2 RCD's on circuit

[westward10]

It is all very well having qualifications done from a whiteboard and test rigs, unfortunately this doesn't always transfer to the real world. What is basic and fundamental to some is not necessarily the case for others. The real world is where we gain experience, we have all been there.

 

[rolyberkin]

Is @hightower says a C&G 2357 is not just about new fits it has a test and inspection element and also fault finding, judging by your previous posts I suspect you have gone through a very quick course and may be in well above your head. If you really don't know the answers to your questions you really should not be undertaking work for people and should get yourself on an apprenticeship or some on the job experience with an experienced electrician!

 

[buzzlightyear]

she uses the shed as a massage parlour,
has the shed got any lighting on that 32amp mcb/rcd ?

 

[hightower]

Isn't 2357 an apprenticeship, that should have been completed on the job?

 

[Leesparkykent]

Isn't 2357 an apprenticeship, that should have been completed on the job?

Might of done the 2356 level 2&3 then the bridging unit, portfolio and AM2.

 

[joebell25]

Before removing the RCD in the shed, you may want to first ensure that the earthing system hasn't been changed to a TT system for the shed consumer unit.

 

[HandySparks]

Before removing the RCD in the shed, you may want to first ensure that the earthing system hasn't been changed to a TT system for the shed consumer unit.

The OP says that there's a 30mA RCD in the board supplying the shed. This would still provide protection even if the shed earthing is TT.

 

[Octopus]

The OP says that there's a 30mA RCD in the board supplying the shed. This would still provide protection even if the shed earthing is TT.

I was pondering about this advice .... I've seen it locally too where a DIYer assured me that TT'ing a shed would stop the shed circuit tripping his up front single RCD..

 

[Wilko]

I was pondering about this advice .... I've seen it locally too where a DIYer assured me that TT'ing a shed would stop the shed circuit tripping his up front single RCD..

Any electrons escaping down the shed's rod will inbalance the L/N feed all the way back, I'd have thought.

 

[hightower]

Is that a point open to debate though - if you TT an outbuilding should you have it's own RCD in there too (even if the upfront one will protect)? Or would you say it's perfectly acceptable to have an RCD at the CU, TT the outbuilding, and not install a second RCD at the outbuilding.

 

[HandySparks]

Is that a point open to debate though - if you TT an outbuilding should you have it's own RCD in there too (even if the upfront one will protect)? Or would you say it's perfectly acceptable to have an RCD at the CU, TT the outbuilding, and not install a second RCD at the outbuilding.

I can't see the point of a local RCD if the supply is on an RCD. After all, it doesn't make any difference whether earth fault current returns entirely via a copper wire or via the bulk of the earth to the star point of the local supply transformer.

 

[rolyberkin]

Surely the point of a local RCD is convenience in resetting. Best to feed the MCB via swa from a non RCD protected MCB, that way if the RCD trips you don't have to traipse back to the house to reset.

 

[Leader]

My tutor said that you should run SWA from a Henley block to the new CU which will then have it's own main switch etc. Is that just overkill?

 

[HandySparks]

My tutor said that you should run SWA from a Henley block to the new CU which will then have it's own main switch etc. Is that just overkill?

Ask your tutor how he would terminate SWA into a Henley block using the correct gland and without leaving the insulation exposed. And what would he be using for fault protection on the SWA?

 

[kingeri]

My tutor said that you should run SWA from a Henley block to the new CU which will then have it's own main switch etc. Is that just overkill?

What, without overcurrent / fault protection?

 

[Leader]

Yes, thinking about it, it does sound crazy, but then he did actually get fired half way through my course due to his, er, eccentricity. I'll make sure I change my notes on that!!

 

[westward10]

My tutor said that you should run SWA from a Henley block to the new CU which will then have it's own main switch etc. Is that just overkill?

I think your tutor may of meant to make the cable off in an enclosure at the TT end, fit service terminal blocks in the enclosure to supply the board. Then again he may have been a fruit loop.