extend ring final

[Young Dave]

Hi Chaps
I am just starting out in this profession and eager to learn so sorry if questions seem a bit daft.
If you need extend a second floor ring main which runs through four rooms by a further two sockets , and you have no idea where the first or last socket is where do you break into the ring ? and what is the best way to work out which direction the conductors are running .
can you join it at any point ? or could you add the two sockets through a fused spur from a handy socket ?
I should say there are no load or vault drop issues the circuit is wired in 2.5 T&E from a 32amp RCBO .
Also i am aware you cant put power an I.T cables in the same enclosure but is permissible for them to cross ? basic stuff i know but like help.
When testing this for minor works cert would you test from the end of your new conductors only or do go back to the C.U and test the whole circuit ?

 

[GT1]

Your altering the circuit and become liable for it and it's overcurrent protection. So Zs figure from your new sockets apply back to the board.
Break into the ring wherever is convenient and extend it or as you have said spur from FCU.
Notifiable Work remember....

 

[telectrix]

beg to differ with you GT1, on not notifiable if not in a kitchen or special location. and @ dave, yes, they can cross.

 

[wade88]

Notifiable jobs include new circuits back to the consumer unit, and extensions to circuits in kitchens and special locations. Non of which applies here so MWC is acceptable as Tele says

 

[GT1]

Yes. Your right.
Not notifiable. Apologies.
Curse of the night shift worker. Only half a brain cell awake at a time !!
D'oh.

 

[telectrix]

what, a whole half, lol.?

 

[needasparks]

Welcome Dave, You say no volt drop issues but also mention 2nd floor ring so i guess it would be a very long run and may be outside 100m/2. so best check max Zs values comply with that run.

 

[BlueToBits]

90% of the time you can probably break into the ring at any point or add any number of sockets in the ring or after a spurred FCU if you prefer. You just have to ensure your design complies with the regulations and it is suitable for the intended load. The remaining 10% of the time you may have to take other action, and unfortunately you need experience and knowledge to recognise when this is necessary.

 

[Heisenberg]

Welcome Dave, You say no volt drop issues but also mention 2nd floor ring so i guess it would be a very long run and may be outside 100m/2. so best check max Zs values comply with that run.

Its funny that you mention 100m/2 in this way, as I have always taken this to mean the floor area of the rooms served by the ring, but you seem to be implying that you have to take into consideration the distance the ring is away from the OCPD??

 

[Young Dave]

Thanx for all your advice chaps , so on the testing side of things then all the tests for the cert would have to be carried from the CU even though you have only added a small extention to it, would this be the same if you extended a lighting Loop ? I can see see where I'm going with installation Certs but minor works is giving me grief .

 

[telectrix]

MWC cert. asks for details of the modified circuit, so yes , you test the whole of the circuit that you have altered.

 

[oracle]

Dave, the one part of your question not dealt with is identifying the incoming and outgoing tails of your open ring. May i suggest that you pick a conductor on either one, clip your one meter lead to it, and with an R2 lead (wander lead) on your meter go from socket A to socket B C etc, taking a reading at each. this will show which way your ring is going as the resistance will either increase (outgoing) or decrease (incoming)

Works for me, I hope it helps you.

 

[needasparks]

Its funny that you mention 100m/2 in this way, as I have always taken this to mean the floor area of the rooms served by the ring, but you seem to be implying that you have to take into consideration the distance the ring is away from the OCPD??

Thats what I always take into concideration or you could have a situation where a ring is fed 3 miles away. the route to the POU is taken into the calculation when doing the design. A great many offices have this same situation where the area served is only small and well within limits but distrobution point is quite a run so 4mm is used but for some reason in a domestic situation we all look to 2.5mm being fine for anything without doing any sort of calculation.
In saying that how many houses are over two floors so its not normally a problem. I was just highlighting what could be a situation when adding to an existing ring that may already be at its limit with regards to max Zs for its run, I guess not a lot will happen though as its over two floors away and for a couple of extra sockets.