Wiring tester shows all outlets in house are "incorrect"

[hawkman]

I recently received one of these RCD testers as part of an eBay purchase. I hadn't really thought to test the wiring in my house before, but when I plugged it into the first socket in my house, it showed "incorrect" with L and N reversed. Thinking this might just be one outlet, I tested others - they all are reversed!

Questions:

• Is this a serious issue requiring immediate attention?
• Would this be the result of something mis-wired at the consumer unit?
• How could this have happened?

Thanks in advance.

 

[Andy™]

yes
maybe
many possibilites

first of all, best to confirm that it really is wrong polarity. basic tester like that are very limited in function and at best can give some indication but they are not designed for proper testing & fault finding

 

[hawkman]

I had another consumer unit installed during a garage renovation. I checked the outlets in there with the tester and they all registered as "correct".

I've got a Fluke 117 multimeter, would I be able to diagnose this situation better using it? If so, what would be the recommended approach?

*edit* I read this on another forum: "Measure between the earth and the (alleged) L, then between the earth and the (alleged) N at each socket. In the absence of any polarity reversals, you should see ~230/240V between L and E and a very low voltage (if any) between N and E." Does this make sense?

 

[Fleeting]

That type of tester gives rudimentary results, having said that it is indicating an issue but from afar it is impossible to give an accurate assessment. I would suggest you consult an electrician as it certainly requires attention.

 

[binky]

I recently received one of these RCD testers as part of an eBay purchase. I hadn't really thought to test the wiring in my house before, but when I plugged it into the first socket in my house, it showed "incorrect" with L and N reversed. Thinking this might just be one outlet, I tested others - they all are reversed!

Questions:

• Is this a serious issue requiring immediate attention?
• Would this be the result of something mis-wired at the consumer unit?
• How could this have happened?

Thanks in advance.

At the price of this gadget, I doubt it's very accurate.

 

[Murdoch]

I suspect you’ve just wasted £30

get a local spark to use a proper tester

 

[hawkman]

Just tested with my Fluke 117 true RMS multimeter and I’m getting 238v from E to N. That’s not right.

I’m thinking something has been done by the electrician that installed my consumer unit in the garage - after he installed it, two of my low voltage lights weren’t working properly and I needed to change the transformers. He swore up and down that it was a coincidence but my electrical engineering degree background suspected a bad ground. I’m not an electrician so I didn’t suspect this L N reversal issue.

I do need an electrician. Anyone want to bid on the job?

 

[Andy™]

L-N reversal is not likely to cause the transformers to fail

238v N-E is a problem though

 

[Murdoch]

Just tested with my Fluke 117 true RMS multimeter and I’m getting 238v from E to N. That’s not right.

I’m thinking something has been done by the electrician that installed my consumer unit in the garage - after he installed it, two of my low voltage lights weren’t working properly and I needed to change the transformers. He swore up and down that it was a coincidence but my electrical engineering degree background suspected a bad ground. I’m not an electrician so I didn’t suspect this L N reversal issue.

I do need an electrician. Anyone want to bid on the job?

dare I ask if sad spark gave you any certificates ?

you mention the garage but what about the hous?

had a smart meter fitted ?

 

[Geoff1946]

Sorry, but if you really have an electrical engineering degree I find it rather odd that you are asking these questions here, and for that matter can't work out what's wrong.

 

[ProDave]

Post a picture of the wiring inside your shiny new CU with the front cover off.

If as looks likely you really do have reverse polarity then your "electrician" didn't do any testing then did he, not even with a plug in socket tester.

 

[monkey5]

Is there a Henley block, did he need to fit one when the new board was fitted, maybe reversed In there.

 

[hawkman]

That is exactly what happened. I just had a professional NAPIT registered electrician come to basically swap the L and N wires going into the CU. The previous "electrician" neither did any testing NOR did he even mark the wires with blue/brown. Two grey wires are VERY easy to confuse.

This could have been deadly. But thankfully a small amount of £ and it's fixed. I'm not sure what to do next, should I pursue some kind of sanction against the previous "electrician" who did this?

 

[monkey5]

My guess is if they did no testing or issue a certificate they couldn't care less if you pursued them, so would be wasting your own time. Easy to make that mistake if cables have identical coloured insulation, but also would have been found when the testing was done. Luckily it's been found and In the mean time no-one got hurt.

 

[hawkman]

Luck. Yes. I bought a multimeter on eBay and the seller threw in a plug tester. I laughed and thought nothing of it. Until it arrived and I used it. The rest you can see above.

I know there is a lot of hate about these testers but if I hadn’t used it, I wouldn’t have found this issue. And correspondingly found a great actual electrician.

 

[Kot]

My guess is if they did no testing or issue a certificate they couldn't care less if you pursued them, so would be wasting your own time. Easy to make that mistake if cables have identical coloured insulation, but also would have been found when the testing was done. Luckily it's been found and In the mean time no-one got hurt.

So lets just pursue them when someone gets hurt or killed?

 

[mort2376]

Did the original electrician claim to be a member of a scheme ? Napit, Niceic, Stroma etc.

If yes the report to that scheme as they are more than likely not members and committing fraud by claiming to be.

 

[binky]

Luck. Yes. I bought a multimeter on eBay and the seller threw in a plug tester. I laughed and thought nothing of it. Until it arrived and I used it. The rest you can see above.

I know there is a lot of hate about these testers but if I hadn’t used it, I wouldn’t have found this issue. And correspondingly found a great actual electrician.

We have to be suspicious of cheap test gear, as our lives can depend on it. Trouble with plug in testers is that no earth can also be shown as reversed polarity on some makes.

 

[ProDave]

Glad it is all sorted.

The two "grey" wires will have had a coloured inner core, they are insulated and sheathed cables and strip the grey sheath will reveal one has a brown core and the other has a blue core. It is normal to leave just enough sheath stripped inside the CU to see the colours. But I have seen 2 cables with the same colour core used so never under estimate how people can do things wrong.

Knowing now the incompetence of the installer, it is probably worth getting an EICR done, so see what less obvious faults he may have left behind.

Those cheap socket testers get a lot of flack, but this post has shown they can be useful and can identify genuine faults. The main point is they should not under any circumstances be your only test, and there are some faults that they cannot detect.

And thanks for letting us know the outcome, so many never come back to tell what the fault turned out to be.

 

[Murdoch]

At the very least you should contact the "electrician" or whoever did the garage fuseboard in writing and confirm to them what THEY got wrong and at the same time ask them for the EIC and Part P certificate for the new fuseboard.