Earthing

[crazyelec]

just wondering about earthing up gurders in a factory. the factory was once one big area, but has been previously split up into 4 seperate warehouses. all with individual 3 phase fed into them. im working on one individual warehouse, and wondering if i have to bond the gurders, water, air and gas up. the supply cable is 240mm, (so the earth is to be 50mm to bond up the gurders, water, air and gas). does this have to be done now each unit has its own supply or does is not matter as it is done at one end of the building as it was originally. also another question is that attatched to the gurder is a 6 inch trunking. does the trunking need to have a seperate earth bond or will the earth connected to the gurder be adequate?

 

[Des 56]

Are these 3 installations with three supplies or one installation with one metered position feeding three seperate areas?

If they are seperately metered
I would say that they are three seperate installations and require earthing and bonding as per 17th for each installation

One meter and one origin one set of main bonds

 

[Guest123]

Hi.

I would say you need to bond any services that enter your warehouse back to your MET, particularly if you have your own metered supply.

No telling what the other owners of the other warehouses may or may not do with the pipework before it gets to your warehouse.

 

[Darkwood]

Are these 3 installations with three supplies or one installation with one metered position feeding three seperate areas?

If they are seperately metered
I would say that they are three seperate installations and require earthing and bonding as per 17th for each installation

One meter and one origin one set of main bonds

May i correct you, if you have one meter at origin and supplies out to 3 partitioned off units then each unit requires equipotential bonding to their own dist' board, the gas water oil sevices etc must be bonded where they enter each premise and the structural as close to sub-mains, particular attension must be payed to the sub- mains supply earth in that it is adequately sized to allow for the necessary bonding cables especially in tncs (pme) systems as the eddie current can flow in one end of the building and out the other end.

 

[Des 56]

May i correct you, if you have one meter at origin and supplies out to 3 partitioned off units then each unit requires equipotential bonding to their own dist' board, the gas water oil sevices etc must be bonded where they enter each premise and the structural as close to sub-mains, particular attension must be payed to the sub- mains supply earth in that it is adequately sized to allow for the necessary bonding cables especially in tncs (pme) systems as the eddie current can flow in one end of the building and out the other end.

Thanks for the clarity

I dont dis agree with you

I was making the point that the installation could be one or three installations and the main bonds (50mm) installed for suitability at the point of origin(there could be 3 or 1 point of origin)

What I may have added and point out if I am wrong is that the 3 areas would be unlikely to have overcurrent and cable sizes the same as the supply feeding the installation and the 50mm bonds would be at that origin,the sub mains would have thier own MET and local main bonding at their point of entry and would then be sized for that sub main conductor size in their own equipotential zone and the sub main earth as 50mm, then perhaps only 10 or 16mm localised bonding

 

[Darkwood]

Thanks for the clarity

I dont dis agree with you

I was making the point that the installation could be one or three installations and the main bonds (50mm) installed for suitability at the point of origin(there could be 3 or 1 point of origin)

What I may have added and point out if I am wrong is that the 3 areas would be unlikely to have overcurrent and cable sizes the same as the supply feeding the installation and the 50mm bonds would be at that origin,the sub mains would have thier own MET and local main bonding at their point of entry and would then be sized for that sub main conductor size in their own equipotential zone and the sub main earth as 50mm, then perhaps only 10 or 16mm localised bonding

This is an area il have to look into although i see your point but im agreed on the seperate 50mm in each area if their are seperate supplies to each unit.