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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
 
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?
 
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
 
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
 
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
 
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?
 
Yep found them thanks mate
6 064 16 LEGRAND 6a RCBO 30ma 10ka B TYPE
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  • TT system, RCD or RCBO {filename} | ElectriciansForums.net
  • TT system, RCD or RCBO {filename} | ElectriciansForums.net
  • TT system, RCD or RCBO {filename} | ElectriciansForums.net
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  • TT system, RCD or RCBO {filename} | ElectriciansForums.net
£25.95
 
A N-E fault on the lighting circuit you have altered will possibly take out the RCD serving the rest of the installation. The only way to prevent that is a device which disconnects the N.
 
A N-E fault on the lighting circuit you have altered will probably take out the RCD serving the rest of the installation. The only way to prevent that is a device which disconnects the N.
Ah yes I didn't think about the DP, if I remember theres a reg aswell that says TT systems need a DP..... they don't like making it too easy for the sparks do they haha!
 

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