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I'm not sure if this is a reasonable question or so stupid it shouldn't be asked. If the latter than I apologise and hope I don't get too much negativity back.

So I want to perform the test Continuity of ring final conductors on an existing ring main. Because I'm lazy and its dark outside, could I do this whilst the rest of the CU is live?

My thoughts are to pull the MCB for that circuit and pull the earth cables from the bar out too. Then for neutral, first check the neutral bar in the CU is at the same potential as earth by using a cheap multi meter to check for continuity to earth. If good, then remove the neutrals for that circuit.

Then with both cables removed, carry out the testing as per normal.
 
Do you know the different steps for checking continuity of an RFC?

Have you got the means to carry out safe isolation ? And the said steps?

Do you know how to interpret the results and what you’re looking for, or trying to confirm while carrying out the tests?
 
Hi - imagine you were changing a broken outlet on that RFC. After safe isolation you would have both ends of the ring available, all 6 conductors :) .

Hi. Thanks for that thought. But if you did your testing there, the neutral and earth would still be connected to the earth and neutral bars in the CU so the test wouldn't be valid would it ?

Why would you want to use a cheap multi meter?!!

If you don't need to test very low resistance accurately then why not use one? Obviously for the ring main continuity test itself I will use my multifunction tester.

In general, other than Wilko's interesting post I don't seem to have gained much by posing the question and I should have realised that. Certainly if a professional electrician working on installations every day, I can see why you would never entertain not even a crumb of risk. But in your own house with wifes and babies to worry about.....maybe you still wouldn't but I suppose even if you would you wouldn't suggest its OK on a forum like this.

I'm leaning towards doing it properly with the cu switch in the off position.
 
A confident/competent electrician would almost certainly be able to carry this out without the consumer unit being isolated, this would be their choice but if the option is there to isolate it then this is the suggested option. In your case isolate and ensure it is dead using a proprietary test device.
 
using a cheap multi meter to check for continuity [from neutral] to earth

This may give you an invalid reading. Although there should be continuity, the resistance to the point at which N & E connect is not zero, especially on a TN-S supply where that point is at the local substation down the road. Load current passing through the resistance of the neutral cable causes voltage drop, which is then superimposed on the meter's measurement voltage. Meters and MFTs are designed to reject minor line frequency interference, but adding a few volts of 50Hz plus all the 3rd harmonic and hash to the meter's few hundred mV of measurement can throw it completely out. Continuity tests only work properly on de-energised conductors.

Anyway, what good is knowing that there is continuity now, if you knock the main switch and the neutral breaks first, or something goes high-resistance while you are putting pressure on the neutral bar, etc.

Please isolate it.
 
But in your own house with wifes and babies to worry about.....maybe you still wouldn't but I suppose even if you would you wouldn't suggest its OK on a forum like this.

That is exactly the reason you shouldn't put yourself at risk, your wife and children. Is it worth risking your wife becoming a widow and your children growing up without a father?
 
Hi. Thanks for that thought. But if you did your testing there, the neutral and earth would still be connected to the earth and neutral bars in the CU so the test wouldn't be valid would it ?
Source URL: Ring main continuity test - https://www.electriciansforums.net/threads/ring-main-continuity-test.181316/#post-1594305

I think what was being suggested was, isolate the circuit, then perform your continuity testing at an outlet on the circuit, therefore avoiding the need to take the cover off & go poking about in a live board.
But if you're testing at an outlet, and you remove the conductors from the earth and neutral bars your not going to have continuity are you?!! Sorry if this is negative but this is pretty basic stuff for someone who claims to own a multifunction tester.
 
Last edited:
Hi. Thanks for that thought. But if you did your testing there, the neutral and earth would still be connected to the earth and neutral bars in the CU so the test wouldn't be valid would it ?
Source URL: Ring main continuity test - https://www.electriciansforums.net/threads/ring-main-continuity-test.181316/#post-1594305

I think what was being suggested was, isolate the circuit, then perform your continuity testing at an outlet on the circuit, therefore avoiding the need to take the cover off & go poking about in a live board.
But if you're testing at an outlet, and you remove the conductors from the earth and neutral bars your not going to have continuity are you?!! ion tester.
Sorry if this is negative but this is pretty basic stuff for someone who claims to own a multifunction
Hi. Thanks for that thought. But if you did your testing there, the neutral and earth would still be connected to the earth and neutral bars in the CU so the test wouldn't be valid would it ?
Source URL: Ring main continuity test - https://www.electriciansforums.net/threads/ring-main-continuity-test.181316/#post-1594305

I think what was being suggested was, isolate the circuit, then perform your continuity testing at an outlet on the circuit, therefore avoiding the need to take the cover off & go poking about in a live board.
But if you're testing at an outlet, and you remove the conductors from the earth and neutral bars your not going to have continuity are you?!! Sorry if this is negative but this is pretty basic stuff for someone who claims to own a multifunction tester.

Hey,steady on...i've got a torch...but i'm not a midwife ;)
 
Hi. Thanks for that thought. But if you did your testing there, the neutral and earth would still be connected to the earth and neutral bars in the CU so the test wouldn't be valid would it ?
Source URL: Ring main continuity test - https://www.electriciansforums.net/threads/ring-main-continuity-test.181316/#post-1594305

I think what was being suggested was, isolate the circuit, then perform your continuity testing at an outlet on the circuit, therefore avoiding the need to take the cover off & go poking about in a live board.
But if you're testing at an outlet, and you remove the conductors from the earth and neutral bars your not going to have continuity are you?!! Sorry if this is negative but this is pretty basic stuff for someone who claims to own a multifunction tester.

Yes I realised that and what I was saying was if you do that your circuit is not fully isolated because it is connected to the neutrals and earths of other circuits in the CU. I can see though that you should be able to obtain a consistent set of results doing that and it does seem to be an interesting and practical way of doing it. Still I'd rather do it exactly as proscribed and shall isolate the board before fully isolating the circuit under test.
 
Since it was so quick to do, I decided to try Wilko's kind suggestion. I've only done the easy first part partly because I know it is a ring (its in my house and I've seen it) and partly because I just wanted a sanity check before doing a load of other work and then a final test.

Anyway, the numbers around the ring in ohms were:
L 0.18
N 0.17
E 0.41

This is 2.5mm twin and earth.

That last reading was higher than I would expect since I think it should be around 0.3 but not sure if its anything to worry about. Perhaps my earthing terminals are not as tight as the others.
 
Since it was so quick to do, I decided to try Wilko's kind suggestion. I've only done the easy first part partly because I know it is a ring (its in my house and I've seen it) and partly because I just wanted a sanity check before doing a load of other work and then a final test.

Anyway, the numbers around the ring in ohms were:
L 0.18
N 0.17
E 0.41

This is 2.5mm twin and earth.

That last reading was higher than I would expect since I think it should be around 0.3 but not sure if its anything to worry about. Perhaps my earthing terminals are not as tight as the others.

The 2 most likely reasons for the discrepancy from the x1.666 ratio are:
  • The cable is over 40 years old, and still had a 1mm earth with the 2.5mm live cores.
  • There is at least one case of a poor connection. Quite often you will find the result improves incrementally after reterminating the earths in each socket.
BTW, if this is the main ring circuit for the house, it appears to be quite small, and may indicate that a number of sockets (usually the downstairs ones) have been wired as spurs from a small ring. This is not a major problem, but isn't ideal for any modifications, and usually indicates an old installation.
 
Since it was so quick to do, I decided to try Wilko's kind suggestion. I've only done the easy first part partly because I know it is a ring (its in my house and I've seen it) and partly because I just wanted a sanity check before doing a load of other work and then a final test.

Anyway, the numbers around the ring in ohms were:
L 0.18
N 0.17
E 0.41

This is 2.5mm twin and earth.

That last reading was higher than I would expect since I think it should be around 0.3 but not sure if its anything to worry about. Perhaps my earthing terminals are not as tight as the others.
Your cpc will have higher resistance because the conductor is smaller.
 

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