30ma for existing 16mm T+E submain ??

[tomchester999]

Hello all!

I am working in a property with 3 old rewirable fuseboards, each fed from mcb's in a modern consumer unit at the incoming supply.

We want to change the 3 fuseboards to 17th ed RCD etc. However, as the 16mm T+E is less than 50mm in the wall I wonder whether I should protect each submain at the source with 30ma RCD or RCBO or just leave it as it is (currently 100ma at source)

Obviosly if it were to trip 2 floors down it would be really annoying, but do I need the protect the 16mm in the wall? Running new supplies in armoured is out of the question unfortunately..


thanks in advance for any advice!

 

[tomchester999]

It is a TT system..

 

[telectrix]

did a similar job in some flats. RCBO for each 16mm fitted in main CU. 2 years on and no tripping problems. in this case, though, the landlord lives on site, so not a problem to reset. also, it saves fitting RCD protection in each sub-main.

 

[bigdavs83]

I would be seriously tempted to protect with 30ma at the source purely to protect the 16mm t&e. It may as you say be a nuisance should it trip at the source but better that than the alternative

 

[D Skelton]

You could just ensure that the work you do meets current regulations. You didn't install the T+E submain did you?!

Just sayin...

 

[ipf]

With you there D. There is a 100mA, after all.

 

[Engineer54]

With you there D. There is a 100mA, after all.

The trouble with that is, any 30mA RCD devices downstream won't discriminate with the upstream 100mA RCD, ...unless you change it out for a S type 100mA RCD that is!!

 

[ipf]

The trouble with that is, any 30mA RCD devices downstream won't discriminate with the upstream 100mA RCD, ...unless you change it out for a S type 100mA RCD that is!!

Problems, problems......