Cable Connection To Earthing Rod Clamp

[GavinK]

Does anyone have a photo clearly showing how the cable should be connected to the earthing rod ? Should it be 'welded' on or just use the clamp ? Is it a good/bad idea to cover the connection with a bit of grease to prevent rusting ? Couldn't find anything on google. Thanks.

[sirineou]

a copper clamp on a copper earthing rod is sufficient,, Grease is not necessary, it will only attract dirt . For pictures do a search on Google "electrical ground earthing rod" and choose images.

[Crossy]

As above ^^^.

To protect from corrosion avoid the connection contacting the soil and paint the connection with acrylic paint.

[Daffy D]

I smothered my connection in Vasaline and put a small plastic container upside down over it.

:-)

[electau]

Connection to a vertical electrode can be made using 2 U- bolts, they should be galvanised or stainless steel. Protect from corrosion using a metalic paint. The electrode should be exposed to the weather and not encased in concrete, the electrode should be attached to the building or structure to prevent mechanical damage.

[travelmann]

Before clamping coil the earth wire ( stripped bare) around the earth conductor, gives more of a surface area for the clamp to bite down on.

[Crossy]

Nobody actually seems to bother, but the Thai regulations require exothermic welding to attach the cable to the rod. See page 20-22 (Chapter 6) of http://www.pea.co.th.../groundwire.pdf

[electau]

Nobody actually seems to bother, but the Thai regulations require exothermic welding to attach the cable to the rod. See page 20-22 (Chapter 6) of http://www.pea.co.th.../groundwire.pdf

This is one method but it is not very practicable for the average electrical installation. Compliant methods may be U-bolts, split bolt clamps, earth clips that clamp around the electrode etc. (Copper C clamps are available but require a hydraulic crimping tool.)

The conection of the earth conductor to the electrode should cover a minimum of 80% of the contact area.

The electrode should not be encased in concrete. It should be exposed to the weather and the connection protected by a metallic paint. It must be visible for the purposes of inspection and testing, it must be protected against mechanical damage by affixing to the building or structure.

　

[Pib]

Nobody actually seems to bother, but the Thai regulations require exothermic welding to attach the cable to the rod. See page 20-22 (Chapter 6) of http://www.pea.co.th.../groundwire.pdf

Why do most grounding diagrams, like shown in above document, seem to imply/show the grounding wire connection to the ground electrode being "under" ground/foundation level versus above ground level where the connection can be easily accessed, inspected, painted, etc. Now actual pictures taken with a camera (versus just cartoon/sketch type diagrams) will show an above ground connection but the diagrams/sketches seem to imply underground...not only in above document but many English language documents I've seen and it's not uncommon for only diagrams/sketches to be shown in the documents.

[electau]

The reason that the earthing connection is above ground in an electrical installation is for visible checking, and mandatory testing requirements. It may be in a clearly indentified ground level accessable enclosure for mechanical protection providing it can be readily accessed.

The main earth and electrode is the most important connection in an electrical installation (along with protective earthing conductors) as this forms the basic electrical protection against the hazards of electric shock. Earthing conductors do not normally carry current except under earth fault conditions.

(AS3000 describes the requirements for earthing and earth electrodes and this is the reference that has been used).

[electau]

One would surmise that the connections shown on that PEA drawing is the system of connection to earth electrodes on the distribution system. In that case they are buried.

The distribution system and the electrical installation have different requirements.

[Crossy]

One would surmise that the connections shown on that PEA drawing is the system of connection to earth electrodes on the distribution system. In that case they are buried.

The distribution system and the electrical installation have different requirements.

Nope, it's like that in the domestic installation document too and also specifies exothermic welding as the approved connection method.

Nothing wrong with the rod connection being below ground level, but it must remain accessible for maintenance and inspection so an earth pit with a lid (length of 3" PVC pipe) is wise.

[p_brownstone]

How does one calculate the required sizes / gauges for the Grounding Rod and the connecting Cable?

Patrick

[Pib]

Even this Schneider Electric Thailand document which shows wiring of a Square D Customer Unit Load Unit and a RCBO shows the grounding connection being made 0.3M below earth level where it connects to a 2.4M long ground electrode. Seemingly inconsistencies between different electrical documents I've seen sure can make it confusing for the layman/Do-It-Yourself type. I know I sure would want the grounding connection point above ground where it could be easily inspected/repaired.

Consumer Unit_Load Center.pdf

Regarding the electrical distribution system in my western Bangkok moobaan, I will say that MEA (a.k.a., Bangkok Electric Company) has used a combination of grounding electrode connection methods for their distribution transformer case/neutral wire. Where there the transformer support poles are mounted in sidewalks, they just drilled a hole through the concrete sidewalk, drove the ground electrode to within a few inches of the sidewalk top, and then made the connection at that point--above ground...no sign of any other protection such as paint ever being applied. In other transformer locations where there is no concrete/sidewalk around the transformer support poles, you see the transformer case and neutral ground wires disappear into the earth where hopefully they are connected to a grounding electrode....you can pull on the wires and they won't come up. I've dug once about 6 inches down and did not find the connection point/electrode. I expect MEA probably pounds the grounding electrode into the ground about three-quarters of the way, stops and makes the grounding wire connection, and then pounds the electrode all he way in to below earth level.

Heck, a few months ago I noticed the neutral grounding wire coming down the pole to earth was completely broke a few inches above ground level...the other side of the wire continued on down into the earth to the grounding electrode. The wire was secured to the pole but this 10mm size multi-stranded ground wire was completely broke...maybe a lighting strike zapped it. Rather than calling the electric company and trying to explain the problem (not that it's really a problem with all the other grounding points around the moobaan) I just bought a 30 baht grounding U-bolt at Global and bolted the wires together....at least I know the transformer feeding my house and other nearby is fully grounded....to include the other transformer grounding wire hooked to the transformer casings. Might help to fend off lightning surges before the surges arrive the electrical service entrance of my home.

[electau]

http://www.erico.com/products.asp?folderID=41

http://www.thaitechno.net/t1/productdetails.php?id=6786&uid=34871

[phoneguy702]

Exothermic welding is the method used in commercial installations, for residential it is seldom used due to cost. Any electrical wiring/lighting/supply shop will stock the 1.8 meter rod, the brass clamp and will sell you the correct size wire. just tell them the size of your meter, incoming cable size and main breaker rating and it's a done deal. The connection is normally just below ground level and covered by a plastic landscaping box or 3-4" pvc pipe with a removable cover, you have no need to inspect the connection unless there is a problem so covering it keeps little hands from causing trouble. painting the connection with zinc chromate spray paint is preferred but any acrylic spray paint will do the job. Just be sure the connection is clean and tight before painting so you seal a good connection.

[electau]

PEA/MEA requirements. Main Earth electrode.

Type of electrode. Vertical

Material. Solid HD copper round section.

Size. 16mm ( 5/8inch)

Normal manufactured length. 2.4 meters.

Depth in soil (min) 2.4 meters.

Type of connection. isothermic weld.

Location of connection. 300mm below ground level.

　

AS3000. Electrical Installations.

Type of electrode. Vertical.

Material. Copper clad steel solid round section.

Size. 12.7mm(12mm).

Normal manufactured length. 1.5 and 2.0 meters.

Depth in soil (min) Aust. 1.2 meters. NZ. 1.8meters.

Type of connection. Approved connection to be made by a suitable device in accordance with the manufacturers specification that provides adequate electrical conductivity.

Location of connection. Above ground, or in an approved pit suitably identified for the purpose with its cover above ground level.

Corrosion protection required. Yes.

Test point available. Yes, the electrode.

Max resistance of the main earth conductor to the earth electrode. 0.5ohms.

AS3000 permits the use of alternative solutions for the designer and installer also alternative materials and types of material (excluding aluminium)

PEA/MEA use the prescriptive approach. AS3000 uses alternative solutions to obtain the desired result.

Minimum size of main earth. PEA/MEA 10sqmm.

Minimum size of main earth. AS3000. minimum 4.0sqmm in practice with individual domestic installation it is 6.0sqmm. Size is based on the CSA of the incoming comsumers mains in sq mm. so 16sqmm mains would have a minimum of a 6sqmm main earth.

　

Edited July 15, 2012 by electau

[canopy]

In the US, acorn clamps are approved for the connection. Recently I noticed in electrical shops in Thailand that ground rods come with an acorn clamp, something that never used to be the case. I have never seen acorn clamps sold separately. Ground rods sold in electrical shops are not copper, that is only a plating. I bought solid copper rods in china town Bangkok and acorn clamps in the US because I wanted the best ground.

Just connecting the ground even to an acorn clamp needs done with care. The cable does not go between screw and rod. It goes on the other side between clamp and rod. The cable is above the clamp and turned downward. And there are more important details that should be met on the connection. Due to the life or death importance of a ground, the materials and workmanship should meet or exceed every part of the specification. This is not an area to skimp or turn a blind eye to bad practices.

[electau]

Alternative materials AS3000.

Materials and dimensions of earth electrodes shall be selected to withstand corrosion and have adequate mechanical strength.

Type of electrode . Vertical.

Material. Steel.

Surface treatment. Copper clad, copper plated, stainless (clad).

Minimum dimensions. 12mm circular rod

Surface treatment. Hot dipped galvanised. Minimum dimensions 16mm.or a section with a minimum cross sectional area of 200sqmm and no part less than 3mm thick.

Non ferrous ( excluding Aluminium). solid. minimum 12mm.

The surface treatment of the steel electrode. is to protect against corrosion.

　

Edited July 17, 2012 by electau

[electau]

In the US, acorn clamps are approved for the connection. Recently I noticed in electrical shops in Thailand that ground rods come with an acorn clamp, something that never used to be the case. I have never seen acorn clamps sold separately. Ground rods sold in electrical shops are not copper, that is only a plating. I bought solid copper rods in china town Bangkok and acorn clamps in the US because I wanted the best ground.

Just connecting the ground even to an acorn clamp needs done with care. The cable does not go between screw and rod. It goes on the other side between clamp and rod. The cable is above the clamp and turned downward. And there are more important details that should be met on the connection. Due to the life or death importance of a ground, the materials and workmanship should meet or exceed every part of the specification. This is not an area to skimp or turn a blind eye to bad practices.

Contact surface area between the soil and the electrode surface will be the determining factor. The actual soil resistance is uncontrollable, and may vary from a few ohms to over a thousand ohms.

Edited July 17, 2012 by electau

[canopy]

As far as contact area, that is why it is not unusual for a house in the US to have 8 ground rods, each one being of large diameter and long--each much bigger than the ones you see in Thailand. Besides contact surface area, other factors impact resistance such as moisture of the soil. Ground rods should be buried away from the house where they will be in contact with damp soil, not under the house where the soil is dry.

[electau]

As far as contact area, that is why it is not unusual for a house in the US to have 8 ground rods, each one being of large diameter and long--each much bigger than the ones you see in Thailand. Besides contact surface area, other factors impact resistance such as moisture of the soil. Ground rods should be buried away from the house where they will be in contact with damp soil, not under the house where the soil is dry.

AS3000.

Earth electrodes must be installed where exposed to the weather eg on an outer wall of a building or structure.

When carrying out earthing tests there is no specific resistance to earth required for the electrode at an electrical installation connected to an MEN system.

However the impedance of the combined earthing system must meet the earth fault -loop impedance requirements.

However US requirements under the NEC code may require a minimum earth resistance and this is why it may be required to have additional electrodes. This may be required when using a TT system.

In practice the main earth and electrode on a MEN system carries very little current under fault conditions as to be disregarded. The main function of the main earth and electrode is to maintain zero volts between the neutral and earth. Fault current returns to the point of supply through the MEN link and the neutral conductor.

With TT systems the fault current is low and may not be sufficient to operate a protective device within the required disconnection times so RCD protection is employed. In this case fault current flows in the main earth and electrode.

Edited July 18, 2012 by electau

[canopy]

Code in the US requires at least 2 rods spaced minimum 6' apart unless you can prove <=25 ohms resistance with one rod. Code requires rods to be minimum 8' long and minimum 5/8" diameter. Above code is 8 rods spaced 8-20' apart and tied to well casing if available.

[Neeps]

For the connection protection, I recommend the use of Denso Tape (waxy cloth). This should be checked every year and renewed if necessary.

The Earth Electrode in all purposes should be installed inside an "Earth Pot" (UK Terminology), away from Soil for inspection purposes. Can be a cement made purpose buy or a simple 4" PVC pipe.

[Neeps]

And hopefully the attachment helps people regarding Earthing Electrodes. From IEE.

scan0002.pdf

[bbradsby]

am seeing several materials mentioned here for rod & clamps. the homeowner is advised that using different metals for conductor (wire), ground rod & clamp will cause a galvanic (electrolytic) reaction and the connection will fail due to corrosion. Especially, don't use galvanized connectors with copper rod - that would last maybe a year. Use brass clamps for a copper rod.

[electau]

Hot dipped galvanised clamp or stainless steel is permitted under AS3000 providing that all connections are protected from corrosion by the use of a metallic paint.

Aluminium must not be used as an earth electrode, but aluminium may be used as a main earth conductor providing that the CSA is not less than 16sqmm.

Aluminium to copper (brass) terminations are available.

Clipsal (Schneider) manufacture earth clamps in hot dipped galvanised and brass for earth electrodes.

Edited August 21, 2012 by electau

[Crossy]

Electau has the critical point, the joint must be protected from moisture, with no electrolyte galvanic corrosion will not occur. UK regs suggest an acrylic paint but metallic paint or a waterproof tape wrap would work, there is no argument that it must be accessible for checking and maintenance.

As for rod material, pretty well anything metallic and reasonably corrosion resistant (Aluminium is a definite no-no) will work. Copper (expensive), copper clad steel, stainless steel or hot-dip galvanised steel are all OK.

[David006]

all good info......recon someone should pin this thread..regular mini series...

Seems a lot of rules and regs covering connection type and material which are ,atleast in Thailand, mostly ignored...especially the bit about "inspection and maintenance". Looking around at the EPA infrastructure and observing the euphemistic "inspection" done at our house..quite sadly laughable really.

Gotta go... busy day ahead breaking up the concrete apron around the house to inspect and maintain my clamped and lanolin greased ground connections...lol

Sorry for being a being so cynical.:-)

BTW for some reason your link to the Thai rules froze Firefox and converted my mouse pointer to ineffective cross hairs ?

[bbradsby]

with a bolt/screw-type tightener that fixes a typical clamp to the ground rod, a paint-on coating will be penetrated and allow galvanic reaction between dissimilar metals. if painted after the connection is made, the coating won't work at the connection point. and keeping moisture out of a ground rod connection in LoS is a bit idealistic. I'd recommend copper conductor & rod and bronze clamp rod, or stainless steel clamp if the conductor must be aluminum. then apply protective coating and enclose in 4"ABS pipe section with cap.