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Type A V/S Type B Earthing

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  • Type A V/S Type B Earthing
WHICH IS RECOMMENDED BY STANDARDS?
CONCRETE EMBEDDED FOUNDATION EARTH ELECTRODE (TYPE “B” EARTHING AS PER IS/IEC 62305)

V/S

SOIL EMBEDDED EARTH ELECTRODE (TYPE “A” EARTHING AS PER IS/IEC 62305)

Concrete used for the foundations of buildings has a certain (relative comparison) conductivity and generally “a large contact area” with the soil. Bare metal electrodes completely embedded in concrete ( at a depth of 5 cm minimum) is strongly recommended for earthing purposes, as they are highly protected against corrosion, normally for the whole life time of the building as per IEC 60364: Low voltage electrical installations, Part 5-54: Selection & erection of electrical equipment- Earthing arrangements & protective conductors. It is recommended that the conductive effects of the reinforcement of the building should also be used, wherever possible but the aim should be towards using it rather than leaving it.


The “only economical solution” is the use of concrete embedded foundation earth electrode during the erection of the building (itself) to obtain lower earth resistance value which is long standing because:


1) It does not necessitate additional excavation works

2) It is erected at a depth which is normally free from negative influences resulting from seasonal weather conditions

3) It provides good contact with the soil

4) It extends over practically all of the building’s foundation surface and results in minimum earth electrode impedance which can be best obtained with this surface.

5) It also provides optimal earthing arrangement for lightning protection system

6) From the beginning of the erection of the building, it can be used as earth electrode for the electrical installation of the construction site resulting in huge savings as we can do away completely with temporary earth electrodes

7) Provides a good basis for the main protective bonding, as bonding gets preference over earthing itself as per standards.

Only in the case, where the foundation has to use certain insulating measures against water, the following alternate measures shall be used:

- For earthing, additional concrete embedded foundation earth electrode below the ISOLATED FOUNDATION shall be used.

- Earthing arrangement around the building shall be used- I.e. RING EARTHING.

-Lastly, if the above options are not possible practically, type A earth rods shall be used as a last option.


Finally, concrete embedded foundation earth electrodes of single foundation (eg. large hall) should be connected to other parts of concrete embedded foundation earth electrodes by using suitable earthing conductors to abide “GLOBAL EARTHING CONCEPT” as described in IS 3043- Code of practice for earthing.


Only stainless-steel electrode shall be installed directly from foundation concrete into the soil to avoid corrosion effects. Hot dip galvanised steel shall not be used for this purpose.


After preparing the connected reinforcement, but before the concrete is poured, a survey & documentation record of the arrangement should be made by a skilled person containing description, plans & photos and should form part of the whole documentation for the electrical installation.


As this is a specialised process, contact JEF for all your foundation earthing projects.