Earthing Galvanised conduit boxs in garden

[holmslaw]

..

 

[RF Lighting]

Tell me how it is physically possible earth a T&E cable at both ends

 

[ban-all-sheds]

Holmslaw - the only way for RF to prove that there is no regulation requiring XYZ would be for him to copy and paste all 216 pages of the Wiring Regulations here, invite people to read them, and point out that when they get to the end they won't have found a regulation requiring XYZ.

'twas ever thus with calls for people to prove that something does not exist.

OTOH, if you think he is wrong, and that there is a regulation requiring XYZ all you have to do is to quote the 2 or 3 lines in question.

 

[JonoPashley]

Tell me how it is physically possible earth a T&E cable at both ends

Ring Final or High Integrity Earthing but then its not going to be one continuous run, but could be said to be earthed at both ends?

 

[RF Lighting]

So it wouldn't be possible on a standard radial circuit arrangement then would it?

So according to holmslaw, virtually every lighting circuit in this country does not comply with BS7671, as they are only earthed at one end.

 

[JonoPashley]

Sounds correct to me. Would make Cooker, Shower, Immersion Circuits etc fail to comply also as these are usually a standard radial.

 

[ban-all-sheds]

Ring Final or High Integrity Earthing but then its not going to be one continuous run, but could be said to be earthed at both ends?

Please let's not go there again....

 

[securespark]

I think what Holmslaw is trying unsuccessfully to say is that the armour should be connected at the supply end to the supplier's earth terminal and at the other end to the earth terminal of the equipment that cable is supplying.

As opposed to just relying on the use of one of the cable's cores for the earth connection.

I think...

 

[ban-all-sheds]

Provided it complies (and it always will, unlike the armour) then there's nothing wrong with "relying" on a cable core to be an effective cpc, just like we always do with the (undersized, please note) cpc in twin & earth.

Unless you're using it in a situation where the cable requires earthed mechanical protection is there any need to earth the armour at all?

 

[securespark]

Consider a situation where the SWA is connected to an insulated CU and the armour is not connected to earth at that end. A core is connected to earth in the CU and at the destination of the circuit, the earth core is connected to the armour.

Could there be the faintest possibility that the armour could be damaged and the earth core severed before any other, leaving the cable unprotected?

Regulation 522.8.10 states "......a cable buried in the ground shall incorporate an earthed armour......", so strictly speaking, by installing as per the above scenario, you have complied with that regulation.

But surely the best way would be to terminate the SWA so as the armour and a core are connected to earth at the supply?

This way, the armour is connected to earth without having to rely on a cable core to achieve that connection.

 

[RF Lighting]

I completely agree that connecting the armour at the supply end is the best way to earth the armour.

I was just trying to explain holmslaw that earthing the armour at the load end of the cable does comply with the regs.

He seems unable to understand this, and went off on one calling me incompetent again.

 

[RF Lighting]

Provided it complies (and it always will, unlike the armour) then there's nothing wrong with "relying" on a cable core to be an effective cpc, just like we always do with the (undersized, please note) cpc in twin & earth.

The CPC isn't undersized in T&E. The adiabatic equation shows that a CPC smaller than the line and neutral conductors is sufficient.

Unless you're using it in a situation where the cable requires earthed mechanical protection is there any need to earth the armour at all?

I would think it should be. You should tie any unused conductors in a cable to earth anyway.

 

[securespark]

I completely agree that connecting the armour at the supply end is the best way to earth the armour.

I know! And I understand your point about the regs. What you suggested does indeed comply. But, as I illustrated, I would much prefer to do it from the supply end.

I've never understood name-calling just because of a disagreement you f*t Yorkshire tw*t.

 

[holmslaw]

..

 

[braychurchmouse]

Please excuse my question from a non-electrician. Have been following this discussion with interest as previous occupants of my son's house had garden wiring put in with armoured cable etc and RCD etc etc.

I would like at some stage to get an approved electrician in to check the wiring is safe. I am more concerned about safety than merely conforming to regulations (as some of you seem to disagree so much on their interpretation ). I just want someone to check, that in their qualified opinion, the wiring is as safe as possible, even if it means exceding the regulations' requirements. eg earthing at both ends makes sence to me even if it isn't a requirement of the regulations.

So my question is this...is it possible to contract someone to make these examinations and tests, and how would I phrase the requirement? Would they be able to pronounce the wiring safe without digging up half the garden?

Oh yes and as a minor postscript I wondered about RFs opinion that...

You should tie any unused conductors in a cable to earth anyway.

I have this thought that someone connects the unused red or brown wire in a cable at one end to earth and then someone else later decides that its a good idea to connect the other end to live source.....and the earth is only connected at one end...and....?