swa buried

[electrocuted]

good evening,

I have to run a feed to a shed on a TT installation.The cable is clipped then buried.

I have 2 questions.

1- I'm using a henley block to feed the supply. do I need to RCD the cable at source and then just mcbs in the shed ?.

2- Can I use 2 core and add rod at the shed?.

Cheers.

 

[Lillpete]

1, Depending on the Ra you would need to RCD to get your disconnection times down to 2 secs (am I right on the time for distribution circuit??)

You will need to fit a fused isolator or something rather than just splitting the tails.

2, I sometimes use the armouring as the earth for the cable so 2 core works for me (although it tends to be PME or TNS so I pop a rod in for the shed)

 

[electrocuted]

1, Depending on the Ra you would need to RCD to get your disconnection times down to 2 secs (am I right on the time for distribution circuit??)You will need to fit a fused isolator or something rather than just splitting the tails.

2, I sometimes use the armouring as the earth for the cable so 2 core works for me (although it tends to be PME or TNS so I pop a rod in for the shed)

I'm obviously using a breaker from the henley block.My question is since the shed sockets and light are rcd protected.Do I need to rcd the swa at source or not?

 

[Lillpete]

Because the armouring is earthed it only requires an RCD if the earth fault loop is too high to get the required disconnection time, which being a TT supply is likely

 

[NozSpark]

ALL cables in a TT installation require RCD protection for fire protection and 30mA for shock protection,, so it needs RCD protection at the source.

You could have a 100mA 'S' type at the source and then 30mA for the final circuits

 

[Lillpete]

Although your right that TT needs RCD in most cases I don't think its an actual regulation,

It depends on the earth being decent and reliable

Disconnection needs to be 0.4 secs on TT distribution

 

[tom1]

i dont think its a reg but just near enough unachivable without an rcd

 

[Lillpete]

i dont think its a reg but just near enough unachivable without an rcd

Agreed

 

[batty]

Very unlikely loop will be low enough without an RCD on TT system to comply so RCD will be needed and would you really want to risk putting a circuit on TT system without an RCD remember its your name on the certificate if it goes wrong.