RCD for old installation

[OldPeeBee]

Been asked by an old boy to fit a new cu for him to replace a wood backed 3036 one. He has two boards in the house, both fed independently by pyro from an old cast contactor fed from meter in 25mm tails. 2nd board is slightly more modern with Type 2 MCBs but no RCD provision, but is 15m away from meter in main hall of house. Told him that I would want to remove the contactor and the pyro feeds.

1. Am I right in that I will need a switch fuse to protect such a length of tails. Tails will be run in trunking and ceiling void.

2. Will I be alright to connect the 2nd board ( obviously after testing) even though there is no RCD provision for the circuits.

 

[Lurch]

What's wrong with the pyro? If it tests out then I'd leave it in. Yes you'll need switch fuses for those lengths (over 2 or 3m generally).

As for connecting the 2nd board, the whole installation sounds like it needs a bit more than a board change, no reason to not put the 2nd board on an RCD is there?

 

[davey81]

I would fit a switch fuse for a 15m tails run, I believe this is a DNO rule so you could contact them to see if its required. Could you supply the 2nd CU off the new one your fitting?

If your not working on the circuit of the 2nd board there is no requirement to update them to 17th, however if they supply anything outdoors/showers/sockets I would recommend to the cust they have RCD fitted.

 

[batty]

Why is there a contactor is this board for night store heaters?

 

[OldPeeBee]

Sorry, I mean isolator - big cast job. Reason for moving board 1 is for access, so pyro needs replacing. Was going to remove both pyro feeds which would facilitate removing isolator.

 

[Badger]

Sorry, I mean isolator - big cast job. Reason for moving board 1 is for access, so pyro needs replacing. Was going to remove both pyro feeds which would facilitate removing isolator.

if you have to replace those pyros go with armoured

 

[Lurch]

if you have to replace those pyros go with armoured

For what reason? Concentric is much easier, 6191Y would be easier than a 25mm 3 core SWA under the floor and also to terminate, tidily. 6242Y would probably suffice if push came to shove.

The cable at the very bottom of the list for domestic submains is always SWA.

 

[steptoe]

you say tails?

do you actually mean tails?

tails are recommended max length at 2m (I think.)

 

[ianmacd]

Can you not extend those circuits back to the meter location and use one larger CU?

 

[jimleen]

One big CU sounds good, but if the pyro tests out you'd be as well to use it. What's the second board for anyway? Might just be for heaters.