rcd between board?

[wannabesparky]

i was just wondering if someone could enlighten me please as im still learning.
I have a TT installation
100A main fuse
wylex 12 way split load board 100A 100ma rcd & 30ma time delay rcd
between the board and the main fuse there is a 63A rcd of some sort, this isnt right is it because the 63A would trip out before the rcds in the board.
What i dont understand and just cant get my head around is:

• if there is a 100A main fuse and there is a 100A rcd in the board which will trip first?
• And what should be between the board and the main fuse instead of the 63A rcd?

Any help would be much appreciated, thank you.

 

[spark1]

Is it not a 100ma Time delayed Rcd and a standard non delayed 30ma RCD ?
The 100A Main Fuse and the 100A/100Ma rcd perform 2 completely seperate functions!
The 63A Rcd whatever its tripping current may be [Not stated in post] appears to be incorrect in this set up and should be removed,as discrimination in the event of an Earth Fault will not be achieved.


spark1

 

[Guest123]

Hi.

Sounds like there was a recent mains upgrade carried out and whoever carried it out didn't bother removing the old RCD that was probably protecting the old wylex re-wireable fuse board.

Ideally this needs removing as like Spark1 has said in the event of fault all circuits will be lost causing great inconvenience.

 

[wannabesparky]

yes spark1
it is a 100ma Time delayed Rcd and a standard non delayed 30ma RCD, sorry i wrote it wrong.

so if the 63A rcd before the board is removed what should replace it if anything at all?

 

[Spudnik]

Adding to this, the old type RCD was used as protection for the tails as well as the installation.

Nowadays, most CU's are insulated and so dont need the protection up front.

 

[wannabesparky]

yes spark1
it is a 100ma Time delayed Rcd and a standard non delayed 30ma RCD, sorry i wrote it wrong.

so if the 63A rcd before the board is removed what should replace it if anything at all?

 

[baldsparkies]

To answer your last post the 63A RCD serves no purpose in your install if I am reading you correctly ie TT system Cut out to meter 100ma time delayed RCD feeding split load board with standard 30ma rcd and mainswitch. This would give you protection to all circuits via the 100ma delayed rcd with shock protection via the 30ma rcd on the relevant circuits all in all a good set up with correct discrimination.
The only bad apple in your barrel is that 63A unit which would be better of in the bin.

Hope this helps.

 

[Spudnik]

Baldy (if i may call you that).

All circuits must now be protected with 30mA RCD.

So yes, split load with 10mA upfront, but the 'unprotected' side should have 30mA RCBO's instead of MCB's

 

[baldsparkies]

Tis true sir,agreed. His configeration sounded typically pre july 2008 throw in a code 4 for good measure or a code 2 and cover your back hence my comments.

I would still bin the 63A RCD though

PS.
I would go with a new 17th edition board rather than RCBO's have you seen the price of those puppy's wow!

 

[spark1]

Baldy (if i may call you that).

All circuits must now be protected with 30mA RCD.

So yes, split load with 10mA upfront, but the 'unprotected' side should have 30mA RCBO's instead of MCB's

If upgrade is proposed I would suggest a Dual 30mA RCD Board or a 100A Main Isolator Board with seperate RCBOs for All relevant circuits.........oooohh Costly though !


spark 1

 

[Spudnik]

Indeed i agree there chaps, however, if the CU is metal clad then the tails need an RCD too.

If its an insulated then yes, ditch that 63.

Dont forget disconnection times are lower now for TT.

 

[wannabesparky]

thank you all for your answers, very helpful