TT system, RCD or RCBO

[Bobby34]

At the risk of asking a silly question could someone advise me on the following:

Client has a TT system with only half the circuits covered by an RCD, they want a light adding on a light circuit thats currently not covered by the rcd.

Now with half circuits not going to meet the disconnection times if I work on just the lighting circuit would I still have to cover all the circuits that haven't got an RCD with a new RCD or am I allowed to cover just the lighting circuit with an RCBO because that's the circuit i'l be working on?

Because of the results when testing I'm thinking i'm going to have to cover all the circuits but I'm just wanting to check the RCBO route incase the IR is low (old wiring) and nuisance tripping could occur (I know the clients won't be wanting to pay extra if I have to start going digging).

Thanks in advance

 

[buzzlightyear]

want a light adding on a light circuit thats currently not covered by the rcd.

is the full system not covered by a rcd alone ?

 

[Welchyboy1]

Well you need to at least ensure your work fully complies so an rcbo would acheive this and limit the potential problems from protecting multiple other circuits with another RCD
If your using an rcbo is the CU at the origin of the installation?
However you also have a duty of care having seen the installation and the problem with the unprotected circuits, i would at least put this in writing to the customer and quote him to allow you to correct the problem, making sure you press on him its a problem thats needs resolving quickly

Is it possible to get a PME connection?

 

[Bobby34]

No only half the circuits are protected by an rcd, the other half are not, as I think about it from a safety point of view to be fair I'm thinking I should protect them all but I can see how the conversation will go haha

 

[Nigel]

You only have to ensure the circuit you have altered complied with BS7671.

It would be very advisable to get the client to upgrade them all however.

 

[Bobby34]

Welchyboy yes I totally agree I think that is a good way to do it if they refuse to go ahead with the rcd route thanks

 

[buzzlightyear]

dont forget that the rcbo must now match the original board .

 

[Bobby34]

Thanks essex, yea I think il just prepare the reasons in client speak why they should bite the bullet, and if they are adamant then like welchyboy states put it in writing that this needs to be rectified asap, cheers guys appreciate the advise

 

[buzzlightyear]

there is going to be a lot of disgruntle customer now ,cant get a match mcb or rcbo ,me needs to change the board ££££££££££.

 

[Welchyboy1]

When i say in writing, i mean by email if poss

As this is time and date stamped

 

[Bobby34]

The fusebox is a tenby I can't seem to find any tenby rcbo's in the usual merchants but have read Wylex fits Tenby? Does anyone know if Tenby is still going or if they merged with any other manufacturer?

 

[buzzlightyear]

but have read Wylex fits Tenby

read post #7

 

[Welchyboy1]

Tenby are now legrande try them on ebay

 

[Welchyboy1]

Legrand

 

[Bobby34]

Yep found them thanks mate