New Consumer Unit Installation - L&N Reverse at the sockets

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Vol

Hi there, I'm a newbie to the forum. I'm an ordinary senior citizen householder but while not an electrician, I do take notice and read up on all the stuff the electricians are doing in my house. I have just had a modern, metal consumer unit installed after the removal of the old traditional fuse box. The installation went pretty well with very few curses! :) Given the old wiring in the house, everyone was pleasantly surprised when both RCDs stayed good and the supply uninterrupted.
As a final check before leaving, the electrician inserted a socket tester. In every location tried, the socket tester showed L&N Reverse. I bought s socket tester and confirm the same readings: L&N Reverse. I haven't checked every single socket but that is the pattern.
One problem is that I have no way of telling if the old fuse box situation would have given the same L&N Reverse readings, ie did the electrician change anything or just carry on an existing (hidden) error?
Firstly, is this in any way a dangerous situation given the RCDs are quite happy? If dangerous, what should be done immediately?
Secondly, how could this reversal have occurred? The electrician simply reinserted the live and neutral cables appropriately as they were removed. The meter tails were changed cos the existing were only 16mm. Could the tails have been reversed somehow?
Anything else you guys can suggest?
Thanks for reading the newbie panic post! I would appreciate any input, thanks..
 
'Electrician' really should have known RCD's wouldn't cause a problem before he turned the installation back on. Sounds like not a lot of testing has been carried out here.

Would be interested to see the installation certificate (not likely I know). Was it Dave from the pub who fitted the new CU and whoever it was do they own the proper test equipment or was one of these used?

SOK22.jpg
 
Hi telectrix, thanks for your quick comments. The electrician is coming back indeed and he will try to resolve the issue. On the day, he was flummoxed about the reasons why but as the RCDs were working well, he felt it safe to go (I knew in advance he had an unbreakable appointment later and to be honest, I agreed it seemed OK - which it has proved to be, so far). I am still awaiting the installation certificate, which has been promised.
It's odd, looking at the words it might seem that the electrician was a bit of a cowboy, I thought far from it. he was very conscientious it seemed to me. And the safe RCD situation seemed to trump all?
 
Has he given you any form of certificate?

What testing did he undertake, as just plugging one of those testers in means little to nothing on whether the circuit is safe to energise.

He may have been a very friendly guy, but if you've not received certification and the electrician has not notified building control. You could have been left with a potentially unsafe install and find problems if you ever come to sell the house.
 
Hi mattg4321, no it wasn't Dave from the pub :). s far as I am aware electricians don't have a similar scheme to the Gas Safe scheme when I can look up and check the credentials of a self-declared "electrician". Please let me know if there is such a scheme and I would use it.
The questions in my post were the most important bits. The key question was "is the situation dangerous and if so, what has to be done immediately". Any advice on that? The second question was about how it could have occurred?
Thanks for the input.
 
Vol said:
Hi telectrix, thanks for your quick comments. The electrician is coming back indeed and he will try to resolve the issue. On the day, he was flummoxed about the reasons why but as the RCDs were working well, he felt it safe to go (I knew in advance he had an unbreakable appointment later and to be honest, I agreed it seemed OK - which it has proved to be, so far). I am still awaiting the installation certificate, which has been promised.
It's odd, looking at the words it might seem that the electrician was a bit of a cowboy, I thought far from it. he was very conscientious it seemed to me. And the safe RCD situation seemed to trump all?
Click to expand...
Just because the rcd does not trip doesn't mean its safe in the terms you think it is, as highlighted by cross polarity at the socket outlets.
Polarity is a test done before the installation is energised, even a basic check with a 2 pole voltage tester at the incoming tails would have gave an indication as would a ze test.
I would check the tails coming into the meter from the cut out as well.
At the meter terminals it should be left to right
L N N L
 
Hi Rob, thanks. The very reason I am asking these questions on this forum is because I am aware already of the potential ramifications of a dodgy installation. Everyone seems focused on questioning the parentage of the electrical installer (and by implication, my own sanity for contracting with him in the first place), whereas what I really really want to know if the L&N Reversal is (actually and actively) dangerous and what to do if it is. Secondly, I would like to know how the problem might have arisen (and thus how it may be resolved) and thus be better informed when that, or another more like, electrician comes back to put things right.
I take your point about these little plug in devices. There should have been a more systematic testing of the circuit. But honestly,
I felt secure with the safe operating presence of the RCDs which I understood rightly or wrongly was one of the fundamental bases of the most recent code.
Thanks again for your input.
 
Vol said:
Hi mattg4321, no it wasn't Dave from the pub :). s far as I am aware electricians don't have a similar scheme to the Gas Safe scheme when I can look up and check the credentials of a self-declared "electrician". Please let me know if there is such a scheme and I would use it.
The questions in my post were the most important bits. The key question was "is the situation dangerous and if so, what has to be done immediately". Any advice on that? The second question was about how it could have occurred?
Thanks for the input.
Click to expand...
A Consumer unit change falls under "notifiable work" under Part P of the building regs. You can download a copy of this online which would make it clearer. He may have not got round to this yet as with the certificate. I usually issue certs within a week of completion.

The simple fact is that the reversed polarity that has been discovered should have really been found and rectified before he left. This would have shown up if he tested properly. If one point is showing L&N Reverse then it would suggest it's local to that point. If it's all of them then i'd hazard a guess that the reverse is at the board end which is then effecting the rest of the circuit.
 
Vol said:
The questions in my post were the most important bits. The key question was "is the situation dangerous and if so, what has to be done immediately". Any advice on that? The second question was about how it could have occurred?
Thanks for the input.
Click to expand...

It is potentially dangerous and despite the pressing appointment it should have been rectified before the electrician left.

Were all of the circuits (lights, immersion, cooker etc) tested? What did the tester look like that he used?

We all have bad days, but I'm surprised that the problem is proving difficult to diagnose. I would seriously consider getting a second opinion.
 
In Scotland you could check if he is a member of Select or NICEIC. However, as has been discussed on here before, membership of these bodies doesn't ultimately prove the competence of the electrician. Nor does non membership prove they are not competent!
 
Wow, I'm so impressed and grateful for the comments and advice! (NB I found myself sounding a bit defensive in my last posts but I'm not really.)
The consumer unit is a BG 16-Way Dual RCD Metal Consumer Unit & 12 MCBs sourced from Screwfix. It seems to have a decent enough reputation and seemingly ticks all the boxes.
If Part P doesn't apply in Scotland (where I am located), is the work there still notifiable in some other way?
I know it is almost impossible for qualified electricians to say, yeah, go on, it's probably safe. However, is there any substantial reason why my usual electrical load through fridges, washing machine (cool washes only), dishwasher (wash programmes only, no drying), TV etc should not continue over the weekend? If I cannot find an electrician to come out over the weekend, then it would be first thing next week. Does that timescale sound OK?
Thanks again, you've been very helpful.
 
Previous post #8 referencing polarity testing is the information you need to take to the electrician when he returns.
Polarity is there for a reason - one being that a single pole switch on a socket or such like will open the line conductor and not the neutral which can have And can lead to other dangerous issues so basically it's got to be right otherwise it's wrong - hope it get sorted quickly.
 
A live-neutral reverse has the potential to cause harm
In the case of a light,a person could insert a lamp,unknown to the person (because of the reversal) the neutral of that light will be live and could cause injury
A appliance left plugged in will also have the neutral connections live whether its switched off or not
It is a potentially dangerous fault and needs rectifying
 
One of the VERY first steps is to CONFIRM polarity and earthing on the supply to the main switch.... so this must have been missed... so any certificate can be viewed with suspicion.

As for the RCD .... most don't care which way round the L&N are - all they do is monitor the "balance" - so again if the so called spark doesn't understand this ......

Have you paid him?
 
how did the electrician test?
Did he just plug his radio in?o_O
Sorry re read the original op.
He even identified L-N reverse and then left without identifying the problem!?
 
Vol said:
Hi there, I'm a newbie to the forum. I'm an ordinary senior citizen householder but while not an electrician, I do take notice and read up on all the stuff the electricians are doing in my house. I have just had a modern, metal consumer unit installed after the removal of the old traditional fuse box. The installation went pretty well with very few curses! :) Given the old wiring in the house, everyone was pleasantly surprised when both RCDs stayed good and the supply uninterrupted.
As a final check before leaving, the electrician inserted a socket tester. In every location tried, the socket tester showed L&N Reverse. I bought s socket tester and confirm the same readings: L&N Reverse. I haven't checked every single socket but that is the pattern.
One problem is that I have no way of telling if the old fuse box situation would have given the same L&N Reverse readings, ie did the electrician change anything or just carry on an existing (hidden) error?
Firstly, is this in any way a dangerous situation given the RCDs are quite happy? If dangerous, what should be done immediately?
Secondly, how could this reversal have occurred? The electrician simply reinserted the live and neutral cables appropriately as they were removed. The meter tails were changed cos the existing were only 16mm. Could the tails have been reversed somehow?
Anything else you guys can suggest?
Thanks for reading the newbie panic post! I would appreciate any input, thanks..
Click to expand...
He, the Electrician, let you with reversed polarity? yes he should have rectified the fault Imediatly
Vol said:
Hi Rob, thanks. The very reason I am asking these questions on this forum is because I am aware already of the potential ramifications of a dodgy installation. Everyone seems focused on questioning the parentage of the electrical installer (and by implication, my own sanity for contracting with him in the first place), whereas what I really really want to know if the L&N Reversal is (actually and actively) dangerous and what to do if it is. Secondly, I would like to know how the problem might have arisen (and thus how it may be resolved) and thus be better informed when that, or another more like, electrician comes back to put things right.
I take your point about these little plug in devices. There should have been a more systematic testing of the circuit. But honestly,
I felt secure with the safe operating presence of the RCDs which I understood rightly or wrongly was one of the fundamental bases of the most recent code.
Thanks again for your input.
Click to expand...
Vol said:
Wow, I'm so impressed and grateful for the comments and advice! (NB I found myself sounding a bit defensive in my last posts but I'm not really.)
The consumer unit is a BG 16-Way Dual RCD Metal Consumer Unit & 12 MCBs sourced from Screwfix. It seems to have a decent enough reputation and seemingly ticks all the boxes.
If Part P doesn't apply in Scotland (where I am located), is the work there still notifiable in some other way?
I know it is almost impossible for qualified electricians to say, yeah, go on, it's probably safe. However, is there any substantial reason why my usual electrical load through fridges, washing machine (cool washes only), dishwasher (wash programmes only, no drying), TV etc should not continue over the weekend? If I cannot find an electrician to come out over the weekend, then it would be first thing next week. Does that timescale sound OK?
Thanks again, you've been very helpful.
Click to expand...
Vol, you need to, contact this Idiot, he is a Muppet for leaving you in this predicament, as others have said reversed polarity could be potentially dangerous, I take it you have paid him? Sorry for the sentence in between don't know what happened there
 
I've just checked and it seems that the L&N Reversal is prevalent in every socket across every zone in the house. Does that imply that the problem could well be at the "source" maybe the swapped meter tails?
I see the point that if the socket is switched off, the connection might still be live under a reversed polarity situation. One of my first purchases when I recently bought the house and saw the inaccessibility and age of the old fuse box, was 10 large automatic lights, the kind that go on only if the electricity supply cuts. These are currently (no pun intended :) ) behaving "normally", ie they are off until the socket is switched off. Does that mean that polarity doesn't matter to these lights or that the socket switch IS switching off the live feed?
 
Pete999, I think it is Muppets all round in this case, him and me. But this electrician talked a good game, professed 17th Ed tested/qualified and although I'm not an electrician I have been around electrical work all my life from my Dad (electronics engineer) on. I'm actually very safety conscious and regulations aware. And he was hard working and conscientious - right up to the reverse polarity issue I accept :( . However, until the industry has a similar scheme to Gas Safe then these problems will continue to occur I suppose.
OK, the problem will be resolved early next week and much care will be taken between now and the fix.
Thanks again
 
Sounds like reverse polarity at the consumer unit. This should be rectified immediately and if he isn't willing to resolve this ASAP then threaten him with legal action and get another electrician in to resolve the issue and get some kind of written evidence to use against the original installer.
 
Des56, I didn't just go out and buy a socket tester thing. I looked up the kind of testing that an ordinary consumer can undertake by themselves and this socket tester device was suggested. If it read the same as what the electrician had found, then I had at least proved it was not a single device fault. I didn't go out at all. I ordered it online.
But you seem to be implying something, I'm not sure what. You say "I ask because it seems such an unusual action for a customer". The product I bought had over 1000 purchases and a 4.9 out of 5 stars from 64 reviewers. What else is available for an ordinary consumer who is concerned about an electrical function/socket?
Everyone else today has given good advice and everybody on this thread talks like a good professional. But so did the electrician who came to me. On the doorstep, how is the consumer meant to be able to tell who is the competent professional as apart from the incompetent professional (as an earlier poster talked about).
 
Can you take a picture of the consumer unit and the tails going into the meter?
We might be able to help if we can see the unit.

On the note of if a person is competent then being an Approved NICEIC electrician(or similar) is a start.I know alot of people on here don't like the relevant schemes but in order to be in them,you have to prove your qualifications,have insurance in place,have your test meters calibrated and pass a yearly inspection.While none of the above proves that you'll get a quality job,it does at least prove that the person your hiring has obtained the skills to become approved.Unlike the bloke down the pub who does a bit of electrics on the cheap.
 
Last edited:
I asked because it is the first time in 50 years that I have heard of an installation being left with a known reverse polarity issue
Its the first time I have known of a customer, having been made aware of the problem, then sourcing electricians test equipment to check an installation constructed by another
I asked.you answered,thank you for the response
 
To answer you question on relative safety at this time. The line and neutral reversal is a problem if you have a secondary fault occur before the situation is resolved. As an example should your washing machine develope a fault. It is possible the plug fuse will blow but this will only disconnect on the now neutral line. There will remain live power feeding into the machine. My advice until the situation rectified would be to unplug any metal cased equipment you have where ever possible. E.g. washing machine, dish washer etc any any equipment you do not required powered up. No one can guess if or when a fault may occur.
I am not a professional electrician by the way but I believe I am correct in my thought process. I am sure others can confirm or correct if necessary.
 
He is not an electrician if he left you with reversed polarity after changing your CU.

It's not a difficult problem to figure out and most likely is something to do with the installation process of the CU.

The fact that he only noticed reversed polarity after plugging in a tester says to me he's not even done the basic testing required for this type of work.

Just can't believe it's been left like that
 
mache said:
To answer you question on relative safety at this time. The line and neutral reversal is a problem if you have a secondary fault occur before the situation is resolved. As an example should your washing machine develope a fault. It is possible the plug fuse will blow but this will only disconnect on the now neutral line. There will remain live power feeding into the machine. My advice until the situation rectified would be to unplug any metal cased equipment you have where ever possible. E.g. washing machine, dish washer etc any any equipment you do not required powered up. No one can guess if or when a fault may occur.
I am not a professional electrician by the way but I believe I am correct in my thought process. I am sure others can confirm or correct if necessary.
Click to expand...

Fuses will only blow in the event of overcurrent fault, faults to earth will not cause fuse to blow because they are effectively not in circuit. RCD's will continue to operate in the event of a live to earth fault, but some RCD's only break on one pole, so in this situation the circuit would still remain live.
Circuits not protected by an RCD will only have to fuse in the cut out (100A?) as protection, which could cause a major fault, fire, etc.
Also remember any Edison screw light fittings will be backwards so the threaded part will now also be live.
I cannot believe this 'electrician' has cleared off for the weekend and left this.. it needs to be addressed now
 
With the correct test instruments then its pretty easy to determine where the live neutral reverse has taken place.Even if the bloke had an appointment then fixing this kind of fault wouldn't have taken long to find if you have the experience.I agree with everyone else's opinion ,that it needs sorting asap.
 
Des 56 said:
I asked because it is the first time in 50 years that I have heard of an installation being left with a known reverse polarity issue
Its the first time I have known of a customer, having been made aware of the problem, then sourcing electricians test equipment to check an installation constructed by another
I asked.you answered,thank you for the response
Click to expand...

Are you thinking what I'm thinking and probably what everyone else is thinking, or am I being just too cynical suspicious. ;)
 
I thought what you are thinking last night, but then I thought Nah can't be, then I thought yes we all could be right
 
thing is, everything will work OK, but should you switch something off at it's switch, it will be switching the neutral instead of the line, so there is a potential, if not immediate, danger. have you had a new meter installed lately?
 
The CU was changed on Friday of last week, the 28th April.
The electrician is coming over on Monday to resolve the problems.
Surely the RCD on a new CU is active on both live and neutral? Whereas it might not pick up a complete line reversal cos "things remain in balance wrt earthing", surely it would pick up a fault even on the neutral line? Does the RCD switch off both lines or just the presumably live line? If only the live line, then that doesn't seem like a well planned solution to me - for an RCD device to be fully safe, it has to switch off both live and neutral, or am I misunderstanding? It is dealing with a fault, how does the RCD know the nature of the fault, it's job has to be to cut off any possibility of current reaching the device or appliance, that should mean cutting off both live and neutral, in my humble opinion.
The point raised by mache about a faulty washing machine etc continuing to be live due to the neutral line issue is worrying. Won't the earthing system within the appliances keep the outside surfaces safe though? Also the issue of the Edison screw bulbs having a live screw casing is worrying too, although we have few of those and nobody will go near them until the electrician has done his stuff.
 
Vol said:
The CU was changed on Friday of last week, the 28th April.
The electrician is coming over on Monday to resolve the problems.
Surely the RCD on a new CU is active on both live and neutral? Whereas it might not pick up a complete line reversal cos "things remain in balance wrt earthing", surely it would pick up a fault even on the neutral line? Does the RCD switch off both lines or just the presumably live line? If only the live line, then that doesn't seem like a well planned solution to me - for an RCD device to be fully safe, it has to switch off both live and neutral, or am I misunderstanding? It is dealing with a fault, how does the RCD know the nature of the fault, it's job has to be to cut off any possibility of current reaching the device or appliance, that should mean cutting off both live and neutral, in my humble opinion.
The point raised by mache about a faulty washing machine etc continuing to be live due to the neutral line issue is worrying. Won't the earthing system within the appliances keep the outside surfaces safe though? Also the issue of the Edison screw bulbs having a live screw casing is worrying too, although we have few of those and nobody will go near them until the electrician has done his stuff.
Click to expand...
 
Some information to add, On May 16th the electricity company (the main electricity infrastructure company not the name on the electricity bills) comes to upgrade the supply side meter at the close mouth (for those that don't know, close is the entrance way to a Glasgow tenement). That will be upgraded in order for me to have SMART gas and electricity meters installed. This, with the CU replacement, is part of the general upgrade of systems in the house.
The supply side upgrades will include a new isolation unit as the existing fuse box with the big ceramic cartridge fuses is well out of date. I obviously don't actually know what they will be changing/installing as they don't share that information with me, of course! :)
 
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