Bonding 18th edition ?

Are there new rules for main protective bonding in the 18th ed.?


However, there are some new rules allowing switching devices in the protective conductor


Legh

I think the only new 'rule' is the sentence in 411.3.1.2 which is a long-overdue correction of the long-standing error in 544.1.2.


Unfortunately, the error in 544.1.2 has not been removed.




Anyway - neither of these affects the correct application of main bonding which, like the physics, has not changed.


Namely, that main bonding is applied to extraneous-conductive-parts and not applied to parts which are not e-c-ps..

I.E.T. On Site Guide page 47. Also B.S. 7671 411.3.1.2.


Main protective bonding is to be installed complying with Chapter 54 and shall connect the main earthing terminal to extraneous-conductive-parts including:


Water installation pipes,


Gas installation pipes,


Other installation pipework and ducting,


Central heating and air conditioning systems,


Exposed metallic structural parts of the building.


Metallic pipes entering the building having an insulating section at their point of entry need NOT be connected to the protective equipotential bonding.


So a metal water  pipe with a plastic meter or plastic pipe fitting at the point of entry may negate the need for main bonding of the internal installation water pipework. Or if the incoming water pipe is plastic the same applies.


Of course metal pipes buried in a conductive damp screed or in the ground inside a house may need bonding if they are extraneous conductive parts. Some older houses have old iron pipes buried in the ground.


Z.

geoffsd:

I think the only new 'rule' is the sentence in 411.3.1.2 which is a long-overdue correction of the long-standing error in 544.1.2.


Unfortunately, the error in 544.1.2 has not been removed.

Anyway - neither of these affects the correct application of main bonding which, like the physics, has not changed.

Namely, that main bonding is applied to extraneous-conductive-parts and not applied to parts which are not e-c-ps..

 

Hi Geoff

Could you explain the error in 544.1.2.

As far as I can see, services entering any building which have a ground potential, pressumably because they are made of metal) must be bonded to the MET. What is wrong with that?


Legh

544.1.2 The main protective bonding connection to any extraneous-conductive-part such as gas, water or

other metallic pipework or service shall be made as near as practicable to the point of entry of that part into the

premises. Where there is a meter, isolation point or union, the connection shall be made to the consumer’s hard metal

pipework and before any branch pipework. Where practicable the connection shall be made within 600 mm of the

meter outlet union or at the point of entry to the building if the meter is external.

Ah, I stand corrected.


I now see it says "isolation point" instead of "insulating section" so it has been corrected.


My apologies.



It is still not best to connect the main bond to the consumer's side.