Tracing Wires? Tracking my ring main.

[dhutch]

For a number of reasons including investigating the ease of spliting it into two or more rings I would like to trace where the wires are that make up my ringmain, or atlease workout the order of sockets.

Excluding gaining magic powers, what is the best way of tracing the wires?

Obviously you could take all the sockets off and set about buzzing out all the wires, but would you be able to determine cable lenghts by measuring the resistance and hence by measuing back to the CU from each socket (possably after disconnecting one end of the ring) and therefore work out the order? Ive used simular techniques for testing/fault finding the wiring of pyrotechnics but the wire gauge is smaller and each pyro a fairly well know resistance.

If I have the ring split I will get an regisitered electrian in to do it, but im interested in scoping out the job before hand and am happy to do any of the donkey investigation work beforehand. No qualifications in electrical instalations (bar my pyroticket) but am a graduate mechanical engineer. Test equpment wise I have a fluke75 and a socket tester but thats about it!


Daniel

 

[davelx]

A number of ways to determine the order without needing to worry about the resistance values. e.g.:

Disconnect circuit at CU and remove all sockets.
Link L & N of one circuit cable at the CU, then with a continuity tester check between L & N at each cable on each socket - that will give you the first socket on that leg from the CU. Label it up.

Now remove the link at the CU and link L & N of the other cable in that first socket, then find then next socket along by checking continuity between L & N at each remaining socket, etc.etc.

(you could use igniters and PP3 to do this too )

 

[riveralt]

For a number of reasons including investigating the ease of spliting it into two or more rings I would like to trace where the wires are that make up my ringmain, or atlease workout the order of sockets.

This raises the question why ring final circuits and why not radial final circuits? It also raises the issue of what type of Consumer Unit you have, is their any space and will the new circuits by RCD protected?

Excluding gaining magic powers, what the best way of tracing the wires?

Simplest is to isolate all the circuits bar the the ring final circuit you want to test and use your plug in socket - this will identify which socket is on which MCB.

Obviously you could take all the sockets off and set about buzzing out all the wires, but would you be able to determine cable lenghts by measuring the resistance and hence by measuing back to the CU from each socket (possably after disconnecting one end of the ring) and therefore work out the order?

Not sure why you would want to know the order of the sockets and the lengths of the cables when you seem to be suggesting you intend to replace one ring final circuit with two - its a ring so provided it doesn't exceed 100 sq metres on a 32Amp MCB and its not in a high use location like a kitchen the length of the cable and location of the sockets shouldn't matter.

If I have the ring split I will get an regisitered electrian in to do it, but im interested in scoping out the job before hand and happy to do any of the donkey investigation work beforehand.

Splitting the ring is not an easy thing to do and while you may want to do the donkey work you will have gain permission of the electrician you hire before you do anything.

I have a fluke75 and a socket tester but thats about it!

Not great but adequate for dead testing if necessary.

Best advice would be to get an electrician in now rather than wasting your time - he will quickly(????) be able to identify which sockets belong to which circuit and give you the best advice on what options you have available.
(????) Because if the previous occupier of the property has been a diy nut job who doesn't know what they have been doing and have extended and extended the ring final circuits which junction boxes etc then it could be a long and complicated job. Had one recently where the consumer unit suggested two ring final circuits but the evidence suggested four. Previous owner had buried a RCD fused connection unit under plaster on a wall - not in a safe zone and run two more 'rings' from that FCU RCD. That took two days to try and sort out.

 

[dhutch]

...you could use igniters and PP3 to do this too ...

I like that idea.

Obviously the way you discribe would work very nicely, but does require de-wiring all sockets on the ring which I was slightly trying to avoid at this stage, if only because they are wired with really very stingy cable lenght which makes getting them back on a right pain!

 

[OwainDIYer]

Put a time domain reflectometer across one end of the ring, and test the ring - you should get the total cable length.

Break the ring at each socket in turn, and you should build up a map of cable lengths to each break in turn.

You need to make friends with a telephone linesman

 

[Sherbertlion]

You could check at the CU that you have some form of a ring, then get a long lead linked to one of the conductors on one leg and test at each socket to give you an idea of the order and possible cable lengths. Won't tell you about any hidden junctions and may be interesting if you have any interconnections etc

 

[dhutch]

This raises the question why ring final circuits and why not radial final circuits? It also raises the issue of what type of Consumer Unit you have, is their any space and will the new circuits by RCD protected?

Because if the previous occupier of the property has been a diy nut job who doesn't know what they have been doing and have extended and extended the ring final circuits which junction boxes etc then it could be a long and complicated job.

The CU is a new 16way '17th Ed' affair with six of the 10 mcbs unused so there is plenty of free space there, installed as part of the sale.

There is only one ring main and a radial to the conservatory ring. From what ive seen and been told the ring runs round the 1st floor sockets, with spurs from each of these to feed a single ground floor socket.

However this must have been altered (as the lighting has been) when one of the four bedrooms has been turned in the bathroom where of cause the sockets have clearly been removed but im unsure what the ring does.

Equally the kitchen has far more sockets than the room above it. some of which have two cables not one, so either the ring goes through some of them but not all, or they are radial off the ring. I wouldnt even like to guess.

I understand the house was fully re-wired in the early 80's by the council shortly before being sold into private ownership, and is largely as was, but clearly changed in places.

After some corrections the house has passed a full electrical survey by an apparently niceic registered electrician as part of the sale, but I have already found things that I'm sure I shouldn't.


Daniel

 

[dhutch]

You could check at the CU that you have some form of a ring, then get a long lead linked to one of the conductors on one leg and test at each socket to give you an idea of the order and possible cable lengths. Won't tell you about any hidden junctions and may be interesting if you have any interconnections etc

Thats the sort of thing I was hoping I could do, I just didnt know if, with the kit I have, I would have enough resolution to be able to distinguish order.

Put a time domain reflectometer across one end of the ring, and test the ring - you should get the total cable length.

I have just googled such a device, very interesting! As you say, you wouldnt buy one for the job, but i'll bear it in mind.


Daniel

 

[martinxxxxxx]

Put a time domain reflectometer across one end of the ring, and test the ring - you should get the total cable length.

Break the ring at each socket in turn, and you should build up a map of cable lengths to each break in turn.

You need to make friends with a telephone linesman

What setting do you have to use for t&E

 

[OwainDIYer]

Put a time domain reflectometer across one end of the ring, and test the ring - you should get the total cable length.

What setting do you have to use for t&E

I'd expect to calibrate using a spare length of typical cable.

You can hire TDRs calibrated for power cable testing.

Or a capacitance meter would probably do, that's what we did in the old days to trace faults, to get the locations of each socket on the ring, but not measure it to the ft.

 

[bernardgreen]

There are ways to map out the routes of ring final cables using constant current sources put DC along one of the conductors and then measuring voltages on that conductor at each socket referenced to the current source.

Or a less reliable method

After identifying all the sockets that are fed by the MCB you can then map out the socket routing using the voltage drops along the cables when a significant load ( 2 Kw kettle or similar ) is taking current from one of those sockets Plugging it in at various sockets and measuring voltage drops from CU along the neutral to each of the sockets will tell you where current is flowing. It then takes a lot of diagnostic analysis to create the route map of the cable. But even then you will not find hidden nasties.

Measure using a long wander lead. Measuring the voltage live to neutral will not give any useable information as the incoming voltage will be continuously varying far more than the voltage drop.

Read more: //www.diynot.com/forums/viewtopic.php?p=2085052#2085052#ixzz1l1DU99rf

Putting pulsed DC currents of several amps along one conductor enables a magnetic compass to be used as a cable detector. When it is near the cable with the pulsed DC the needle will move with the pulsed current. Not 100% effective but still a useful method to trace cables that are not in the "safe" zones.

 

[martinxxxxxx]

I've got a thingymagig to to it.