Distribution circuit with cables buried in walls

[wattsy]

Hi All

I have got to quote for a distribution circuit to a garage Cu.

My Question is if you bury the cables in the wall how can you provide the 30mA protection required for that cable and still achieve discretion because the garage board will also have a 30mA RCD.

Do you just provide the 30mA protection from the board in the house and have a main switch Cu in the garage?

Hope this makes sense i've had a long day!
Many Thanks

 

[Hawk81]

if you have a 30mA rcd in the house then no need to put one in the garage. if feeding the garage with swa the you can take it from a non rcd way and put a rcd at the garage end

 

[davelerave]

ya -you should use swa or whatever appropriate installation method so you don't have to rcd the sub-main

that way the rcd is 'local' to the final circuits it's protecting and you don't have the walk back to house and lights+sockets tripping together etc. etc.

 

[sjm]

If you don't want to use swa check out Guardian cable or any cable to BS 8436.

 

[ezzzekiel]

surface mounted in conduit or trunking - anyway to avoid the nusience of additional rcd

 

[wetny]

Use time selective in the house. Pricey though.

 

[Hawk81]

Use time selective in the house. Pricey though.

explain further please

 

[bleach]

Would the SWA still need 30ma protection though if its run passes through and down a stud wall?

 

[Thefailsafe2012]

Use time selective in the house. Pricey though.

I thought that time delayed 30ma we're really rare to find here?

 

[bartkusal]

I thought that time delayed 30ma we're really rare to find here?

I would even come with the statement that they dont exist due to the fact that it is 30 ma and all 30 ma range is supposed to trip within 40 ms. Time delay is on 100 ma and up as some have mentioned.​

 

[Knobhead]

Lazarus has arisen, alive and well in this topic.

 

[newbec]

I would even come with the statement that they dont exist due to the fact that it is 30 ma and all 30 ma range is supposed to trip within 40 ms. Time delay is on 100 ma and up as some have mentioned.​

Also to comply with the requirements for additional protection, which is what the aim is here, a 30mA RCD must trip within 40mS @ 150mA. So no S type RCD would comply no matter what it is rated at.

 

[Thefailsafe2012]

I would even come with the statement that they dont exist due to the fact that it is 30 ma and all 30 ma range is supposed to trip within 40 ms. Time delay is on 100 ma and up as some have mentioned.​

Ah

That'd be why I have never seen one eh?

Ta Bart

 

[BruceB]

Time delayed 30 mA rcds do exist.
RCDs > Time Delayed > T100-30-2TD - Protek Circuit Protection
But as newebec says they do not meet the additional protection requirements.

 

[Darkwood]

They do exist but as already mentioned the installation wouldn't comply as the time delay would mean max trip times exceeded - Refer to Appendix 3 - table 3A with also reference to 415.1.1 as it seems to confuse so many so i have supplied the regulations, i had a lengthy debate on here explaining to a member why his submains didn't comply and after many lengthy posts i pointed out the regs to which all replies stopped. ...