Confused here...Detached garages and earth rods...

[Electricalserv]

TN-S system. 20m run of 4.0mm SWA to ne CU in garage, supplying 3 lights and 4 sockets. RCD protected, lights on 6A breaker, sockets on 20A breaker.

Does this need and earth rod and why?

Why is the 3rd core of SWA not effiecient?

I'm confused because reading some older posts people are saying out buildings need an earth rod if not connected to existing house...

Napit have this on their website.... http://www.napitonline.com/downloads/CP 5 07 16th P 8-9 Supply to Detached Outbuilding.pdf

No sign of earth rod mentioned....

 

[Paul.M]

You've just opened a can of worms!

 

[Knobhead]

Makes sense to me except for the T+E in earthenware pipe. So long as you have a good CPC why fit a spike?

 

[Electricalserv]

Makes sense to me except for the T+E in earthenware pipe. So long as you have a good CPC why fit a spike?

Thats my point and its obviously a major issue because there is many a post about it. Napit have issues that and also IQ posted this....

http://www.electriciansforums.net/e...159-good-guide-exported-pme-outbuildings.html

So why then am I confused as to why we people say an earth rod is needed???

 

[Deleted member 26818]

Look at it this way.
If the supply is TN-C-S/PME, then any extraneous-conductive-parts will require bonding and the minimum CSA allowed by BS7671 is 10mm².
What would work out cheapest, running an extra 10mm² minimum conductor to an outbuilding?
Or banging in a rod and RCD?

 

[Electricalserv]

Look at it this way.
If the supply is TN-C-S/PME, then any extraneous-conductive-parts will require bonding and the minimum CSA allowed by BS7671 is 10mm².
What would work out cheapest, running an extra 10mm² minimum conductor to an outbuilding?
Or banging in a rod and RCD?

Its not though its TN-S and has no extraneous conductive parts.

 

[Deleted member 26818]

There is no requirement to rod an outbuilding in BS7671.
However, it is or used to be the case with PME, that the DNO should be informed and their permission obtained before exportation of the earth.
If they refuse permission, then a rod would have to be installed.
However they normally only refuse when the building is metal clad.

 

[Davidpyne]

So no earth rod required in a detached garage if supplied from PME?

 

[Engineer54]

No!! But if the garage had any extraneous metalwork/services, then to to cover the PME main bonding (not earthing) requirements either the SWA supply cable would have to be min' 3 core 10mm, or a separate 10mm bonding conductor will need to be provided. This is not the case with a TN-S supply!!


You are by the way, ''Extending'' the main house/property's equipotential zone, not exporting it!!

 

[Knobhead]

So no earth rod required in a detached garage if supplied from PME?

Time to stop being a Pyne, I’ve just looked at you’re past record.

 

[NDG Elecs]

Does the steel wire of SWA not become extraneous though.......! If buried of course.....

Sorry, couldn't resist!

 

[GLENNSPARK]

Does the steel wire of SWA not become extraneous though.......! If buried of course.....

Sorry, couldn't resist!

you can carry out a test to verify...
what you do is drive in a test spike and IR test between the armourings and the spike....

 

[Spoon]

Time to stop being a Pyne, I’ve just looked at you’re past record.

So how do you get to look at the past record of someone...
Ive gone into Advanced Search and put his name in the relevant field. I only get 1 result back "Polegate second fix electricians wanted" but he has 9 posts...
Where am I going wrong...

 

[HandySparks]

So how do you get to look at the past record of someone...
Ive gone into Advanced Search and put his name in the relevant field. I only get 1 result back "Polegate second fix electricians wanted" but he has 9 posts...
Where am I going wrong...

Clicking on a member's name at the side of one of their posts pops up a box with a few options, one of which is "View Forum Posts".