soil" - and that is always going to be a subjective rather than an objective assessment.
Looking in particular at that Note; as I said before I don't think ground covered in concrete can be considered "ground that is exposed to weather".
But an argument could be made that concrete amounts to "covers that reduce loss of moisture".
That comes down to installer's (or rather certifier's) opinion, plus Inspector's opinion.
Using an enclosure designed for the purpose removes the subjectivity, because all the ones i know about allow surface water to drain into the enclosure to keep the soil moist (even if it is only the upper portion of a vertical electrode, or the near end of a horizontal one.
And also provides a very tidy solution, in line with good trade practice.
Basically I don't want to be in coroner's court answering questions about why I left a steel spike sticking up out of the ground for a child to fall onto.
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Fact is, we don't have any specific performance requirement for installation earth electrodes.
None of them will ever be effective enough to allow sufficient fault current to flow for operation of an overcurrent device within time limit.
Which is why, for "TT" installation, there's always a 'front end' RCD that will operate within time limit on the level of earth fault current that is likely to flow (and any exposed conductive parts upstream of that RCD - up to & including main switchboard enclosure - gets earthed to the incoming 'neutral').
But carrying earth fault current is not what the installation electrodes are there for under the "MEN" system.
Their real task is simply to keep the distribution 'neutral' at close to earth potential.
And they don't need to be (individually) very good to do that, as long as there are enough of them.
Ohm's Law says that a number of high impedances in parallel adds up to a low overall impedance, and that's what's needed
But to me the question isn't really about effectiveness of the electrode; it's more compliance with the requirement.
Which is "effective contact with moist soil" - and that is always going to be a subjective rather than an objective assessment.
Looking in particular at that Note; as I said before I don't think ground covered in concrete can be considered "ground that is exposed to weather".
But an argument could be made that concrete amounts to "covers that reduce loss of moisture".
That comes down to installer's (or rather certifier's) opinion, plus Inspector's opinion.
Using an enclosure designed for the purpose removes the subjectivity, because all the ones i know about allow surface water to drain into the enclosure to keep the soil moist (even if it is only the upper portion of a vertical electrode, or the near end of a horizontal one.
And also provides a very tidy solution, in line with good trade practice.
Basically I don't want to be in coroner's court answering questions about why I left a steel spike sticking up out of the ground for a child to fall onto.
--------
Fact is, we don't have any specific performance requirement for installation earth electrodes.
None of them will ever be effective enough to allow sufficient fault current to flow for operation of an overcurrent device within time limit.
Which is why, for "TT" installation, there's always a 'front end' RCD that will operate within time limit on the level of earth fault current that is likely to flow (and any exposed conductive parts upstream of that RCD - up to & including main switchboard enclosure - gets earthed to the incoming 'neutral').
But carrying earth fault current is not what the installation electrodes are there for under the "MEN" system.
Their real task is simply to keep the distribution 'neutral' at close to earth potential.
And they don't need to be (individually) very good to do that, as long as there are enough of them.
Ohm's Law says that a number of high impedances in parallel adds up to a low overall impedance, and that's what's needed