Main Switch (Domestic - London)

[JohnD]

I was doing some minor repairs in my mothers house in London today. I noticed she has two CUs (the second one more recent, for electric shower and sockets in a room converted for disabled use). They are fed from a Henley Block on the Meter board.

I had the idea that there ought to be a Main Switch to turn off all power in the house, but it doesn't seem to be a requirement when I look at my OSG, did I imagine it?

It would have been useful because the shower CU does not include an RCD, which I could easily fit in place of the DP switch if the tails were cold.

Does anyone know if I can get London Electric to fit one, or will they say it is part of consumers installation and nothing to do with them (except for connecting the new tails)? I am anyway going to ask them to come and fit a proper TNC-S as the MET is connected to a pipe clamp on the incoming cable armour (!)

 

[Adam_151]

Its one of those regs thats never really understoof in the same way twice, every istallation should have a single main switch, but what consitutes an installation? thats what no one can agree on

 

[Big_Spark]

It is NOT a Regulation, simply a recommendation...

London Electric may fit one..see what they say

 

[Qedelec]

It is a requirement though, if you have two consumer units connected to a Henley Block, to have adequate labeling.
This should state that there are multiple means of isolation and great care should be made to ensure a circuit is disconnected BEFORE attempting maintenance.

 

[JohnD]

Thanks. Is there any standard wording? I have been making stick-on labels to identify the CUs and circuits, as well as labels for FCUs to say what they control, and the fuses that should be fitted.

On the subject of a main switch, if they say I have to provide one myself, with new tails to go to the meter and the existing tails supplying the Henley Block, am I allowed to put it on the Supplier's board, like the Henley Block, or should I fasten it to a new flameproof board on the wall? All the existing tails are in 16mm red and black with grey sheathing, aren't tails are supposed to be in 25mm now?

 

[ban-all-sheds]

If you put it on the supplier's board, who will ever know?

 

[JohnD]

Ha Ha! But, after I've fitted it, I was going to ask the supplier to pull the main fuse and connect the tails, not something I've ever wanted to do, so they would see it then.

 

[ban-all-sheds]

They probably won't do that - they'll be working on the basis of you using a qualified electrician to fit the switch, who they will allow to pull the fuse.

 

[JohnD]

I can see the last electrician did that, because the seal is broken. Can I open it in safety? 100A black plastic service head, fitted 1995.

 

[plugwash]

you aren't supposed to touch it but since the seals are already gone and you have someone to blame for that i can't see how they can pin it on you.

as for the safety of doing it the important thing is to stop current flow (using the main switches of all consumer units) before you pull the fuse to remove the risk of arcing.