Socket Tester Neutral Fault

[Crofty]

Today I was doing an EICR and went around a couple sockets with a Megger MST220 socket tester just to see if there was anything obvious, all three green lights came on saying everything was fine and correct. When I took the faceplate off to do my R1 R2s I got readings of 0.60 on R1 but then >2000 on Rn. I know socket testers shouldn't be relied on and I only use it to see if there if anything obvious before I take the faceplate off but surly it should of shown a natural fault?

 

[littlespark]

No… socket testers can’t be relied on.

I had a known fault on a double socket… one side worked, the other doesn’t.
My little socket-and-see tester showed perfect on the working side, and and an L-N reverse on the other.

How does that work?

 

[Crofty]

No… socket testers can’t be relied on.

I had a known fault on a double socket… one side worked, the other doesn’t.
My little socket-and-see tester showed perfect on the working side, and and an L-N reverse on the other.

How does that work?

Yeah that is one of them magic sockets I mainly use it to plug in to see if there is anything obvious before I go taking the faceplate off but a 0.60 and >2000 I thought it'll pick that up no problem and being a Megger I have actually emailed Megger to see what they say... I am expecting a 'Don't rely on them' Kind of answer though.

 

[littlespark]

Tbh, I use mine just to know if I’ve got the right circuit isolated because it makes a buzzing noise when powered.

 

[Crofty]

Tbh, I use mine just to know if I’ve got the right circuit isolated because it makes a buzzing noise when powered.

That is the number 1 reason I have it too really, it's not very loud but the sound travels quite far. I use it kind of like the death pens, if that say's its live, then I will take it as live but if it doesn't, I will double check with a tester. I just thought an obvious netural fault like that wouldn't be hard for even the cheapest tester to pick up so I thought maybe I am using it wrong... Even though I can only use it one way by plugging it in

 

[westward10]

Is this a ring final or radial.

 

[westward10]

I don't understand if you are doing R1 R2 readings you quote Rn.

 

[pc1966]

I got readings of 0.60 on R1 but then >2000 on Rn. I know socket testers shouldn't be relied on and I only use it to see if there if anything obvious before I take the faceplate off but surly it should of shown a natural fault?

The socket testes only need a couple of mA to drive the LEDs, so a complete open should be flagged, but anything below 20k ohm-ish is going to light things just fine.

Their main utility is showing L-N reversal, or completely open E, and to a degree letting you hear when you have opened the correct breaker for a circuit etc. So better than nothing, but hardly an alternative to a MFT!

 

[Rockingit]

I don't understand if you are doing R1 R2 readings you quote Rn.

Nor me. If you're in the middle of r1r2 (assuming r not R, not that it matters...) then simply jumping to rn is always going to get you an open circuit!

Because it only ever takes seconds to do, I always do end-end on RFC conductors anyway right at the start because that can save you a whole heap of grief and time in tracking down an open circuit later on and also gives you a gauge for equal conductor resistances / distance. Had a scam inspector ask me once why I did that when it's not mandated to which I asked back why would you not?

 

[loz2754]

If testing a ring final circuit for end to end continuity, then even if rn is open circuit, a plug in socket tester will not detect this as it will still "see" one of the two neutral conductors.
Unless there is more than one break in the continuity of rn. (Same applies of course to each of r1 and r2)

 

[pc1966]

If testing a ring final circuit for end to end continuity, then even if rn is open circuit, a plug in socket tester will not detect this as it will still "see" one of the two neutral conductors.
Unless there is more than one break in the continuity of rn. (Same applies of course to each of r1 and r2)

Good point!

I had been assuming it was a non-functioning socket going undetected and not an RFC break.

 

[Crofty]

If testing a ring final circuit for end to end continuity, then even if rn is open circuit, a plug in socket tester will not detect this as it will still "see" one of the two neutral conductors.
Unless there is more than one break in the continuity of rn. (Same applies of course to each of r1 and r2)

That is what I was looking for, thank you!

 

[westward10]

So this is a ring final circuit?

 

[mainline]

The socket testes only need a couple of mA to drive the LEDs, so a complete open should be flagged, but anything below 20k ohm-ish is going to light things just fine.

Their main utility is showing L-N reversal, or completely open E, and to a degree letting you hear when you have opened the correct breaker for a circuit etc. So better than nothing, but hardly an alternative to a MFT!

And even a mft won't quickly show E N reversal.

 

[7029 dave]

End to end test on RFC is very important,you don't want any breaks on this kind of circuit.

 

[MDJ]

Today I was doing an EICR and went around a couple sockets with a Megger MST220 socket tester just to see if there was anything obvious, all three green lights came on saying everything was fine and correct. When I took the faceplate off to do my R1 R2s I got readings of 0.60 on R1 but then >2000 on Rn. I know socket testers shouldn't be relied on and I only use it to see if there if anything obvious before I take the faceplate off but surly it should of shown a natural fault?

it only tells you the polarity is correct, it isn't for readings and is an indicator only, no different from a volt stick, both convenient but unreliable really.

 

[pc1966]

And even a mft won't quickly show E N reversal.

It will if its RCD protected

 

[mainline]

It will if its RCD protected

Only if you run a test, it won't by just plugging it in.

 

[pc1966]

Only if you run a test, it won't by just plugging it in.

I often run the no-trip Zs as a quick check, as it verifies all conductors look OK and if N-E swap then RCD trips on the high current PSCC side.

But more generally as N & E are electrically so similar there is not any trivial check without added work, like isolating the N at the CU.

 

[nicebutdim]

Only if you run a test, it won't by just plugging it in.

It's a tester. Its intended purpose is running tests.