Cable calculation

[Nigel]

So why is this done out there, having main switch on the board rated higher than the fise in the head, it dont make sense the fuse in the head would alway blow first.

Do you not think it a good idea to have a switch rated equal or higher to the current that could be drawn through it?

 

[Simon Burton]

What Reg are you referring to?

Under the Electricity safety, quality and continuity regulations 2002 you cannot use a suppliers earth to an out building, on a TNC-S Earthing arrangement, so the detached garage effectively becomes a TT installation with an earth electrode installed in the ground.

 

[Simon Burton]

Under the Electricity safety, quality and continuity regulations 2002 you cannot use a suppliers earth to an out building, on a TNC-S Earthing arrangement, so the detached garage effectively becomes a TT installation with an earth electrode installed in the ground.

Ok lets say you exported the earth on a tncs to an outbuilding, and then lets say you lost your neutral at the main incoming, if you had a live to earth or neutral short, every thing connected to earth would become live under fault conditions, hence why you need to rod and not export form the main earth to exterior building ect

 

[Nigel]

Under the Electricity safety, quality and continuity regulations 2002 you cannot use a suppliers earth to an out building, on a TNC-S Earthing arrangement, so the detached garage effectively becomes a TT installation with an earth electrode installed in the ground.

You are incorrect.

 

[Deleted member 26818]

There are a couple of reasons why you would not export a PME earth.
One could be if the exterior of the outbuilding is metal, and the other is if there are extraneous conductive-parts which would require bonding.
At the end of the day, it boils down to cost.
Is it cheaper to run a 3 core 10mm2 armour or a 2 core armour and install an earth rod.

 

[Nigel]

Ok lets say you exported the earth on a tncs to an outbuilding, and then lets say you lost your neutral at the main incoming, if you had a live to earth or neutral short, every thing connected to earth would become live under fault conditions, hence why you need to rod and not export form the main earth to exterior building ect

So why is it matter if it is an outbuilding or not? That would still happen in a building that is not an outbuilding.

 

[Simon Burton]

You are incorrect.

Section 705
705.411.4
Read that little paragraph mate, starts with tncs shall not be used.

 

[ipf]

So why is it matter if it is an outbuilding or not? That would still happen in a building that is not an outbuilding.

….deleted

 

[Nigel]

Section 705
705.411.4
Read that little paragraph mate, starts with tncs shall not be used.

That is for agriculture and horticulture premises. Is that what you are working on?

 

[Bait Account]

That is for agriculture and horticulture premises. Is that what you are working on?

says it’s a stable in the op.

 

[Simon Burton]

You are incorrect.

Section 705
705.411.4
Read that little paragraph mate, starts with tncs shall not be used.

So why is it matter if it is an outbuilding or not? That would still happen in a building that is not an outbuilding.

I dont make the regs, it was a question i had of the nic eic on the onsite assessment

 

[Simon Burton]

That is for agriculture and horticulture premises. Is that what you are working on?

I did say i was working on a stables

 

[Simon Burton]

I did say i was working on a stables

Special location,

 

[Deleted member 26818]

Section 705
705.411.4
Read that little paragraph mate, starts with tncs shall not be used.

I dont make the regs, it was a question i had of the nic eic on the onsite assessment

No.
It states that TN-C shall not be used.

 

[westward10]

A common mistake, you are so unfamiliar with seeing TN-C you brain reads TN-C-S.

 

[Nigel]

Special location,

I missed that. Apologies.

 

[Nigel]

No.
It states that TN-C shall not be used.

A TN-C-S is still a TN-C.

 

[Deleted member 26818]

A TN-C-S is still a TN-C.

TN-C-S is where the DNO supply is TN-C but is presented to the customer as TN-S.

 

[Nigel]

TN-C-S is where the DNO supply is TN-C but is presented to the customer as TN-S.

What?

A TN-C-S is where the earth is taken from the PEN within the installation.

A TN-C is where the same connection is made outside of the installation.

 

[westward10]

A TN-C system has a combined neutral/earth on the service side and throughout the consumers installation, very unusual.