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House ring main failed - help!


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8 minutes ago, system 4-50 said:

There will be 2 live wires and 2 neutral wires for the ring main going into the MCB in the consumer unit. 

I would disconnect 1 live AND its associated  neutral and insulate the ends. Then I would open a socket half way around the ring and separate the two sets of wires and insulate all of them. You have now divided the ring main into 2 legs, one of which is connected to the cu. Safely energise at the CU. If the RCD does not trip then then the leg you have energised is ok and the fault is on the other leg.  Stick a lamp into various sockets to see which sockets are on the energised leg. Repeat the process with the other leg.  When you have identified the failing leg, then halve it and repeat the process.  Eventually you should be able to determine which is the failing length of cable. Examine for for faults in either the live or the neutral line.  This should work without many more tools than a screwdriver or 6.  Anybody want quible with the method?  (Don't overload the ringmain when divided.)

I like the idea of splitting the ring and narrowing things down, but I don’t like the idea of opening up the consumer unit.... not sure why as I would happily do it on the boat.

 

I don’t have a Megger, so that’s not an option.

 

I think I’m going to open a socket and see how I go. If I feel comfortable, I’ll keep going and see if I find the loose wire, or whatever it might be.

 

If I don’t find the problem, or I don’t fell comfortable, we’ll get an electrician in.

 

Thanks again for the advice and info!

 

 

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13 minutes ago, Richard10002 said:

I like the idea of splitting the ring and narrowing things down, but I don’t like the idea of opening up the consumer unit.... not sure why as I would happily do it on the boat.

 

Because it's not a criminal offence to completely disconnect the boat from the supply?

 

 

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26 minutes ago, Richard10002 said:

I like the idea of splitting the ring and narrowing things down, but I don’t like the idea of opening up the consumer unit.... not sure why as I would happily do it on the boat.

 

I don’t have a Megger, so that’s not an option.

 

I think I’m going to open a socket and see how I go. If I feel comfortable, I’ll keep going and see if I find the loose wire, or whatever it might be.

 

If I don’t find the problem, or I don’t fell comfortable, we’ll get an electrician in.

 

Thanks again for the advice and info!

 

 

Are you sure there is not something like a dishwasher or fridge still plugged in somewhere before you start ripping things to bits. 

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47 minutes ago, system 4-50 said:

There will be 2 live wires and 2 neutral wires for the ring main going into the MCB in the consumer unit. 

I would disconnect 1 live AND its associated  neutral and insulate the ends. Then I would open a socket half way around the ring and separate the two sets of wires and insulate all of them. You have now divided the ring main into 2 legs, one of which is connected to the cu. Safely energise at the CU. If the RCD does not trip then then the leg you have energised is ok and the fault is on the other leg.  Stick a lamp into various sockets to see which sockets are on the energised leg. Repeat the process with the other leg.  When you have identified the failing leg, then halve it and repeat the process.  Eventually you should be able to determine which is the failing length of cable. Examine for for faults in either the live or the neutral line.  This should work without many more tools than a screwdriver or 6.  Anybody want quible with the method?  (Don't overload the ringmain when divided.)

Not really a quibble, but it can be shown mathematically that dividing the ring main into halves is not the quickest way to find the fault.

If you split the ring close to one end, the chances are that the fault will almost certainly be in the longer section, but on the other hand if it is in the short section you have made a lot of progress. It turns out that the optimum division for finding the problem section quickest is not half and half, but 1/3 and 2/3.

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From past problems.

 

Is there an external socket that could have got wet?

Door bell transformer?

Socket in a garage?

Do you have suspended ground floors or solid?  Solid may have got damp somewhere  or suspended could have a puddle under with a junction box in the water?

TV aerial amplifier or CCTV?

Has anything been changed to cause a fault?

2 minutes ago, twbm said:

 

Just about .. it was certainly well cooked. 

Had that with a gecko in the South of France. Got into the pool control box and shorted the pcb, burnt a track off!   one very dead lizard.

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I'm sure there is a 2 year jail sentence for looking in the direction of a consumer unit, or at any device that some group have managed to get a monopoly on.  I'm fortunate that a ) the lead seal on my incomer fuse spontaneously falls off at regular intervals - I've complained to my supplier and they have done nothing about it, and b ) the state has not managed to install a camera in my smart meter (yet).

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5 hours ago, TheBiscuits said:

 

Because it's not a criminal offence to completely disconnect the boat from the supply?

 

 

Its not a criminal offence to open the cu only to add new circuits or replace it. Nothing to stop you replacing the mcb etc on a like for like basis either.

 

Technically it's only an offence if you don't notify the local authority or use an incompetent person to certify. you can still do the work

Edited by jonathanA
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Just now, jonathanA said:

Its night a criminal offence to open the cu only to add new circuits or replace it. Nothing to stop you replacing the mcb etc on a like for like basis either.

 

Technically it's only an offence if you don't notify the local authority or use an incompetent person to certify. you can still do the work

 

Breaking the seal and pulling the supply fuse is though I think.

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True but all mine were missing when I moved in ....(seals that is not fuses)

 

I would just point out that pulling the commercial fuses is something that you do need to know what your doing at lot of energy between you and the next fuse in the substation ....

Edited by jonathanA
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1 minute ago, TheBiscuits said:

 

Breaking the seal and pulling the supply fuse is though I think.

I have done that a few times in the past, but we had a good working arrangement with the Eastern Electricity Board and would ring them and tell them so they could reseal them.

 

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2 minutes ago, TheBiscuits said:

 

Breaking the seal and pulling the supply fuse is though I think.

I managed to overload our supply fuse recently, when the man from the board changed it he said that now the seals are specific to each electrician so they know who last changed the seal.

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43 minutes ago, TheBiscuits said:

 

Breaking the seal and pulling the supply fuse is though I think.

A few years back the electricity board (yeah, I know they aren’t that any more) came round and fitted an switch disconnector between the CU and the meter. The terminal cover at the meter side of the switch has a company seal on the screw, the one at the CU end doesn’t. I thought they’d done that pretty much everywhere now.

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6 hours ago, David Mack said:

Not really a quibble, but it can be shown mathematically that dividing the ring main into halves is not the quickest way to find the fault.

If you split the ring close to one end, the chances are that the fault will almost certainly be in the longer section, but on the other hand if it is in the short section you have made a lot of progress. It turns out that the optimum division for finding the problem section quickest is not half and half, but 1/3 and 2/3.

You can find that the fault disappears from both legs at some stage, which is a bit puzzling and causes you to question  just how the ring runs.   Having opened up even more sockets, you finally work out that a pinched neutral wire wire was released at some stage.  Then you need  to remember which socket was the culprit.

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1 hour ago, ditchcrawler said:

I have done that a few times in the past, but we had a good working arrangement with the Eastern Electricity Board and would ring them and tell them so they could reseal them.

I was present when my uncle told the grumpy man he would have to take up his grumbles with grandad as it was he that had broken the company seal.  

 

Even less than happy when informed that Grandad died in 1968.

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11 hours ago, TheBiscuits said:

 

Because it's not a criminal offence to completely disconnect the boat from the supply?

 

 

I’ve no idea what you are talking about. I was talking about the consumer unit, whereas I think you are talking about the sealed fuse where the supply comes into the house.

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11 hours ago, ditchcrawler said:

Are you sure there is not something like a dishwasher or fridge still plugged in somewhere before you start ripping things to bits. 

Assuming I’ve identified all the sockets on the ring, I’m as sure as I can be :) 

 

The fridge is now on an extension lead on a different ring, the dishwasher is on a different ring, and works fine.

 

I’ve done all my “ripping things to bits” now, see below :) 

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Okay.... took the cover off the old metal consumer unit. Nothing obviously wrong or loose, but very cramped and crowded, so put the cover back on. I suspect we could do with a new one.

 

Opened up one, then all of the sockets on the ring. No obvious loose, or damaged, wires, so closed them all up again and decided to call in an electrician tomorrow.

 

On a better day, with better tools, I might have undone and remade all of the connections, but it didn’t feel like a safe thing to do.

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Richard10002. Most consumer units are quite cramped and crowded so I wouldn’t go to expense of a new one just for that.

No jail time for taking cover off, they are all talking about the seals on the incoming electricity company’s meter and fuse.

I think you have done a good job so far and taken the right decision getting the sparky in.

All the best.

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9 hours ago, Richard10002 said:

Okay.... took the cover off the old metal consumer unit. Nothing obviously wrong or loose, but very cramped and crowded, so put the cover back on. I suspect we could do with a new one.

 

Opened up one, then all of the sockets on the ring. No obvious loose, or damaged, wires, so closed them all up again and decided to call in an electrician tomorrow.

 

On a better day, with better tools, I might have undone and remade all of the connections, but it didn’t feel like a safe thing to do.

Just had a thought, do you have a burglar alarm on a fuse but unswitched spur?

 

I do feel for you, I have just had an electrical inspection carried out on a 10 year old bungalow and its going to cost me £200 for remedial work,, one of points being poor continuity of the ring main. Now remind me again why I did an apprenticeship and sat my City and Guilds to become an electrician.

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