Testing Equipment

[morpheus83uk]

Hello,

I am looking at these to test some of my sockets around the house for easy diagnosis and also to check if something is live what are peoples thoughts:

Socket Tester:

http://www.screwfix.com/p/lap-ms6860d-socket-tester/91596

AC Voltage Detector Pen:

http://www.screwfix.com/p/lap-ms8902h-ac-voltage-detector-pen/88495

Both are LAP and have very good reviews I thought I would ask peoples experiences of this sort of equipment before purchase.

Thanks

James

 

[PrenticeBoyofDerry]

I only use the plug-in detectors as a quick reference to what sockets belong to which circuit.

And volt sticks on the occasion that I need to confirm cables are live, when it is impossible to take a two pole reading.

But I have never used LAP testing equipment.

 

[morpheus83uk]

Thanks for the reply.

Do you think they are any good then and worth having?

Thanks

James

 

[Taylortwocities]

I would only use this sort of thing for a very quick, very basic, that it is on or off. They are not designed for diagnosis.

Socket "testers" for instance will give you an "ALL OK" reading even if the earth and neutral are reversed.

AC detector pens are unreliable, may not indicate when power is on,
can indicate when power is off (due to induced voltages from other circuits)

Doing any meaningful work on electrical circuits requires a two probe voltage tester like this http://www.tester.co.uk/martindale-vi13800-voltage-indicator
to ensure safe isolation.
And proper test equipment to provide any diagnosis of wiring circuit issues.
SOmething like this http://www.tester.co.uk/megger-mft1710-multifunction-installation-tester

 

[morpheus83uk]

Thanks for the reply I will have another think and check out the links you have posted.

 

[JohnW2]

Socket "testers" for instance will give you an "ALL OK" reading even if the earth and neutral are reversed.

As a matter of interest, is there any live test (other than an RCD test, if there is an RCD) that will reliably detect a N-E reversal (particularly in a TN-C-S installation)?

Kind Regards, John

 

[plugwash]

Not in a normal installation.

 

[JohnW2]

Not in a normal installation.

Thanks - that's what I thought. As I said, if the circuit is RCD protected, then, in the presence of an N-E reversal, standard RCD testing would presumably fail to get the RCD to operate, and would therefore flag up that something was wrong, which would hopefully lead to further investigation. Of course, if that just happened when testing at, say, one socket on a circuit, but the RCD tripped OK when tested from other places on the circuit, that would point the finger very firmly at the one socket (N-E reversal or no E).

Kind Regards, John

 

[plugwash]

As I said, if the circuit is RCD protected, then, in the presence of an N-E reversal, standard RCD testing would presumably fail to get the RCD to operate

Only if the N-E reversal is downstream of the RCD.

Of course unless the load is very small a N-E reversal downstream of a RCD is very likely to get noticed during normal use of the installation due to unwanted RCD trips.

 

[JohnW2]

As I said, if the circuit is RCD protected, then, in the presence of an N-E reversal, standard RCD testing would presumably fail to get the RCD to operate

Only if the N-E reversal is downstream of the RCD.

Well, yes, of course - but this discussion (my question) arose out of a comment about plug-in socket testers - obviously downstream of any RCD protecting the circuit. At least in a domestic environment, I would have thought that N-E reversals upstream of RCDs in the CU would be all-but unknown - the mind boggles at how it would be achieved

Of course unless the load is very small a N-E reversal downstream of a RCD is very likely to get noticed during normal use of the installation due to unwanted RCD trips.

That's true - but, again, I think the discussion was really about how a DIYer (or anyone) could check a newly-installed socket before it had been in-service.

In fact, I was just a little intrigued by TTC commenting that a plug-in socket tester could not detect a N-E reversal (sort-of implying that "an electrician's expensive kit" could), since I couldn't think of any live test, with any sort of equipment, which could reliably (if at all) detect such a fault.

Kind Regards, John

 

[plugwash]

Well an electrician may well notice that loop impedance readings are not as expected and investigate further, it's just not really a reliable test because P-N and P-E loop impedances can be very close and there are many things that can impact the P-E loop impedance (supplementary bonding, cross connection of earths through signal cables etc)

What concerns me more about most socket testers is they give no indication of the quality of the earth (though with pervasive RCDs that is less of an issue than it used to be)

 

[Taylortwocities]

You are quite right, and you have been careful to qualify that the problem is with detecting this in a "live" test.

But before this the usual dead tests (which include Zs and polarity) will have flagged a N-E reversal - downstream of the CPD/RCD.

What I was trying to flag, is that your average DIYer will never carry out the proper tests as they do not have the knowledge, or even the basic equipment to do it. For most it's usually a process of "plug something in and see if it works". I would include a socket tester in the group of "plugging something in and seeing if it works" items.

 

[JohnW2]

Well an electrician may well notice that loop impedance readings are not as expected and investigate further, it's just not really a reliable test because P-N and P-E loop impedances can be very close and there are many things that can impact the P-E loop impedance (supplementary bonding, cross connection of earths through signal cables etc)

I would have doubted that the difference between P-N and P-E loop impedances would often be large enough to even alert an electrician to a possible N-E reversal, particularly in a TN-C-S installation, in which those incidental paths to earth will (in an intact installation) affect the P-N impedance just as much as the P-E one - one is, after all, essentially just looking at the difference between R1 and R2.

What concerns me more about most socket testers is they give no indication of the quality of the earth (though with pervasive RCDs that is less of an issue than it used to be)

Some do give an estimate of EFLI ... see: https://www.tlc-direct.co.uk/Images/Products/size_3/TMEZ150.JPG (for some reason I can't get the image to embed in this post) ... obviously far short of a proper measurement, but (in a TN installation) the 0/1.7/5/10 Ω ought to give a reasonable indication of whether anything is amiss.

Kind Regards, John

 

[JohnW2]

You are quite right, and you have been careful to qualify that the problem is with detecting this in a "live" test. But before this the usual dead tests (which include Zs and polarity) will have flagged a N-E reversal - downstream of the CPD/RCD.

Indeed. That was really my point - that it's not for no reason that plug-in testers cannot detect N-E reversals (and have that written all over them), it's because no live testing device could detect it .

When you talk about a dead 'Zs' test, do you mean measurement of R1 and R2 (and maybe Rn) - and then perhaps determining Zs by calculation (R1+R2+Ze)?

What I was trying to flag, is that your average DIYer will never carry out the proper tests as they do not have the knowledge, or even the basic equipment to do it. For most it's usually a process of "plug something in and see if it works". I would include a socket tester in the group of "plugging something in and seeing if it works" items.

I can't disagree with the generality of your sentiments - but, given that DIY happens, and if we're talking about a sockets circuit, using a plug-in socket tester (particularly if it's one that gives an indication of EFLI) is surely a major advance on not undertaking any tests, even in the hands of someone whose 'understanding' is limited, isn't it? You have identified the main thing (N-E reversal) that will not be picked up by such a device and, to be frank, anyone capable of creating a N-E reversal did not ought to be anywhere near anything electrical - I'm maybe missing something, but I can't think of any way that it can be achieved by anyone with the slightest understanding of what they are doing.

Kind Regards, John

 

[EFLImpudence]

I'm maybe missing something, but I can't think of any way that it can be achieved by anyone with the slightest understanding of what they are doing.

We do come across it.

I think the point raised about socket testers and N-E reversal is important because even with such an occurrence the tester reads "wiring correct".