Rcd protection

[piz]

Hello again
I know this might sound stupid bit it aint if you dont know
I do some Electrical work for one of the national kitchen diy stores only just started and on my paper work it says
install RCD protection to existing ring main
ok I can obtain a rcd shower/garage unit with an rcd and 32amp mcb a henley block double pole and some 25mm tails break in to the main tails screw on my mini unit remove the ring from the old wylex board connect it to the new breaker and then it is protected not to forget the earth
is there any other way someone said it can be done with some 6mm cable but i was unsure what he meant
guess this is a long winded way any ideas or better ways would be great
Cheers

 

[roonbergz]

put a rcbo on the wlyex board providing its compatable what make n model is the board..if its nsb...there about £30

u also need to be qualified to test the work and sign it off cuz kitchen is a special location

 

[Darkwood]

Think hes get the old rewirable hence he cant fit an rcbo, i assume your mate might be talking about feeding a rcd unit from you existing board by the 32a mcb or rewirable and then running the ring out of the rcd unit, as long as the rcd unit is 32a rated or more your ok.

 

[piz]

sorry yes old board but still cant work out how to do it can you explain in more detail please

 

[Spudnik]

Agree with Mr Wood.

6mm from 30A fuse to one of these:

32 Amp 30mA RCD 2 Pole - Wylex

In one of these:

2 Way Insulated Enclosure

Then whip out the tails from the old wylex and connect up to the RCD.

If they are too short, then extend them inside the main CU.

 

[ajelec10]

Agree with last two post as you will avoid having multipule main switches

 

[piz]

God its hard

Think I got it after a drawing or 6

old wylex fuses run a 6mm cable from the 30amp re wireable fuse to the 32amp 30ma rcd incomming supply same with neutral and earth
then extend ring net live and cpc if required and put in out going side job done is that right looks old prob cos not used to it

 

[Darkwood]

Sounds like you got it but you might find it hard finding a 32a rated rcd 40a is more common as long as its bigger than the 30amp fuse your ok.

 

[piz]

Cheers guys

 

[Mark.W]

A quick question soz if this sounds dumb, but why 6mm? It's a ring main or am I missing something?

 

[DeanoZX7R]

Without consulting my guide, I'm guessing it doesn't have to be 6mm cable, just sufficiently rated to withstand the possible trip current for the RCD be it 32A or 40A....

 

[Darkwood]

Without consulting my guide, I'm guessing it doesn't have to be 6mm cable, just sufficiently rated to withstand the possible trip current for the RCD be it 32A or 40A....

Think you getting mixed up here the cable from c.u. to rcd unit has to be able to carry the same as the ring main was designed to carry and be rated for the 30a fuse/ 32amp mcb that is fitted, the rcd is a monitoring device for earth leakage only and can be rated anything above the mcb, so a 63amp rcd unit still only requires a 6mm cable.

 

[Mark.W]

Think you getting mixed up here the cable from c.u. to rcd unit has to be able to carry the same as the ring main was designed to carry and be rated for the 30a fuse/ 32amp mcb that is fitted, the rcd is a monitoring device for earth leakage only and can be rated anything above the mcb, so a 63amp rcd unit still only requires a 6mm cable.

Then why 6mm cable? a ring is surely designed using 2.5mm cable, so wouldn't you use 2.5mm?

 

[Spudnik]

6mm cable is capable of carrying 32A comfortably.

2.5 is only rated at around 27A.

Come on now, basic stuff!!!!

 

[scotsparky]

brighsparkst there taking a 6mm to the new RCbo unit from the 30A BS3036 Its like a short sub main to a new D.b as rings are 2x2.5 = 5mm 6mm will be fine