changing CU in a flat

[Naz]

Hi

been asked to change out old bakelite fuse box to new 17th edition cu in a flat in a block, no isolation to the fuse box in the flat, briefly looked at supply downstairs, looks like 3 phase supply split to supply single phase to each flat. Cant see any individual fuse's for each flat, wondering best way to isolate flat supply or risk moving tails over live?

Naz

 

[malcolmsanford]

There must surely be a DNO cut-out that as fuses in them?

 

[nickblake]

What is needed there is 3 switch fuses or a small CDU with circuit protection for each flat im asuming that each flat is supplied with a 16mm TWE or is it individual 25mm tails ,anything more than 3 meters away from the supply needs the tails protecting and also if the cables are less than 50mm from the surface will also need RCD protecting . more details of the supply would be good Pics even better

 

[Naz]

thanks for replies

will take a closer look at situation, supply from ground floor comes in and disappears into box section trunking, what comes out supplies digital meters and on to the flats. Flat in question is on the first floor so old cu is at 20 meters away. DNO fuse are not immediately obvious on the ground floor, not saying there arent any....

will write more this week

regards

 

[Guest123]

Could there be a ryfield unit there???

 

[FatBob]

Flats normally have a CDU as Nick says. If you look in the flats CU, it will most likely be fed from 16mm TE. If it's 25mm tails, ask for local isolation.

Working live requires training, and it is not necessary for this kind of job.

 

[Naz]

thanks for all

have arranged a revisit this week, to check all these points

Naz

 

[SPARTYKUS]

Flats normally have a CDU as Nick says. If you look in the flats CU, it will most likely be fed from 16mm TE. If it's 25mm tails, ask for local isolation.

If you have to ask about working live, the answer will always be no.

Or much smaller diameter MICC ....

 

[Naz]

hi

further to my orig post, have taken a detailed look at the set up, have found the fuse, so safe isolation will not be a problem, the wiring is pre 17th, ie red and black, do not see any cpc's at this point since no earth bar in old unit, the wiring is all enclosed in earthed steel conduit, the tails are 10mm. Have also been fortunate to find an old periodic inspection report. It states that there are cps for rings and lights? so will need to look for these. Only real issue I can not sus at the mo is finding a new CU that will fit so I do not have to cut the conduit to size, do regs allows cus to be drilled to allow snug fit of conduit? I suppose IP rating will not be affected.

 

[malcolmsanford]

Naz you may find that your CPC is the conduit, You will have to be careful here what you do and before you start "cutting" things have a go round with a wander lead and see if your getting continuity at each point by doing an R2

Normally a good indication that the conduit is the CPC is that it is all bushed at the CU and at the back boxes. Also most conduit installs of this age utilize a flush CU, is the one existing flush?

 

[Naz]

Hi

thanks for your reply, it makes sense about the conduit being the cpc's, the steel is bushed as you have indicated, I will take my own continuities prior the work just to check and the subsequently to ensure continuity. Have not checked situation at back box's yet but will do

again many thanks

Naz