My first EICR and I'm confused! I'm industrial this is domestic

[Inteificio]

All the sockets are fine.
When separating the legs I've identified which sockets are on which side.

Fortunately as only one ring socket is on one leg I'm pretty certain the fault lies between that socket and another. Finding the 'another' will be a faf.

My next step is to remove all the ring socket covers and separate the cables. A bit of long leading the N will help find the dodgy leg.

I can then remove that one cable from each end leaving (hopefully) two spurs.

What a faf.

I hope the actual exam isn't this bad or I'm going to run out of time massively!

 

[brianmoooore]

If the fault is near to one end of the RFC, you are going to end up with a spur that loops back on itself, so are going to end up with a spur that uses much more cable than one that was designed as a spur from the start.
You will need to check that loop impedance and voltage drop are all acceptable, and access the likely maximum load of the circuit, to ensure it doesn't exceed the rating of the smaller MCB.

 

[UNG]

All the sockets are fine.
When separating the legs I've identified which sockets are on which side.

Fortunately as only one ring socket is on one leg I'm pretty certain the fault lies between that socket and another. Finding the 'another' will be a faf.

My next step is to remove all the ring socket covers and separate the cables. A bit of long leading the N will help find the dodgy leg.

I can then remove that one cable from each end leaving (hopefully) two spurs.

What a faf.

I hope the actual exam isn't this bad or I'm going to run out of time massively!

Rather confused by the fact that you have identified what sockets are on each side of the fault but then you say you haven't and that finding the other socket on the ring will be a faf

I would suggest buying a cheap continuity tester https://cpc.farnell.com/tenma/ten01049/continuity-tester/dp/IN05723 rather than spending a lot of time removing all the sockets

With the continuity tester you can work along one leg of the ring quite quickly and identify where the break is and then do the same on the other leg which should bring you to a point where you can then diagnose the cause of the fault and repair the ring

 

[pc1966]

The zs/rn readings are so low that they are useless for analysis.

What are you using to measure things?

Generally speaking Zs measurements are not that precise, not when you get down to under an ohm and more so if "no trip" due to RCD action so testing at very small L-E currents, so you are unlikely to get far finding a RFC break on that alone.

However, DC low ohm measurements using a typical MFT or similar usually are good enough but you have to allow for dirty switch contacts and socket pins so sometimes you have to insert/remove the test plug adaptor (or lead) a couple of times and operated the switch a could of times to get a low stable reading.

Even then you are likely to only reliably see differences in cable distance of several meters as, for example 2.5m T&E has R1+R2 of about 0.02 ohm/meter and (I guess) most low ohm meters likely to be at hand resolve around 0.01 ohm.

 

[pc1966]

I would suggest buying a cheap continuity tester https://cpc.farnell.com/tenma/ten01049/continuity-tester/dp/IN05723 rather than spending a lot of time removing all the sockets

I don't think that is CAT rated, so I would rather not use it on anything that might be live!

Maybe a cheap voltage tester that has a continuity buzzer?

 

[UNG]

I don't think that is CAT rated, so I would rather not use it on anything that might be live!

Maybe a cheap voltage tester that has a continuity buzzer?

So is he is going to disconnect all the sockets while they are live, I think that would be a no

Given the OP is an industrial electrician I would like to think he would be able to use a simple continuity tester to locate a simple ring circuit fault

 

[Inteificio]

I'm using a Megger mft1721.
I've also got my fancy multimeter for precise testing.

You're right, the Zs is useless for this, I'll do a dc test as that may have more accuracy. Good tip, thanks.

What I'm hoping is that the failure is directly between two ring sockets. All I need to do is identify the cable between and disconnect it at both ends.
If that is the case then I know which socket is on one side. I don't know where the next one in the supposed ring is (there are 3 probables).
Unfortunately I don't know where the spurs cut in, which adds a wild card.



Hopefully the accuracy of the r1rn dc test will give clues.

As for splitting the ring, my whole house was using 14A in total. This circuit is just skirting board sockets. Unless I suddenly start loving electric room heaters the load will be limited.

Now the question is do I fit the b16 from my spares, or go buy a b20


P.s. That's a good tip about turning the sockets off before splitting them too. I wish I'd known that last night as the burns on my hands are really smarting this morning

 

[UNG]

I'm using a Megger mft1721.
I've also got my fancy multimeter for precise testing.

You're right, the Zs is useless for this, I'll do a dc test as that may have more accuracy. Good tip, thanks.

What I'm hoping is that the failure is directly between two ring sockets. All I need to do is identify the cable between and disconnect it at both ends.
If that is the case then I know which socket is on one side. I don't know where the next one in the supposed ring is (there are 3 probables).
Unfortunately I don't know where the spurs cut in, which adds a wild card.



Hopefully the accuracy of the r1rn dc test will give clues.

As for splitting the ring, my whole house was using 14A in total. This circuit is just skirting board sockets. Unless I suddenly start loving electric room heaters the load will be limited.

Now the question is do I fit the b16 from my spares, or go buy a b20


P.s. That's a good tip about turning the sockets off before splitting them too. I wish I'd known that last night as the burns on my hands are really smarting this morning

While splitting the ring is an easy fix and while it is very rare that a cable is at fault I think actually locating / repairing the fault would be more beneficial from a learning point of view for you

 

[pc1966]

So is he is going to disconnect all the sockets while they are live, I think that would be a no

Given the OP is an industrial electrician I would like to think he would be able to use a simple continuity tester to locate a simple ring circuit fault

Here, no it should be fine to use that kit.

It is more of a general dislike on my behalf of having test equipment that is not mains-fault rated in use where mains is about. Sooner or later we all make a mistake and probe the wrong circuit (or discover they are mislabelled somewhere) that is live, and then having something that does not explode on you is nice.

 

[Inteificio]

Here, no it should be fine to use that kit.

It is more of a general dislike on my behalf of having test equipment that is not mains-fault rated in use where mains is about. Sooner or later we all make a mistake and probe the wrong circuit (or discover they are mislabelled somewhere) that is live, and then having something that does not explode on you is nice.

I think we all knew what you meant.

Exploding kit aka audiovisual alert.