Problem this afternoon

[uksparks]

Hi,

Got called to a customer today, background is he has been doing some DIY... he had replaced a load of light fittings and plug sockets, he said we extended this one here and burried it in the wall etc... found one twisted together with tape, no connectors etc... anyway..

The problem is, since yesterday, he said the plugs downstairs don't work... hmmm

I plugged the socket tested in, beep beep beep beep beep, Earth and Live Reverse.... so i go to another, and get the same, then go to another, and its already beeping at me without switching the switch on, its a Fluke socket tester, first two are lit up, then switch it on then its just the first one so suggest Live earth reverse.

I then get the MFT out, plug it in at a socket,

Line to Neutral = 5.5v
Line to Earth = 230v
Neutral to Earth = 230v

Hmm, that's not right...

I pulled off all the face plates down stairs that I could that appears to be on that circuit one at a time thinking ill find the problem, but nope, nothing, all seemed in order (a mess but in the right holes). They said they did not extend or chop any circuits on the plugs, only the lights (they work fine).

Oh its a radial by the way.

So then the lounge, I took the faceplate off, left all conductors hanging (terminated in wagos) turned back on, same problem on sockets, but the ones he had changed were all dead, so im thinking must be somewhere else, put it back together.

Looked at the consumer unit, dual split board, a mess, blatant cowboy who fitted it, everything in the wrong places etc, but anyway, RCD protected. So the circuit was holding fine, as was the RCD.

I put a jumper between Line and Earth and then went round the sockets to get an R1+R2, all seemed pretty much in order, went round everything I could find, all seemed to be ok.

Then hooked Line to Neutral, went round the sockets, not a bloody sausage, nothing, not on any socket anywhere, nothing hooked off the circuit.

Then hooked Neutral to Earth and got a reading on everything.

So then I thought, well everything appears to be in the correct places so what the hells going on... I said it Friday night, I want to go home now thanks, and am going back next Tuesday and have left the circuit off.

My next step is to remove all faceplates on the circuit, so perhaps 15 say, then try to connect one at a time and see what happens.

Has anyone got a better suggestion as ill be honest, im stumped on this, I normally find these things quick and move on, but I spent 2.5 hours then this evening and couldn't work it out.

He assures me he has only changed Faceplates, only 4 of them down stairs in the lounge, you could see they were new. He has not touched anything else on the plug circuit.

 

[uksparks]

I unplugged everything and also switched all FCU's off by the way. It will probably be obvious to me when I go back.

 

[davesparks]

how can 230v go up the neutral and down the earth if its broken / disconnected somewhere?

230V doesn't go up or down anywhere, it exists at a point (any point) relative to another point.

Neutral is normally at 0 volts relative to earth ,ie. connected to earth, and live is at 230volts relative to neutral (and earth).

In your situation the connection to neutral has been broken at some point so everything which is the other side of the break will be effectively floating and not have any potential (voltage) relative to live or neutral. Except when a load is connected to the circuit, at which point the floating neutral wire becomes connected to live (via the load) and will therefore have a potential of 230volts relative to earth.

 

[jaypp]

and its already beeping at me without switching the switch on

are they only switching 1 pole? Also re DIY, explain to customer (tactfully) that the longer it takes, the more it costs and if he can remember seeing 'someone' doing j.b's etc and where, it will save £'s, then the canary will sing!

 

[uksparks]

Yes it must be so single pole. I cannot believe thT he only changed three faceplates, it's not possible to create this problem.

 

[uksparks]

230V doesn't go up or down anywhere, it exists at a point (any point) relative to another point.

Neutral is normally at 0 volts relative to earth ,ie. connected to earth, and live is at 230volts relative to neutral (and earth).

In your situation the connection to neutral has been broken at some point so everything which is the other side of the break will be effectively floating and not have any potential (voltage) relative to live or neutral. Except when a load is connected to the circuit, at which point the floating neutral wire becomes connected to live (via the load) and will therefore have a potential of 230volts relative to earth.

As everything was unplugged this is what is not helping, I'll let you know how I get on when I go back.

 

[davesparks]

are you sure everything is unplugged and disconnected from the circuit? If a diyer has been at large then there could be anything connected to that circuit including lights, showers, cookers, next doors cat etc.

And what are you using to measure the voltage? an AVI? if not then you may be chasing a ghost voltage.

 

[Richard3009]

Wander lead and methodically go down each core, the broken circuit has to show.

 

[davesparks]

Wander leads? testing each core? what is this?

1- Split the circuit in half, find which half contains the fault.
2- split the faulty half in half again and find which half contains the fault.
3- split the faulty half in half again and find which half contains the fault.
...........
hey presto! you've found the fault.

 

[Richard3009]

If any load has been tapped off the ring and you have a broken neutral this problem would appear, you need to find where the neutral is open circuit

 

[uksparks]

I am confident everything was unplugged, I went through very room myself and made sure. I used my Fluke MFT to measure the voltage and twiddled the thing to switch it between conductors etc.

I split the ring in one place and it knocked out the room he claimed to have been messing with, the problem was still there, so therefore the problem must be somewhere else, either it's a whopping coincidence that it's gone funny when he changed the faceplates, or he is not telling me something...

 

[uksparks]

I see what you mean now about the neutral being broken and voltage going through the line to neutral then to earth.

 

[basejumper31]

Reading the above.. holy hell, what am I getting into training for this profession!! lol. Joking, I enjoy the challenge, but, wow, I can kinda see why this takes many years to get proficient at!

Good luck when you go back on Tuesday. Also nice to see such an active and helpful community!

(UkSparks hope you don't mind this off-topic comment.. I will ofc delete if you do)

Have a great wkend everyone.

 

[Richard3009]

Wander leads? testing each core? what is this?

1- Split the circuit in half, find which half contains the fault.
2- split the faulty half in half again and find which half contains the fault.
3- split the faulty half in half again and find which half contains the fault.
...........
hey presto! you've found the fault.

Radial circuit don't split it, just run wander lead from CU to each N connection until you lose continuity, then try to figure out the physical routing of cables and hunt down the nasty connection junction box or connector block

 

[davesparks]

Radial circuit don't split it, just run wander lead from CU to each N connection until you lose continuity, then try to figure out the physical routing of cables and hunt down the nasty connection junction box or connector block

Why use a wander lead? you have all the conductors you need already installed in the circuit.

I was explaining the method of fault finding any standard circuit, be it ring or radial.

In this case you can quite easily test voltage at each socket and identify where the neutral becomes broken without use of either wander lead or splitting the circuit. Where it's good there will be negligible voltage between N and E and nominal 230V between L and N, where its bad there will be nominal 230V between N and E and negligible V between L and N.

 

[davesparks]

I see what you mean now about the neutral being broken and voltage going through the line to neutral then to earth.

I don't think you do, the voltage is not going through anything. Voltage is a measure of the electrical potential at a point, it doesn't travel anywhere.

I am constantly amazed at the number of people who struggle with this concept, everybody learns this stuff at school yet nobody seems to understand!