No reading N-N end to end on a ring main

[pc1966]

Well harmonised fixed wiring starts 2006-era (from memory) so it might overlap, but interesting point.

 

[freddo]

2004 it began, just after I started work.

 

[Kuba]

How old do you think this CU is? I have put new earth sleeving on each cpc but yeah wiring seem post 2006 (except for one room where they kept the old switched line to a pendant).

 

[littlespark]

I would have changed the board if I could but that would mean I’d have to interrupt my neighbours supply (cut out has two separate lines but both neutrals go into same enclosure) so pulling out both fuses at once to do it safely would have been the way? Not to keen on bothering them (they’re both teachers and school online so need power on)... and I could just add an rcd and put a lock on my main switch, quick and easy hopefully ?

Why would pulling your fuse disrupt next door?
Anyway, that’s a job for the fairies.

As implied earlier, you have to be careful working anywhere near a live board... remember, you’ll only get a serious belt once in a lifetime!

 

[Kuba]

Why would pulling your fuse disrupt next door?
Anyway, that’s a job for the fairies.

As implied earlier, you have to be careful working anywhere near a live board... remember, you’ll only get a serious belt once in a lifetime!

Thanks for the warning. I’m aware of the danger and always try to work safe and isolate where I can.

When you look at the picture you can see that both neutrals come from the same enclosure. If a fairy came and pulled my fuse, there would still be a potential risk of current on a neutral in my main switch through parallel paths?

Ps my supply is the brown cable and my neighbours fuse blocks the enclosure from opening where the neutral is.

 

[Kuba]

If anyone reading is interested, I added a rcd to the board. Did tests and everything came out satisfactory. Just need new labels. Ideally I would have changed the whole board but will wait with this until after pandemic when I can work in an empty house and not be distracted. Happy days ?

 

[westward10]

Why didn't you just replace the main switch with the rcd instead of doctoring one in.

 

[Kuba]

Why didn't you just replace the main switch with the rcd instead of doctoring one in.

I have read about rcd being used as a main switch and seen mixed opinions, being against/ok with regs, bad practise etc etc so decided to keep it in case.

 

[Risteard]

I have read about rcd being used as a main switch and seen mixed opinions, being against/ok with regs, bad practise etc etc so decided to keep it in case.

An RCCB can be used as the main switch. Not sure how it could be considered bad practice.

 

[static zap]

An RCCB can be used as the main switch. Not sure how it could be considered bad practice.

Does get me worried about , IR tests for rest of installation !

 

[Risteard]

Does get me worried about , IR tests for rest of installation !

I'm not following you. There is double pole disconnection with either a switch disconnector or an RCCB.

 

[static zap]

Does get me worried about , IR tests for rest of installation !

Was more thinking ,of a reluctance to have an " RCD" type Master switch.
( any defects getting ignored - Must admit I am guilty of skimming thread...
my brain solving other issues at moment )
as I took RCCB on just 1 circuit ! (and not IR test- risks to RCCB)

 

[telectrix]

Why didn't you just replace the main switch with the rcd instead of doctoring one in.

i'd think he did it that way or he would have had to work live or diss, tail/s from meter. ( assuming no up front isolator. ).

 

[kropaske]

I added a rcd to the board.

You don't have any selectivity now between rcd and downstream mcb's, an earth fault will likely trip your rcd which means you will loose whole installation. IMHO better option would be to install individual rcbo's

 

[telectrix]

You don't have any selectivity now between rcd and downstream mcb's, an earth fault will likely trip your rcd which means you will loose whole installation. IMHO better option would be to install individual rcbo's

think OP has done it temporary till he can get round to replacing CU.

 

[Kuba]

think OP has done it temporary till he can get round to replacing CU.

Exactly, yes. And I agree ? will be swapping it for a new CU eventually.

All points regarding rcd as a main switch taken on board, every day is a learning day ?‍

Ps as I said earlier, isolating the board by pulling the main fuse doesn’t make it 100% safe because neutral shares same enclosure with my neighbours installation. Please tell me if I’m wrong? I posted some pictures earlier in the thread for you to see what I’m on about ?
The only way to look inside is to pull my neighbours fuse because it blocks the lid where neutrals are terminated and I want to avoid doing that.

 

[telectrix]

pull the tails out of the meter in that case.

 

[brianmoooore]

You've posted a pic. of your CU with two grey tails going into it, and you've posted a pic of your service head with a blue, red, and brown tail leading from it. Could you post a pic of where these tails meet, please.
Should be a meter somewhere.

 

[Strima]

On a TNC-S theoretically the neutral and earth should be at the same potential as they're linked at the supply head.

On a TN-S theoretically the earth and neutral could be at the same potential as they're linked at the transformer but there may be resistance differences on the cables and sheath causing a potential difference.

On a TT neutral and earth potentials could be significantly different.

TBH with a shared supply I'd take the much safer option of dropping the tails out of the consumer side of the meter, technically these belong to the consumer so they have the legal right to do this although breaking the seals on the meter could be classed as criminal damage as they belong to the supplier... ??

If possible I would add a main isolator switch to avoid this in the future and make additions/alterations much easier and safer.

As for having an RCD main switch I try to avoid them as one fault will effect the whole installation.

 

[Kuba]

You've posted a pic. of your CU with two grey tails going into it, and you've posted a pic of your service head with a blue, red, and brown tail leading from it. Could you post a pic of where these tails meet, please.
Should be a meter somewhere.

Here’s a pic of the whole thing. TNS system. Quite tight for space if I added an isolator before the CU. I had to pull up my cables from the board as I had no space inside and kept the slack for future when I upgrade it. I will be using some fire rated glands. Ps, yes, my neighbours have their rcd as a mains switch I know ?