RING MAIN CONFUSION

[Nelly72]

Hi guys.

Having a weird problem in a house that has suddenly happened.

One half of the ring main has 240ish volts (fluctuates of course), and the other half is dropping to 210v - This is when I test L-N and L-E…. N-E shows nothing. Whenever I plug a table lamp in the the faulty side of the ring, the voltage goes to 13v while I have my Meggar with my socket adapter plugged into the same socket

The ring continuity readings at the DB are normal, with no breaks in any of the 3 pairs. I was thinking i wouldn’t have a neutral but it’s continuou, and I do get a voltage reading across L-N at all sockets, only half of them drop to 210v as stated above.

I have little experience in fault finding, please go easy on me ahah. Any advice/help is appreciated.

 

[DefyG]

Have you carried out IR tests on the circuit/

 

[Nelly72]

Yeah they are fine

 

[DefyG]

Yeah they are fine

Ok, just thinking it may have been something like a fault we looked into few years back, which turned out to be high resistance fault in cable!

 

[MDJ]

Yeah they are fine

I doubt it, can you explain how you carried out IR tests to the circuit< where you tested and what voltage etc? what was plugged in and what was the actual readings, I doubt very much all was fine if what you posted originally is accurate, also what do you mean by 3 pairs of cables?

 

[Nelly72]

L-N-E not showing low IR readings at the DB on the sockets ring. 500v. Everything unplugged from all sockets, and the neutrals took out the neutral bar, same goes for the earths.

With 3 pairs I meant the Ls - Ns - Es continuity. Was getting 0.34 for lines and neutrals. 0.59 for earths

So, half the sockets at one side are showing 240v, the other half are showing 210v - across L-N, L-E, 0 volts across N-E.

When measuring the voltage with my plug in adaptor from my Meggar at a double socket, I plugged in a table lamp into the other side of the socket, and it dropped to 13v or there abouts. Bulb starts to flicker. This only happens on the sockets that measure 210v, but not on the ones that are healthy at 240v

 

[Rockingit]

I’d be checking the terminations at each outlet - sounds to me like there’s something that’s making enough contact under no load to still be in circuit for resistance tests but failing when under load - and if it’s dropping that much then it’s also probably likely to be one distant end of the RFC from the source.

 

[EddieB]

Yeah they are fine

I would definitely disconnect the ring at every socket split everything and start testing each individual leg, something somewhere is going to show up, if it doesn’t start replacing the the accessories one by one and see what happens

 

[Pretty Mouth]

Assuming this really is a true ring, a single point of high resistance couldn't cause a voltage drop anything like that at multiple points, even if it was completely open circuit, and under full load. It would have to be high resistance at at least 2 points of the same live conductor. Seems unlikely given the results you are getting.

Is it possible that you are looking at two different circuits? Or perhaps a radial serving the faulty sockets spurred from the ring?

 

[pc1966]

Is it possible that you are looking at two different circuits?

They ought to be able to check for the voltage going completely off using one MCB off at a time to confirm that.

Or perhaps a radial serving the faulty sockets spurred from the ring?

That would be my assumption, that the multiple points must be on some segment that is not part of the RFC end-end r1/r2/rN test.