CU reconfiguration

[Observer]

This is the inside view of the main CU in my house (there is a second 4 way CU not shown). The cables in the incomer are 16mm feed from the (isolatable) meter and feed to the second CU. The shroud at the top of the picture is the incoming SWA cable from the meter which is on the other side of the house (result of major extension and relocation of CU).

I am planning to do the following reconfiuration work and, when that's done, I intend to call in a sparks for a full PIR.

Circuit 2, on the non-RCD side as seen, is the radial circuit mentioned in this thread. I intend to move it to the RCD side of the board and, as you can see, I have crimped on some additional lengths of 2.5mm in preparation. The reason it is on the non-RCD side is because there is a freezer on the circuit and the sparks who installed the CU recommended it should be so. However, the circuit also feeds an external socket as well as two kitchen sockets close to the back door so it should be RCD protected on that account.

The 'anomalies' I note are:

Circuit 14 is: (i) a ring main serving basement games room, utility room and two power points in garage (each spurred off power point on the other side of the wall to the utility room); (ii) 2.5mm radial feed for power to the basement lobby (2 x 13A sockets) and a walk-in cupboard (1 x 13A socket); and (iii) feed to FCU for garage door lifter (not actually installed yet). The blue tape identifies the feeds for the radial and the garage door. Four conductors in one MCB seems a bit untidy so I'm thinking of moving the garage door feed to circuit 3, which is a 16A MCB presently supplying boilers, alarm and bell (all on individual FCUs). Alternatively, I could move the radial to circuit 3 which would give 16A protection for the cable but I would lose the RCD protection (not absolutely necessary as the sockects are not adjacent to any outside doors).

Circuit 8 (6A MCB lighting circuit) has two conductors. I haven't identified which conductor does what but the maximum combined load is less than the MCB rating so I don't think I need to be too concerned about it.

Circuit 3 (16A MCB) also has two conductors - one feeds a FCU for the boilers and the other feeds 2 x FCUs for the alarm and bell transformer.

My plan for the reconfiguration is to remove the conductors for circuit 2 (MCB, neutral bar and earth bar), remove the busbar and MCB, then slide over all the MCBs up to and including the RCD, moving the neutrals and earths along one at a time, then re-install the circuit 2 MCB as circuit 10.

Does all that seem the right way to go about it? And is there anything else I should be considering before (and for the purposes of) the PIR I intend to have carried out afterwards?

 

[sailpower]

Did the sparks who installed it provide you with a full EIC (Electrical Installation Certificate)?

 

[Observer]

Did the sparks who installed it provide you with a full EIC (Electrical Installation Certificate)?

No - but it was done in 1999 so would that have been the norm then?

 

[Adam_151]

Did the sparks who installed it provide you with a full EIC (Electrical Installation Certificate)?

No - but it was done in 1999 so would that have been the norm then?

No, you still should have receieved an EIC, but I'm not too supprised you didn't get one tbh

 

[tim-spam]

Why not just replace the 2 kitchen sockets and the external socket with sockets with an inbuilt RCD?

 

[Observer]

Why not just replace the 2 kitchen sockets and the external socket with sockets with an inbuilt RCD?

What's the advantage? I have a perfectly good RCD at the CU. The only downside of using it (AFAICS) is the theoretical risk of losing freezer contents if it trips sometime I'm not around to notice it. I guess the total value of the freezer contents is ~£50 and that's a lot less than the cost of replacing ordinary sockets with RCD ones.

 

[JohnD]

You mention "The cables in the incomer are 16mm feed from the (isolatable) meter and feed to the second CU. "
Would it not be neater, as you have an upstream isolator, to put the supply through a henley block, thence a pair of tails to each CU?

It would have the advantage of making your big CU slightly less full.

Circuir 14 is extremely busy, would you not be able to move all? most? some? of the non-ring outlets onto the ring, or onto spurs from it?

 

[Observer]

Would it not be neater, as you have an upstream isolator, to put the supply through a henley block, thence a pair of tails to each CU?

It would have the advantage of making your big CU slightly less full.

Circuir 14 is extremely busy, would you not be able to move all? most? some? of the non-ring outlets onto the ring, or onto spurs from it?

I understand splitting the incomer at a Henley block with separate tails for each CU would be "best practice" but not sure that it would be "neater". It would mean disconnecting SWA; re-terminating in a new enclosure; tails from enclosure to Henley block; 2 x tails from Henley to CUs. Quite a lot of additional work which I wouldn't want to do and would be loath to hire a sparks to do (on grounds of cost and disruption) unless there is a real safety issue with the existing connections. Is there? Apart from the physical constraint of terminating two large conductors in a single isolator, is there anything actually wrong with the way it's been done? It occurs to me that it has the advantage that I could reconfigure the main CU without losing all power to the house (the feed to the second CU would remain live). Or is that a Bad Thing? [edit] Thinking aloud here but that would mean moving the RCD while it's still live so would be a Bad Thing.[/edit]

I agree cct 14 is too busy. I can't do much about the radial as it is buried cable running in opposite direction to the ring. There is one fixed appliance on it (a fridge) but otherwise it's only occasional load (vacuum cleaner). I could move it to the 16A boilers/alarm/bell MCB (as I noted in my first post), which would give it a more correct MCB rating but I'd lose the RCD protection. Or I could move the garage door lifter (which is only a feed for future possible use anyway) to the 16A MCB, and doesn't need RCD protection as it terminates in a FCU. I favour the latter because it seems more logical/consistent to have all power outlets RCD protected rather than some which aren't.

I do have two spare ways in the second CU so I could move one or two of the non-RCD protected circuits to the second CU which would free up a way or two in the main board, which could be on the RCD side or not, as appropriate. I could then give the basement radial (and the garage door lifter) its own way in main CU. However, that would mean removing the second CU and crimping and pulling new lengths of cable through. I'm not sure that is really necessary but happy to listen to arguments why it should be done.