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

[Kuba]

I’m doing some tests on my board at home in order to prepare it for an upgrade. It’s an old plastic GE board with no rcd protection. Doing continuity of ring final circuit on the main ring. When it comes to end to end tests at the consumer unit I’m getting no reading between neutrals. All good between L-L and E-E. Figure of eight and I’m testing L-N on sockets and all readings come good (0.45-0.50 ohms) in every room. What could be the cause of this? ? Neutrals terminated badly at a socket somewhere? Rodents? JB?

Would taking one leg of ring out and looking with a Martin dale be a quick solution to find it before I start looking by splitting the ring?

Insulation resistance was L-N >299Mohms, L-E >299Mohms but N-E only 8Mohms.

 

[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 ?

 

[littlespark]

Your neighbours have their CU in your property? We thought it was just a fuse

 

[Kuba]

Your neighbours have their CU in your property? We thought it was just a fuse

It’s a shared communal hallway. Victorian house split into two flats.

 

[telectrix]

easy fit an isolator to the right of that caution label. just dress neighbour's tails out the way.

 

[brianmoooore]

There's no shared neutral after all. There's a second grey neutral hidden behind the blue.
The pipe clamp used to take the earth off of the incomer is a cause for concern.

 

[telectrix]

and we can see wet-pants knows about the 150mm clearance from electrical services. ????