Problem of the week, too many wires in a socket.

[ProDave]

This is one I found on Monday:

You are tasked with the seemingly easy job of replace all the switches and sockets in a kitchen with shiny new posh ones.

All is going well, until you unscrew one of the old sockets to find it has 4 wires connected to it. Being three 2.5mm twin and earth, and one 1.5mm twin and earth.

The questions:

What's wrong with what you have found? (hint more than one thing wrong)

What tests would you do to establish what all the wires are for?

What might you do to put it all right?

I know you are unlikely to guess exactly what I found, but it will be interesting to see how you would proceed.

 

[Apache]

Can I play?

 

[SLIPSHOD & SLAPDASH]

I have found exactly the same many a time, normally its around 5pm on a Friday. I wont say yet what all the cables do.

 

[batty]

I think all the students have been frightened off.

 

[apprentice87]

Hi there,

Well, I am a newbie, so i will have a go!!

There is no knowing what someone has done, so i would disconnect all the wires having first taken a photo so i can but them back if needs be..

Then either by turning the power back [probably] or using a continuity tester i would see which pair of wired fed the thing, and then trace the others with a meter and a long test lead to see just where they DO go...

john

 

[ProDave]

You are on the right lines of testing what does what, but NOT by powering it up to do live testing.

There's a simple way to determine which two are the actual ring final, with the circuit still dead. Care to suggest what that method is?

Then you just have to determine what the other two are.

Look around, see what's where. In this case there's an FCU directly above the socket that feeds a cooker hood. What testing would you do to see if one of them connects to that?

 

[a1]

Posts removed Badger, and all posts that referred to yours.

IT IS A STUDENT QUESTION !!!

 

[steptoe]

naughty Badger, :slap

 

[apprentice87]

Hi Again!!

To find out which is the ring i would just get my little continuity tester, [it lights up an led when you touch the probes together] or my voltage probe that buzzes would do the same, connect it to the one neutral in one cable, and then see which other neutral in one of the other cables it was "paired" with. I would do the same then with the two phase conductor ends, and the cpc's too.

Having done that and identified them i would do the same but with my meter to check the ring out while i was there, you know r1 rn the same and that the resistance of the cpc end to end had the right relationship with that of the live conductors, bering in mind that it is of a different csa. You know what i mean!!

As for the FCU and the socket, i would just stick my socket adaptor thingy in the socket, and once again, use the continuity tester to match socket holes, with cable ends. That would sort that out.

I would also check that the FCU connections matched up with the ones in the socket, [you never know!!]

So up to now i have found the ring ends and the cable feeding the socket, so that is three of them, the fourth must be the feed then if i am understanding the setup you describe correctly, [a radial feeding a ring connected up in the backbox..]

I would do the same from the wires i suspected were the feed by connecting the continuity tester to the one end and by using my long test lead the other ends in the CU. At the same time i would discover which MCB fed the circuit, and if there were any other cables also connected to the same MCB.

All just a question of matching a cable end with the connections to the MCB in the CU and its associated neutral, and matching cable ends to the FCU and identifying the ring ends. I would do a little drawing, and mark the cable ends with a marker pen as i went along, to keep track of everything.

john..

 

[SLIPSHOD & SLAPDASH]

What do you think the 1.5 is doing ? remember its in a kitchen.

 

[ProDave]

Having done that and identified them i would do the same but with my meter to check the ring out while i was there, you know r1 rn the same and that the resistance of the cpc end to end had the right relationship with that of the live conductors, bering in mind that it is of a different csa. You know what i mean!!As for the FCU and the socket, i would just stick my socket adaptor thingy in the socket, and once again, use the continuity tester to match socket holes, with cable ends. That would sort that out.

I would also check that the FCU connections matched up with the ones in the socket, [you never know!!]

So up to now i have found the ring ends and the cable feeding the socket, so that is three of them, the fourth must be the feed then if i am understanding the setup you describe correctly, [a radial feeding a ring connected up in the backbox..]

I would do the same from the wires i suspected were the feed by connecting the continuity tester to the one end and by using my long test lead the other ends in the CU. At the same time i would discover which MCB fed the circuit, and if there were any other cables also connected to the same MCB.

It's not a radial feeding a ring.

So you have identified that two of them loop back to each other so they must be the two ends of a ring. You can confirm that if you want to by testing with a wander lead back to the CU. You already know which MCB feeds the circuit, as you have already isolated the circuit to work on it.

So you still need to identify the other two cables. I told you there was an FCU nearby. Might it be good to unscrew the cover of that to have a look, and you might then be able to do some useful testing to see if you can identify the function of another one of the cables.

Another useful tool in this situation is ask the customer, has there been any electrical work done recently. His answer to that question was "An electrician friend fitted an outside security light a while ago" So you might want to find the switch that feeds that and have a look how it's wired.

 

[apprentice87]

Hi Slipshod,

Ahh i had forgotten about the 1.5, as i wrote my answer at about 3 in the morning, I got arc eye too!! hardly see the computer!!!

Anyway, the 1.5....

Nobody would wire a radial in 1.5 nor a ring either. As there is evidence of silly things, no doubt whoever did it only did simple things and whould not have attempted to run the original circuit. So at a guess, i would say they 1.5 has been used to wire a spur to the socket and hence the FCU and the cooker hood.

Once you had found where all the cables went though, all would be clear, and i think that would be all you could do. Trying to second guess what some numpty has done would be impossible!!

I have only very limited experience, but judging by some of the things i have seen, you lot must come across trully unbelievable things!!!

PS. you do not want arc eye!! I have never ever had it before, [which is a miracle considering the amount i have had to do with welding [i am a welder] but i do not want it again!!!! It does not hurt as much as people say, but it is like looking through a thick fog.......

Anyone want a free plasma cutter, very little use!!!!!

john.

 

[adam1984]

Ill have a go.

continuity test to find ring cables. Once established put them to one side.

2 spurs from socket. I

I think the 1.5mm cable is powering the FCU for the hood and the person who put this in thought it would be ok to use the 1.5mm cable as the rating of the hood is 5amp (just guessing) or the 1.5mm is powering a PIR outside light and the 2.5mm cable is runing to the fused spur.

I would do continuty test on all items to establish the above.

Thats my guess!

Adam

 

[ProDave]

adam pretty much has it.

Two of the 2.5's are the 2 legs of the ring.

The other 2.5 is the spur to the FCU for the cooker hood.

The 1.5 was fitted by the owners "electrician friend" and feeds via a light switch to a 500W outside PIR light. confirmed by testing continuity from the light switch.

You have already said you can't have 2 spurs off one socket. and you have already noted 1.5 is no good on a circuit protected by a 30A MCB

So you can re connect the two rings legs and the spur to the FCU into the new socket.

But what are you going to do to get the outside light working again and to comply with regs?

Tip it's a timber stud wall, so pulling extra cables is relatively easy.

 

[adam1984]

Woohoo!

With regards to the PIR light I would take the feed away froim the original overcrowded ring socket and connect it to an "untouched" ring socket and spur off of that. I would change the light swith to a FCU with a 3 or 5 amp fuse in it.

The issue of RCD might come up so if i had to make the FCU a RCD FCU I would.

 

[ProDave]

Woohoo!With regards to the PIR light I would take the feed away froim the original overcrowded ring socket and connect it to an "untouched" ring socket and spur off of that. I would change the light swith to a FCU with a 3 or 5 amp fuse in it.

The issue of RCD might come up so if i had to make the FCU a RCD FCU I would.

That's good thinking, and shows there's more than one solution to a problem. It also shows you need to see the whole install to arrive at a solution.

In this case there was no other socket to spur from, this was the only socket in that corner of the kitchen. You could have added another socket, solely for the purpose of enabling you to add another spur (but would raise the RCD issue). But my chosen solution was to extend the 1.5mm cable and take it up the wall to the existing FCU. So that FCU now feeds the cooker hood and the outside PIR light.

Regarding RCD's I took the view that I was not altering the existing cable or it's run, and my extension of that cable was >50mm deep (100mm stud wall forming the inner leaf of a cavity wall) so no need for RCD protection on my new bit of cable.

 

[Richard Sutcliffe]

In this case there was no other socket to spur from, this was the only socket in that corner of the kitchen. You could have added another socket, solely for the purpose of enabling you to add another spur (but would raise the RCD issue). But my chosen solution was to extend the 1.5mm cable and take it up the wall to the existing FCU. So that FCU now feeds the cooker hood and the outside PIR light.

Is the FCU the only way of isolating the PIR or is there a dedicated switch after the FCU? For practicality I would personally (if in my own home) of wanted to have a seperate switch for both the hood and PIR. Possibly extend the ring to go - socket - FCU to cooker hood - FCU to PIR - Maintenance free junction box within cavity wall joining back to the other leg of the ring which was going into the socket (or a second socket outlet near by depending on location). Obviously this would be an ideal if it were my own home and the customer may just want less hassle.

 

[ProDave]

There is an ordinary light switch (6A rating) feeding the PIR light, another reason why it was wrong to be fed directly from the ring final.

Yes it's not ideal having one FCU feeding two things, but remember, I was there to just do a simple swap of the switches and sockets so wanted the quickest solution to the problem.

 

[Richard Sutcliffe]

There is an ordinary light switch (6A rating) feeding the PIR light, another reason why it was wrong to be fed directly from the ring final.Yes it's not ideal having one FCU feeding two things, but remember, I was there to just do a simple swap of the switches and sockets so wanted the quickest solution to the problem.

In a situation like this would you put various options to the customer or just carry out the cheapest and advise the customer what needed doing?

 

[Sidewinder]

Anyone want a free plasma cutter, very little use!!!!!john.

I'll be there at 07:00 in the morning, please have the plasma cutter packaged and ready for me!

Hope your eyes are better soon, I never had the cloudy bit, just the sandy feeling.