house earth vs garage earth spike

I get the arguments about conductivity I really do and it does make sense but more often than not 10mm is used because of mechanical protection not because it needs a 10mm cable to be able to dissipate the current.

 

not quite true if it was only based on not having mechanical protection then 4mm would be the minimum CSA.

 

I always thought it was a bit funny relying solely on the armour csa for exporting supplies - 2c + e any day - negates all the borderline calcs and stuff.

 

Remember mate you only need to worry about this IF your cpc is also your Equip. Pot. conductor. So this would only really matter if you wanted to export to somewhere like a swimming pool or 2nd dwelling where you would need to bond. A shed would really not matter. You could use the armour no problem even if it was pme as it's only working as the cpc. Looking at the charts the armour size only really starts to get too small if the cable is a stupid size, like over 50mm.

 

Thanks Mr C

 

In a domestic envionment I would agree. However in industrial I have seen so many damaged glands where the armour has corroded or been pulled out I always insist on using an extra core. I have seen water treatment plants where the corrosion had led to almost complete loss of earth continuity to the supply. Factories where machines have beem moved and strands have been pulled out of the gland.

If I am gonna sign it off I want to see a core used and the armour is just thare for mechanical protection as its name suggests.

Kind regards

 

I have to agree with you 100%, like you i've seen cables pulled out of the gland many times.

 

Welcome to the forum TP&N

Kind regards

 

Hence why regular I&T is required.

 

Yes, but unfortunately with larger sites it gets overlooked so often due to cost.

Kind regards

 

I concur, a properly supported cable with a gland that's been correctly made off shouldn't be an issue. I can understand in a wet environment such as a marina, water treatment plant, etc not relying on the armour and possibly it might be better practise to use a separate CPC or an internal core. In such an environment the shroud could collect/hold moisture but again shouldn't be an issue if the gland was heat shrinked/denso taped before the shroud was pushed up.

 

IMO 5 years should be the norm for all none hazardous installations.

 

Not your problem. You can only install to the regs and the regs say an installation should be inspected at regular times.

 

Personally prefer to go that litle bit further than the Regs require. The OPs question was domestic and that is fine. Industrial however is whole different ball game.

Kind regards

 

I know. That is all I do.

 

I think this has been a good thread that's had a few healthy debates beats the usual "I brought a new light, how do I connect it up" threads lol.

 

Just enjoying a late lunch and read this thread and agree with you Leesparky a very good and interesting thread well presented.
If we run out any armoured to machinery always 2 core plus earth but in the case of an outbuilding /Garage we usually make it a TT instalation this is subject to design stage criteria. Ref NOTE 3 I beleive NEIC are looking for 100 ohm resistance to encompass all (please correct )

7.2.9 Additional protection against electric shock
NOTE 1
In conformity to BS 7671:2008+A1, the resistance of the earth electrode should be less than 50/IΔn where IΔn is the rated operating current of the RCD.
NOTE 3 For a 30 mA RCD at 230 V, this would allow a resistance to earth of 1667 Ω.
However, a note to BS 7671:2008, Table 41.5 advises the resistance be as low as practicable and a value exceeding 200 Ω might not be stable.