Intermittent sockets, wiring and fuses fine

[Lorzor]

I had a quick job yesterday where the customer said he lost power to some kitchen sockets, I went round and he had an old wilex board with rewireable fuses. All the sockets in the house were on two 30A fuse wires. Most sockets in the kitchen were in a ring on 1 and the rest of the house must have been on the other (oddly there were some sockets in the kitchen on the other too). I didn't do any testing on the other circuits and the fuses were fine.

Basically all I did was remove the 5 affected sockets and check the wiring in them, they were all fine apart from one where some of the cables were loose, I reconnected it and did an IR and all was fine. I replaced the fuse and all the sockets were working. Even though the wires came out they only came out when I removed the socket from the pattress but I thought that must have been the fault.

Except they rang me this morning to say it has happened again and it was when the dryer was on, they also said it happened last time when the dryer was on.

How can they have a complete loss of power (less than 1v measured) on these sockets if the wiring is good and the supply is good? Bearing in mind I managed to remake the circuit just by removing some sockets and removing a fuse then replacing them. I just want some ideas of where to start when I go back tomorrow. All I can think of IF the wiring is definitely good is some kind of thermal cutoff switch hidden away somewhere. I think that's pretty unlikely - could there be some connection issues in the old board?

 

[Midwest]

Have you started at the beginning with your testing?

 

[Lorzor]

Well no, I didn't see the point.

Their circuits haven't been touched for years. When I found the fault in the socket and when I replaced the fuse the circuit came back up - I saw no reason to continue with fault-finding.

 

[Pete999]

Well no, I didn't see the point.

Their circuits haven't been touched for years. When I found the fault in the socket and when I replaced the fuse the circuit came back up - I saw no reason to continue with fault-finding.

There is fault finding and Testing

 

[Midwest]

Well no, I didn't see the point.

Their circuits haven't been touched for years. When I found the fault in the socket and when I replaced the fuse the circuit came back up - I saw no reason to continue with fault-finding.

Fault finding can be difficult and time consuming. You can try and wing it, and you might be lucky.

The alternative, is to test the circuit from the beginning, as if it was new to try and locate the fault. As it is, you don't know what the fault is, other than it is an intermittent fault, resulting in no supply.

 

[Lorzor]

So the recommendation is I just start the fault-finding from the start? I was looking for some more targetted advice, I don't want to be here all day doing continuity checks on every length of wire if I don't have to. Obviously I do want to do it properly though.

EDIT: I was just hoping that someone might have had a more simple solution they may have come across in the past.

 

[Lorzor]

Fault finding can be difficult and time consuming. You can try and wing it, and you might be lucky.

The alternative, is to test the circuit from the beginning, as if it was new to try and locate the fault. As it is, you don't know what the fault is, other than it is an intermittent fault, resulting in no supply.

You're not kidding. I put in a CU for a customer last week and I had 0.1MOhm IR L-N on an unidentified circuit (they all were unidentified). I had the washing machine out, the dishwasher, dryer, about 15 sockets and I couldn't find it. Turned out to be the light in the cooker hood (not the light itself, the T&E leading to it that I couldn't access). You live and learn - check the easy stuff before you go pulling out cookers, 4 hours wasted .

 

[Midwest]

So the recommendation is I just start the fault-finding from the start? I was looking for some more targetted advice, I don't want to be here all day doing continuity checks on every length of wire if I don't have to. Obviously I do want to do it properly though.

EDIT: I was just hoping that someone might have had a more simple solution they may have come across in the past.

It sounds like you may have a lose connection, you could check at the socket used by the tumble dyer, but the fault could be elsewhere. As you've found another socket with lose connections, I would recommend you start at the beginning, starting with continuity of ring final conductors, and analysing the results. Otherwise, as you've found out, you've think you've rectified the fault, when in fact you've rectified one of several faults.

Alternatively, you could invest in a crystal ball.

 

[Lorzor]

It sounds like you may have a lose connection, you could check at the socket used by the tumble dyer, but the fault could be elsewhere. As you've found another socket with lose connections, I would recommend you start at the beginning, starting with continuity of ring final conductors, and analysing the results. Otherwise, as you've found out, you've think you've rectified the fault, when in fact you've rectified one of several faults.

Alternatively, you could invest in a crystal ball.

OK, seems fair enough.

 

[rugbyspark1]

YES, proper testing can be long and painful. Usually split circuits in half and work from there. The last one I had a couple of weeks ago took nearly all day !!. Kitchen fitters had covered up box and cables, pushed in cables and shorted to side of box, work done 7 yrs ago !.
Needed cupboards removing from wall to find fault !.

 

[Midwest]

This one was hidden, about 50 years ago;

 

[westward10]

If it were a lose connection on a ring final I would not expect several sockets to be non functional unless they are a radial.

 

[Midwest]

Unless its only 'lose' when the tumble dryer gets going

Edit; the OP will only find out, when it's tested properly and from the begining

 

[HandySparks]

...I replaced the fuse and all the sockets were working.

Had the fuse actually blown or did you just change it anyway?

 

[Lorzor]

Had the fuse actually blown or did you just change it anyway?

Nope, fuse was fine.