Adding RCD to a ring final.

[walllis]

Hello.

I currently have an old rewirable fuse box, so no rcd protection. I'd like to add a couple of outside sockets, but instead of using rcd sockets I thought about adding protection for the whole circuit.

My idea to get an rcd (2 module) in a encloser and connect the two ends of the ring final into the output, then connect 6mm twin/earth from the rcd to the 30A fuse where the circuit was supplied from.

I can't see anything wrong with this idea, I was hoping for any feedback. thanks!

 

[flyingsparks]

That's fine..

 

[riveralt]

That's fine..

Surely we then have a radial circuit protected by the fuse leading to a ring final circuit protected by the RCD - Is that allowed?

 

[ebee]

It is well known as a "lollipop circuit".

Why should it not be allowed?

Providing all criteria are met ref loading, distribution of load around the ring, ins res , etc etc.
Unorthodox but certainly allowed. Not one of your standard circuits though but not that uncommon.

(if the radial portion is existing (say kitchen cooker circuit now no longer used) or if the radial does not require RCD protection)

Admittedly adding the RCd at source of the radial would be my preferred option though if possible.

 

[walllis]

Thank you for the clarification. I may use a 4 way encloser and do the same for both rings.

 

[Speakercon]

I see no problem with it, except the possibly of a fault outside tripping your inside sockets. Not massively likely but if you have a fridge/freezer on that circuit it could be a problem.

 

[walllis]

I was also considering replacing the consumer unit. I feel confident doing this myself and I could also add a few circuits and such.

My only concern was testing, do I understand correctly that the counsel will do the testing and sign it off (I will want to notify of course). I have a rough idea of what tests are involved but i have no testing equipment.

 

[JohnW2]

It is well known as a "lollipop circuit". Why should it not be allowed? Providing all criteria are met ref loading, distribution of load around the ring, ins res , etc etc. Unorthodox but certainly allowed. Not one of your standard circuits though but not that uncommon.

A much-discussed topic! Electrically speaking, it's not really significantly different from a standard ring final, so there's no real reason why it should not be allowed (although it might confuse some people testing the installation). Indeed, if one wants to be pedantic, every ring final could be argued to be a 'lollipop', in as much as there are some conductors within the fuse housing or MCB before the circuit splits into the two legs of the ring.

However, whether is is actually 'allowed' by the regs is a more debatable matter. Ring finals (circuits which have cables with lower CCCs than the 30/32A OPD protecting them) are only allowed because of the specific 'dispensation' in 433.1.103 (supplemented by Appendix 15), and it is far from certain that the dispensation extends to lollipop circuits (even though, electrically speaking, it should). A Jobsworth of an inspector would certainly have something to argue about, even if (s)he eventually lost!

I certainly happily lived with a lollipop circuit for a good few years, having inherited a ring circuit in the cellar whch was fed by what I assume had once been a cooker circuit.

Kind Regards, John

 

[PrenticeBoyofDerry]

I was also considering replacing the consumer unit. I feel confident doing this myself and I could also add a few circuits and such.

My only concern was testing, do I understand correctly that the counsel will do the testing and sign it off (I will want to notify of course). I have a rough idea of what tests are involved but i have no testing equipment.

You can hire the equipment, but likely the best option would be to employ a self cert electrician.
Cost of notification fee and hiring of equipment, could well cost as much as having someone who is competent doing it.

 

[walllis]

Am I wrong in thinking that the person who is sent to inspect my work will not do the testing?

 

[riveralt]

Am I wrong in thinking that the person who is sent to inspect my work will not do the testing?

That's a double negative there.
If you decide to go down the Building Control route - then you must inform them before you start the work and pay their not insignificant fee.
They will decide based on your competence and the type of work that is being carried out to what extent they will inspect the work.
They will carry out any testing required or sub-contract it to someone on their behalf.

 

[walllis]

Am I wrong in thinking that the person who is sent to inspect my work will not do the testing?

That's a double negative there.
If you decide to go down the Building Control route - then you must inform them before you start the work and pay their not insignificant fee.
They will decide based on your competence and the type of work that is being carried out to what extent they will inspect the work.
They will carry out any testing required or sub-contract it to someone on their behalf.

Does that mean they may not do any testing at all if I'm not selected? Would the work then not comply as i wont have a results sheet, and I would want to have it tested for piece of mind anyway. If they dont test it then I would want to do it myself, but then whats the point in notifying them just to confirm what I've already done!

 

[JohnW2]

Does that mean they may not do any testing at all if I'm not selected? Would the work then not comply as i wont have a results sheet, and I would want to have it tested for piece of mind anyway. If they dont test it then I would want to do it myself, but then whats the point in notifying them just to confirm what I've already done!

I would somewhat doubt that they would issue a Completion Certificate (i.e.'sign it off') unless it has been fully tested by someone - be that themselves, someone to whom they subcontract the job (probably at your expense) or someone else they regard as 'competent' (maybe yourself, or an electrician employed by you).

Kind Regards, John